• 专利附录
  • 专利说明
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    • 专利摘要:
    A laser component is provided, including a laser medium (10) and a transparent heat transmitting member (20), at least one of which is an oxide. The bonding surfaces of the laser medium (10) and the transparent heat transmitting member (20) are exposed to an oxygen plasma, and then the bonding surfaces are contacted without heating. The laser medium (10) and the transparent heat transmitting member (20) are bonded to atomic levels, their thermal resistance is low, and no significant residual stress is generated because the bonding occurs at the temperature normal. The process of exposure to an oxygen plasma ensures the transparency of their binding interface. The laser medium (10) and the transparent heat transmitting member (20) are stably bonded through an amorphous layer.
    公开号:FR3058584A1
    申请号:FR1760183
    申请日:2017-10-27
    公开日:2018-05-11
    发明作者:Takunori Taira；Arvydas KAUSAS；Lihe ZHENG
    申请人:Inter University Research Institute Corp National Institute of Natural Sciences；
    IPC主号:
    专利说明:

    Holder (s): INTER-UNIVERSITY RESEARCH INSTITUTE CORPORATION NATIONAL INSTITUTES OF NATURAL SCIENCES.
    Agent (s): CABINET BEAU DE LOMENIE.
    164) LASER COMPONENT.
    FR 3 058 584 - A1
    16 /) A laser component is provided, including a laser medium (10) and a transparent heat transfer member (20), at least one of which is an oxide. The bonding surfaces of the laser medium (10) and the transparent heat transfer member (20) are exposed to an oxygen plasma, and then the bonding surfaces are contacted without heating. The laser medium (10) and the transparent heat transmission member (20) are linked to atomic levels, their thermal resistance is low, and no significant residual stress is generated because the bond takes place at temperature. normal. The process of exposure to an oxygen plasma guarantees the transparency of their binding interface. The laser medium (10) and the transparent heat transmission member (20) are stably linked by an amorphous layer.
    (have)
    (a2)
    (83)
    12,14,16
    03) (j1) _10_
    TECHNICAL FIELD The present description discloses a laser component in which a laser medium and a transparent member for heat transmission are linked, a method of manufacturing the laser component, and a laser device which uses the laser component.
    STATE OF THE ART [0002] A solid material is known which emits light when it is irradiated with an excitation beam. For example, a solid material doped with a rare earth element such as Nd: YAG, Yb: YAG, Tm: YAG, Nd: YVO 4 , Yb: YVO 4 , Nd: (s-) FAP, Yb: (s-) FAP, Nd: glass and Yb: glass, or a solid material doped with a transition element like Cr: YAG and Ti: AI 2 O3 emits strong light when it is irradiated with the excitation beam. These types of solid materials can be arranged in a resonator which resonates at a particular wavelength to obtain a laser resonator.
    A solid material is also known which emits an output laser beam when it is irradiated with an excitation beam and an input laser beam, the output laser beam being amplified with respect to the input laser beam. When this type of solid material is used, a laser amplifier is obtained. In the present description, these two types of solid materials are called optical gain materials.
    In addition, a solid material is known which emits an output laser beam with a wavelength different from that of an input laser beam when it is irradiated with the input laser beam. When this type of solid material is used, a wavelength converter is obtained. In the present description, this type of solid material is called nonlinear optical material.
    In the present description, the optical gain material and the nonlinear optical material will be collectively called the laser medium.
    The laser medium in operation generates heat. In particular, the optical gain material generates a large amount of heat due to its quantum defects which accompany the excitation. When the laser medium is overheated, the resonance efficiency is degraded due to the non-uniform distribution of the refractive indices in the laser medium, the thermal lens effect caused by thermal expansion, and also problems related to birefringence. thermal caused by the photoelastic effect, and the laser medium is ultimately damaged due to the stress exerted on it. Due to reasons as above, cooling is essential in a solid laser device or the like which uses the solid material. Furthermore, in order to prevent the quality of the beam of the laser beam from being degraded, the laser medium must not simply be cooled, but also precautions are necessary for the formation of warping and the like inside the laser medium, and to obtain this measurement, the cooling must be carried out so that a distribution of the temperature inside the laser medium is uniform. A cooling technique is essential to facilitate a large laser beam emission, and a technique configured to cool the laser medium efficiently and with a uniform temperature distribution is required.
    U.S. Patent No. 5,796,766 describes a laser component provided with a function for cooling a laser medium. In this technique, the laser medium has the shape of a circular disc, and it transmits heat to a transparent heat-transmitting member similarly having the shape of a circular disc. In the present description, a flat surface of the circular disc-shaped laser medium will be called the first end surface, and another flat surface thereof will be called the second end surface. In the technique of U.S. Patent No. 5,796,766, a first member transmitting heat in the form of a circular disc is brought into contact with the first end surface of the laser medium in the form of a circular disc, a second member transmitting heat in the form of a circular disc is brought into contact with the second end surface of the laser medium in the form of a circular disc, and the laser medium is cooled from the first and second end surfaces.
    [0005] U.S. Patent No. 5,796,766 describes methods for causing the laser medium and the heat transmitting member to come into contact with each other, including: (1) a method for bringing the two members into contact with each other by mechanical force (what the US patent No. 5,796,766 described as an optical contact), (2) a method of adhesion of the two members by an adhesive, (3) a method of fixing the two members by an epoxy resin, and (4) a method of the two members by diffusion.
    It has been found from studies carried out by the present inventors that the methods (1) to (3) mentioned above cannot sufficiently cool the laser medium due to the too high thermal resistance between the laser medium and the member transmitting transparent heat. That is, it has been found that the intensity of the laser beam cannot be increased to a level required by users of the laser device due to overheating of the laser medium. In the case of (1), due to the discontinuity of substances at an interface, phonons are dispersed by this discontinuous interface. That is, it results in an increase in thermal resistance, and this makes it unable to provide an essential solution. In addition, the adhesive and the epoxy resin layer in (2) and (3) create thermal resistance. In addition, they pose serious damage problems due to the degradation of the resin during high power operation. According to the method of (4), although the thermal resistance between the laser medium and the member transmitting the heat can be reduced sufficiently, because they are linked to a high temperature, a difference between the coefficients of thermal expansion of the medium laser and the member transmitting the heat causes a strong residual stress which acts on the laser medium during operation at room temperature. The residual stress causes an optical distortion in the laser medium which degrades the quality of the beam.
    In view of the foregoing, a technique for bonding to activated surfaces of the laser medium and of the transparent member for heat transmission has been developed, and this is described in Hiroki TOGASHI, Creation and Evaluation of Yb: YAG / Diamond Composite Structured Laser Using Normal Temperature Bonding, Master's Thesis, Chuo University (2013) (hereinafter 'TOGASHI). In TOGASHI, YAG which is a type of laser medium and diamond which is a type of transparent heat-transmitting organ are linked by binding to activated surfaces. The bond to activated surfaces can be called bond at room temperature or bond at normal temperature because the members are brought into contact without heating.
    In this description, bonding with activated surfaces designates the projection of an atomic beam of inert gas onto bonding surfaces of the two members which must be bonded to activate the bonding surfaces, bringing the activated bonding surfaces into contact with one another. with each other, and causing the two members to bind to their atomic levels by atomic bonds that appear on the activated bonding surfaces. According to this activated surface bonding method, the bonding can be carried out at normal temperature, and the problems associated with a residual stress do not appear. In addition, the bonding that occurs at atomic levels can sufficiently reduce the thermal resistance between the two members. Other references, Eiji HIGURASHI, Ken OKUMURA, Kaori NAKASUJI, and Tadatomo SUGA, Surface activated bonding of GaS and SiC wafers at room temperature for improved heat dissipation in high power semiconductor lasers, Japanese Journal of
    Applied Physics, 54 030207 (2015) (in the following HIGURASHI et al) and Yoichi SATO, Akio IKESUE and Takunori TAIRA, Tailored Spectral Designing of Layer-by Layer Type Composite Nd ^ ScAUOn / Nd-.YaAlsOn Ceramics, IEEE Journal of Selected Topics in Quantum Electronics, Vol. 13, no. 3 May / June (2007) (in the following SATO et al), will be described later.
    SUMMARY In the TOGASHI technique, if IYAG and the diamond could be linked in a satisfactory state by the conventional activated surface bonding, the laser medium could be cooled efficiently and uniformly, and it could be a revolutionary technique allowing emission at high power by the laser device. In reality, however, an optically degraded layer such as a colored layer or the like is formed at an interface of IYAG and diamond which are bonded by means of conventional activated surface bonding. In addition, the bond reliability of YAG and diamond is poor, and long-term use degrades the bond interface. These problems are not limited to the case where the laser medium is a YAG. When the laser medium is an oxide, an oxygen defect appears during a surface activation process due to light elements such as oxygen which are removed, and it is assumed that the optically degraded layer like the colored layer or the like is formed due to this oxygen defect. The optically degraded layer, like the colored layer, also appears at the bonding interface when the transparent heat-transmitting member is made of oxides. If one or both of the laser medium and the transparent heat-transmitting member are oxides, their bonding may not be lasting, or a phenomenon in which their bonding surfaces become colored may occur with bonding to surfaces activated conventional, and it is therefore difficult to link them while maintaining transparency.
    Studies by the present inventors have enabled high power emission, the maximum value of which in a resonator reaches several tens of MW (megawatts), using a laser chip device with a length of a few mm. In general optical systems, a loss of around 1% is allowed. However, when their power reaches several tens of MW, the loss of 1% would be equivalent to the absorption of a power of several hundred kW; and optical components in this system may be damaged. A trivial loss leads to serious accidents with a high intensity laser, so that a loss or absorption to a degree that would generally be admissible is not tolerable for the high intensity laser device. The colored layer which appears at the level of the bonding interface of IVAG and the diamond in the technique of TOGASHI is thin, however, such a trivial colored layer causes a loss in the laser beam at high intensity, which prevents the laser device smart to reach a high power broadcast. Conventional activated surface bonding cannot achieve interface transparency at a level necessary for laser components for a high intensity laser device.
    In addition, when the laser medium and the transparent heat transfer member are linked by connection to activated surfaces, a connection to activated surfaces between heterogeneous materials is produced. When one or both of the members are an oxide, it becomes difficult to bond heterogeneous materials by binding to activated surfaces. HIGURASHI et al. describes a case study of heterogeneous activated surface bonding which binds GaAs, which is a type of laser medium, and SiC, which is a type of heat transmitting member. According to HIGURASHI et al. GaAs and SiC are linked by binding to activated surfaces in a state in which an amorphous layer is located between GaAs and SiC. When the amorphous layer is placed between the two members, reliability of the bond can be obtained. However, when one of the two members or both members is an oxide, it becomes difficult to achieve stable bonding with activated surfaces of heterogeneous materials via the amorphous layer even if the method of binding with activated surfaces described in HIGURASHI et al. is employed.
    The present description discloses a technique which employs an oxide for at least one of a laser medium and of a member transmitting transparent heat, and which provides a solution to a problem by the technique of bonding to activated surfaces. conventional. The disclosed technique provides a transparent link interface which can be used for a high intensity laser device.
    Furthermore, the present description discloses a laser component: which has a low thermal resistance between a laser medium and a member transmitting transparent heat, at least one of which is an oxide; in which a strong residual stress does not act on the laser medium after the bonding; and which has high transparency at an interface between the laser medium and the transparent heat transmitting member, i.e. a laser component with low loss which is suitable for a high intensity laser device is disclosed here. In addition, a method of manufacturing this laser component, and a laser device using this laser component are disclosed.
    Furthermore, the present description discloses a laser component: which has a low thermal resistance between a laser medium and a member transmitting transparent heat, at least one of which is an oxide; in which a strong residual stress does not act on the laser medium after the bonding; and in which the laser medium and the transparent heat-transmitting member are stably linked via an amorphous layer, that is to say a laser component capable of undergoing long-term use with a High intensity laser device is disclosed here. In addition, a method of manufacturing this laser component, and a laser device using this laser component are disclosed.
    (Method of manufacturing a laser component)
    The present description discloses a new method of manufacturing a laser component in which a laser medium and a transparent heat transmission member are linked, and at least one of the laser medium and the transparent heat transmission member is an oxide. The method includes: exposing a bonding surface of the laser medium and a bonding surface of the transparent heat transmitting member to an oxygen plasma; the projection of an atomic beam of inert gas onto the bonding surfaces of the laser medium and of the transparent member for heat transfer under vacuum after exposure; and the binding to activated surfaces of the bonding surfaces of the laser medium and of the transparent member for transmitting heat by bringing the bonding surfaces into contact after the projection.
    In a connection with conventional activated surfaces, it has been difficult to link the laser medium and the transparent heat-transmitting member by connection with activated surfaces when at least one of the laser medium and the transparent member heat transmission is an oxide. In the manufacturing process mentioned above, the exposure of the two bonding surfaces to the oxygen plasma is carried out before the bonding to activated surfaces. By carrying out this pretreatment step, the laser medium and the transparent heat-transmitting member can be linked by bonding to appropriately and stable activated surfaces even if at least one of the laser medium and the transparent transmitting member of heat is an oxide (for example, even if at least one of them is a YAG). In other words, by carrying out this pretreatment step, it is possible to prevent the transparency of a interface for linking the laser medium and the transparent heat-transmitting member from being degraded. In addition, by carrying out this pretreatment step, the laser medium and the transparent heat transmission member are stably linked by means of an amorphous layer, and the reliability of the connection is thus improved.
    (Laser component in which no colored layer is observed)
    According to the technique disclosed here, as the bonding to activated surfaces can be appropriately accomplished even if at least one of the laser medium and the transparent heat-transmitting member is an oxide, a laser component in which no tarnished layer or no colored layer is observed at the interface can be obtained. The laser component disclosed here has a fine or clear transparency at the interface of the laser medium and the transparent heat-transmitting member, that is to say that no tarnished or colored layer is observed at the interface. The present description collectively describes tarnishing and coloring as being coloring.
    According to this laser component, it is possible to prevent the laser component from being damaged due to optical loss at the interface even if the laser component is used for a high intensity laser device.
    (Laser component using an amorphous layer)
    According to the technique described here, a laser component comprising a laser medium and a transparent heat-transmitting member, which are linked by the activated surface bond, in which at least one of the laser medium and the transparent member for transmitting heat is an oxide, and in which the laser medium and the transparent heat-transmitting member are stably linked via an amorphous layer, which is transparent for an excitation beam, can be obtained. A high intensity laser beam can pass through the laser medium, the amorphous layer and the transparent member for heat transmission substantially without loss of energy. According to this laser component, the reliability of the link is guaranteed even if it is used for the high intensity laser device and long-term use becomes possible. For example, the laser medium can be an optical gain material. For example, the laser medium can be a non-linear optical material.
    As it has been found that the laser component in which no colored layer is observed and the laser component in which heterogeneous materials are bonded via an amorphous layer as mentioned previously can be produced by exposure to plasma other methods have also been studied. As a result, it has been found that a method which performs binding to activated surfaces after cleaning the bonding surfaces using a gel is also effective, and the laser components mentioned above can also be performed by this method.
    The laser medium and the transparent heat transmission member can be linked by connection to directly activated surfaces. Heterogeneous materials can be linked by binding to activated surfaces. The connection to activated surfaces can be accomplished after having arranged a dielectric multilayer film on one or both of the laser medium and the transparent heat-transmitting member and in particular between them. When the dielectric multilayer film is used, a reflection property at the interface of the laser medium and the transparent heat transmitting member can be adjusted. For example, it becomes possible to adjust to a property whereby a high reflectance is manifested for a specific wavelength and a low reflectance is manifested for other wavelengths. When the dielectric multilayer film is intended to be formed, a film made of a homogeneous material as the counterpart bonding surface (homogeneous film) can be disposed on an outermost surface of the dielectric multilayer film. In this case, the dielectric multilayer film covered by the homogeneous film and the bonding surface of its counterpart can be bonded by bonding to homogeneous activated surfaces. The dielectric multilayer film and the bonding surface of its counterpart member can be bonded by bonding to heterogeneous activated surfaces without the homogeneous film.
    When a difference between the refractive indices of the laser medium and of the transparent heat transmission member is equal to or greater than 9%, a loss by reflection at the interface becomes greater than 0.3%, and l The use of the laser component is therefore limited. In such a case, it is preferable to use an intermediate layer having a refractive index which is close to a median value of the refractive indices of the laser medium and of the transparent heat-transmitting member. That is, an intermediate layer which establishes relationships in which a difference between the refractive indices of the laser medium and the intermediate layer is less than 9%, and a difference between the refractive indices of the intermediate layer and of the transparent member for heat transmission is also less than 9% is used, and arranged in particular between the laser medium and the member transmitting transparent heat. By doing so, a laser component whose loss at the interface is less than 0.3% can be obtained. In particular in cases where the laser medium is YVO 4 and the transparent member for heat transmission is diamond, this technique of using the intermediate layer is effective.
    In the case of the use of the intermediate layer, the laser medium and the transparent heat transmission member can be linked by bonding to homogeneous activated surfaces by placing intermediate layers on the bonding surfaces of the laser medium and of the transparent heat transmitting member. Two levels of intermediate layers can be provided by differently configuring the intermediate layer on the side of the laser medium and the intermediate layer on the side of the member transmitting transparent heat. If the difference between the refractive indices of the laser medium and of the transparent heat-transmitting member is significant, two levels of intermediate layers, namely an intermediate layer having the refractive index close to that of the laser medium and a layer intermediate having the refractive index close to that of the member transmitting transparent heat, can be used together. Alternatively, an intermediate layer or intermediate layers can be arranged on one of the bonding surfaces of the laser medium and the transparent heat-transmitting member, and these members can be bonded by bonding to heterogeneous activated surfaces. Before the formation of the intermediate layer, a dielectric multilayer film can be provided. In the case of the formation of one or more films on one of the members and of the realization of the connection thereafter, the one or more films can be arranged on the transparent member for heat transmission and the laser medium is bonded to the latter, or the one or more films may be placed on the laser medium and the transparent heat transmission member is linked to the latter. In both cases, excellent quality bonding surfaces can be obtained by pretreatment of the bonding surfaces by exposing them to oxygen plasma and then bonding them. Exposure to oxygen plasma can be accomplished after placing the intermediate layer (s), or the intermediate layer (s) can be formed after exposure to oxygen plasma.
    According to the technique disclosed here, it is possible to provide a laser component in which a plurality of laser media and a plurality of transparent heat transfer members are provided, and the plurality of laser media and the plurality of members Heat transfer transparencies are arranged in series in an order in which the laser media and the transparent heat transfer members appear alternately. This type of laser component is useful for laser resonators, laser amplifiers, and wavelength converters. For example, a thickness of each laser medium in a lamination direction may be equal to or less than one fifth (1/5) of a diameter of the laser medium.
    In the case of the arrangement of the plurality of laser media in series, the same laser media can be arranged, or else the laser media can be configured differently, in particular comprising different types of laser media. For example, the laser media can include a group of laser media having the same luminescent center element and different base materials, and the group of laser media is arranged in series. For example, the laser media can include a group of laser media having the same base material and different luminescent center elements, and the group of laser media is arranged in series. For example, the laser media can include a group of laser media having different luminescent center elements and different base materials, and the group of laser media is arranged in series. For example, the laser media can have different dopant concentrations, the dopant concentration of the laser medium arranged in the vicinity of an end face intended to be exposed to the excitation beam can be lower than the dopant concentration of the medium laser arranged at a distance from the end face. For example, the dopant concentration of a laser medium arranged on an incident side of an excitation beam can be set low, and the dopant concentration of a laser medium arranged on an opposite side can be set high. When a relationship in which a concentration of dopant is low in a position where an intensity of the excitation beam is high and a concentration of dopant is high in a position where the intensity of the excitation beam is low is satisfied, a difference in position-dependent heat emission can be suppressed small, and a local overheating occurrence can be suppressed. This structure is effective for laser amplifiers. When excitation beams are projected onto a stack of the plurality of laser media from the two end surfaces, the concentration of dopant in positions close to the end faces should be low, and the concentration of dopant in positions away from the end faces should be high. In this arrangement, the dopant concentration is low in a position in which the intensity of the excitation beam is high, and the dopant concentration is high in a position in which the intensity of the excitation beam is low, by so the difference in position dependent heat generation can be eliminated.
    A wavelength converter in which non-linear optical materials having different thicknesses are arranged in series is also useful. A wavelength converter which can be used with several input laser beams having different wavelengths can be realized.
    A laser resonator or a laser amplifier in which laser media of different types are arranged in series is also useful. For example, when optical gain materials of different types, which add a common luminescent center substance in different types of base materials, are arranged in series, a resonant wavelength of the laser resonator can be configured as 'a broad band as described in SATO et al. The technique of SATO et al. is limited to a combination of two types of ceramic optical gain materials, however, the technique described here is not limited to ceramic materials, and a number of types is not limited, and a structure in which transparent members of heat transmission are arranged between optical gain materials to achieve cooling can be obtained.
    In the case of series arrangement of the plurality of laser media and the plurality of transparent heat-transmitting members, it is preferable in certain cases to arrange the transparent heat-transmitting members at respective ends of such a series arrangement. In a laser device, an accumulation of electric field easily occurs in the vicinity of an interface between a laser medium and a space due to their discontinuity. When the intensity of the laser beam increases, a degree of accumulation of electric field becomes higher, and the laser medium can be damaged by the accumulation of electric field generated in the vicinity of the interface between the laser medium and space. . This problem becomes preponderant for cases where the laser media are amorphous or ceramic. This is because the presence of grain boundaries creates regions which are inherently non-uniform in a planar distribution of an electric field in the vicinity of such boundaries. In addition, even if the end surfaces are uniformed by polishing or the like, the crystal grains and grain boundaries have different polishing rates, and furthermore the hardness also becomes different depending on the orientations even for the same type of crystal grains. Thus, compared to a material constituted by a uniform region throughout, in particular by a single crystal, the surface precision of ceramic materials is lower. Therefore, even if a coating to attenuate the accumulation of electric field that can occur at the end surfaces is achieved, the lower surface precision of bottom layers thereof has the effect that an accuracy of surface of coated surfaces is also less. As a result, an optical damage threshold of ceramic laser media is reduced by about a figure compared to that of a single crystal. In cases where a maximum value exceeds several megawatts, especially with a giant pulsed laser, a failure mode thereof is serious and can significantly affect the laser performance. Thus, a capacity for resistance to optical damage can be increased by the bonding to activated surfaces of a uniform material, in particular a transparent single crystal or a single transparent crystal, to the end surfaces of ceramic laser media. The arrangement of a coating on the end surfaces of transparent single crystals or of a single transparent crystal, that is to say at the end faces of transparent heat transmitting members, for example arranged at the ends of the Arrangement in series, or arranged at the end faces of the laser medium, further increases the capacity for resistance to damage. The heat dissipation effect can also be increased by the connection of transparent heat transfer members to the end surfaces of the series arrangement and a high performance power laser device is made possible in the together.
    When the laser medium is ceramic, the bonding of the transparent material of single crystals or of a single crystal to the two end faces of the ceramic laser medium, in particular each of the transparent heat-transmitting members arranged at the ends of the arrangement in series, is effective in increasing the capacity for resistance to damage. When the laser medium and the transparent material are repeatedly and successively stacked, the bonding of the transparent materials to the two end faces of the stack is effective in increasing the capacity for resistance to damage. It is also effective whether the transparent material is made of single crystals or a single crystal, and the transparent material has a high thermal conductivity.
    According to one aspect of the present disclosure, each of the laser media can be a non-linear optical material, the laser media includes a group of laser media having different thicknesses, and the group of laser media is arranged in series.
    BRIEF DESCRIPTION OF THE DRAWINGS Figures l (al) to l (a3) - 101) to 103) schematically show different embodiments;
    Figures 2 (1) - 2 (5) show a laser component of a first embodiment and a method of manufacturing the same;
    Figures 3 (a) and 3 (b) explain the laser components of the second and third embodiments;
    Figs. 4 (1) - 4 (5) show a laser component of a fourth embodiment and a method of manufacturing it;
    Figs. 5 (a) and 5 (b) explain laser components of the fifth and sixth embodiments;
    Figs. 6 (1) to 6 (5) explain a laser component of a seventh embodiment and a method of manufacturing it;
    Figure 7 shows a laser device of a first embodiment;
    Figure 8 shows a laser device of a second embodiment;
    Figure 9 shows a laser device of a third embodiment;
    Figure 10 shows a laser device of a fourth embodiment;
    Figure 11 shows a laser device of a fifth embodiment;
    Figure 12 shows a laser device of a sixth embodiment;
    Figure 13 shows a laser device of a seventh embodiment;
    Figure 14 shows a laser device of an eighth embodiment; and Figure 15 shows a laser device of a ninth embodiment.
    DETAILED DESCRIPTION [0025] Figures 1 of (al) to (a3) - (jl) to (j3) show different embodiments. The letters in Figure 1 show types of embodiments, and the numbers show processing orders of the manufacturing process. Figures 1 of (al) to (a3) show a combination of a laser medium 10 and a transparent heat transmission member 20 which are linked by connection to heterogeneous activated surfaces, and show a case in which a difference between the refractive indices of these members is less than 9%. In this case, the laser medium 10 and the transparent heat transmission member 20 can be directly linked by bonding heterogeneous surfaces. A reference sign 30 in Figure 1 from (al) to (jl) shows that the bonding surfaces of these members are exposed to an oxygen plasma. By adding this preprocessing, the transparency of an interface after having linked them can be maintained at a high level. In addition, combinations of materials which cannot be bound by binding to activated surfaces without carrying out this pretreatment can be bound by binding to activated surfaces. For example, although it is difficult to bond by activated surfaces a YAG and sapphire stably, a YAG and sapphire can be stably linked by heterogeneous activated surfaces by performing the pretreatment. When the heterogeneous activated surface bonding is accomplished, an amorphous layer is formed at the interface. An amorphous layer is very thin, and its representation will be omitted from the drawings.
    The projection of an oxygen plasma is intended to clean the bonding surfaces, and it aims to obtain the same effect as a projection of an atomic beam of inert gas which will be described below. Therefore, in a connection with conventional activated surfaces, the projection of an oxygen plasma and the projection of an atomic beam of inert gas were not carried out in combination. In addition, in a surface activation process, oxygen must be removed from an outermost surface layer of a bonding face which is stabilized by bonding with oxygen. It is a natural assumption that oxygen will not be removed through the use of oxygen plasma, so a concept of exposure to oxygen plasma has never been considered. According to the present studies, it has been found that the degradation of transparency at the interface can be prevented and that a variety of materials which can be bound by binding to activated surfaces can be increased by adding the projection of a plasma d oxygen before binding to conventional activated surfaces. In addition, in the case of the heterogeneous bond of the laser medium and of the member transmitting the transparent heat, they bind firmly via the amorphous layer.
    Note that a reference sign 40 in Figures 1 of (a2) to 02) shows that a beam of argon ions is projected onto the bonding surface of the laser medium 10 and the bonding surface of the transparent heat transfer member 20, and FIGS. 1 from (a3) to (j3) show a laminated structure of a laser component in which the laser medium 10 and the transparent heat transmission member 20 are linked by bond with activated surfaces. As mentioned previously, the representation of the amorphous layer is omitted. An inert gas other than argon can be used.
    Figures 1 of (bl) to (b3) show an embodiment in which a dielectric multilayer film 22 is formed on a surface of the transparent heat transmission member 20, the exposure to a plasma of oxygen is accomplished next, and heterogeneous activated surface binding is accomplished next. By using the dielectric multilayer film 22, a reflection property at the bonding interface can be adjusted. In this case also, an amorphous layer which is not shown is formed between an upper surface of the dielectric multilayer film 22 and a lower surface of the laser medium 10.
    Figures 1 of (cl) to (c3) show an embodiment in which an intermediate layer 24 is formed on the surface of the transparent heat transmission member 20, exposure to an oxygen plasma is accomplished next, and heterogeneous activated surface binding is accomplished next. In a case where the difference between the refractive indices of the laser medium 10 and of the transparent heat transmission member 20 is equal to or greater than 9%, a loss at the interface becomes problematic. In such a case, it is preferable to produce the intermediate layer 24 with a material having a refractive index which is close to a median value of the refractive indices of the laser medium 10 and of the transparent heat-transmitting member 20, with which a difference with the refractive index of the laser medium 10 is less than 9% (preferably less than 6%), and a difference with the refractive index of the transparent heat-transmitting member 20 is also less 9% (preferably less than 6%). By keeping the difference between the refractive indices less than 6%, the loss at the interface can be suppressed to less than 0.1%. If the difference between the refractive indices of the laser medium 10 and the transparent heat transmission member 20 is less than 9%, the loss at the interface is less than 0.3%, and, as shown in the figures l (a), l (b), l (d), the intermediate layer 24 may not be provided. If the difference between the refractive indices of the laser medium 10 and of the transparent heat transmission member 20 is 6 to 9%, it is advisable to use the intermediate layer 24, the difference in refractive index with each of the refractive indices of the laser medium 10 and of the transparent heat transmission member 20 is less than 6%. When such an intermediate layer 24 is used, the loss at the interface can be suppressed to less than 0.1%. In this case also, an amorphous layer which is not shown is formed between an upper surface of the intermediate layer 24 and the lower surface of the laser medium 10.
    The intermediate layer 24 can be formed after having exposed the laser medium 10 and the transparent member for transmitting heat 20 to the oxygen plasma and having further exposed them to an atomic beam of inert gas. Their connection to activated surfaces can be carried out in an order of projection to the ion of inert gas, the formation of the intermediate layer 24, and the bringing into contact of the laser medium 10 and of the transparent member for heat transmission 20 and applying pressure to them.
    Figures l (dl) to (d3) show an embodiment in which a film 26 having the same composition as the laser medium 10 (hereinafter called homogeneous film 26) is formed on the surface of the member heat transfer transparency 20, after which exposure to oxygen plasma is accomplished, and homogeneous activated surface bonding is accomplished thereafter.
    Figures l (el) to (e3) show an embodiment in which the dielectric multilayer film 22, the intermediate layer 24 and the homogeneous film 26 are formed on the surface of the transparent member for heat transmission 20 in this order, after which exposure to an oxygen plasma is carried out, and the homogeneous activated surface bonding is then carried out. The dielectric multilayer film 22 can be omitted if the reflection property at the interface is not a problem. If the difference between the refractive indices of the laser medium 10 and of the transparent heat transmission member 20 is less than 9%, the intermediate layer 24 can be omitted. If the heterogeneous bond can be achieved, the homogeneous film 26 can be omitted.
    Figures l (fl) to (f3), l (gl) to (g3), (hl) to (h3) and (il) to 03) show cases in which a dielectric multilayer film 12, a layer intermediate 14, a homogeneous film 16 or a combination of these layers is formed on the laser medium 10. The same component as that shown in FIG. 1 (b3) can be obtained if the dielectric multilayer film 12 is formed, the same component as that shown in Figure l (c3) can be obtained if the intermediate layer 14 is formed, the same component as that shown in Figure l (d3) can be obtained if the homogeneous film 16 is formed, and the same component as that shown in Figure 1 (e3) can be obtained if the dielectric multilayer film 12, the intermediate layer 14 and the homogeneous film 16 are all formed.
    Figures l (jl) to (j3) show an embodiment in which the intermediate layers 14, 24 are formed respectively on the laser medium 10 and the transparent member for heat transmission 20. The intermediate layers 14 and 24 can have the same composition. In this case, the intermediate layers 14, 24 play the same role as the homogeneous films 16, 26, and the homogeneous activated surface bonding can be accomplished. The intermediate layers 14, 24 may have different compositions. In this case, the loss by reflection becomes less than 0.3% if the refractive indices vary in an order of the laser medium 10, the first intermediate layer 14, the second intermediate layer 24 and the transparent member for heat transmission 20 , and the differences between the refractive indices at their respective interfaces are less than 9%. Reflection loss less than 0.1% is obtained if the differences between the refractive indices at the respective interfaces are less than 6%. In this case, an amorphous layer which is not shown is formed between a lower surface of the first intermediate layer 14 and an upper surface of the second intermediate layer 24.
    If the intermediate layers 14, 24 do not play the role of homogeneous films, a homogeneous film can be formed on one or both intermediate layers 14, 24. In addition, in addition to the intermediate layers 14, 24, the one or two dielectric multilayer films 12, 22 can be formed.
    The technique described here can be applied to laser components having a combination of dYAG and sapphire, or a combination of YVCL}, an intermediate layer and diamond, or the like.
    EMBODIMENTS [First embodiment]
    Figures 2 (1) to 2 (5) show an embodiment which combines Figures l (b) and l (d), and in which the intermediate layer 24 of Figure l (e) is omitted. The laser medium 10 is a YAG (refractive index = 1.82), and the transparent heat transmission member 20 is sapphire (refractive index = 1.75). A difference between the refractive indices of these members is 3.8% (less than 6%), and this corresponds to a case where the intermediate layer 24 is not necessary. Here, the difference between the refractive indices is calculated by a formula of (difference between the higher refractive index and the lower refractive index) divided by (higher refractive index).
    In this embodiment, the dielectric multilayer film 22 is formed on a surface of a sapphire substrate which is intended to be the transparent member for heat transmission 20, and a thin film of YAG which is intended to be the homogeneous film 26 is formed on a surface of the dielectric multilayer film 22. These films are both formed by sputtering. These samples are exposed to an oxygen plasma 30 (Figure 2 (2)), and an environment in which these samples are placed is set to be vacuum, a beam of high-speed argon ions 40 is projected onto the surfaces of connection of these samples (Figure 2 (3)), and the connection surfaces after the projection mentioned above are brought into contact and pressurized (Figure 2 (5)). The connection surfaces can be brought into contact without heating, that is to say at room temperature. By doing so, the homogeneous film 26 and the laser medium 10 are bonded by the homogeneous activated surface bond, and they are bonded in a state in which thermal resistance between the laser medium 10 and the transparent heat transmitting member 20 is weak. In Fig. 2 (1), the reference signs 17 and 27 show surfaces of samples placed in an atmospheric environment, and these are surfaces stabilized by bonding with oxygen and the like. A reference sign 30 shows the projection of an oxygen plasma, and a reference sign 40 shows the projection of a beam of argon ions at high speed. When these processes are implemented, as shown in Figure 2 (4), activated atomic bonds 19, 29 appear on the bonding surfaces of materials, and materials are bound to atomic levels by these atomic bonds which are bonded between they. As the pretreatment of the exposure to an oxygen plasma is carried out, the binding surface of IVAG (laser medium 10), which consists of oxide, is not transformed as regards its quality by the binding to activated surfaces, so that the transparency of an interface between IVAG and the sapphire substrate does not deteriorate. In addition, since the binding to activated surfaces is carried out at normal temperature, no significant residual stress acts on IYAG (laser medium 10).
    (Second embodiment)
    Figure 3 (a) shows a diagram of the second embodiment corresponding to Figure 2 (1). The laser medium 10 is a YAG (refractive index = 1.82), the transparent heat transfer member 20 is diamond (refractive index = 2.42), and a difference between their refractive indices is 24, 8% (greater than 9%), which corresponds to a case where the intermediate layer 24 is necessary. The intermediate layer is not limited to one layer, and may consist of several layers. When two layers are used, a difference between the refractive indices of the laser medium 10 and the first intermediate layer, a difference between the refractive indices of the first intermediate layer and the second intermediate layer, and a difference between the indices of refraction of the second intermediate layer and the transparent heat-transmitting member can all be suppressed to less than 9%. For example, when sulfa is used for the first intermediate layer and TiO 2 is used for the second intermediate layer, the difference between the refractive indices of the adjacent members can be eliminated in an interval of about 9%, and an optical loss can thus be deleted. In this case, an amorphous layer which is not shown is formed between an upper surface of the intermediate layer 24 and a lower surface of the YAG 10, so that the connection between them is established stably. The dielectric multilayer film 22 can be omitted.
    (Third embodiment)
    As shown in Figure 3 (b), the dielectric multilayer film
    22, the intermediate layer 24 and the homogeneous film 26 can all be used.
    (Fourth embodiment)
    FIGS. 4 (1) to 4 (5) show an embodiment in which the dielectric multilayer film 12 and the homogeneous film 16 are provided on the side of the laser medium 10. The dielectric multilayer film 12 corresponds to the dielectric multilayer film 22 in the Figure 2 and the homogeneous film 16 corresponds to the homogeneous film 26 in Figure 2. The same effect as that of the case of Figures 2 (1) to (5) can be obtained.
    (Fifth embodiment)
    FIG. 5 (a) shows an embodiment in which the intermediate layer 14 corresponding to the intermediate layer 24 in FIG. 3 (a) is provided on the side of the laser medium 10. The same effect as that of the case of FIG. 3 (a) can be obtained. In this case, an amorphous layer which is not shown is formed between a lower surface of the intermediate layer 14 and an upper surface of the transparent heat-transmitting member 20, so that the connection between them is established stable.
    (Sixth embodiment)
    FIG. 5 (b) shows an embodiment in which the dielectric multilayer film 12 corresponding to the dielectric multilayer film 22 in FIG. 3 (b), the intermediate layer 14 corresponding to the intermediate layer 24 in FIG. 3 (b) and the homogeneous film 16 corresponding to the homogeneous film 26 in FIG. 3 (b) are provided on the side of the laser medium 10. The same effect as that of the case in FIG. 3 (b) can be obtained.
    (Seventh embodiment)
    Figures 6 (1) to 6 (5) show an embodiment in which the intermediate layer 14 is provided on the bonding surface of the laser medium 10, and the intermediate layer 24 is provided on the bonding surface of the member heat transfer transparent 20.
    The intermediate layer 14 and the intermediate layer 24 can also serve as homogeneous films. As an alternative, the intermediate layers 14 and 24 can configure a two-layer structure of the intermediate layer which attenuates the difference between the refractive indices by two different levels. In this case, an amorphous layer which is not shown is formed between the intermediate layer 14 and the intermediate layer 24, so that the connection between them is established stably.
    Different types of known laser media can be used. For example, an oxide with a rare earth dopant, an oxide with a transition metal dopant and an oxide which acts as a colored center and the like can be used as the optical gain material. Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm and Yb can be cited as examples of rare earth dopants intended to be a luminescent center. Ti, V, Cr, Mn, Fe, Co, Ni and Cu can be cited as examples of transition metal dopants intended for use as a luminescent center. Garnet materials such as YAG, YSAG, YGAG, YSGG, GGG, GSGG and LuAG, fluorinated materials such as YLF, LiSAF, LiCAF, MgF 2 and CaF 2 , vanadate materials such as YVO 4 , GdVO 4 and LuVO 4 , materials based on apatite such as FAP, sFAP, VAP and sVAP, materials based on alumina such as AI 2 C> 3 and BeAI 2 O3, materials based on dioxides or trioxides such as Y 2 O 3 , Sc 2 O 3 and Lu 2 O 3 , and tungstate materials such as KGW, KYW can be cited as examples of types of base materials. The basic material can be single crystals, a single crystal, an amorphous material or a ceramic material. In addition, it can be different types of non-crystalline glasses. LN, LT, KTP, KTA, RTP, RTA, LBO, CLBO, CBO, BBO, BiBO, KBBF, BABF, crystallized quartz, COB, YCOB, GdCOB, GdYCOB, YAB, KDP, KD * P and ZGP can be cited as examples of non-linear optical materials.
    Sapphire, diamond and YAG without dopant can be cited as examples of members transmitting transparent heat. Sic can also be used as a member transmitting transparent heat, however its transparency is currently insufficient so that its use is limited, as its arrangement outside a resonator. PbCI 2 , Ta 2 O 5 , TiO 2 , HfO 2 , ZnS, ZnSe, NdO 2 and ZrO 2 can be cited as examples of intermediate layers for diamond. AI2O3, Y2O3, La2O3, MgO, PbF2, SC2O3 and YAG can be cited as examples of intermediate layers for sapphire.
    In the following, laser devices which use laser components will be described.
    (Laser device of the first embodiment)
    Figure 7 shows what is called a chip laser resonator. A transparent heat transmission member 20A is linked by connection to activated surfaces to a left end surface of the laser medium 10, and a transparent heat transfer member 20B is linked by connection to activated surfaces to a right end surface of the laser medium 10. Although not shown, dielectric multilayer films are formed on the left end surface of the transparent heat transmitting members 20A and the right end surface of the transparent heat transmitting members 20B , and the reflection properties at their interfaces are adjusted as follows:
    the left end surface of the transparent heat-transmitting member 20A is non-reflective for a wavelength of the excitation beam but highly reflective for a wavelength of the laser beam;
    the right end surface of the transparent heat-transmitting member 20A is non-reflective for the wavelength of the excitation beam and also non-reflective for the wavelength of the laser beam;
    the left end surface of the transparent heat transmission member 20B is non-reflective for the wavelength of the excitation beam and also non-reflective for the wavelength of the laser beam; and the right end surface of the transparent heat transmitting member 20B is highly reflective for the wavelength of the excitation beam and partially reflective for the wavelength of the laser beam.
    In this embodiment, a resonator system is included between the left end surface of the transparent heat transmitting member 20A and the right end surface of the transparent heat transmitting member 20B, and the transparent heat transmission member 20A and transparent heat transmission member 20B are arranged in a resonator in this system.
    When the laser medium 10 is made of ceramic, and the transparent heat transmitting members 20A, 20B are made of a single crystal or are amorphous, the damage resistance capacity of the chip laser resonator is improved.
    For example, YAG, YVO 4 or (s-) FAP with additives of luminescent center elements can be used as laser medium 10, YAG without additives, sapphire or diamond can be used as transparent transmission members heat 20A, 20B. If the differences between the refractive indices between the laser medium 10 and the transparent heat transmission members 20A, 20B are less than 9%, the intermediate layer is not necessary. For example, if the laser medium 10 is YAG or (s-) FAP with the additives of luminescent center elements, and if the transparent heat transfer members 20A, 20B are YAG without additives or the sapphire, the layer or layers intermediaries are not required.
    If a laser medium is YVO 4 with additives of luminescent center substances, and if the transparent heat-transmitting members are made of sapphire, a difference between the refractive indices becomes 19%, in which case the use of the layer (s) intermediaries is preferable. It is preferable to use one or more types of sulfa, S1O2 and HfO having refractive indices which are the median values of the refractive indices of the members mentioned previously as intermediate layer (s).
    If the laser medium is YVO4 with the additives of luminescent center substances, and if the transparent heat-transmitting members are made of diamond, it is preferable to use one or more types of T1O2, ZnS and Ta 2 O 3 having the indices of refraction which are the median values of the refractive indices of the members mentioned previously as intermediate layer (s).
    The dielectric multilayer film can be formed between the transparent heat transmission member 20A and the laser medium 10 and between the transparent heat transmission member 20B and the laser medium 10. In this case, a homogeneous film having the same material with a counterpart bonding surface may be formed on an outermost surface of the dielectric multilayer film to effect the homogeneous activated surface bonding, or else the homogeneous film may not be formed to effect the heterogeneous activated surface bonding . In the latter case, an amorphous layer is formed at the bonding interfaces and thus facilitates bonding.
    When the excitation beam is projected on the left end surface of the transparent heat transmission member 20A, this chip laser resonator emits the laser beam from the right end surface of the transparent heat transmission member heat 20B. It should be noted that the transparent heat transmission member 20B on one side which emits the laser beam can be omitted in certain cases.
    (Laser device of the second embodiment)
    As shown in FIG. 8, a Q switch 10B can be inserted between the laser medium 10A and the transparent heat transmission member 20B, and these members can be linked by connection to activated surfaces. In this case, the activated surface bonding is accomplished by providing a multilayer dielectric film between the switch Q 10B and the transparent heat transfer member 20B, and this multilayer dielectric film is adjusted to have a reflection property of being highly reflecting for the wavelength of the excitation beam and is configured to partially reflect the wavelength of the laser beam. In addition, the bonding to activated surfaces is accomplished by providing a dielectric multilayer film between the laser medium 10A and the transparent heat transmitting member 20A, and this dielectric multilayer film is adjusted to have a reflection property of being non-reflective for the wavelength of the excitation beam but is configured to reflect the wavelength of the laser beam. In this case, the transparent heat transmission members 20A, 20B are located outside the laser resonator system. The transparent heat transmission members 20A, 20B can be arranged inside the laser resonator system as shown in FIG. 7, or the transparent heat transmission members 20A, 20B can be arranged outside the system of a laser resonator as shown in FIG. 8. According to the technique described here, a link interface which maintains its transparency to a degree by which a high power laser can enter into resonance even if the transparent heat-transmitting members are arranged at inside the resonator system.
    (Laser device of the third embodiment)
    As shown in FIG. 9, the transparent heat transmission member 20C can be inserted between the laser medium 10A and the switch Q 10B, and these members can be linked by connection to activated surfaces.
    It is preferable to increase a diameter of the transparent heat transmission members 20A, 20B, 20C so that it is larger than the diameter of the laser medium 10A and of the switch Q 10B.
    In this case, a relationship is established, in which these series laser components are housed in a cylinder having a high thermal transmittance, and the outer circumferential surfaces of the transparent heat transmitting members 20A, 20B, 20C are in contact with an inner circumferential surface of the cylinder. The heat coming from the laser medium 10A is transmitted to the cylinder via the transparent heat transmission members 20A, 20C.
    The heat from the switch Q 10B is transmitted to the cylinder via the transparent heat transfer members 20C, 20B. When the cylinder is cooled, the laser medium 10A and the switch Q 10B are also cooled.
    (Laser device of the fourth embodiment)
    FIG. 10 shows a laser resonator which allows high power emission by arranging several series of the chip laser resonator of FIG. 7 and by connecting them in series. In the description which follows, if phenomena which appear in the laser media 10A, 10B ..., the laser media 10 will be described by omitting the letters added in the reference signs. The same applies to transparent heat-transmitting members 20. In the case of FIG. 10, a dielectric multilayer film which is non-reflective for the wavelength of the excitation beam but highly reflective for the laser beam is formed on the left or right end surface of the transparent heat transfer member 20 which is located on a leftmost side. A dielectric multilayer film which is highly reflective for the wavelength of the excitation beam and which partially reflects the laser beam is formed on the left or right end surface of the transparent heat transmitting member 20 which is located on the rightmost side. The transparent left-hand heat transfer member 20 and the transparent right-hand side heat transfer member 20 can be arranged inside or outside the resonator system, however, the remaining transparent heat transfer members 20 located between them are arranged inside the resonator system.
    A thickness of each laser medium 10 is preferably equal to or thinner than a fifth (1/5) of the diameter of the laser medium. When they are thinned to this degree, the temperature distribution along an optical path in the laser medium becomes uniform, and the quality of the beam is significantly improved.
    Laser media of different types can be arranged in series. For example, when several types of optical gain materials which add a common luminescent center substance in different types of base materials are arranged in series, a resonant wavelength of the laser resonator can be configured as broadband as described in SATO et al. Several types of optical gain materials with different luminescent center substances can be arranged in series. For example, Tm: YAG, transparent heat transmitting member, Ho: YAG, and transparent heat transmitting member can configure one unit, and the multiple units can be arranged in series repeatedly. Therefore, a phenomenon in which a light emission from Tm excites Ho can be obtained.
    (Laser device of the fifth embodiment)
    Figure 11 shows an embodiment in which a spatial modulation element 60 is inserted into the multi-level chip laser resonator of Figure 10. The spatial modulation element 60 controls a spatial mode of the laser beam. A hard opening or a soft opening can be inserted in place of the spatial modulation element 60. The spatial modulation element 60 and the like can be bonded by binding to activated surfaces to their adjacent material.
    (Laser device of the sixth embodiment)
    Figure 12 shows a pulse laser resonator which inserts a Q switch 62 into the multi-level chip laser resonator of Figure 10. A saturable element, EO, AO, MO, or a nonlinear optical element can be used to in place of the Q switch 62. The Q switch 62 and the like can be bonded by activated surfaces to their adjacent material. In addition, in the case of a saturable absorbent element, it can be divided into a plurality to disperse the accumulation of heat produced, and they can be linked in a state in which a transparent heat-transmitting member is disposed between these divided saturable absorbent elements.
    (Laser device of the seventh embodiment)
    Figure 13 shows a pulse laser resonator which combines Figures 11 and 12.
    (Laser device of the eighth embodiment)
    FIG. 14 shows a laser amplifier in which optical gain media 10 and transparent heat transmission members 20 are arranged in series in an order in which they appear alternately. The adjacent members are each linked by connection to activated surfaces. The respective interfaces are adjusted to have one of the following reflection properties:
    1) all interfaces are non-reflective for the wavelengths of the excitation beam and the laser beam. If a YAG is used as optical gain media 10 and if sapphire is used as transparent heat transmitting members 20, they can be linked by bonding to heterogeneous activated surfaces. When YAG and sapphire are bonded by binding to activated surfaces, the reflectance at their bonding interface becomes 0.1% or less, and there is no need to provide a non-reflective coating by the dielectric multilayer film or the middle layer. In addition, YAG and sapphire both contain AI2O3, which further eliminates the need for the homogeneous film;
    2) one of the left and right interfaces of the transparent heat transmission member 20 which is on the rightmost side is highly reflective for the wavelength of the excitation beam but not reflective for the length of wave of the laser beam, and all the remaining interfaces are non-reflective for the wavelength of the excitation beam and that of the laser beam; and
    3) in 1) and 2) above, one of the left and right interfaces of the transparent heat transfer member 20 which is on the leftmost side is non-reflective for the excitation beam but highly reflecting for the wavelength of the laser beam.
    In this device, the left end surface is irradiated with the excitation beam, and the incoming laser beam is introduced from the right end surface. By doing so, a laser beam is emitted from the right end surface. The emitted laser beam has a higher or amplified intensity compared to that of the incoming laser beam.
    In this embodiment, the dopant concentration of the luminescent center element in the optical gain media 10 on the left side, where the strong radiation of the excitation beam is produced, is set low, and the dopant concentration of the luminescent center member in right gain media 10 on the right side, where the excitation beam fades, is set high. Therefore, the excitation beam is not drastically absorbed in localized areas, and an adjustment can be made to standardize the absorption over an entire excitation area. The temperatures inside the laser device can be uniform, and local overheating can be prevented. Alternatively, parts in the vicinity of the respective ends and a central part of a series connection can be distinguished, and the concentration of dopant of the luminescent center element in the parts in the vicinity of the respective ends can be set. low, and the dopant concentration of the luminescent center element in the central part can be set high. This arrangement is useful when excitation beams are projected on the two end faces of the series connection.
    A chip laser, a fiber laser, a rod laser and a disc laser can be cited as examples of light sources for the amplifier.
    In a device which arranges a plurality of homogeneous laser media in series and which uses them for amplification, the amplification rate can be increased. As an alternative to this, a laser amplifier with different types of laser media arranged in series inside is also useful. If a range of wavelengths of an incoming laser beam is wide, the use of several types of laser medium allows the amplification of the entire range of wavelengths of the incoming laser beam. In all of the above cases, overheating of the laser media can be prevented because each laser media is cooled from its two side surfaces.
    (Laser device of the ninth embodiment)
    As shown in FIG. 15, a wavelength converter can be constituted by the structure of FIG. 14. In this case, non-linear optical elements are used as laser media 10 in place of the optical gain media. In this case, the thicknesses of the non-linear optical elements can be made to vary, and such non-linear optical elements can be arranged in series. By doing so, the incoming laser beam can be converted to a laser beam with large wavelength widths. Alternatively, conversion to a laser beam having a plurality of independent wavelengths can be made possible.
    A wavelength converter can be produced by means of the structure in FIG. 7. A series connection which links a plurality of non-linear optical materials with different thicknesses can be used as the laser medium 10 in FIG. 7.
    In addition, the link can be accomplished so that the direction of non-linear polarization is reversed at a coherence length of a target wavelength, or so that near phase matching is achieved, in which time halts are repeated. In the quasi-phase matching, a fluctuating structure to widen the range or control a phase relationship can be incorporated.
    As a resonator profile, a parallel plate resonator is suitable for high power emission than a stable resonator. Figures 7 to 13 show parallel plate resonators. The excitation zone must be widened to further increase the transmitted power, however, the conventional technique had difficulties in widening the excitation zone due to insufficient gain. The laser resonator disclosed here is capable of enlarging the excitation area, since its transparency is high and overheating is less likely to occur. An unstable cavity resonator can be constructed using this feature. The technique described here facilitates the unstable cavity resonator.
    The technique which achieves exposure to oxygen plasma before binding to activated surfaces is especially effective in binding the laser medium and the transparent heat transmitting member, however, it is not limited to this. For example, it is also effective in the case of bonding of a laser medium consisting of oxide to a member transmitting non-transparent heat (metallic heat sink such as Cu or CuW). In this case, the dielectric multilayer film is formed on the surface of the laser medium to adjust it to have a total reflection property. An alumina film, or a metallic film such as Au, AuSn is formed on an outermost surface of the dielectric multilayer film. These laser medium and metal heat sink are exposed to oxygen plasma, and then are linked by binding to activated surfaces. As a result, the thermal resistance between the laser medium and the metal heat sink is kept low, and the reliability of the connection is improved.
    In addition, the oxygen plasma pretreatment can be replaced by another cleaning process, which is a cleaning process with less damage.
    The technique described here is particularly effective in cases where at least one of the laser medium and the transparent heat transfer member is an oxide, however, it is not limited to these, and it is effective also for cases where at least one of the laser medium and the transparent heat transfer member contains a light element. In particular, in cases where the light element included in the first to third periods of the periodic table is contained, the transparency and stability of the bonding surface can be improved by subjecting the member containing it to exposure to a plasma d oxygen for prewash.
    Specific examples of the present invention have been described in detail, however, these are only indications constituting examples so that they do not limit the scope of the claims. For example, the laser media and transparent heat transmitting members appear alternately in the embodiments, however, there are cases where the laser media appear consecutively at the parts in the series arrangement. In such a case, the consecutive laser media can be considered collectively as a laser medium. Thus, this is also in accordance with the rule according to which the laser media and the transparent heat-transmitting members appear alternately.
    The technique described in the claims includes modifications and variations of the specific examples presented above. The technical features described in the description and the drawings may be useful technically alone or in different combinations, and are not limited to the combinations as originally claimed. In addition, the technique described in the description and the drawings can simultaneously achieve a plurality of objectives, and its technical importance lies in the fact of achieving any one of such objectives.
    权利要求:
    Claims (21)
    [1" id="c-fr-0001]
    1. A method of manufacturing a laser component which links a laser medium (10) and a transparent heat transmission member (20), characterized in that at least one of the laser medium (10) and transparent heat transfer member (20) is an oxide, the method comprising:
    exposing a bonding surface of the laser medium (10) and a bonding surface of the transparent heat transfer member (20) to an oxygen plasma;
    projecting an atomic beam of inert gas onto the two vacuum bonding surfaces after exposure; and bringing the bonding surfaces into contact after the projection.
    [2" id="c-fr-0002]
    2. Method according to claim 1, wherein the bonding surfaces are brought into contact without heating.
    [3" id="c-fr-0003]
    3. Laser component, characterized in that it comprises a laser medium (10) and a transparent member for heat transmission (20), where at least one of the laser medium (10) and for the transparent member for transmitting heat (20) is an oxide, the laser medium (10) and the transparent heat-transmitting member (20) are linked via an amorphous layer, and the amorphous layer is transparent to an excitation beam .
    [4" id="c-fr-0004]
    4. The laser component according to claim 3, wherein the laser medium (10) is an optical gain material.
    [5" id="c-fr-0005]
    5. The laser component according to claim 3, wherein the laser medium (10) is a non-linear optical material.
    [6" id="c-fr-0006]
    6. Laser component according to any one of claims 3 to 5, further comprising:
    a dielectric multilayer film (22) disposed between the laser medium (10) and the transparent heat transmission member (20).
    [7" id="c-fr-0007]
    7. Laser component according to any one of claims 3 to 6, further comprising:
    an intermediate layer (24) disposed between the laser medium (10) and the transparent heat transmitting member (20), where a difference between the refractive indices of the laser medium (10) and the intermediate layer (24) is less than 9%, a difference between the refractive indices of the intermediate layer (24) and of the transparent heat-transmitting member (20) is less than 9%, and a difference between the refractive indices of the laser medium ( 10) and the transparent heat transmission member (20) is equal to or greater than 9%.
    [8" id="c-fr-0008]
    8. Laser component according to any one of claims 3 to 7, where a plurality of laser media (10) and a plurality of transparent heat transmission members (20) are provided, and the plurality of laser media (10) and the plurality of transparent heat transmitting members (20) are arranged in series in an order by which the laser media (10) and the transparent heat transmitting members (20) appear alternately.
    [9" id="c-fr-0009]
    9. The laser component according to claim 8, wherein a thickness of each laser medium (10) in a layering direction is equal to or less than one fifth (1/5) of a diameter of the laser medium (10).
    [10" id="c-fr-0010]
    10. Laser component according to any one of the claims
    8 and 9, where the laser media (10) includes different types of laser media, and the laser media (10) of different types are arranged in series.
    [11" id="c-fr-0011]
    11. The laser component according to claim 10, in which the laser media (10) comprise a group of laser media having the same luminescent center element and different base materials, and the group of laser media is arranged in series.
    [12" id="c-fr-0012]
    The laser component according to claim 10, wherein the laser media (10) comprise a group of laser media having the same base material and different luminescent center elements, and the group of laser media is arranged in series.
    [13" id="c-fr-0013]
    13. The laser component according to claim 10, wherein the laser media (10) comprise a group of laser media having different luminescent center elements and different base materials, and the group of laser media is arranged in series.
    [14" id="c-fr-0014]
    14. Laser component according to any one of claims
    8 to 13, where the laser media (10) have different dopant concentrations, the dopant concentration of the laser medium arranged in the vicinity of an end face intended to be exposed to the excitation beam is less than the concentration of dopant of the laser medium arranged at a distance from the end face.
    [15" id="c-fr-0015]
    15. Laser component according to any one of claims 8 to 14, provided that claim 8 does not depend on claim 4, wherein each of the laser media (10) is a non-linear optical material, the laser media comprise a group of laser media having different thicknesses, and the group of laser media is arranged in series.
    [16" id="c-fr-0016]
    16. Laser component according to any one of the claims
    8 to 15, where the transparent heat transmission members (20) are arranged at respective ends of a series arrangement.
    [17" id="c-fr-0017]
    17. The laser component according to claim 16, wherein each of the transparent heat transmission members (20) arranged at the ends of the series arrangement is made of a single crystal, and the laser media (10) are made of ceramic. .
    [18" id="c-fr-0018]
    18. The laser component as claimed in claim 17, in which the end faces of the transparent heat transmission members (20) arranged at the ends of the series arrangement are coated.
    5
    [0019]
    19. Laser component according to any one of claims
    3-18, where the laser medium (10) is made of ceramic, and the transparent heat transfer member is made of a single crystal (20).
    10
    [0020]
    20. Laser component according to any one of claims
    16 to 19, where the transparent heat transmission members (20) are arranged at the two end faces of the laser medium.
    15
    [0021]
    21. The laser component as claimed in claim 20, in which the end faces of the transparent heat transmission members (20) arranged at the end faces of the laser medium (10) are coated.
    1/9
    12,14,16
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    CM
    O
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    CO CM O CM CN CM
    U7 ns CO CM O
    CM CM CM
    O CO CM O st CM CM CM
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    同族专利:
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    优先权:
    申请号 | 申请日 | 专利标题
    JP2016211991A|JP6245587B1|2016-10-28|2016-10-28|Laser parts|
    JP2016211991|2016-10-28|
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