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    • 专利摘要:
    Segmented Vertical Cavity Surface Emitting Laser The invention discloses a Vertical Cavity Surface Emitting Laser Device (100). The Vertical Cavity Surface Emitting Laser Device (100) includes a first electrical contact (105), a substrate (110), a second electrical contact (135), and an optical resonator. The optical resonator is arranged on a first side of the substrate (110). The optical resonator includes a first reflective structure comprising a first distributed Bragg reflector (115), a second reflective structure comprising a second distributed Bragg reflector (130), an active layer (120) arranged between the first reflective structure and the second structure reflective and a guide structure (132). The guide structure (132) is arranged to define a first relative intensity maximum of an intensity distribution in the active layer (120) at a first lateral position of the optical resonator so that a first light emitting zone (124) is provided, the guide structure (132) being arranged to define at least a second relative intensity maximum of the intensity distribution in the active layer (120) at a second lateral position of the optical resonator so that a second light-emitting region (124) is provided, the guide structure (132) being further arranged to reduce an intensity of the intensity distribution between the at least two light-emitting regions (124) during operation of the a Vertical Cavity Surface Emitting Laser device, and the guiding structure (132) being arranged in a stack of layers of the first distributed Bragg reflector (115) or the The third distributed Bragg reflector (130). The invention furthermore discloses the optical sensor (300) comprising such a Vertical Cavity Surface Emitting Laser device (100), a mobile communication device (380) comprising such a sensor optical system (300) and a method of manufacturing the Vertical Cavity Surface Emitting Laser Device (100). Figure 2
    公开号:FR3076960A1
    申请号:FR1872510
    申请日:2018-12-07
    公开日:2019-07-19
    发明作者:Holger Joachim Mönch；Stephan Gronenborn
    申请人:Koninklijke Philips NV；
    IPC主号:
    专利说明:

    Technical Field The invention relates to a vertical cavity surface emission laser device (also known by its English acronym VCSEL, or Vertical Cavity Surface Emitting Laser) comprising a guide structure arranged to provide separate optical modes. The invention further relates to an optical sensor comprising such a VCSEL device and a mobile communication device comprising such an optical sensor. The invention further relates to a corresponding method of manufacturing such a VCSEL device.
    PRIOR ART [0002] VCSEL's addressable networks are becoming increasingly important in the field of sensors for depth imaging as well as for printing / additive manufacturing. Depending on the implementation, it cannot be tolerated that a single pixel breaks down. Such a single pixel failure would result in total device failure. This makes pixelated networks with large VCSELs (large light-emitting areas) problematic, as the failure rate of a single pixel increases with the size of the VCSEL.
    Technical problem An object of the present invention is to provide a VCSEL device offering high output power and improved reliability.
    The invention is defined by the independent claims. The dependent claims define advantageous embodiments.
    According to a first aspect, a VCSEL device is proposed. The VCSEL device includes a first electrical contact, a substrate, a second electrical contact, and an optical resonator. The optical resonator is arranged on a first side of the substrate. The optical resonator comprises a first reflecting structure comprising a first distributed Bragg reflector (in English DBR or distributed Bragg reflector), a second reflecting structure comprising a second DBR, an active layer arranged between the first reflecting structure and the second reflecting structure and a guide structure. The guide structure is arranged to define a first relative intensity maximum of an intensity distribution in the active layer at a first lateral position of the optical resonator so that a first light-emitting area is provided. The guide structure is further arranged to define at least a second relative intensity maximum of the intensity distribution in the active layer at a second lateral position of the optical resonator so that a second light-emitting area is provided. The guide structure can be arranged in (inside) a stack of layers of the first DBR or of the second DBR. The guide structure is further arranged to reduce an intensity of the intensity distribution between the at least two (or more) light-emitting zones during operation of the VCSEL device. The laser emission is inhibited between the two, three, four or more light emitting zones. The two, three, four or more in a maximum of relative intensity are separate or more precisely essentially independent of each other. Different optical modes (two, three, four or more) can contribute to the maxima of relative intensity in different lateral positions. The guide structure can be arranged so as to reduce an intensity of at least one optical mode contributing to at least one of the first or second maximum intensity relative to the outside of at least the first or second emitting zone. of light, so that a lateral extension of the light-emitting area is linked to the respective lateral position of the optical resonator. The first and second electrical contacts are arranged to electrically pump the active layer. The first or second reflective structure may include reflective elements which are not included in the first or the second DBR contributing to the total reflectivity of the first or second reflective structure. The active layer may include two, three, four or more light emitting zones across the lateral extent of the active layer which are defined by the guide structure. The stack of layers of the optical resonator arranged on the first side of the substrate is characterized by a thickness of between 5 and 20 μm. The substrate is generally characterized by a thickness of between 100 and 600 μm so that a second side of the substrate opposite the first side is separated from the first side by at least 100 μm.
    The term “surface cavity laser with vertical cavity” also includes what are called surface emission lasers with vertical external cavity (in English VECSEL or Vertical Extemal Cavity Surface Emitting Lasers). The abbreviation VCSEL is used for both types of lasers. The term "layer" does not exclude that the layer may comprise two or more sublayers.
    Addressable networks of VCSEL or VECSEL devices are becoming increasingly important in the field of sensors for depth imaging as well as for printing / additive manufacturing. Depending on the implementation, it cannot be tolerated that a single pixel breaks down. Such a failure would cause a total failure of the device.
    VCSEL devices can fail because defects develop in the crystal, which absorb part of the laser radiation and raise the laser threshold.
    By this absorption, the local temperature in the region of the defect increases and the defects increase, leading to an even higher absorption and ultimately to total failure.
    Even in large diameter VCSEL devices, the individual locations in the opening are connected by optical modes having either an intensity profile over the entire opening or plane waves passing through the set of the opening. A local fault would therefore absorb the optical power supplied by optical modes with intensity profile extending through the active area or by plane waves propagating through the active area.
    For this reason, "workarounds" implement a small network for a pixel, each element of the network (VCSEL with low active area) being imaged using optical means on a single pixel of the setting. implemented. This requires significant effort and space which is not compatible with mass applications.
    In particular, VCSEL devices emitting from below emitting laser light through the substrate with a complete metallic anode contact can be dimensioned to a relatively large diameter (total active surface of more than 200 μm 2 , preferably more than 400 pm 2 and even more preferably more than 600 pm 2 ) to allow more powerful implementations. The flip-chip mounting of the transmitter from below on an electronic pilot allows individual "pixel" addressing. Such an architecture is most compact but is not used today because of the reliability problem mentioned above.
    The VCSEL device according to claim 1 makes it possible to produce a large area VCSEL device with an optical separation of different light-emitting zones through the opening. The relative maxima of the intensity distribution remain in defined parts of the opening or of the active zone and do not mix. An advantage of the separation of the light emitting zones over the lateral extent of the active zone of the connected active layer is that a single region of such a faulty light emitting zone causes the laser emission of the respective light emitting area of the device. Consequently, the optical intensity in this region is reduced (and because of the separation, the other regions do not contribute by their intensity) and local warming by absorption is avoided. The fault does not spread further and the damage remains localized. The distribution of the intensity is therefore such that there is essentially no transfer of energy between, in particular, the neighboring light-emitting zones and the corresponding relative intensity maxima. Each relative intensity maximum and each contributing mode or optical modes derives the majority of its gain from the associated lateral position in the optical resonator (position of the associated light-emitting area) and only a minority of the neighboring regions.
    A size of the light emitting areas is at least 3pm 2 . The light emitting zones are included in an active zone of the active layer of at least 200 pm 2 .
    The guide structure can be a localized element consisting, for example, of a single layer of the optical resonator. The guide structure can alternatively comprise a multitude of interacting layers so that (as well as the only localized element) maxima of relative intensity separated by two, three, four or more light-emitting zones are linked to the respective location in the optical resonator.
    The guide structure can be arranged inside a stack of layers of the first distributed Bragg reflector or of the second Bragg reflector distributed in a vertical direction of the Surface Emission Laser device with Vertical Cavity. The vertical direction may designate a vertical direction of the vertical cavity of the Vertical Cavity Surface Emitting Laser device.
    The guide structure can be arranged in the optical resonator and (completely) enveloped by it. The guide structure can be arranged in the optical resonator and completely surrounded by it. The guide structure can be arranged inside the optical resonator, in particular inside the first DBR or inside the second DBR. The guide structure can be arranged in the first DBR or the second DBR and completely enveloped by it. The guide structure can be arranged in a stack of layers of the first DBR or of the second DBR so that the optical guide structure is surrounded or encapsulated by the first or the second DBR. An advantage of this approach can be a more homogeneous growth process of adjacent layers, for example between the active layer and a layer of the first or second DBR. The guide structure can be arranged so that at least one layer (or a sequence of at least two layers) of the stack of layers of the first and / or of the second DBR is arranged in contact with the guide structure, said layer or sequence of layers of DBR in contact with the guide structure being arranged in a vertical direction of the vertical cavity of the Surface Emission Laser with Vertical Cavity.
    At least a first layer of the first DBR can be arranged above the guide structure in a vertical direction of the vertical cavity of the Surface Emission Laser with Vertical Cavity and at least a second layer of the first DBR can be arranged below the guide structure in a vertical direction of the vertical cavity of the Surface Emission Laser with Vertical Cavity. The same can apply to the second DBR.
    An advantage of the arrangement of the guide structure in (inside) a stack of layers of the first DBR or of the second DBR can be improved structural integrity of the device. Consequently, the device can be better adapted to demanding application scenarios, more stable with respect to vibrations and / or can offer improved reliability, for example in automotive applications. For example, a (single) mesa structure can be provided which includes the guide structure rather than providing separate mesas which are separated by trenches and / or electrical contacts between the separate mesas.
    The guide structure can for example be arranged to provide a lateral variation of the reflectivity of the first reflecting structure or of the second reflecting structure parallel to the active layer. The lateral variation of the reflective material can be obtained by means of a single layer or of a combination of two or more layers. The guide structure can for example be arranged in a stack of layers of the first DBR or of the second DBR. The guide structure may include a variation of a thickness of at least one layer of the first DBR reflector or of the second DBR. The guide structure may alternatively or moreover comprise a lateral variation of a reflectivity of the first electrical contact or of the second electrical contact.
    The guide structure may alternatively or additionally comprise oxidized regions in at least one layer of the first distributed Bragg reflector or of the second distributed Bragg reflector. The oxidized regions are arranged to reduce the intensity between the at least two light-emitting zones. The oxidized region can be arranged to modify the resonance conditions in the optical resonator in a lateral direction and / or to provide local current confinement of the electric current at the locations of the light emitting areas. The oxidized region can, for example, be arranged in an opening in the oxide, surrounding the at least two light-emitting zones.
    The optical resonator may further comprise a phototransistor (PT) or bipolar phototransistor with distributed heterojunction (in English HPT or "distributed Heterojunction bipolar PhotoTransistor"). The HPT comprises a collector layer, a photosensitive layer, a base layer and an emitter layer. The HPT is arranged so that there is an optical coupling between the active layer and the HPT to ensure confinement of the active carrier by means of the HPT.
    The use of a HPT (monolithically integrated) particularly close to the active layer can allow effective containment of the charge carriers by controlling the injection of carriers as a function of the local intensity of the real profile of the mode of laser emission which is influenced by the optical guidance provided by means of the optical guidance structure. Therefore, the injection of carriers can be locally adapted to the request of the laser emission mode and vice versa. The HPT acts effectively as a current confinement layer or structure. The advantage of adding the phototransistor is that it transforms a slight optical modulation into a strong differentiation of the laser emission and non-laser emission zones and inhibits the flow of current between the segmented regions, thus increasing efficiency. The HPT therefore supports the separation of the optical modes by amplifying, for example, a slight optical guidance provided by the guidance structure.
    The HPT with optically sensitive collector-base junction can be designed to avoid optical absorption. The photosensitive layer can be a quantum well layer or a massive layer (in English “bulk layer”). Solid layers are, for example, homogeneous layers with a thickness of 10 nm or more in which the effects of quantum mechanics can be neglected.
    The HPT is arranged in the VCSEL so that the sensitivity to light which is generated by means of the active layer of the VCSEL in combination with the optical resonator provided by the first and second DBRs is sufficiently high. The HPT can, for example, be a pnp HPT which is arranged directly above the active layer, that is to say on the side of the active layer which is oriented opposite the usually conductive substrate n. In an alternative approach, it may be possible to arrange an npn HPT directly under the active layer. "Directly" means that the PNT or HPT npn HPT is arranged as close as possible to the active layer. This does not preclude the fact that one or more intermediate layers may be necessary to improve, for example, the performance and / or reliability of the VCSEL. It may also be possible to stack the HPT in the first or second DBR after, for example, three or five pairs of mirror layers. The layered structure of the HPT can even be integrated into one of the DBRs. The thickness of one or more of the HPT layers can be adapted to the emission wavelength of the VCSEL (quarter wave layer) in the respective material. One or more layers of HPT can in this case be used to increase the reflectivity of the respective DBR. It may even be possible to use two HPTs: one below and one above the active layer.
    Positioning the HPT directly above or below the active layer can have the advantage that, due to the low lateral conductivity between the HPT and the active layer, the optical mode best corresponds to the profile of the carriers. respective load.
    The concentration of dopants in the collector layer, the base layer and the emitter layer may be less than 10 19 cm 3 . The dopants of the HPT layers cause optical losses such that a low level of doping is preferred. The emitting layer of the HPT is the layer having the highest doping concentration.
    The concentration of dopants in the emitting layer can for example be as low as 5 * 10 18 cm 3 or even 2 * 10 18 cm 3 . The dopant concentration can be as low as l * 10 18 cm 3 in the base layer and 4 * 10 17 cm 3 in the collector layer in case of dopant concentration of 2 * 10 18 cm 3 in the layer of transmitter to reduce optical losses by means of charge carriers.
    The thickness of the base layer can be 100 nm or less. The HPT can be a pnp HPT which is arranged between the active layer and the second DBR. The base layer may in this case have a thickness of approximately λ / 4 of the emission wavelength of the VCSEL in the material of the base layer.
    The emission wavelength may depend on the material of the substrate. A GaAs substrate can be used for an emission wavelength between 650 nm and around 1600 nm. A VCSEL with an InP substrate can emit laser light at an emission wavelength greater than or even much greater than 1500 nm. The thickness of the collector layer can be in the range of λ / 2 of the emission wavelength of the VCSEL in the material.
    The guide structure can be arranged outside of a current flow which can be supplied by means of the first electrical contact and the second electrical contact during the operation of the VCSEL device. The optical confinement by means of the guide structure does not interact directly with the current confinement supplied by means of the HPT. The flow of current is not disturbed through the guide structure. There can be an indirect interaction because the optical guidance determines the positioning of the relative intensity and therefore of the area or more precisely of the volume in which the HPT becomes conductive. The separation of, in this case, optical guidance and confinement of the current can allow a defined position of the separate relative intensity maxima. Channeling electrical current through HPT improves efficiency, and HPT inhibits current along parts of non-laser emission that could be caused by local failure of one of the layers of the VCSEL device.
    The guide structure can, for example, be arranged to provide on the lateral cross section of the regions of the optical resonator an effective optical length allowing resonant laser operation interrupted by regions having a different effective optical length inhibiting laser operation.
    The guide structure can, for example, be arranged to reduce the effective optical length of the optical resonator in regions where resonant laser operation is inhibited. A reduction in effective optical lengths can, for example, be made possible by local oxidation of one or more layers of the first or second DBR, as described above.
    The guide structure can alternatively or moreover be arranged to increase the effective optical length of the optical resonator in the regions where the resonant laser operation is activated. An additional structured layer (for example, SiO 2 or SiN x ) can be provided or a thickness of one or more layer (s) of semiconductor (for example, one or more layer (s) of Al y Ga ( i_ y) As) can be structured in order to modify the resonance conditions in the lateral direction of the optical resonator. The guide structure can be incorporated into the layer structure of the first or second DBR. The corresponding DBR can in this case be a dielectric DBR comprising pairs of non-conductive dielectric layers with different refractive indices, for example layers of Nb 2 0 5 , TiO 2 , TaO 2 , Si 3 N 4 and SiO 2 .
    The guide structure can alternatively or moreover be arranged to ensure local confinement of the current in the at least two light-emitting zones. The guide structure can for example comprise the first or the second electrode, the first or the second electrode being arranged to induce a distribution of electric current corresponding to the distribution of intensity through the active layer. The first or second electrode can, for example, be structured to allow local current induction. The guide structure may alternatively or moreover comprise at least one layer of reduced lateral electrical conductivity in zones corresponding to a zone of reduced intensity between the at least two light-emitting zones. A doping profile of one or more semiconductor layer (s) can, for example, be arranged so that the electrical conductivity towards the light-emitting areas is increased and the electrical conductivity of the areas situated between the emitting areas light is decreased.
    The VCSEL device can be arranged to emit laser light through the substrate (emitter from below). The transmitters from below allow fairly large active areas as described above. The bottom emitter or the optical resonator may include an extended optical cavity, through the substrate. The guide structure can comprise a lateral structuring of a second side of the substrate opposite to the first side of the substrate. The guide structure may alternatively or additionally comprise other layers deposited on the second face of the substrate supporting guidance of the separate relative intensity maxima (providing a lateral variation of optical feedback in the extended optical cavity).
    The VCSEL device can be understood by an optical sensor. The optical sensor can be understood by a mobile communication device. The optical sensor can also be used in automotive applications, in particular for autonomous driving. The VCSEL device can further be used in network layouts for, for example, printing or high power applications such as additive manufacturing.
    In another aspect, a method of manufacturing a surface emission laser with a vertical cavity is proposed. The process includes the following steps:
    providing a first electrical contact, providing a substrate, providing a first DBR, providing an active layer, providing a second DBR, providing a second electrical contact, providing a guide structure which is arranged to define a first relative maximum intensity of an intensity distribution in the active layer at a first lateral position of the optical resonator so that a first light-emitting zone is provided, the guide structure being arranged to define at least a second relative intensity maximum of the distribution intensity in the active layer at a second lateral position of the optical resonator so that a second light emitting area is provided, the guide structure being further arranged to reduce an intensity of the intensity distribution between the at least two light emitting zones during the operation of the Ve Cavity Surface Emission Laser device rticale.
    The steps do not necessarily have to be carried out in the order indicated above. The guide structure can, for example, be understood by the first electrical contact, the first DBR, the second DBR or the second electrical contact. The substrate can optionally be removed. The various layers can be deposited by epitaxial methods such as MOCVD (Epitaxy in vapor phase with organometallic or in English “MetalOrganic Chemical Vapor Deposition”), MBE (Epitaxy by molecular jet or in English “Molecular Beam Epitaxy”), etc.
    It will be understood that the VCSEL device described above and the method have similar and / or identical embodiments, in particular, as defined in the dependent claims.
    It will be understood that a preferred embodiment of the invention can also be any combination of the dependent claims with the respective independent claim.
    Other advantageous embodiments are defined below.
    Brief Description of the Drawings These aspects of the invention, as well as others, will appear with reference to the embodiments described below and will be explained in this regard.
    The invention will now be described, by way of example, on the basis of embodiments with reference to the accompanying drawings.
    In the drawings:
    [Fig. 1] shows a schematic diagram of a cross section of a first VCSEL device with a guide structure;
    [Fig.2] shows a block diagram of a cross section of a second VCSEL device with a guide structure;
    [Fig.3] shows a block diagram of a top view of a third device
    VCSEL;
    [Fig.4] shows a block diagram of a cross section of a fourth VCSEL device;
    [Fig.5] shows a block diagram of a cross section of a fifth VCSEL device;
    [Fig.6] shows a block diagram of an optical sensor comprising the VCSEL device;
    [Fig.7] shows a block diagram of a mobile communication device comprising the optical sensor;
    [Fig.8] shows a block diagram of a process flow of a process for manufacturing a VCSEL device.
    In the figures, identical numbers refer to identical objects throughout the description. The objects illustrated in the figures are not necessarily drawn to scale.
    Description of the Embodiments Various embodiments of the invention will now be described by means of the figures.
    The Eig. 1 shows a block diagram of a first VCSEL 100 device with a guide structure 132. The first VCSEL 100 device is a VCSEL emitting from below emitting laser light through a substrate 110 (emission direction indicated by the arrow). The emission wavelength of the VCSEL device 100 must therefore be arranged so that the substrate 110 (for example made of GaAs) is transparent for the emission wavelength. On a first side of the substrate 110 is provided a first DBR 115 comprising 25 pairs of layers with a first and a second refractive index. The pairs of layers of the first DBR 115 comprise layers of AlGaAs / GaAs. The thickness of the layers is adapted to the emission wavelength of the VCSEL in order to provide the required reflectivity of approximately 98%. The first DBR 115 is partly etched to deposit a first electrical contact 105 (contact n). The layer of the first DBR 115 on which the first electrical contact is provided 105 can be characterized by an increased electrical conductivity (high doping) in order to distribute the electric current in the lateral direction parallel to the structure of the layers of the VCSEL 100 device (layer current distribution). An active layer 120 is provided on the first DBR 115. A second DBR 130 is provided on the active layer 120. The second DBR 130 comprises 40 pairs of layers with a first and a second refractive index. The pairs of layers of the second DBR 130 here also include layers of AlGaAs / GaAs. The thickness of the pair of layers is adapted to the emission wavelength of the VCSEL in order to provide the required reflectivity of more than 99.9%. A second electrical contact 135 (contact p) covers the second DBR 130. A guide structure 132 is integrated in the second DBR 130. The guide structure 132 may comprise oxidized regions of one or more of the layers of the second DBR 130 in order to to provide a lateral variation of the resonance condition through the active area 128 (see Fig. 3) of the active layer 121 as defined by the opening in the oxide provided by the current confinement layer 123. The structure guide 132 may alternatively or additionally comprise several layers of the second DBR 130 having a variable doping profile to provide a lateral variation of the electrical conductivity (subsequent proton implant, diffusion doping, etc.). There may be one or more intermediate layers, not shown for clarity, which can for example be used to match the crystal parameters.
    The Lig. 2 shows a block diagram of a second VCSEL 100 device with a guide structure 132. The second VCSEL 100 device comprises a network of VCSEL emitting from below which are arranged on a common substrate 110. Each VCSEL of the network VCSEL includes a layer arrangement similar to that described with reference to Lig. 1. Each VCSEL of the VCSEL network is coupled to a lens structure 112 etched in a second side of the substrate 110 opposite to the first side of the substrate 110. The lens structure 112 is arranged to focus the laser light emitted via the second side of the substrate 110 (indicated by the arrow). The lens structure 112 further provides optical feedback due to differences in the refractive indices (GaAs ~ 3.4 and air 1). The lens structure 112 therefore forms part of the optical resonator and defines an extended optical cavity. Each VCSEL in the VCSEL network is therefore a vertical extended cavity surface emission laser (VECSEL). Another difference compared to the VCSEL 100 device shown in Lig. 1 is that the guide structure 132 is not integrated in the second DBR 130. The guide structure 132 comprises a second structured electrode. The second structured electrode provides local induction of electric current in order to electrically pump separate relative intensity maxima so that there are a multitude of light-emitting areas. In addition, the metal of the second electrode contributes to the reflectivity of the DBR-p and the structure laterally and therefore supports guidance in this regard.
    [0056] FIG. 3 shows a block diagram of a top view of a third VCSEL device 100 through the active layer 120. The cross section shows a network of six VCSEL emitting from below through the active layer. The general configuration of each VCSEL is similar to that described with reference to FIG. 1. The second electrical contact 135 completely covers the second DBR 130 (see also Fig. 4). The second electrical contact 135 contributes to the reflectivity of the second reflecting structure comprising the second DBR. The second electrical contact is arranged to provide a lateral variation of the reflectivity so that the resonance conditions vary laterally through the optical resonator in order to provide separate optical modes with a distinct intensity profile, so that there is seven light-emitting areas 124 in the active area 128 of the respective active layer 120. Each VCSEL may possibly include a structured current distribution layer (not shown) supporting optical guidance by inducing the current in positions where the resonance conditions of the optical resonator allow the emission of laser light. The gain in cavity can be modified laterally by a different reflectivity of the mirrors, in this case the second DBR 130 (DBR-p), since its surface is easily accessible for treatment. The structuring of, for example, the thickness of the covering layer (the outermost layer in the second DBR) by etching, the modification of the reflectivity of the second electrode 130 (made of metal) as described above. above or the partial deposition of materials modifying the reflectivity allow such a guide structure. A specific class of such materials is that of dichroic materials, which would also allow local electrical isolation and / or variation of optical feedback.
    [0057] FIG. 4 shows a block diagram of a fourth VCSEL 100 device with a guide structure 132. The arrangement is very similar to that described with reference to FIG. 2. The second electrode 135 of the VCSELs of the VCSEL network completely covers the second DBR 130. The second side of the substrate 110 is unlike the embodiment described with reference to FIG. 2, arranged so that laterally varying optical feedback is provided on each active area. The second side of the substrate 110 is etched forming a guide structure 132. The localized external feedback of the guide structure 132 on the respective active area generates local (relative) intensity maxima of the intensity distribution in the active layer 120. Alternatively, a structured glass plate can be provided to allow such local optical feedback. It is possible to provide only local modulation of planar surface feedback, i.e. regions with higher and lower reflectivity, as described with reference to FIG. 3. It should however be noted that a stable cavity rests on a thermal lens which develops in the material. Due to the symmetry and major influence of the heat flow to the outside of the mesa of the respective VCSEL, such a thermal lens will probably cover the entire transmitter from below and will not show the desired substructure. Therefore, it may be advantageous to use a guide structure 132 with many small curved mirrors, as illustrated in FIG. 4, instead of a simple flat surface with modulated reflectivity. Another embodiment would consist of small microlenses and a flat (common) mirror forming the network of stable cavities within the large electrically pumped region of each VCSEL in the VCSEL network.
    [0058] FIG. 5 shows a schematic diagram of a cross section of a fifth device of VCSEL 100. The fifth device of VCSEL 100 is a VCSEL emitting laser light from the substrate 110 (emitter upwards, laser emission indicated by the arrow ). On the second side of the substrate 110, a first electrical contact 105 is provided. On the first side of the substrate 110 is provided a first DBR 115 comprising 40 pairs of layers with a first and a second refractive index. The pairs of layers of the first DBR 115 comprise layers of AlGaAs / GaAs. The thickness of the layers is adapted to the emission wavelength of the VCSEL 100 device in order to provide the required reflectivity of more than 99.9%. Above the first DBR 115 is an active layer 120 ant. The active layer 120 includes a quantum well structure for the generation of light. A current injection layer n (not shown) can be arranged between the first DBR 115 and the active layer 120. A distributed HPT 125 is provided on the active layer 120. A current spreading layer 127 is arranged above 1ΉΡΤ distributed 125. A second DBR 130 is provided on the current spreading layer 127. The second DBR 130 is a dielectric DBR comprising pairs of non-conductive dielectric layers with different refractive indices, such as for example layers of Nb 2 0 5 , TiO 2 , TaO 2 , Si 3 N 4 and SiO 2 . The number of pairs of layers depends on the materials and the desired reflectivity. The thickness of the pair of layers is adapted to the emission wavelength of the VCSEL 100 device in order to provide the required reflectivity of approximately 97%. A second ring-shaped electrical contact 135 is arranged around the second dielectric DBR 130 above the current spreading layer. The VCSEL device 100 emits laser light in the direction of the arrow via the second dielectric DBR 130. The guide structure 132 comprises a layer of structured SiO 2 . The structured SiO 2 layer is incorporated between the current spreading layer 127 and the second DBR 130. The SiO 2 layer is deposited on the current spreading layer 127 and then etched to provide a lateral variation of optical feedback . The dielectric layers of the second DBR 130 are then deposited on the structured layer of SiO 2 and on the current spreading layer 127, where the current spreading layer 127 has been exposed by etching the layer of SiO 2 . The layer of structured SiO 2 locally increases the effective optical length and therefore the resonance condition of the optical resonator, so that the laser is only activated at the positions of the remains of the layer of structured SiO 2 .
    [0059] FIG. 6 shows a cross section of an optical sensor 300. The optical sensor 300 comprises a VCSEL 100 device as described above, a transmission window 310 and a control circuit 320 for electrically controlling the VCSEL 100 device. control circuit 320 is electrically connected to the VCSEL 100 device to supply power to the VCSEL 100 device in a defined manner. The control circuit 320 includes a memory device for storing data and instructions for operating the driver 320 and a processing unit for executing data and instructions for operating the control circuit 320. The optical sensor 300 includes further a photodetector 350 and an evaluator 360. The photodetector 350 is in this case a photodiode but can be any device, preferably semiconductor, which can be used to detect the laser light emitted by the VCSEL device 100 The photodetector 350 must be as sensitive as possible for the photons emitted by the VCSEL 100 device and must have a rapid measurement time. A preferred technology is, for example, avalanche effect photodiodes or even more so-called SPAD (in English “Single Photon Avalanche Diodes”, as well as arrays of these. The evaluator 360 comprises at least one memory device such as a memory chip and at least one processing device such as a microprocessor. The evaluator 360 is adapted to receive data from the control circuit 320 and possibly from the photodetector 350 or from the VCSEL device 100 in order to determine an instant tl at which the emitted laser light 315 leaves the optical sensor 300. The evaluator 360 determines in further on the basis of this instant tl and of the repetition rate supplied by means of the control circuit 320, if a reflected laser light 317 detected by the photodiode comes from the laser pulse emitted at the instant tl. An instant t2 is recorded if the reflected laser light 317 comes from the laser pulse and the distance to the object which reflects the laser pulse is calculated by means of the travel time At = t2-t 1 and the velocity of the laser pulse c. A small part of the emitted laser light 315 can be reflected at the transmission window 310 and used as a control signal 319. The control signal 319 is received by the photodetector 350 much earlier than the reflected laser light 317. The 360 evaluator is therefore able to differentiate between the reception of the control signal 319 and the reflected laser light 317. The signal intensity of the received control signal 319 is compared by means of the 360 evaluator with respect to at a reference signal strength stored in the memory device of the evaluator 360. The evaluator 360 sends a power reduction signal to the control circuit 320 as soon as the intensity of the received control signal 319 exceeds a threshold value based on the intensity of the reference signal in order to guarantee the safety of the eye of the optical sensor 300. The time between the reception of the control signal 319 and the reflected laser light 317 may be quite short. It may therefore be advantageous to use a separate control signal 319 independent of the emitted laser light 315. The separate control signal 319 can be a very short laser pulse emitted between two laser pulses of the emitted laser light 315. Furthermore, it may be advantageous to implement a feedback structure in the transmission window 310 so that the signal strength of the control signal 319 is sufficiently high. The feedback structure can for example be a small part of the surface of the transmission window 310 which is inclined relative to the rest of the surface of the transmission window 310. The position and the angle of inclination are chosen such that so that the control signal 319 is directed to the photodetector 350.
    The Lig. 7 shows a block diagram of a mobile communication device 380 comprising an optical sensor 300 similar to that described with reference to Lig. 6. The optical sensor 300 can for example be used in combination with a software application executing on the mobile communication device 380. The software application can use the optical sensor 300 for uses in detection. These detection uses can be journey time measurements for distance detection, autofocus of a camera, 3D imaging of a user interface based on a scene or a gesture.
    The Lig. 8 shows a block diagram of a process flow of a method for manufacturing a VCSEL 100 device. A GaAs 110 substrate is provided in step 410. A first DBR 115 is provided on a first side of the substrate 110 in step 420 and an active layer 120 is provided in the next step 430 on the first DBR 115. A second DBR 130 is provided in step 440 on the active layer 120. A first electrical contact 105 is provided in step 450. The first electrical contact 105 is attached to a second side of the substrate 110. A second electrical contact 135 is provided to electrically pump the VCSEL device together with the first electrical contact 105 in step 460. A structure guide 132 is provided in step 470.
    Other approaches for implementing the guide structure 132 can be: 1. In a bottom emitter of large diameter, for example, localized regions can be defined by oxidation. While the large diameter bottom emitter is created by etching and oxidizing mesa from the outside of the mesa, oxidation can occur for local separation through small holes etched into the surface. This allows for close spacing of the regions located inside the large transmitter from below, providing a large optically almost continuous transmitter. It should be noted that even imperfect electrical insulation by oxidation is tolerable since the optical separation with oxidized aluminum is very strong due to the large step in the refractive index. Imperfect electrical insulation can therefore reduce efficiency (current being injected into regions that do not produce a laser effect), but the relative intensity maxima remain separate. The entire structure can have a continuous metal electrode connected to the electrical control.
    2. The electrical separation can also be carried out by implantation of protons, similar to that described above, with the difference that the implantation of protons does not induce a strong optical guiding effect. The electrical separation can be combined with another optical guiding method similar to the methods described above.
    3. The substructure for localized optical modes can be enabled by a buried heterostructure. This means that the wafer is extracted from the epitaxy reactor during growth and structured laterally by lithography and etching. Then the growth is brought to completion. This allows only part of the DBR to match the resonance conditions.
    4. The guide structure 132 can be a gain guide structure which can be designed by simply structuring the anode metal or the electrical connection of the semiconductor to this anode metal. The lateral conductivity of DBR-p must be kept low in order to maximize the separation of the relative intensity maxima (and of the corresponding optical mode or modes) while avoiding the heavily doped layers.
    Although the invention has been illustrated and described in detail in the drawings and the description above, such illustrations and description should be considered as given by way of illustration or example and not restrictive.
    On reading the present description, other modifications will appear to those skilled in the art. Such modifications may involve other features which are already known in the art and which can be used in place of or in addition to the features already described herein.
    The variations of the embodiments described can be understood and carried out by a person skilled in the art, from a study of the drawings, the description and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "one" or "one" does not exclude a plurality of elements or steps. The mere fact that certain characteristics are cited in dependent claims which are different from each other does not mean that a combination of these measures cannot be used to advantage.
    No reference sign in the claims should be interpreted as limiting the scope.
    List of reference signs [0071] - 100 VCSEL device [0072] 105 first electrical contact [0073] 110 substrate [0074] 112 lens structure 112 [0075] 115 first distributed Bragg reflector [0076] 120 active layer [0077 ] 123 current confinement layer [0078] 124 light emission zone [0079] 125 bipolar phototransistor with distributed heterojunction [0080] 127 current spreading layer [0081] 128 active zone [0082] 130 second Bragg reflector distributed [0083] 132 guide structure [0084] 135 second electrical contact [0085] 300 optical sensor [0086] 310 transmission window [0087] 315 emitted laser light [0088] 317 reflected laser light [0089] 319 control signal [ 320 control circuit [0091] 350 photodetector [0092] 360 evaluator [0093] 380 mobile communication device [0094] 410 step of supplying a substrate [0095] 420 step of supplying a first distributed Bragg reflector [009 6] 430 step of supplying an active layer [440] step of providing a second distributed Bragg reflector [0098] 450 step of providing a first electrical contact [0099] 460 step of providing a second electrical contact [0100] 470 step of supplying a guide structure.
    权利要求:
    Claims (1)
    [1" id="c-fr-0001]
    [Claim 1] [Claim 2] [Claim 3]
    claims
    A Vertical Cavity Surface Emission Laser device (100), wherein the Vertical Cavity Surface Emission Laser device (100) includes a first electrical contact (105), a substrate (110), a second electrical contact (135) and an optical resonator, the optical resonator is arranged on a first side of the substrate (110), the optical resonator comprises a first reflecting structure comprising a first distributed Bragg reflector (115), a second reflecting structure comprising a second reflector of distributed Bragg (130), an active layer (120) arranged between the first reflecting structure and the second reflecting structure and a guide structure (132), in which the guide structure (132) is arranged to define a first maximum of relative intensity of an intensity distribution in the active layer (120) at a first lateral position of the optical resonator so a first light emitting area (124) is provided, in which the guide structure (132) is arranged to define at least a second relative intensity maximum of the intensity distribution in the active layer (120) in a second lateral position of the optical resonator so that a second light-emitting area (124) is provided, in which the guide structure (132) is further arranged to reduce an intensity of the intensity distribution between the at least two light emitting zones (124) during the operation of the Vertical Cavity Surface Emitting Laser device (100), and in which the guide structure (132) is arranged in a stack of layers of the first distributed Bragg reflector ( 115) or the second distributed Bragg reflector (130).
    A Vertical Cavity Surface Emitting Laser device (100) according to claim 1, wherein the guide structure (132) is arranged within a stack of layers of the first distributed Bragg reflector (115) or the second Bragg reflector distributed (130) in a vertical direction from the Vertical Cavity Surface Emission Laser device (100).
    A Vertical Cavity Surface Emission Laser device (100) [Claim 4] [Claim 5] [Claim 6] [Claim 7] [Claim 8] [Claim 9] according to claim 1 or 2, wherein the structure of guide (132) is arranged to reduce an intensity of at least one optical mode contributing to at least one of the first and second relative intensity maxima outside of at least the first or the second light-emitting zone (124 ) so that a lateral extent of the light emitting areas (124) is related to the respective lateral position of the optical resonator.
    A Vertical Cavity Surface Emission Laser device (100) according to any one of the preceding claims, wherein the guide structure (132) is arranged to provide a lateral variation of a reflectivity of the first reflecting structure or of the second reflecting structure parallel to the active layer (120). A Vertical Cavity Surface Emission Laser device (100) according to any one of the preceding claims, wherein the guide structure (132) is arranged in the optical resonator and completely enveloped therein.
    A Vertical Cavity Surface Emission Laser device (100) according to any one of the preceding claims, wherein the guide structure (132) comprises a thickness variation of at least one layer of the first Bragg reflector distributed (115) or the second distributed Bragg reflector (130).
    A Vertical Cavity Surface Emission Laser device (100) according to any one of the preceding claims, wherein the guide structure (132) comprises a lateral variation of a reflectivity of the first electrical contact (105) or the second electrical contact (130).
    A Vertical Cavity Surface Emitting Laser device (100) according to any one of the preceding claims, wherein the guide structure (132) comprises oxidized regions in at least one layer of the first distributed Bragg reflector (115) or the second distributed Bragg reflector (130), in which the oxidized regions are arranged to reduce the intensity between the light emitting regions (124).
    A Vertical Cavity Surface Emitting Laser device (100) according to any one of the preceding claims, wherein the optical resonator comprises a bipolar distributed heterojunction phototransistor (125), the bipolar distributed heterojunction phototransistor (125) comprises a collector layer (125a), a photo20 layer [Claim 10] [Claim 11] [Claim 12] [Claim 13] [Claim 14] [Claim 15] sensitive (125c), a base layer (125e) and an emitting layer (125f), the bipolar distributed heterojunction phototransistor (125) being arranged so that there is an optical coupling between the active layer (120) and the bipolar distributed heterojunction phototransistor (125) to ensure containment of active carriers at the means of the distributed heterojunction bipolar phototransistor (125); in particular in which the guide structure (132) is arranged outside a current flow which can be supplied by means of the first electrical contact (105) and the second electrical contact (135) during the operation of the device Vertical Emission Surface Laser (100).
    A Vertical Cavity Surface Emission Laser device (100) according to any one of the preceding claims, wherein the guide structure (132) is arranged to provide on the lateral cross section of the regions of the optical resonator an effective optical length allowing resonant laser operation interrupted by regions having a different effective optical length inhibiting laser operation.
    A Vertical Cavity Surface Emitting Laser device (100) according to any one of the preceding claims, wherein the guide structure (132) is arranged to provide local current confinement at the light emitting areas (124 ).
    A Vertical Cavity Surface Emission Laser device (100) according to any one of the preceding claims, wherein the optical resonator comprises an optical cavity extended through the substrate (110), and wherein the guide structure (132 ) comprises a lateral structuring of a second side of the substrate (110) opposite to the first side of the substrate (110).
    An optical sensor (300) comprising the Vertical Cavity Surface Emitting Laser device (100) according to any one of the preceding claims.
    A mobile communication device (380) comprising at least one optical sensor (300) according to claim 13.
    A method of manufacturing a Vertical Cavity Surface Emission Laser, the method comprising the steps of: providing a first electrical contact (105), providing a substrate (110), providing a first reflector Distributed Bragg (115), providing an active layer (120), providing a second distributed Bragg reflector (130), providing a second electrical contact (135), providing a guide structure (132) which is arranged to define a first relative intensity maximum of an intensity distribution in the active layer (120) at a first lateral position of the optical resonator so that a first light-emitting area (124) is provided, the guide structure (132) being arranged to define at least a second relative intensity maximum of the intensity distribution in the active layer (120) in a second lateral position of the optical resonator so that a second the light emitting area (124) is provided, the guide structure (132) being further arranged to reduce an intensity of the intensity distribution between the at least two light emitting areas (124) during operation of the lightning device. Vertical Emission Surface Laser, and the guide structure (132) being arranged in a stack of layers of the first distributed Bragg reflector (115) or the second distributed Bragg reflector (130).
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    同族专利:
    公开号 | 公开日
    CN111699598A|2020-09-22|
    GB2570565A|2019-07-31|
    EP3496216A1|2019-06-12|
    EP3721513A1|2020-10-14|
    WO2019110744A1|2019-06-13|
    US20200303902A1|2020-09-24|
    GB201819993D0|2019-01-23|
    EP3761464A1|2021-01-06|
    DE102018131615A1|2019-06-13|
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    法律状态:
    2019-12-19| PLFP| Fee payment|Year of fee payment: 2 |
    2020-05-15| PLSC| Search report ready|Effective date: 20200515 |
    2021-05-14| RX| Complete rejection|Effective date: 20210407 |
    优先权:
    申请号 | 申请日 | 专利标题
    EP17206157.4A|EP3496216A1|2017-12-08|2017-12-08|Segmented vertical cavity surface emitting laser|
    EP17206157.4|2017-12-08|
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