• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
  • 法律状态
  • 优先权
    • 专利摘要:
    Method for characterizing an ultra-short pulse, comprising: delivering a reference pulse of known duration to a first detector with a prohibited band less than the photon energy of the pulse to be characterized and to a second detector with a prohibited band greater than energy per photon of the pulse to be characterized and less than twice the energy per photon of the pulse to be characterized: obtain in said first detector a monophotonic signal of reference Storef proportional to the duration of the reference pulse: obtaining in said second detector a biphotonic reference signalberef proportional to the duration of the reference pulse; send the detectors an ultra-short pulse to characterize; obtaining in said first detector a monophotonic signal Sto proportional to the duration of the ultra-short pulse to be characterized; obtaining in said second detector a biphotonic signal Sbe proportional to the duration of the ultra-short pulse to be characterized; obtaining the duration of the pulse to be characterized from said monophotonic signals, said biphotonic signals and the known duration of the reference pulse. Device for the characterization of an ultrashort pulse. (Machine-translation by Google Translate, not legally binding)
    公开号:ES2724110A1
    申请号:ES201830207
    申请日:2018-03-02
    公开日:2019-09-06
    发明作者:Santos Raúl Montero；Aldama Asier Longarte；Frejo Iker Lamas；Alvarez Iván Vila；Garcia Marcos Fernandez
    申请人:Euskal Herriko Unibertsitatea；Consejo Superior de Investigaciones Cientificas CSIC；Universidad de Cantabria；
    IPC主号:
    专利说明:

    [0001]
    [0002]
    [0003]
    [0004] FIELD OF THE INVENTION
    [0005] The present invention belongs to the field of laser devices and the devices used for the characterization of laser radiation. Specifically, the invention is related to devices and methods for determining the duration of ultra-short pulses.
    [0006]
    [0007] BACKGROUND OF THE INVENTION
    [0008] The special characteristics of ultra-short laser pulses, typically of less than 1 PS duration (1ps = 10-12 seconds) have given rise to a multitude of scientific, technological, medical and industrial applications, although their controlled handling is a challenge technological. Due to the dispersion phenomena that suffer this type of pulses in their propagation through the material means, one of the main bottlenecks is related to the diagnosis and control of their temporal characteristics. The duration of these pulses is shorter than the resolution of any electronic instrument, which requires the use of optical methods for its characterization. In the simplest of them, called the intensity autocorrelation (AC) method, the pulse whose temporal profile is to be known is divided into two replicas that interact with a variable optical delay in an optical medium whose response is non-linear with intensity (typically second harmonic generation) (Sager, L. and Oberlé, J. "How to Measure the Characteristics of Laser Pulses" In Claude. Rulliere (Ed.), Femtosecond Laser Pulses -Principies and Experiments, Second Edition (pp 195-222) Springer New York (2005) ISBN-0-387-01769-0). The amplitude of the response of the medium as a function of the delay between the pulses is given by the integral of convolution of the pulses, from which the temporal profile of the pulse can be inferred. This relationship is not unique, so it is necessary to assume that the pulse has a certain shape in its temporal profile (Gaussian, hyperbolic secant squared, Lorentzian, etc.), which implies a certain ambiguity in the result. In an analogous way it can be obtained more detailed information on the temporal profile by cross correlation of the pulse to be diagnosed with a shorter one whose profile is known.
    [0009]
    [0010] However, the complete characterization of a laser pulse not only involves the temporal profile, but also its spectrum and phase. There are more sophisticated techniques that allow access to this information. Among them, the most popular are interferometric autocorrelation (IAC), FROG (Frequency resolved optical gating) and SPIDER (Spectral Phase interferometry for Direct Electric field Reconstruction). The FROG technique consists in collecting the spectrum of the second harmonic wave generated by interacting the two replicas of the pulse in a non-linear medium depending on the delay between the two. Next, using an iterative reconstruction algorithm, the spectral phase of the pulse is extracted (Rick Trebino and Daniel J. Kane, "Using phase retrieval to measure the intensity and phase of ultrashort pulses: frequency-resolved optical gating," J. Opt Soc. Am. A 10, 1101-1111 (1993)). In the SPIDER method, the interaction in the non-linear medium occurs between the pulse to be diagnosed and a replica whose phase has been altered in a controlled manner. In this way, a spectral interferogram is obtained from which pulse phase information can be obtained (C. Iaconis and IA Walmsley, "Spectral phase interferometry for direct electric-field reconstruction of ultrashort optical pulses," Opt. Lett. 23, 792-794 (1998)).
    [0011]
    [0012] In general, the previous methodologies (FROG and SPIDER) and others derived from them, provide accurate information on the temporal distribution of the electromagnetic field, but are technically and economically costly. For this reason, and although the AC only allows to know the time profile with a certain degree of ambiguity and does not provide any information of the phase, this technique remains one of the most commercially extended due to its simplicity. In this sense, the development of new devices and more compact, robust, easy to handle and cheap methods, capable of providing information on the duration of ultra-short pulses in real time, is a key factor in the development of laser technology.
    [0013]
    [0014] Document CN1145788C describes a method for measuring the width of an ultra-short laser pulse emitted by a laser source based on the Talbot effect. This method is an alternative to the AC, FROG or SPIDER techniques mentioned above, which avoids the use of non-linear crystals that are sensitive to wavelength and Polarization. However, like the mentioned techniques, it requires elements necessary for formation and detection of image and moving parts.
    [0015]
    [0016] WO2006 / 103642A2 describes a method and apparatus for determining the width of ultra-short laser pulses by means of a biphotonic absorption detector. The biphotonic absorption detector is formed by a microcavity that has an active region disposed between a first and a second reflector. This method is an alternative to the AC technique in which a biphotonic detector embedded in a microcavity is used. The method has the advantage that it allows simultaneous spectral characterization of the pulse. However, like the AC technique, it requires elements necessary to divide the beam to be characterized to generate a reference beam, progressively vary the relative delay between the two by means of an optical delay line and combine them again to be sent to the detector. linear, which involves a greater number of optical elements and moving parts, which prevent the possibility of a compact realization. In addition, this method does not allow obtaining the duration of the pulses in a single shot.
    [0017]
    [0018] Document CN104880258A describes a method for measuring the width of an ultra-short pulse using several mirrors, a non-linear glass and two pixelated photoelectric detectors (CCD or CMOS) that are used to measure the autocorrelation trace and the spatial profile. This method is a variation of the single trigger intensity autocorrelation technique (A Brun. P Georges, G Le Saux and F Satin. "Single-shot characterization of ultrashort light pulses." J. Phys. D: Appl. Phys. 24 (1991) 1225 1233) in which a second detector is introduced to correct errors derived from the spatial intensity distribution and obtain a more accurate time profile measurement.
    [0019]
    [0020] In sum, the methods proposed in the previous documents involve measurement with temporal resolution, based on autocorrelation techniques, in which the pulse to be diagnosed is divided into two replicas by means of a beam splitter. One of these replicas is sent to a moving mirror and the other to a fixed one. Then both replicas are combined again (in another or the same beam splitter) so that the variation of the position of the moving mirror allows controlling the relative delay between the pulses when arriving at a detection system with non-linear response to the intensity (typically the combination of a non-linear crystal that generates a radiation, for example of a second harmonic, whose intensity has a non-linear dependence of the incident intensity and a linear detector, or alternatively a biphotonic detector, that is, non-linear).
    [0021]
    [0022] Therefore, there is a need to develop a new device and method for determining the duration of an ultra-short laser pulse, which allows to reduce or eliminate optical elements, moving parts and / or imaging systems, so as to provide a very compact solution. and free of optical alignment.
    [0023]
    [0024] DESCRIPTION OF THE INVENTION
    [0025]
    [0026] The present disclosure provides a new device and method for determining in real time the duration of an ultrashort laser pulse. The pulse duration is determined by simultaneous detection in two detectors: one with a linear response and the other with a non-linear response to intensity. That is, the pulse duration is obtained from the simultaneous measurement of the signal produced by an ultra-short laser pulse in the two aforementioned detectors.
    [0027]
    [0028] In the context of the present invention, "real time" means a time within a range that varies between a lower value Vmin and a higher value Vmax. The higher value Vmax may be equal to or less than, for example, 5 minutes, such as equal to or less than 3 minutes, or equal to or less than 1 minute, or equal to or less than 10 seconds, or equal to or less than 1 second, taking into account current technology, the lower value Vmin may be, of non-limiting form, equal to or greater than 1 ^ s (microsecond, 10 "6 seconds), such as equal to or greater than 0.1 ms (millisecond, 10" 3 seconds), or equal to or greater than 1 ms, or equal or greater than 50 ms, or equal to or greater than 100 ms In embodiments of the invention, the time value within the range that varies between Vmin and Vmax is less than or equal to the trip time of the ultra-short pulses to be measured. , real-time measurement is understood as the measurement that is made between trip and trip of ultrac pulses ortos.
    [0029]
    [0030] After a simple calibration, the device and method allow to obtain in real time the duration of the ultra-short pulse, its energy, through the reading of the linear detector, and peak power. The linear detector provides a signal proportional to the energy of the pulses. Therefore, its measurement gives energy information per pulse. Peak power is obtained as the energy / pulse duration ratio.
    [0031] The device and method allow to characterize ultra-short laser pulses whose wavelength varies in the range of 200 to 3,000 nm (nanometers, 10-9 meters), such as in the range of 650 to 2,000 nm.
    [0032]
    [0033] The device and method of the invention are capable, based on an electronic measurement, of providing in real time a value of the effective duration of an ultra-short laser pulse, assuming a certain form of its temporal profile. That is, the determination of the pulse duration is based on the approximation according to which the particular form of the function that describes the temporal profile is always the same as that of the pulse resulting from the spectral filtering in the calibration (for example a Gaussian, a Lorentzian, etc.), the width of said function being the only difference between the problem pulse and the reference pulse. Unlike the known measurement methods, based on autocorrelation techniques, which use optical measures in which the temporal profile of the pulse is resolved in time from the interaction with a replica of it at different relative delays, the device and method of the present invention do not perform any measurement with temporal resolution, but not that an approximate duration value is provided, without measuring it in the time domain, but by inferring it through the electronic signal of two detectors. The device of the invention can therefore be seen as a sensor capable of providing an approximate value of the pulse duration. The determination of the pulse duration is indirect and, therefore, approximate. However, it has important advantages over other techniques in those cases where detailed information on the intensity profile and phase is not required. Examples of such advantages are: It provides real-time information (for example of the order of 1 ms), shot by shot; It is much cheaper than any other technique; The device is more compact than the devices of other known solutions; The device can be implemented integrated with a power meter or similar instrument; Its handling is simpler and does not require alignment, or advanced knowledge of optics. Therefore, it is very useful in pulse optimization procedures and as a monitoring system for ultra-short pulse lasers, among others.
    [0034] In a first aspect of the present disclosure, there is provided a method for the characterization of an ultra-short pulse, comprising: transmitting a reference pulse of known duration xref to a first detector having a prohibited band less than the photon energy of the pulse to characterize already a second detector that has a prohibited band greater than the energy per photon of the pulse to be characterized and less than twice the energy per photon of the pulse to be characterized, obtaining in said first detector a monophotonic signal of reference Saref that has a linear relationship with the intensity of the pulse of reference and is proportional to the Tref duration of the reference pulse, obtain in said second detector a biphotonic reference signal Spref that has a non-linear relationship with the intensity of the reference pulse and is proportional to the xref duration of the reference pulse, make reaching said first detector or a third detector that has a prohibited band less than the energy per photon of the pulse to be characterized, and said second detector or a fourth detector that has a prohibited band greater than the energy per photon of the pulse to be characterized and less that twice the energy per photon of the pulse to be characterized, an ultra-short pulse to be characterized, obtain in said pr In this third detector or in said third detector, a monophotonic signal Sa has a linear relationship with the intensity of the ultra-short pulse to be characterized and is proportional to the pulse duration x of the ultra-short pulse to be characterized, obtaining in said second detector or in said fourth detector a biphotonic signal Sp which has a non-linear relationship with the intensity of the ultra-short pulse to be characterized and is proportional to the x-pulse duration of the ultra-short pulse to be characterized, obtaining the x-pulse duration of the pulse to be characterized from said monophotonic signals Saref, Sa, of said biphotonic Spref signals, Sp, and of the known duration xref of the reference pulse.
    [0035]
    [0036] In embodiments of the invention, the reference pulse of known duration xref is obtained by passing the ultra-short pulse to be characterized through a filter that has a bandwidth less than that of the ultra-short pulse to be characterized, so that by reducing the width of the ultra-short pulse band to be characterized, the pulse undergoes a temporary widening until reaching approximately the duration corresponding to the Fourier transform of its spectrum, thus being able to determine its duration xref from the transmission curve or by another characterization, such as a characterization by AC or other technique.
    [0037]
    [0038] In embodiments of the invention, the reference pulse of known duration xref and the ultra-short pulse to be characterized are delivered to the corresponding detectors by means of a beam splitter.
    [0039] In embodiments of the invention, the reference pulse of known duration x ref and the ultra-short pulse to be characterized are sent to the detector that has a prohibited band less than the energy per photon of the pulse to be characterized after being transmitted through the detector that has a prohibited band greater than the energy per photon of the pulse to be characterized and less than twice the energy per photon of the pulse to be characterized.
    [0040]
    [0041] In embodiments of the invention, the duration x pulse of the pulse to be characterized is obtained as follows: X pu k o = xre f (Sp ref / (Sa ref ) 2 ) / (Sp / (Sa) 2 )
    [0042]
    [0043] In embodiments of the invention, the wavelength of the ultra-short pulse to be characterized varies in the range of 200 to 3,000 nanometers.
    [0044]
    [0045] In a second aspect of the present disclosure, a device for the characterization of an ultra-short pulse is provided, comprising: means for obtaining a reference pulse of known duration Xref, a first detector having a prohibited band less than the energy per photon of the pulse to be characterized, a second detector having a prohibited band greater than the energy per photon of the pulse to be characterized and less than twice the energy per photon of the pulse to be characterized, optical means for delivering a pulse or a replica thereof to the first detector and the second detector, so that: when said pulse is the reference pulse of known duration xref, in the first detector a monophotonic signal Saref is obtained with a linear relationship with the intensity of the reference pulse and proportional to the duration Xref of the reference pulse, and in the second detector a biphotonic Spref signal is obtained with a non-linear relationship with the intensity of the pu The reference and proportional to the xref duration of the reference pulse; and when said pulse is the pulse to be characterized, in the first detector a monophotonic signal is obtained Sacon linear relationship with the intensity of the pulse to be characterized and proportional to the duration x pulse of the pulse to be characterized, and in the second detector a biphotonic signal is obtained Sp with a non-linear relationship with the intensity of the pulse to be characterized and proportional to the pulse duration x to be characterized, means for recording said monophotonic signals Saref, Sa and said biphotonic signals Spref, Sp, means for obtaining the pulse duration of the pulse to be characterized from said monophotonic signals Saref, Sa, from said biphotonic signals Spref, Sp, and of the known duration xref of the reference pulse.
    [0046] In a third aspect of the present disclosure, there is provided a device for the characterization of an ultra-short pulse, comprising: optical means for dividing a pulse or a replica thereof into two beams, a first detector having a prohibited band smaller than the energy per photon of the pulse to be characterized and a second detector having a prohibited band greater than the energy per photon of the pulse to be characterized and less than twice the energy per photon of the pulse to be characterized, arranged to receive one of said beams; means for obtaining a reference pulse of known duration xref, arranged between said optical means for dividing a pulse or a replica thereof into two beams, and said first and second detector, such that when said reference pulse of known duration xref, A monophotonic Saref signal is obtained at the first detector with a linear relationship with the intensity of the reference pulse and proportional to the xref duration of the reference pulse, and when said reference pulse of known duration xref arrives at the first second detector, a Spref biphotonic signal with a non-linear relationship with the intensity of the reference pulse and proportional to the xref duration of the reference pulse; a third detector that has a prohibited band less than the energy per photon of the pulse to be characterized and a fourth detector that has a prohibited band greater than the energy per photon of the pulse to be characterized and less than twice the energy per photon of the pulse to be characterized , arranged to receive the other one of said beams, so that when said pulse to be characterized reaches the third photodetector, a monophotonic signal is obtained with a linear relationship with the intensity of the pulse to be characterized and proportional to the duration of the pulse to be characterized, and when said pulse to be characterized arrives at the fourth detector a biphotonic signal Sp is obtained with a non-linear relationship with the intensity of the pulse to be characterized and proportional to the pulse duration x to be characterized, means for recording said monophotonic signals Saref, Sa and said biphotonic signals Spref , Sp, means for obtaining the pulse duration x pulse to be characterized from said signal The monophotonic Saref, Sa, of said biphotonic signals Spref, Sp, and of the known duration xref of the reference pulse.
    [0047] In embodiments of the invention, the means for obtaining the reference pulse of known duration xref is a filter that has a bandwidth less than that of the ultra-short pulse to be characterized, so that when crossing the filter, the bandwidth is reduced of the ultra-short pulse to characterize, experiencing the pulse a widening temporal until reaching approximately the duration corresponding to the Fourier transform of its spectrum, thus being able to determine its duration xref from the transmission curve or by another characterization, such as a characterization by AC or another technique.
    [0048]
    [0049] In embodiments of the invention, the duration x pulse of the pulse to be characterized is obtained as follows: X pu k o = xre f (Sp ref / (Sa ref ) 2 ) / (Sp / (Sa) 2 )
    [0050]
    [0051] In embodiments of the invention, the means for recording said monophotonic signals Saref, Sa and said biphotonic signals Spref, Sp, are an oscilloscope or an analog / digital converter.
    [0052]
    [0053] In embodiments of the invention, the means for obtaining the pulse duration of the pulse to be characterized is a signal processing module.
    [0054]
    [0055] In embodiments of the invention, the optical means is a beam splitter that has a reflection / transmission ratio such that more than 50% of the light is sent to the second detector.
    [0056]
    [0057] In embodiments of the invention, the wavelength of the ultra-short pulse to be characterized varies in the range of 200 to 3,000 nanometers.
    [0058]
    [0059] In a fourth aspect of the present disclosure, an energy or power measuring device is provided comprising a device such as those described above.
    [0060]
    [0061] Compared to conventional ultra-short laser pulse characterization methods and devices, in which a complete measurement of the temporal profile (and phase, in some cases) is carried out by autocorrelation techniques, the method and device of the present disclosure allow obtaining the duration of the pulses assuming a certain form of their temporal profile, using two detectors, different from those of known proposals. The proposed method and device do not perform any measurement with temporal resolution, but not that an approximate value of the duration is provided, without measuring it in the time domain, inferring it through the electronic signal of the two detectors and therefore eliminating optical elements , moving parts and / or imaging systems. Therefore, the device can be very compact, allowing its manufacture in about mm3 or even on a smaller scale, and practically free of
    [0062]
    [0063]
    [0064] optical alignment The device can be seen as a sensor capable of providing an approximate value of the pulse duration.
    [0065]
    [0066] Additional advantages and features of the invention will be apparent from the following detailed description and will be pointed out in particular in the appended claims.
    [0067]
    [0068] BRIEF DESCRIPTION OF THE FIGURES
    [0069]
    [0070] To complement the description and in order to help a better understanding of the characteristics of the invention, according to an example of practical implementation thereof, a set of figures in which with character is accompanied as an integral part of the description Illustrative and not limiting, the following has been represented:
    [0071]
    [0072] Figure 1 illustrates a schematic of an electronic device based on a two-detector system (dual detection) for determining the duration of ultra-short laser pulses, in accordance with a possible embodiment of the invention.
    [0073]
    [0074] Figure 2 illustrates a schematic of an alternative electronic device, also based on a dual detection system for determining the duration of ultra-short laser pulses, in accordance with another possible embodiment of the invention.
    [0075]
    [0076] Figure 3 illustrates a schematic of an alternative electronic device, also based on a dual detection system for determining the duration of ultra-short laser pulses, in accordance with another possible embodiment of the invention.
    [0077]
    [0078] Figure 4 illustrates a scheme of an alternative electronic device, also based on a dual detection system for determining the duration of ultra-short laser pulses, in accordance with another possible embodiment of the invention.
    [0079]
    [0080] Figure 5 shows the autocorrelation trace of a 1300 nm problem pulse and the autocorrelation trace of the reference pulse obtained by spectral filtering of the previous one.
    [0081]
    [0082] Figure 6 shows the autocorrelation trace of a 800 nm problem pulse and the autocorrelation trace of the reference pulse obtained by spectral filtering of the previous one.
    [0083] Figure 7 shows the signal produced in the detectors of the embodiment of Figure 1 by a pulse of 1300 nm.
    [0084]
    [0085] Figure 8 shows the signal produced in the detectors of the embodiment of Figure 4 by a pulse of 800 nm.
    [0086]
    [0087] Figure 9 shows a comparison between the results of the characterization of ultra-short laser pulses by this invention and the AC technique.
    [0088]
    [0089] DESCRIPTION OF A WAY TO CARRY OUT THE INVENTION
    [0090]
    [0091] In this text, the term "comprises" and its derivations (such as "understanding", etc.) should not be understood in an exclusive sense, that is, these terms should not be construed as excluding the possibility that what is described and defined may include elements, additional stages, etc.
    [0092]
    [0093] In the context of the present invention, the term "approximately" and terms of your family (such as "approximate", etc.) should be interpreted as indicating values very close to those accompanying said term. That is, a deviation within reasonable limits with respect to an exact value should be accepted, because a person skilled in the art will understand that such deviation from the indicated values may be inevitable due to inaccuracies of measurement, etc. The same applies to the terms "ones", "around" and "substantially".
    [0094]
    [0095] The following description should not be taken in a limited sense, but are provided solely for the purpose of describing broad principles of the invention. The following embodiments of the invention will be described by way of example, with reference to the figures cited above, which show apparatus and results according to the invention.
    [0096]
    [0097] Figure 1 schematizes an electronic device 1 for determining the duration of ultra-short laser pulses according to a possible embodiment of the invention. The device 1 has two detectors 102, 103: One of the detectors 103 has a band prohibited (in English, bandgap) less than the energy per photon of the pulse to be measured, so that upon receiving the ultra-short laser pulse to be measured, this detector 103 produces a monophotonic signal Sa proportional to the intensity I and the effective pulse duration At in the frequency range or working wavelengths. With In other words, this detector 103 has a linear response to the intensity of the pulse to be measured in said frequency range or working wavelengths. As a detector 103 with a linear response to the pulse intensity, for example, a non-limiting form can be used a germanium photodiode (Ge), an indium-gallium arsenide photodiode (InGaAs), a pyroelectric pulse detector intense, or a pixelated detector, such as CCD or CMOS or others. The other detector 102 has a prohibited band greater than the energy per photon of the pulse to be measured and less than twice the energy per photon of the pulse to be measured, so that upon receiving the ultra-short laser pulse to be measured, this detector 102 produces a signal Sp corresponding to a biphotonic absorption proportional to the duration of the At pulse and its intensity squared I2 in the frequency range or working wavelengths. In other words, this detector 102 has a non-linear response to the intensity of the pulse to be measured in said frequency range or working wavelengths. As a detector 102 with non-linear response to the pulse intensity, for example, non-limitingly, a silicon photodiode (Si), a pixelated detector, such as CMOS, CCD or others, or, in general, any other that provides an appreciable nonlinear response and whose linear response is negligible in the desired spectral range. In Figure 1, the ultra-short laser pulse to be measured has been identified with reference 10. It is a pulse of duration less than 1 PS (1ps = 10-12 seconds) and a central wavelength in the range 200 to 3,000 nm. The laser device, not illustrated, with which the pulse 10 has been produced, is outside the scope of the present invention. Note that depending on the response of the detectors, a pulse wavelength should be selected in a more limited range. For example, if a silicon photodiode (Si) is used as a non-linear detector, the central wavelength of the pulse must be in the range 1,150-2,000 nm. In the same way, if it is desired to characterize an ultra-short pulse of a certain wavelength, as a linear detector a detector that provides a linear response at that wavelength must be selected, and as a non-linear detector a detector that provides a response must be selected nonlinear at that wavelength.
    [0098]
    [0099] In the implementation of Fig. 1, in order to deliver radiation 10 to both detectors 102, 103, a beam splitter 101 is used. The arrows at the input and output of the beam splitter 101 indicate the optical path followed by the laser pulse. to diagnose. In embodiments of the invention, in order to obtain a signal to noise ratio
    [0100]
    [0101]
    [0102] suitable in both detectors 102, 103, a beam splitter 101 with a reflection / transmission ratio is chosen such that more than 50% of the light that reaches the splitter is sent to the detector with biphotonic response (i.e., to detector 102). It is necessary to achieve an appropriate signal-to-noise ratio in both detectors, especially in the non-linear one, which normally produces less signal. For example 100 nJ for a cross section of the 2 mm FWHM beam.
    [0103]
    [0104] Alternatively, it is possible to use an electronic device configuration 2 for the determination of the duration of ultra-short laser pulses such as that shown in Figure 2, in which the pulses reach the detector with linear response 203 after being transmitted through a non-linear detector 202. In this configuration, everything indicated in the description of figure 1 relative to detectors 102, 103 is applicable to detectors 202, 203, respectively, of figure 2. This second solution allows for even more compact designs. As can be seen in Figure 2, this configuration does not need a beam splitter.
    [0105]
    [0106] Device 1-2 also includes the optics 104, 204 necessary to obtain a reference measurement. In a possible embodiment, a filter 104, 204 is used which can be bandpass or other, to reduce the pulse bandwidth 10, 20 to characterize and thus obtain a reference measurement of known duration. This optics 104, 204 for calibration is removed to perform the pulse measurements to be characterized.
    [0107]
    [0108] Figure 3 illustrates another alternative embodiment of electronic device 3 for determining the duration of ultra-short laser pulses, in which the beam is divided by a beam splitter 301, similar to the beam splitter 101 of Figure 1, for measurement Simultaneous reference in two systems consisting of two detectors each: in each of the outputs of the beam splitter 301 there is a detector with non-linear response 302, 302 'followed by a detector with linear response 303, 303'. That is, each pair formed by a non-linear detector followed by a linear detector has a configuration similar to that of Figure 2, that is, the pulses reach the detector with linear response 303 (or 303 ') after being transmitted through a non-detector linear 302 (or 302 '). In this configuration, everything indicated in the description of Figure 1 relating to detectors 102, 103 is applicable to detectors 302, 302 ', 303, 303', respectively, of Figure 3. In front of one of the systems or set of detectors (302, 303 or 302 ', 303') a 304 filter is installed, for example by passage of band, to get the calibration. In this embodiment the reference measurement is carried out simultaneously with the measurement of the problem pulse, so, unlike the previous implementations, in this one the filter 304 is not removed once the calibration has been carried out.
    [0109]
    [0110] In implementations in which the Spdel biphotonic absorption signal detector 102, 202, 302, 302 'is low, either because the biphotonic absorption coefficient of the nonlinear detector 102, 202, 302, 302' is low, or because the Pulse intensity to be characterized 10 is low, the device may include optics to focus radiation 10 on detector 102, 202, 302, 302 '. Non-limiting examples of optical elements that can be used for this purpose are a spherical mirror, a parabolic mirror, a lens, or others. Figure 4 shows an electronic device 4 for determining the duration of ultra-short laser pulses, suitable for these circumstances. This embodiment is especially suitable for characterizing the duration of ultra-short laser pulses in the region of 650-1150 nm.
    [0111]
    [0112] In Figure 4, in addition to a beam splitter 401 to deliver to each of the detectors a replica of the pulse to be measured with the appropriate intensity, and two detectors 402, 403 (detector 403 that presents a linear response to the intensity of the pulse to be measured and detector 402 presenting a non-linear response to the intensity of the pulse to be measured) configured as in figure 1, a mirror 407 is included, in this case spherical, to focus the radiation on the detector 402. Note that in Any of the above configurations (Figures 1-3) can be used optics to focus the radiation on the nonlinear detector. As mentioned, the mirror 407 (concave in this embodiment) is necessary when the intensity of the beam or non-linear absorption coefficient is low and a good signal / noise ratio does not occur in the non-linear detector 402.
    [0113]
    [0114] In addition, in the embodiment of Figure 4 an attenuator 408 is used in front of the other detector 403, to prevent excessive radiation from reaching and keep the signal within the linearity range of the detector (for example, <1 V). Note that in any of the previous configurations (Figures 1-3) an attenuator can be used in front of the linear detector. In embodiments of the invention, the need to include attenuator 408 can be avoided by employing a beam splitter with a higher reflection / transmission ratio. For example, if a beam splitter with an 82/18 ratio is used, attenuator 408 may be necessary. If, for example, a beam splitter with
    [0115]
    [0116]
    [0117] a 99/1 ratio, operation without the attenuator 408 would be possible. As a detector 403 with a linear response to the pulse intensity, for example, non-limitingly, a silicon photodiode (Si), a germanium photodiode ( Ge), an indium gallium arsenide photodiode (InGaAs), a pyroelectric detector for intense pulses or a pixelated detector, such as CCD or CMOS or others. As detector 402 with non-linear response to pulse intensity, for example, a gallium phosphorus photodiode (GaP), a silicon carbide photodiode (SiC), a pixelated detector, such as CCD or CMOS or others, or any other that provides an appreciable nonlinear response and whose linear response is negligible in the range of the wavelength of the pulse to be characterized.
    [0118]
    [0119] The method of measuring the duration of an ultra-short laser pulse requires a prior reference measurement of a pulse of known duration. For this, the device 1-4 also includes the optics 104, 204, 304, 404 necessary to obtain said reference measurement. In a possible embodiment, a filter 104, 204, 304, 404 is used, which can be bandpass or other, to reduce the pulse bandwidth 10 to be characterized and thus obtain a reference measurement of known duration . In the implementations of Figures 1, 2 and 4, the filter 104, 204, 404 is arranged in the optical path before the beam splitter 101, 404 in Figures 1 and 4 (in Figure 2 there is no beam splitter, whereby the filter is arranged between the light source, not illustrated, and the first detector 202), and is chosen, for example, with a bandwidth between 4 and 20 times less than that of the pulse to be measured 10. For example, filter 104, 204, 404 is chosen with a bandwidth between 4 and 15 times less, such as between 8 and 15 times less. In this way, by reducing the pulse bandwidth (for example of the pulse to be measured 10), the pulse undergoes a temporary widening until reaching approximately the duration corresponding to the Fourier transform of its spectrum, thus being able to determine its duration and ref from the transmission curve or by another characterization, such as a characterization by AC or another technique. The arrows that appear in figures 1, 2 and 4 next to element 104, 204, 404 indicate that said element has to be inserted in the path of the beam to perform the calibration and then remove it to measure the duration of the problem pulses. The validity of the calibration can be extended for hours or even days, provided that beam characteristics such as spatial profile, wavelength or alignment are not modified.
    [0120]
    [0121]
    [0122] Device 1-4 also includes an electronic means 105, 205, 305, 405 for recording and digitizing the signals of both detectors 102, 103 (or 202, 203; or 302, 303, 302 ', 303', or 402, 403 ). This electronic medium 105-405 may be, for example, an oscilloscope or an analog / digital converter, which may include memory means for storing the recorded signals. Finally, the device 1-4 has a processing means 106, 206, 306, 406 to process the recorded signals from the electronic medium 105-405. The processing medium 106-406 can be implemented by a processor or set of processors, to execute the algorithm to obtain the pulse duration from the readings of the two detectors 102, 103 (or 202, 203; or 302, 303, or 402, 403) and the reference measurement (in the implementation of Figure 3, obtained with additional detectors 302 ', 303'). Memory media external to the electronic medium 105-405 can be used alternatively, for example included in the processing medium 106-406 or external to it, to store the recorded signals and the results of algorithm execution, or any other data that needs to be to stock.
    [0123]
    [0124] When a silicon photodiode is used as a non-linear detector, the implementation of Figure 1 (and Figures 2-3, if similar detectors are used) is suitable for determining the duration of a laser pulse whose wavelength varies in the range of 1,150-2,000 nm (nanometers, 10 "9 meters). The operating range is determined by the bandgap of the detectors. Note that the optical configuration chosen depends mainly on the intensity of the beams and the absorption coefficients. when a gallium phosphor photodiode is used as a non-linear detector, the implementation of Figure 4 is adequate to determine the duration of a laser pulse whose wavelength varies in the range of 650-1,150 nm. The concave mirror is necessary for increase the signal of the non-linear detector A beam of greater intensity (for example 100 times more intense) would not require focusing optics The attenuator is necessary to reduce the intensity of the beam that reaches the linear tector
    [0125]
    [0126] In any of the implementations, the method for determining the duration of an ultra-short laser pulse is performed as follows:
    [0127]
    [0128] Step 1. First, a reference measure must be taken. For this, filter 104, 204, 404, for example band pass filter, is inserted in the path of the beam 10, 20, 40 of the pulse to be measured, which produces a stretch of the beam until reaching the duration and ref. Figures 5 and 6 show the autocorrelation (AC) trace, obtained by means of an intensity autocorrelator, corresponding to the pulse 10, 40 (in Figure 5, for example 1300 nm, using the implementation of Figure 1; in Figure 6, for example 800 nm, using the implementation of Figure 4) when its duration corresponds to the Fourier transform limit (LTF) (black dots), and the reference pulse of the filtrate by means of filter 104, 404 ( gray dots) The radiation of this stretched beam is conducted by the beam splitter to the two detectors: In Figure 1, by the beam splitter 101 to the detectors 102, 103; the same occurs in Figure 2, without a beam splitter, passing first through detector 202 and then through detector 203; in figure 4 by the beam splitter 401 and additional optical elements 407, 408, towards the detectors 402, 403. In the implementation of figure 3, the reference measurement is taken by a filter 304, for example bandpass , which is permanently located at one of the outputs of the beam splitter 301. That is why twice as many detectors are needed: two for the reference measurement and two for the pulse measurement to be characterized. Upon impacting the stretched beam on the detector 103, 203, 303 ', 403, a linear response is produced therein, that is, a monophotonic signal Saref proportional to the intensity and duration xref of the stretched pulse. Upon impacting the stretched beam on the other detector 102, 202, 302 ', 402, a non-linear response is produced therein, that is, a biphotonic Spref signal proportional to the square intensity of the pulse and the duration and ref of the stretched pulse . These two Saref and Spref signals produced in the linear and non-linear detectors respectively are recorded by electronic means 105-405 and stored in memory. To obtain a quality measure and obtain a good signal-to-noise ratio without exceeding the ranges acceptable by the detectors, the intensity of the beam 10, 20, 30, 40 can be adjusted. By way of example, Figure 7 (upper panel) illustrates the transient from a detector (in this case, a Si photodiode) 102 and generated with a pulse 10 of 1300 nm and 10 nJ with the implementation of Figure 1. The Spref signal is obtained as the integral of said transient. Figure 7 (bottom panel) also illustrates the transient from a detector (in this case, a photodiode of Ge) 103 and generated with a pulse 10 of 1300 nm and 1 nJ with the implementation of Figure 1. The Saref signal is obtains as the integral of said transitory. Similarly, Figure 8 (black line) illustrates the transient from a detector (in this case, a GaP photodiode) 402 and generated with a pulse 40 of 800 nm and 60 nJ focused with a spherical mirror f = 50
    [0129]
    [0130]
    [0131] mm with the implementation of Figure 4. The Spref signal is obtained as the integral of said transient. Figure 8 (gray line) also illustrates the transient from a detector (in this case, a Si photodiode) 403 and generated with a pulse 40 of 800 nm and <1 nJ with the implementation of Figure 4. The Saref signal it is obtained as the integral of said transitory.
    [0132]
    [0133] Once the Saref and Spref reference values are stored in memory, together with the xref value entered by the user, this data is valid as long as the spatial conditions (spatial mode or alignment) of the beam to be characterized do not vary.
    [0134]
    [0135] Step 2. In the embodiments of Figures 1, 2 and 4, the filter 104, 204, 404 (for example band pass filter) is removed, so that the beam 10, 20, 40 that impacts the divider of Beam 101, 401 (or arriving at detector 202 in Figure 2) is the original ultra-short pulse beam whose duration is to be measured, that is, of the pulse to be characterized. In this way, the ultrashort pulse beam radiation is conducted by the beam splitter 101, 401 to the two detectors 102, 103 (402, 403) or directly to the detector 202. Note that in the embodiment of Figure 3, no filter 304 is removed, but, having two sets of detectors in each divided beam, the reference measurement and the pulse to be characterized can be performed simultaneously. When the beam strikes the detector 103, 203, 303, 403, a monophotonic signal Sa is produced therein proportional to the intensity and duration of the Tpuiso pulse, while when the beam strikes the detector 102, 202, 302, 402 , there is a biphotonic signal Sp proportional to the square intensity of the pulse and the pulse duration x pulse. These two Sa and Sp signals are recorded by electronic means 105-405 and stored in memory. It should be noted that removing the filter 104, 204, 404 produces a significant increase in beam intensity 10, 20, 40, since the filter, in addition to reducing the bandwidth, reduces the beam intensity, so that this moment its intensity (of the incident beam) can be adjusted again to maintain the signal in both detectors 102, 103; 202, 203; 402, 403; within the optimal ranges of the detectors.
    [0136]
    [0137] Step 3. In the signal processing medium 106-406 the algorithm is executed by which the pulse duration is obtained, which responds to the following equation:
    [0138]
    [0139] Pulse = Tref (S p ^ S a f 2) / (Sp / (S «) 2)
    [0140]
    [0141]
    [0142] The pulse duration is obtained by software that runs on the 106-406 processor at each laser shot. The linear detector provides a signal proportional to the energy of the pulses. Therefore, its measurement directly provides the energy per pulse (when the detector is calibrated in energy). That is, the energy is proportional to Sa. Peak power is obtained as the energy / pulse duration ratio.
    [0143]
    [0144] The measurement method is indirect since it is assumed that the shape of the temporal profile (Gaussian, hyperbolic secant squared, Lorentzian, etc.) of the problem pulse (pulse to be characterized) is equal to that of the reference pulse generated by spectral filtering ( filter 104, 204, 304, 404). For this reason, the method and device of the invention provide very good results in the case of pulses whose temporal profile shows a simple structure. Specifically, the method and device have important advantages over other solutions in those cases where detailed information on the intensity profile and phase is not required. For example: Provides real-time information, shot by shot. It is cheaper than any other technique. More compact than other alternatives. Its handling is simpler and does not require knowledge of ultrashort pulse optics. Therefore, it is very useful in pulse optimization procedures and as an ultrashort pulse laser monitoring system.
    [0145]
    [0146] Two examples are described below based on the implementations of Figures 1 and 4. The first example has been used to determine the duration of a laser pulse whose wavelength varies in the range of 1150-2000 nm (nanometers, 10-9 meters) and with the second example the duration of a laser pulse whose wavelength varies in the range of 650-1150 nm has been determined.
    [0147]
    [0148] Example 1
    [0149]
    [0150] The device 1 of Figure 1 has been implemented to determine the duration of a laser pulse whose central wavelength is 1300 nm. The following configuration has been chosen: The detector 102 with non-linear response to the pulse intensity is a silicon photodiode (Si). The detector 103 with linear response to the pulse intensity is a germanium photodiode (Ge). A beam splitter 101 is chosen that reflects 90% of the radiation to the silicon photodiode (Si) 102 and transmits the remaining 10% to the germanium photodiode (Ge) 103. The beam splitter 101 has been implemented by
    [0151]
    [0152]
    [0153] a sheet of molten quartz with a partial coating of aluminum (Al), so that it provides a reflection of 90%. Note that sending the reflected beam to the non-linear detector 102 prevents the effects of pulse dispersion due to propagation through the beam splitter 101 from influencing the final result. Optics 104 to reduce the pulse bandwidth to be measured has been implemented by a 10 nm bandpass filter (FWHM). As an electronic means 105 for recording and digitizing the signals of both detectors, a 500MHz bandwidth oscilloscope has been used. To process the data from the oscilloscope and obtain the ultra-short pulse duration, a properly programmed personal computer (PC) 106 has been used to process said data.
    [0154]
    [0155] This configuration was used in the characterization of a laser pulse train with a central wavelength of 1300 nm and a bandwidth of 70 nm from a parametric amplifier pumped with a Ti: sapphire laser at a repetition frequency of 1 KHz (not illustrated). The pulse energy at the input of the device 1 is controlled by a neutral filter (not shown) until an appreciable signal is obtained in both detectors 102, 103, within the linear response range of the Germanium detector (20-200nJ / pulse). The cross section of the beam is 2 mm (FWHM).
    [0156]
    [0157] According to the proposed method, a reference measurement was first obtained with the bandpass filter 104. The duration of the pulse resulting from the filtering i ref was determined from an autocorrelation measurement (250 fs = 250x10 "15 seconds FWHM, see figure 5.) It has been verified that this value i ref is independent (<7% deviation) of the dispersion (GDD) of the pulse 10, at least when it is in the range 0-2000 fs2. It allows to use the pulses of the laser beam to be diagnosed as a reference without having to have previous information on its phase or its duration.The value i ref (250 fs) together with the Spref and Saref averages resulting from 1000 samples of the signals from the detectors 102 and 103 respectively registered by the oscilloscope are stored on the hard disk of PC 106 for later application.
    [0158]
    [0159] The filter 104 is then removed and the Sp and Sa signals of the detectors 102 and 103 corresponding to the pulses to be characterized are recorded in real time. Finally, the duration of problem pulses is obtained in real time (in 10 ms when the signal recording and scanning system 105 is an oscilloscope; this time is reduced to 1 ms using an analog integrator system and a digitizer card to record and digitize the signals) using the PC 106 programmed to process the data from the oscilloscope (Sp and Sa) and the values i ref, Spref and Saref stored in memory such as:
    [0160]
    [0161] Pulse = Tref (S p ^ S a f 2) / (Sp / (S «) 2)
    [0162]
    [0163] The results of this example have been compared with those obtained by means of conventional autocorrelation techniques in the case of pulses of duration in the range 35-300 fs. The results are shown in figure 9 (blades). The ordinate axis represents the pulse duration values obtained with the implementation of Figure 1, as a result of the average measurement of 128 laser pulses, and the abscissa represents the values obtained for the same pulses by intensity autocorrelation. The dashed line is shown as a visual reference.
    [0164]
    [0165] Example 2
    [0166]
    [0167] The device 2 of Figure 4 has been implemented to determine the duration of a laser pulse whose central wavelength of 800 nm. The following configuration has been chosen: The detector 402 with non-linear response to the pulse intensity is a gallium phosphor (Photodiode) (GaP) photodiode. The detector 403 with linear response to the pulse intensity is a silicon photodiode (Si). A beam splitter 401 is chosen that reflects 82% of the radiation to the gallium phosphorus photodiode (GaP) 402 and transmits the remaining 18% to the silicon photodiode (Si) 403. In this case it was necessary to place an attenuator 408 in front of the silicon detector (Si) 403 until the maximum signal is set to around 100-200mV). An aluminum spherical mirror (Al) 407 with f = 5 cm was also placed to increase the intensity of the beam over the gallium-phosphorus detector (GaP) 402 to favor biphotonic absorption in this detector 402. The beam splitter 401 is It has been implemented using a sheet of molten quartz with a partial coating of aluminum (Al), so that it provides a reflection of 82%. Optics 404 to reduce the bandwidth of the pulse to be measured has been implemented by means of a 404 nm 3-band pass filter. As an electronic means 405 for recording and digitizing the signals of both detectors, a 500MHz bandwidth oscilloscope has been used. To process the data from the oscilloscope and obtain the Ultrashort pulse duration, a properly programmed personal computer (PC) 406 has been used to process such data.
    [0168]
    [0169] This configuration was used in the characterization of a laser pulse train with a central wavelength of 800 nm and a bandwidth of 25 nm from a Ti: sapphire laser at a repetition frequency of 1 KHz (not shown) . The pulse energy at the input of device 4 (10-100nJ / pulse) is controlled by a neutral filter (not shown) until sufficient but not excessive signal is obtained in both detectors 402, 403 (20-200 mV). The cross section (diameter) of the beam is 8 mm (FWHM) but is reduced to 3 mm by a circular aperture (iris) to accommodate the size of the detectors used (3.6 mm x 3.6 mm).
    [0170]
    [0171] According to the proposed method, a reference measurement was first obtained with the bandpass filter 404. The duration of the pulse resulting from the filtering i ref (385 fs = 385 x 10 "15 seconds, FWHM, see figure 6 ) was determined from an autocorrelation measurement.The value i ref together with the Spref and Saref averages resulting from 1000 samples of the signals from the detectors 402 and 403 respectively recorded by the oscilloscope 405 are stored on the hard disk of the PC 406 for later application.
    [0172]
    [0173] The filter 404 is then removed and the Sp and Sa signals of the detectors 402 and 403 corresponding to the pulses to be characterized are recorded in real time.
    [0174]
    [0175] Finally, the duration of problem pulses is obtained in real time (in 10 ms with the described oscilloscope-PC system; this time is reduced to 1 ms using a system of analog integrators for the signals of the detectors, a digitizer to record the values of the integration and a PC for the storage and processing of data) by means of the PC 406 programmed to process the data coming from the oscilloscope (Sp and Sa) and the values i ref, Spref and Saref stored in memory as:
    [0176]
    [0177] T pulse = T ref (S p ^ S ^) 2) / (S p / (S a ) 2)
    [0178]
    [0179] The results of this example have been compared with those obtained by means of a commercial autocorrelator in the case of pulses of duration in the range 35-300 fs. The results are shown in figure 9 (points and circles). The ordinate axis
    [0180]
    [0181]
    [0182] represents the pulse duration values obtained with the implementation of figure 4, as a result of the average of the measurement of 128 laser pulses, and that of abscissa represents the values obtained for the same pulses by intensity autocorrelation. The dashed line is shown as a visual reference.
    [0183] In both examples, pulse duration values were obtained with an accuracy of 20%, regarding the autocorrelation measurements. The difference with respect to autocorrelation measures depends fundamentally on the deviations of the temporal profile of the pulse with respect to the considered profile and on the dispersion of the pulse in the material that composes the non-linear detector (Si and GaP). That is, the determination of the pulse duration is based on the approximation that the particular form of the function that describes the temporal profile is always the same as that of the pulse resulting from the spectral filtering in the calibration (for example a Gaussian, a lorentzina, etc.), the width of said function being the only difference between the problem pulse and the reference pulse. Deviations from this behavior are the root cause of the error in determining the duration of the pulses. The standard deviation in the measurements (in 128 samples) is 5%.
    [0184]
    [0185] In conclusion, the proposed device and method provide very good results in the case of pulses whose temporal profile shows a simple structure. Specifically, the method and device have important advantages over other solutions in those cases where detailed information on the intensity profile and phase is not required.
    [0186]
    [0187] The invention is obviously not limited to the specific embodiment (s) described (s), but also encompasses any variation that may be considered by any person skilled in the art (for example, in relation to the choice of materials, dimensions, components, configuration, etc.), within the general scope of the invention as defined in the claims.
    权利要求:
    Claims (15)
    [1]
    1. A method for the characterization of an ultra-short pulse (10, 20, 30, 40), which comprises:
    sending a reference pulse of known duration xref to a first detector (103, 203, 303 ', 403) that has a prohibited band less than the energy per photon of the pulse to be characterized (10, 20, 30, 40) and to a second detector (102, 202, 302 ', 402) which has a prohibited band greater than the energy per photon of the pulse to be characterized and less than twice the energy per photon of the pulse to be characterized,
    obtaining in said first detector (103, 203, 303 ′, 403) a monophotonic reference signal Saref that has a linear relationship with the intensity of the reference pulse and is proportional to the duration and ref of the reference pulse,
    obtaining in said second detector (102, 202, 302 ’, 402) a biphotonic reference signal Spref that has a non-linear relationship with the intensity of the reference pulse and is proportional to the duration and ref of the reference pulse,
    sending said first detector (103, 203, 403) or a third detector (303) having a prohibited band less than the energy per photon of the pulse to be characterized, and said second detector (102, 202, 402) or a quarter detector (302) having a prohibited band greater than the energy per photon of the pulse to be characterized and less than twice the energy per photon of the pulse to be characterized, an ultra-short pulse to characterize (10, 20, 30, 40),
    obtaining in said first detector (103, 203, 403) or in said third detector (303) a monophotonic signal Sa that has a linear relationship with the intensity of the ultra-short pulse to be characterized (10, 20, 30, 40) and is proportional to the duration and pulse of the ultra-short pulse to be characterized (10, 20, 30, 40),
    obtaining in said second detector (102, 202, 402) or in said fourth detector (302) a biphotonic signal Sp that has a non-linear relationship with the intensity of the ultra-short pulse to be characterized and is proportional to the duration and pulse of the ultra-short pulse to be characterized (10, 20, 30, 40),
    2
    obtaining the duration and pulse of the pulse to be characterized (10, 20, 30, 40) from said monophotonic signals Saref, Sa, of said biphotonic signals Spref, Sp, and of the known duration Tref of the reference pulse.
    [2]
    2. - The method of claim 1, wherein said reference pulse of known duration xref is obtained by passing the ultra-short pulse to be characterized (10, 20, 30, 40) through a filter (104, 204, 304 , 404) which has a bandwidth less than that of the ultra-short pulse to be characterized (10, 20, 30, 40).
    [3]
    3. - The method of any of the preceding claims, wherein said reference pulse of known duration Tref and said ultra-short pulse to be characterized (10, 30, 40) are sent to the corresponding detectors by means of a beam splitter (101 , 301, 401).
    [4]
    4. - The method of any of claims 1 or 2, wherein said reference pulse of known duration i ref and said ultra-short pulse to be characterized (20) are sent to the detector (203) which has a prohibited band less than the energy per photon of the pulse to be characterized after being transmitted through the detector (202) which has a prohibited band greater than the energy per photon of the pulse to be characterized and less than twice the energy per photon of the pulse to be characterized.
    [5]
    5. - The method of any of the preceding claims, wherein the pulse duration x to be characterized is obtained as follows:
    Pulse = Tref (S p ^ S a f 2) / (Sp / (S «) 2)
    [6]
    6. - The method of any of the preceding claims, wherein the wavelength of the ultra-short pulse to be characterized (10, 20, 30, 40) varies in the range of 200 to 3,000 nanometers.
    [7]
    7. - A device (1, 2, 4) for the characterization of an ultra-short pulse (10, 20, 40), comprising:
    means (104, 204, 404) to obtain a reference pulse of known duration i ref,
    a first detector (103, 203, 403) having a prohibited band less than the energy per photon of the pulse to be characterized (10, 20, 40),
    a second detector (102, 202, 402) having a prohibited band greater than the energy per photon of the pulse to be characterized and less than twice the energy per photon of the pulse to be characterized (10, 20, 40),
    optical means (101, 401,407, 408) to deliver a pulse or a replica thereof to the first detector (103, 203, 403) and the second detector (102, 202, 402), so that: when said pulse is the reference pulse of known duration i ref, in the first detector (103, 203, 403) a Saref monophotonic signal is obtained with a linear relationship with the intensity of the reference pulse and proportional to the xref duration of the reference pulse, and in the second detector (102, 202, 402) a biphotonic Spref signal is obtained with a non-linear relationship with the intensity of the reference pulse and proportional to the duration and ref of the reference pulse; and when said pulse is the pulse to be characterized (10, 20, 40), in the first detector (103, 203, 403) a monophotonic signal is obtained Sacon linear relationship with the intensity of the pulse to be characterized (10, 20, 40) and proportional to the duration and pulse of the pulse to be characterized, and in the second detector (102, 202, 402) a biphotonic signal Sp is obtained with a non-linear relationship with the intensity of the pulse to be characterized (10, 20, 40) and proportional to the duration and pulse of the pulse to be characterized,
    means (105, 205, 405) for recording said monophotonic signals Saref, Sa and said biphotonic signals Spref, Sp,
    means (106, 206, 406) for obtaining the duration and pulse of the pulse to be characterized from said monophotonic signals Saref, Sa, of said biphotonic signals Spref, Sp, and of the known duration and ref of the reference pulse.
    [8]
    8.- A device (3) for the characterization of an ultra-short pulse (30), comprising:
    optical means (301) for dividing a pulse or a replica thereof into two beams,
    a first detector (303 ') having a prohibited band less than the energy per photon of the pulse to be characterized (30) and a second detector (302') that has a prohibited band greater than the energy per photon of the pulse to be characterized and smaller that twice the energy per photon of the pulse to be characterized (30), ready to receive one of these beams;
    means (304) for obtaining a reference pulse of known duration and ref, arranged between said optical means (301) to divide a pulse or a replica thereof into two beams, and said first and second detector (303 ', 302') , so that when said reference pulse of known duration i ref reaches the first detector (303 '), a Saref monophotonic signal is obtained with a linear relationship with the intensity of the reference pulse and proportional to the duration i ref of the reference pulse , and when said reference pulse of known duration i ref, reaches the first second detector (302 '), a biphotonic signal Spref is obtained with a non-linear relationship with the intensity of the reference pulse and proportional to the duration i ref of the reference pulse ;
    a third detector (303) having a prohibited band less than the energy per photon of the pulse to be characterized (30) and a fourth detector (302) that has a prohibited band greater than the energy per photon of the pulse to be characterized and less than two times the energy per photon of the pulse to be characterized (30), arranged to receive the other of said beams, so that when said pulse to be characterized (30) reaches the third photodetector (303), a monophotonic signal Sacon is obtained with linear relationship with the intensity of the pulse to be characterized (30) and proportional to the duration and pulse of the pulse to be characterized, and when said pulse to be characterized (30) reaches the fourth detector (302) a biphotonic signal Sp is obtained with a non-linear relationship with the intensity of the pulse to characterize (30) and proportional to the duration and pulse of the pulse to characterize,
    means (305) for recording said monophotonic signals Saref, Sa and said biphotonic signals Spref, Sp,
    means (306) for obtaining the duration and pulse of the pulse to be characterized from said monophotonic signals Saref, Sa, of said biphotonic signals Spref, Sp, and of the known duration i ref of the reference pulse.
    [9]
    9. The device of any of claims 7 or 8, wherein said means (104, 204, 304, 404) for obtaining the reference pulse of known duration i ref is a filter (104, 204, 304, 404 ) that has a bandwidth less than that of the ultra-short pulse to be characterized (10, 20, 30, 40).
    2
    [10]
    10. The device of any of claims 7 to 9, wherein the duration
    I could characterize the pulse (10, 20, 30, 40) as follows:
    T pulse = T ref (Spref / (Saref) 2) / (Sp / (Sa) 2)
    [11]
    11. The device of any one of claims 7 to 10, wherein said means (105-405) for recording said monophotonic signals Saref, Sa and said biphotonic signals Spref, Sp, are an oscilloscope or an analog / digital converter.
    [12]
    12. - The device of any of claims 7 to 11, wherein said means (106-406) for obtaining the duration and pulse of the pulse to be characterized (10, 20, 30, 40) are a signal processing module .
    [13]
    13. - The device of any of claims 7 to 12, wherein said optical means (101, 401) are a beam splitter that has a reflection / transmission ratio such that more than 50% of the light is sent to the second detector (102, 402).
    [14]
    14. The device of any of claims 7 to 13, wherein the wavelength of the ultra-short pulse to be characterized (10, 20, 30, 40) varies in the range of 200 to 3,000 nanometers.
    [15]
    15. An energy or power measuring device comprising a device according to any of claims 7 to 14.
    2
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    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    CN1317686A|2001-06-01|2001-10-17|中国科学院上海光学精密机械研究所|Method for measuring time duration of ultrashort laser pulse|
    WO2006103642A2|2005-03-30|2006-10-05|The Provost, Fellows And Scholars Of The College Of The Holy And Undivided Trinity Of Queen Elizabeth Near Dublin|A method and apparatus for detecting ultra-short light pulses of a repetitive light pulse signal, and for determining the pulse width of the light pulses|
    EP2075556A1|2007-12-26|2009-07-01|Fastlite|Method and device for measuring the spectral phase or the combined spectral and spatial phase of ultra-brief light pulses|
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