Method and system for measuring gain characteristic parameters of semiconductor laser

Abstract

The invention belongs to the field of semiconductor laser measurement, and particularly discloses a method and a system for measuring gain characteristic parameters of a semiconductor laser. According to the invention, a # imgabs0 #-I curve can be calculated by measuring a U-I characteristic curve of the laser, the value obtained by multiplying the junction voltage by the charge quantity is equal to the difference of the quasi-Fermi level, then a total loss spectrum can be obtained according to the characteristic that the material gain is zero at the quasi-Fermi level, and then the total loss spectrum can be calculated through a measurement spectrum of a certain injection current below a threshold current. Therefore, the mode gain spectrum under the injection current can be extracted, and the gain medium length of the laser can be estimated according to the result of the extracted mode gain spectrum by comparing with a # imgabs1 #-I curve. In the extraction of the gain characteristic parameter, the gain medium length and the end face reflectivity parameter of the semiconductor laser do not need to be known or measured; when the gain is calculated, symmetrical approximation of a gain medium conduction band and a valence band structure is not adopted, and the extracted mode gain spectrum and the total loss spectrum of the laser are relatively accurate.

Description

Technical Field

[0001] The present application belongs to the field of semiconductor laser measurement, and more specifically, relates to a method and system for measuring gain characteristic parameters of a semiconductor laser. Background Art

[0002] The reliability of semiconductor lasers is one of the important issues they face in industrial applications. Although the degradation of semiconductor laser performance can be monitored in a timely manner, the degradation is closely related to the underlying physical mechanisms and parameters of the device. If the underlying physical mechanisms and parameters can be introduced into the design and manufacturing process, appropriate corrective measures can be taken. The gain of a semiconductor laser is one of the important parameters that reflects its underlying physical mechanism. It characterizes the relationship between the material gain of the gain medium in the active region of the semiconductor laser and the change of photon energy, and can reflect the amplification of light of different wavelengths by stimulated radiation through the gain medium by the gain medium. By measuring it, we can not only have a more comprehensive understanding of the characteristics of semiconductor lasers, but also provide an important reference for the selection, combination and application of semiconductor lasers.

[0003] Traditional methods for extracting the net mode gain of FP lasers (Fabry-Perot), such as the Hakki-Paoli method, the Cassidy method, or the Hakki-Paoli method, require the gain medium length of the semiconductor laser resonator and the end reflectivity of the semiconductor laser. In general, these parameters are only known by the original manufacturer and the original design organization, and ordinary users cannot obtain this information. In addition, traditional gain extraction methods cannot decouple the mode gain from the internal loss and can only obtain the net mode gain spectrum. Traditional gain measurement and extraction methods are only applicable to Fabry-Perot lasers.

[0004] For DFB lasers (Distributed Feedback Laser), traditional measurement methods are not applicable. The main reason is that the waveguide grating integrated inside the DFB laser affects the output spectrum. Therefore, there are few reports on the measurement methods of the gain characteristics of DFB lasers. Recently, a method for measuring the gain characteristics of DFB lasers has been reported in the literature, namely the Hakki-Paoli expansion method proposed by M. Vanzi (DOI: 10.3390 / photonics8120542). The core idea of the Hakki-Paoli expansion method is to introduce an additional spectral function H spectrum related to the junction voltage on the basis of the traditional Hakki-Paoli method, and to combine the S spectrum related to the spectrum to achieve the decoupling of the mode gain and the total loss. This measurement method first measures the UI curve to obtain the signal related to the junction voltage. The relevant H spectrum is then measured, and the corresponding spectrum is obtained to get the S spectrum. Since the H spectrum is related to the mode gain spectrum and the absorption spectrum, and the S spectrum is related to the total loss spectrum and the mode gain spectrum, by solving the H spectrum and the S spectrum simultaneously, the total loss spectrum and the absorption spectrum can be obtained, and substituting them into the H spectrum or the S spectrum can obtain the mode gain spectrum. Obviously, since M. Vanzi used the junction voltage and the difference between the quasi-Fermi levels corresponding relationship in the Hakki-Paoli extension method he proposed, and eliminated the influence of the grating. For the measurement of the gain characteristics of DFB lasers, although the method uses an approximation of the symmetric structure of the conduction band and valence band of the gain medium, and the length of the gain medium of the DFB laser needs to be known or measured in advance, this method still has good promotion and reference value. SUMMARY OF THE INVENTION

[0005] Aiming at the defects of the prior art, the purpose of this application is to provide a method and system for measuring the gain characteristic parameters of semiconductor lasers, aiming to solve the problem that the existing measurement methods cannot extract the gain characteristics when the length of the gain medium of the laser is unknown.

[0006] The first aspect of this application relates to a method for measuring the gain characteristic parameters of a semiconductor laser, including: S1. Calculating the junction voltages corresponding to multiple different injection currents below the threshold of the semiconductor laser to be measured; S2. Calculating the difference between the quasi-Fermi levels corresponding to the injection currents based on the junction voltages; S3. According to the characteristic that the material gain is zero at the quasi-Fermi level, determining the total loss values at different photon energies based on the assumed gain medium length, and interpolating to form the total loss spectrum of the semiconductor laser to be measured; S4. According to the measured spectrum of the semiconductor laser to be measured under an injection current below a certain threshold, determining the spectrum containing total loss and mode gain information at this injection current, and calculating the mode gain spectrum at this injection current based on the assumed gain medium length, the spectrum containing total loss and mode gain information at this injection current, and the total loss spectrum formed by interpolation; S5. Adjust the assumed gain medium length and then enter S3 until the condition that "the material gain is zero at the quasi-Fermi level" is satisfied. Take the mode gain spectrum at this time as the measurement result of the gain characteristic parameters, and take the assumed gain medium length at this time as the measurement result of the gain medium length.

[0007] Preferably, step S3 includes the following sub-steps: S31. Obtain the measurement spectra of the semiconductor laser under test at different injection currents below the threshold, where the abscissa represents the wavelength and the ordinate represents the optical power, and calculate the wavelength at which the modal gain is zero based on the difference in quasi-Fermi levels; S32. Map the wavelength at which the modal gain is zero to the measurement spectrum, and determine the peak optical power and valley optical power closest to this wavelength; S33. Calculate the ratio of the peak optical power and valley optical power closest to this wavelength in the spectrum; S34. Use the ratio to inversely obtain the value of the spectrum containing the total loss and modal gain information at the wavelength corresponding to zero modal gain; S35. Calculate the total loss value at the wavelength corresponding to zero modal gain based on the assumed gain medium length and the value of the spectrum containing the total loss and modal gain information at the wavelength corresponding to zero modal gain; S36. Perform interpolation processing on the total loss values at the wavelengths corresponding to zero modal gain under different injection currents below the threshold to obtain the total loss spectrum of the semiconductor laser under test.

[0008] Preferably, the spectral characteristics of the semiconductor laser below the threshold current are expressed as follows:

[0009] Where is the wavelength corresponding to zero modal gain, is the value of the output optical power spectrum at the wavelength ; is the value of the initial power spectrum at the wavelength ; is the spectrum containing the total loss and modal gain information at the wavelength ; is the value of the total loss spectrum at the wavelength ; is the wave number, is the gain medium length, is the internal loss, are the reflectivities of the left and right end faces of the semiconductor laser, respectively.

[0010] Preferably, the inversion formula is as follows:

[0011] Where is the ratio of the peak optical power and valley optical power closest to this wavelength in the spectrum, is the peak optical power near the spectrum at , is the valley optical power near the spectrum at , is the spectrum containing the total loss and modal gain information at the wavelength The value at is the wavelength corresponding to when the modal gain is zero.

[0012] Preferably, step S4 includes the following sub-steps: S41. Obtain the measurement spectrum of the semiconductor laser under test with an injection current below the threshold; S42. Determine the maximum envelope spectrum and the minimum envelope spectrum of the measurement spectrum; S43. Calculate the ratio of the maximum envelope spectrum to the minimum envelope spectrum; S44. Use the ratio of the maximum envelope spectrum to the minimum envelope spectrum to inversely obtain the spectrum containing the total loss and modal gain information at this injection current; S45. Calculate the modal gain spectrum in this injection current case according to the total loss spectrum formed by interpolating the assumed gain medium length, the spectrum containing the total loss and modal gain information at this injection current, and S3.

[0013] Preferably, in step S5, the judgment process for satisfying "the material gain is zero at the quasi-Fermi level" is as follows: Calculate the difference in quasi-Fermi levels according to the wavelength at the zero point of the modal gain; Calculate the junction voltage according to the difference in quasi-Fermi levels; If the calculated junction voltage conforms to the measured junction voltage-injection current curve, it is considered satisfied, otherwise, it is considered not satisfied.

[0014] Preferably, step S1 includes the following sub-steps: S11. Respectively determine the threshold current and internal resistance of the semiconductor laser under test; S12. Calculate the junction voltage corresponding to different injection currents according to the internal resistance of the semiconductor laser under test and the measured U-I combination, where I is the injection current, covering both above and below the threshold current, and U is the voltage applied to the semiconductor laser under test.

[0015] The specific process of respectively determining the threshold current and internal resistance of the semiconductor laser under test is as follows: Measure the P-I curve and U-I curve of the semiconductor laser under test, where P is the output optical power of the device under test; Take the current at the turning point of the P-I curve as the threshold current; Take the slope of the curve above the threshold current of the U-I curve as the internal resistance.

[0016] It further includes: Calculate the absorption spectrum according to the junction voltage, the measurement spectrum, and the modal gain spectrum; Or, calculate the group refractive index dispersion of the gain medium according to the measurement spectrum and the gain medium length.

[0017] The second aspect of the present application relates to a semiconductor laser gain characteristic parameter measurement system, including: at least one memory for storing programs; at least one processor for entering the programs stored in the memory, and when the programs stored in the memory are entered, the processor is used to enter the measurement method as described in the first aspect.

[0018] It can be understood that the beneficial effects of the above second aspect can refer to the relevant descriptions in the above first aspect, and will not be elaborated here.

[0019] Generally speaking, compared with the prior art, the above technical solution conceived by the present application has the following beneficial effects: The present application provides a method for measuring the gain characteristic parameters of a semiconductor laser. By measuring the U-I characteristic curve of the laser, the -I curve can be obtained, and thus the junction voltage of the semiconductor laser at different injection currents can be obtained. The product of the junction voltage and the charge quantity is numerically equal to the difference in quasi-Fermi levels. Then, according to the characteristic that the material gain is zero at the quasi-Fermi level, the total loss spectrum at different photon energies (i.e., different wavelengths) can be obtained. Then, through the measured spectrum of a certain injection current below the threshold current, the mode gain spectrum at this injection current can be extracted, and further, according to the result of the extracted mode gain spectrum, the -I curve is used to estimate the gain medium length of the semiconductor laser. In the extraction of the gain characteristic parameters in the present application, it is not necessary to know or measure the gain medium length and the end face reflectivity parameter of the semiconductor laser; when calculating the gain, the approximation of the symmetry of the conduction band and valence band structures of the gain medium is not adopted, and the extracted mode gain spectrum and total loss spectrum of the laser are relatively accurate. This method is not only applicable to semiconductor laser chips packaged in CoC, but also applicable to semiconductor lasers packaged in TO, butterfly and other packages. It is not only applicable to ordinary FP lasers, but also can be extended to DFB and DBR lasers. Description of the Drawings

[0020] Figure 1 is a flowchart of a method for measuring the gain characteristic parameters of a semiconductor laser provided by an embodiment of the present application.

[0021] Figure 2 is a block diagram of measuring the spectrum and P-I curve of a distributed feedback DFB laser provided by an embodiment of the present application.

[0022] Figure 3 is a P-I curve and a U-I curve diagram of a DFB laser provided by an embodiment of the present application.

[0023] Figure 4 is a relationship diagram of dU / dI-I after taking the derivative of the current I of the U-I curve provided by an embodiment of the present application.

[0024] Figure 5 is the junction voltage provided by an embodiment of the present application and the injection current I -I relationship diagram.

[0025] Figure 6 is a diagram of 16 groups of spectral examples in the range of 3.6 to 15.98 mA obtained by experimental measurement provided by an embodiment of the present application.

[0026] Figure 7The points corresponding to the injection current and the junction voltage of 16 groups of spectra provided by the embodiments of the present application are marked on the -I curve graph.

[0027] Figure 8 The spectrum graph under an injection current of 15.98 mA provided by the embodiments of the present application.

[0028] Figure 9 The total loss spectrum graph obtained by extraction provided by the embodiments of the present application.

[0029] Figure 10 The modal gain spectrum graphs under 7 injection currents of 10.5, 11.5, 12.5, 13.5, 14.5, 15.5, and 15.98 mA obtained by extraction provided by the embodiments of the present application, and the total loss spectrum and the absorption spectrum are plotted therein.

[0030] Figure 11 The zero points of the modal gain spectrum of the extraction result and the corresponding current provided by the embodiments of the present application are plotted on the -I curve.

[0031] Figure 12 The graph of the group refractive index dispersion relationship of the gain medium under 7 injection currents of 10.5, 11.5, 12.5, 13.5, 14.5, 15.5, and 15.98 mA obtained by extraction provided by the embodiments of the present application.

[0032] Figure 13 The comparison between the gain extraction method provided by the embodiments of the present application and the result of the extended Hakki-Paoli method of M. Vanzi.

[0033] Figure 14 The extraction result of applying the gain extraction method provided by the embodiments of the present application to the spectral simulation model of an FP laser.

[0034] In all the drawings, the same reference numerals are used to represent the same elements or structures, where: 1 is a semiconductor laser controller, 2 is a DFB laser, 3 is an optical isolator, 4 is a photodetector, 5 is a spectrometer, 6 is a U-I curve, 7 is a P-I curve, 8 is a total loss spectrum constructed from the total loss at 16 photon energies, and 9 is a total loss spectrum obtained by removing the grating influence on 8 and extending it to the entire measurement range. Detailed implementation manners

[0035] In order to make the objectives, technical solutions and advantages of the present application clearer and more understandable, the present application will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0036] In this application, the term "and / or" describes the relationship between related objects, indicating that there can be three relationships. For example, A and / or B can represent three situations: A exists alone, A and B exist simultaneously, and B exists alone. In this application, the symbol " / " indicates that the related objects are in an "or" relationship. For example, A / B means A or B.

[0037] In the description of the specification and claims of this application, terms such as "first" and "second" are used to distinguish different objects, rather than to describe the specific order of the objects. For example, the first response message and the second response message are used to distinguish different response messages, rather than to describe the specific order of the response messages.

[0038] In the embodiments of this application, words such as "exemplary" or "for example" are used to give examples, illustrations, or explanations. Any embodiment or design solution described as "exemplary" or "for example" in the embodiments of this application should not be construed as being more preferred or having more advantages than other embodiments or design solutions. Rather, the use of words such as "exemplary" or "for example" is intended to present relevant concepts in a specific manner.

[0039] In the description of the embodiments of this application, unless otherwise specified, the meaning of "a plurality of" refers to two or more. For example, a plurality of processing units refers to two or more processing units, and a plurality of elements refers to two or more elements.

[0040] For the convenience of understanding, the following first explains and describes the English abbreviations and related technical terms involved in the embodiments of this application.

[0041] The zero point refers to the value of the independent variable x corresponding to when the function value is zero, that is, the abscissa.

[0042] The following describes the embodiments of this application in combination with the accompanying drawings in the embodiments of this application.

[0043] The measurement principle of this application: When the injected current is lower than the threshold current, the spectrum of the DFB laser approximately satisfies the spectrum formula of the FP laser. The spectral image drawn according to this formula, calculated by the ratio of the maximum value to the minimum value contains information on the modal gain (Γg(λ)) and the total loss ( ). By measuring the U-I characteristic curve of the laser, it can be calculated -I curve, the junction voltage of the semiconductor laser at different injection currents can be obtained. The product of the junction voltage and the charge quantity is numerically equal to the difference in quasi-Fermi levels. Then, based on the characteristic that the material gain is zero at the quasi-Fermi level, the total loss spectrum at different photon energies (i.e., different wavelengths) can be obtained. Then, through the measured spectrum at an injection current below the threshold current, the mode gain spectrum at this injection current can be extracted, and further, according to the result of the extracted mode gain spectrum, it can be compared with the -I curve to estimate the gain medium length of the DFB laser.

[0044] This application calculates by measuring the U-I curve of the laser -I and q = ; More importantly, based on the fact that "the mode gain is equal to zero at ", this application simplifies the solution of the spectral formula to obtain the total loss spectrum Calculate the mode gain spectrum Γg of the laser . On this basis, the absorption spectrum can be further calculated according to the junction voltage, the measured spectrum, and the mode gain spectrum; or, according to the measured spectrum and the gain medium length, the group refractive index dispersion relationship of the active region gain medium can be calculated through the formula of the longitudinal mode interval of the semiconductor laser, so as to provide an important reference basis for the selection of the gain medium.

[0045] As Figure 1 shown, this application provides a method for measuring the gain characteristic parameters of a semiconductor laser, including: First, measure the U-I curve of the laser, and according to the U-I curve and formula (a), obtain the internal resistance : (I > )(a) Among them, is the external voltage of the measured laser, is the injection current of the laser, is the internal resistance of the laser, is the threshold current of the semiconductor laser.

[0046] Then, according to formula (b), obtain the junction voltage : (b) Among them, is the junction voltage, and numerically multiplying it by the charge quantity is equal to the difference in quasi-Fermi levels , that is, , is the quasi-Fermi level of the conduction band in the case of having an injection current, It is the quasi-Fermi level of the valence band when there is an injection current.

[0047] Then, measure the spectra below the threshold current for several groups (the number of measurement groups x determines the number of total loss spectrum sample points and the calculation accuracy). For the selection of specific current values, it should be ensured that the corresponding to the maximum value does not exceed the clamping value, and the minimum value should not be too low (to avoid the influence of measurement background noise).

[0048] The spectral characteristics of the semiconductor laser can be characterized by in formula (c): (c) where is the laser spectrum, is the initial spectrum, denotes taking the spectral intensity, and the spectrum containing total loss and mode gain information , is the wave number, is the length of the gain medium of the resonator of the semiconductor laser, represents the total loss spectrum, is , is , is the internal loss, 、 are the reflectivities of the left and right end faces respectively.

[0049] The following two steps reflect the process of extracting the mode gain: Step 1: Based on the fact that "the mode gain is equal to zero at the difference in quasi-Fermi levels", simplify (c) to formula (d): (d) The explanations of the multiple parameters involved are as follows: is the wavelength corresponding to the difference in quasi-Fermi levels in the measured spectrum and satisfies formula (e): (e) where is the Planck constant, is the speed of light, is the electric charge amount, is the quasi-Fermi level of the conduction band of the gain medium when there is an injection current, is the quasi-Fermi level of the valence band of the gain medium when there is an injection current. is the spectrum containing total loss and mode gain information at the wavelength of , which can be obtained from equation ​ is the ratio of the maximum value to the minimum value of the spectrum near , is the maximum value of the spectrum near , is the minimum value of the spectrum near .

[0050] is the value of the initial power spectrum at the wavelength , is the value of the output optical power spectrum at the wavelength , is the gain medium length, is the end face reflectivity of the laser. It is necessary to measure the spectra of x sets of injection currents below the threshold, and then solve for x through equation (d); after interpolating and extrapolating x to the entire wavelength range, the total loss spectrum is obtained.

[0051] Step 2: Substitute the total loss spectrum into the above equation (c) to solve for the mode gain spectra at different injection currents below the threshold.

[0052] (f) where is the total loss spectrum, is the mode gain spectrum, is the initial power spectrum of the experimentally measured spectrum is the experimentally measured spectrum, is the spectrum defined by equation (c) and obtained from equation (g) that contains information on total loss and mode gain .

[0053] (g) where is the ratio of the maximum envelope spectrum to the minimum envelope spectrum of the spectrum, is the maximum envelope spectrum of the spectrum, is the minimum envelope spectrum of the spectrum.

[0054] It can be seen from equation (f) that by measuring the spectrum of a certain injection current below the threshold, the mode gain at this injection current can be obtained.

[0055] Finally, the absorption spectrum is calculated through equation (h): (h) where is the Planck constant, is the photon frequency, is the electric charge, is the Boltzmann constant, T is the experimental temperature, is the extracted mode gain spectrum, is the junction voltage corresponding to the injection current. Absorption spectrum The physical properties of the gain medium of a semiconductor laser are one of the gain characteristic parameters.

[0056] Furthermore, according to the coincidence between the zero points of the mode gain spectrum curves at different injection currents below the threshold obtained by measurement and the -I curve, the length of the laser gain medium can be estimated , and the group refractive index dispersion relationship of the gain medium can be calculated according to formula (i) and the spectrum: (i) wherein, is the group refractive index dispersion relationship of the gain medium, is the optical wavelength, is the longitudinal mode spacing, L is the length of the gain medium. In the numerator, is the abscissa corresponding to the spectrum, and in the denominator, is the difference between the abscissas of adjacent peaks of the spectrum.

[0057] The obtained measurement results can provide reference values for semiconductor laser simulation and also provide important reference bases for the design and selection of the gain medium in the active region of semiconductor lasers.

[0058] Embodiment Figure 2 is the block diagram of the device for measuring the P-I curve and spectrum of a distributed feedback DFB laser. The device includes a semiconductor laser controller 1, a distributed feedback DFB laser 2, an optical isolator 3, a photodetector 4, and a spectrometer 5.

[0059] First, measure the P-I curve and U-I curve of the DFB laser as Figure 3 shown, where the slope change of the U-I curve 6 tends to be gentle above the corresponding threshold current. When the P-I curve 7 is above the threshold current of 15.98 mA, the slope significantly increases.

[0060] Figure 4 is the dU / dI-I curve plotted by taking the derivative of the current I of the U-I curve and marking the ordinate at the threshold current, and this value is the resistance value of the internal resistance of the DFB laser .

[0061] Figure 5 is to substitute the internal resistance of the DFB laser into the one shown in formula (b) The image obtained from the relationship with I shows that when the injection current exceeds the threshold, it no longer increases, and there is a corresponding relationship with the difference in quasi-Fermi levels Therefore, this image conforms to the physical theory of gain clamping of semiconductor lasers above the threshold, indicating that the obtained curve of the junction voltage varying with current is credible, and the internal resistance value is also credible.

[0062] Figure 6 The 16 groups of spectra (x = 1 to 16) measured experimentally in the range of 3.6 mA to 15.98 mA are plotted on one image, and the junction voltage corresponding to each injection current, from the formula q = The difference in quasi-Fermi levels obtained is marked on each spectrum in the form of a vertical line.

[0063] Figure 7 The junction voltages corresponding to the injection currents of these 16 groups of spectra are marked in Figure 5 It can be seen that Figure 7 the ordinate of the intersection point of Figure 5 corresponds to the position of the difference in quasi-Fermi levels of each spectrum, that is, each vertical line. According to the characteristic that the material gain is zero at the difference in quasi-Fermi levels, and then according to the spectral formula of the DFB laser below the threshold as shown in formula (c), formula (d) can be obtained.

[0064] At this time, the gain medium length is not known, so a value needs to be estimated. After calculation, it can be determined by fitting with the -I curve Here, taking the estimated value = 325 μm as an example, and taking the spectrum of the injection current at the threshold current, that is, 15.98 mA.

[0065] Figure 8 It is to plot Figure 7 the spectrum of the 15.98 mA injection current situation in and the corresponding

[0066] position in the form of a vertical line in the same figure. At using formula (d) to solve for (j) It can be seen that when knowing Figure 8 the ratio of the maximum value to the minimum value of the spectrum at the (that is, the vertical line) of The total loss at point ( ) is obtained. Repeat this process by changing the injection current until 16 spectra are obtained, and 16 points of total loss can be acquired. The photon energy coverage ranges from 0.7724 to 0.8223 eV (1511 - 1608 nm).

[0067] Figure 9 Curve 8 in is the total loss spectrum constructed from the total losses at 16 photon energies. Since the spectra below the threshold are approximated using the FP cavity formula, it is necessary to first remove the influence of the grating on the total loss and extend it to the entire measurement range. The final total loss spectrum is shown as curve 9. Then, substitute this total loss spectrum into formula (f) to obtain the mode gain spectrum at a certain injection current, as shown in the following formula (k): (k) where y represents the spectrum at the y - th group of injection currents.

[0068] Then, use and the junction voltage at the y - th group of injection currents Substitute into (h) to obtain the absorption spectrum .

[0069] Figure 10 The results of mode - gain extraction at 7 injection currents of 10.5, 11.5, 12.5, 13.5, 14.5, 15.5, 15.98 mA (y = 1 - 7) obtained by repeating this method are plotted in the same figure with the total loss spectrum and the absorption spectrum. And make the total loss at the photon energy of 0.8019 eV (corresponding wavelength 1550 nm) corresponding to the grating equal to the mode gain below the threshold to restore the influence of the grating. The zeros of these 7 mode gains should theoretically correspond to the junction voltages at 7 injection currents. Therefore, if the corresponding points are plotted on the - I curve, and if they can coincide well, it indicates that the assumed gain - medium length is credible. Otherwise, it is necessary to change the gain - medium length to make the mode - gain zero fall on the - I curve. As can be seen from the figure, the band - gap energy of this gain medium is approximately 0.724 eV (corresponding wavelength 1716 nm). The total loss spectrum and the absorption spectrum do not change with the current, but the mode - gain spectrum changes with the injection current.

[0070] Figure 11 These 7 zeros (red cross - points) are plotted in the same figure with the - I. As can be seen from this figure, the coincidence of the cross - points with the - I curve is good. Therefore, it can be estimated that the gain - medium length of this DFB laser is 325 μm.

[0071] According to the longitudinal mode spacing formula, the expression (i) of the group refractive index dispersion of the gain medium can be derived. Therefore, from the spectrum at a certain injection current, the group refractive index dispersion of the gain medium at this injection current can be estimated according to the longitudinal mode spacing. Taking the injection currents as 10.5, 11.5, 12.5, 13.5, 14.5, 15.5, and 15.98 mA, the group refractive index dispersions at these currents can be estimated.

[0072] Figure 12 They are the 7 groups of group refractive index dispersions calculated.

[0073] Figure 13 This is the comparison of the extraction results between this method and the M.Vanzi method. It is found that: near the low photon energy, the extraction results are more in line with the theoretical expectations, which indicates that the gain, loss, and absorption spectra of the semiconductor laser extracted by this method are more accurate.

[0074] Figure 14 This is an example of applying this method to the simulation of an FP laser. It can be seen from the figure that the extracted results are in good agreement with the theoretical model. Therefore, the feasibility of this method can be verified.

[0075] It should be understood that the above device is used to execute the method in the above embodiment. For the corresponding program modules in the device, their implementation principles and technical effects are similar to those described in the above method. The working process of this device can refer to the corresponding process in the above method and will not be elaborated here.

[0076] Based on the method in the above embodiment, an embodiment of the present application provides an electronic device, which may include: a processor (Processor), a communication interface (Communications Interface), a memory (Memory), and a communication bus. Among them, the processor, the communication interface, and the memory complete communication with each other through the communication bus. The processor can call the logical instructions in the memory to execute the method in the above embodiment.

[0077] In addition, when the logical instructions in the above memory are implemented in the form of software functional units and sold or used as an independent product, they can be stored in a computer-readable storage medium. Based on such an understanding, the technical solution of the present application, in essence, or the part that contributes to the prior art or a part of this technical solution can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the method described in each embodiment of the present application.

[0078] Based on the method in the above embodiments, an embodiment of the present application provides a computer-readable storage medium. The computer-readable storage medium stores a computer program. When the computer program runs on a processor, the processor is caused to execute the method in the above embodiments.

[0079] Based on the method in the above embodiments, an embodiment of the present application provides a computer program product. When the computer program product runs on a processor, the processor is caused to execute the method in the above embodiments.

[0080] It can be understood that the processor in the embodiments of the present application may be a central processing unit (CPU), or may also be other general-purpose processors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), or other programmable logic devices, transistor logic devices, hardware components, or any combination thereof. The general-purpose processor may be a microprocessor or any conventional processor.

[0081] The method steps in the embodiments of the present application may be implemented in a hardware manner or by a processor executing software instructions. The software instructions may be composed of corresponding software modules. The software modules may be stored in a random access memory (RAM), flash memory, read-only memory (ROM), programmable ROM (PROM), erasable PROM (EPROM), electrically erasable PROM (EEPROM), registers, hard disk, removable hard disk, CD-ROM, or any other form of storage medium well-known in the art. An exemplary storage medium is coupled to the processor so that the processor can read information from the storage medium and write information to the storage medium. Of course, the storage medium may also be a component of the processor. The processor and the storage medium may be located in an ASIC.

[0082] In the above embodiments, it can be implemented in whole or in part by software, hardware, firmware, or any combination thereof. When implemented using software, it can be implemented in whole or in part in the form of a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, the processes or functions described in the embodiments of the present application are generated in whole or in part. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable devices. The computer instructions can be stored in a computer-readable storage medium or transmitted through the computer-readable storage medium. The computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center in a wired manner (such as coaxial cable, optical fiber, digital subscriber line (DSL)) or wirelessly (such as infrared, wireless, microwave, etc.). The computer-readable storage medium can be any available medium that can be accessed by a computer or a data storage device such as a server or data center that includes one or more integrated available media. The available medium can be a magnetic medium (e.g., floppy disk, hard disk, magnetic tape), an optical medium (e.g., DVD), or a semiconductor medium (e.g., solid state disk (SSD)), etc.

[0083] It can be understood that the various numerical numbers involved in the embodiments of the present application are only for the convenience of description and are not used to limit the scope of the embodiments of the present application.

[0084] Those skilled in the art can easily understand that the above is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A method for measuring semiconductor laser gain characteristic parameters, characterized in that, Including: S1. Calculate the junction voltages corresponding to multiple different injection currents below the threshold of the semiconductor laser to be measured; S2. Calculate the difference in quasi-Fermi levels corresponding to the injection current based on the junction voltage; S3. According to the characteristic that the material gain is zero at the quasi-Fermi level, determine the total loss values at different photon energies based on the assumed gain medium length, and interpolate to form the total loss spectrum of the semiconductor laser to be measured; S4. According to the measured spectrum of the semiconductor laser to be measured under a certain injection current, determine the spectrum containing the total loss and mode gain information under this injection current. Based on the assumed gain medium length, the spectrum containing the total loss and mode gain information under this injection current, and the total loss spectrum formed by interpolation, calculate the mode gain spectrum under this injection current; S5. After adjusting the assumed gain medium length, enter S3 until "the material gain is zero at the quasi-Fermi level" is satisfied. Take the mode gain spectrum at this time as the measurement result of the gain characteristic parameter, and take the assumed gain medium length at this time as the measurement result of the gain medium length.

2. The measurement method according to claim 1, characterized in that, Step S3 includes the following sub-steps: S31. Obtain the measured spectra of the semiconductor laser to be measured under different injection currents below the threshold. Among them, the abscissa represents the wavelength, and the ordinate represents the optical power. Calculate the wavelength when the mode gain is zero based on the difference in quasi-Fermi levels; S32. Map the wavelength when the mode gain is zero to the measured spectrum, and determine the peak optical power and valley optical power closest to this wavelength; S33. Calculate the ratio of the peak optical power and valley optical power closest to this wavelength in the spectrum; S34. Use the ratio to inversely obtain the value of the spectrum containing the total loss and mode gain information at the wavelength corresponding to the mode gain being zero; S35. Calculate the total loss value at the wavelength corresponding to the mode gain being zero based on the assumed gain medium length and the value of the spectrum containing the total loss and mode gain information at the wavelength corresponding to the mode gain being zero; S36. Perform interpolation processing on the total loss values at the wavelengths corresponding to the mode gain being zero under different injection currents below the threshold to obtain the total loss spectrum of the semiconductor laser to be measured.

3. The measuring method according to claim 2, characterized in that, The spectral characteristics of the semiconductor laser below the threshold current are expressed as follows: wherein, is the wavelength corresponding to when the mode gain is zero, is the value of the output optical power spectrum at the wavelength of ; is the value of the initial power spectrum at the wavelength of ; is the spectrum including the total loss and mode gain information at the wavelength of ; is the value of the total loss spectrum at the wavelength of ; is the wave number, is the gain medium length, is the internal loss, are the reflectivities of the left and right end faces of the semiconductor laser, respectively.

4. The measuring method according to claim 2, wherein The inversion formula is as follows: Among them, is the ratio of the peak optical power closest to this wavelength and the valley optical power in the spectrum, is the peak optical power of the spectrum near ; is the valley optical power of the spectrum near ; is the value of the spectrum containing total loss and mode gain information at the wavelength of ; is the wavelength corresponding to when the mode gain is zero.

5. The measurement method according to claim 1, wherein, Step S4 includes the following sub-steps: S41. Obtain the measured spectrum of the semiconductor laser to be measured under the injection current below the threshold; S42. Determine the maximum envelope spectrum and the minimum envelope spectrum of the measured spectrum; S43. Calculate the ratio of the maximum envelope spectrum to the minimum envelope spectrum; S44. Use the ratio of the maximum envelope spectrum to the minimum envelope spectrum to inversely obtain the spectrum containing the total loss and mode gain information under this injection current; S45. Calculate the mode gain spectrum under this injection current based on the assumed gain medium length, the spectrum containing the total loss and mode gain information under this injection current, and the total loss spectrum formed by interpolation in S3.

6. The measuring method according to claim 1, characterized in that In step S5, the judgment process for satisfying "the material gain is zero at the quasi-Fermi level" is as follows: Calculate the difference in quasi-Fermi levels based on the wavelength at the zero point of the mode gain; Calculate the junction voltage based on the difference in quasi-Fermi levels; If the calculated junction voltage conforms to the measured junction voltage-injection current curve, it is considered satisfied, otherwise, it is considered not satisfied.

7. The measuring method according to claim 1, characterized in that, Step S1 includes the following sub-steps: S11. Determine the threshold current and internal resistance of the semiconductor laser to be measured respectively; S12. Calculate the junction voltage corresponding to different injection currents according to the internal resistance of the semiconductor laser to be measured and the measured U-I combination, where I is the injection current, covering both above and below the threshold current, and U is the voltage applied to the semiconductor laser to be measured.

8. The measuring method according to claim 7, characterized in that, The specific steps of respectively determining the threshold current and internal resistance of the semiconductor laser to be measured are as follows: Measure the P-I curve and U-I curve of the semiconductor laser to be measured, where P is the output optical power of the device to be measured; Take the current at the turning point of the P-I curve as the threshold current; Take the slope of the curve of the U-I curve above the threshold current as the internal resistance.

9. The measurement method according to claim 1, characterized in that, It further includes: Calculate the absorption spectrum according to the junction voltage, measured spectrum and mode gain spectrum; Alternatively, calculate the group refractive index dispersion of the gain medium according to the measured spectrum and the length of the gain medium.

10. A semiconductor laser gain characteristic parameter measurement system, characterized in that It includes: At least one memory for storing programs; At least one processor for accessing the programs stored in the memory. When the programs stored in the memory are accessed, the processor is used to execute the measurement method according to any one of claims 1 to 9.

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