CN100383541C - Measuring device and measuring method for thermal relaxation time of semiconductor laser - Google Patents

Abstract

A measuring device and its test method of the thermal relaxation time of the semiconductor laser, the constitution of the apparatus is: the output end of the pulse power supply is connected with the semiconductor laser, the collimation system and the spectrometer are sequentially arranged along the laser advancing direction of the semiconductor laser, the photomultiplier is positioned at the output slit of the spectrometer, the output end of the photomultiplier is connected with the input end of the Boxcar integrator, the synchronous output end of the pulse power supply is connected with the trigger input end of the Boxcar integrator through a delay circuit, and the data acquisition card at the input end of the computer is connected with the output end of the Boxcar integrator. The invention has the advantages that: the change relation between the threshold current of the laser and the slope efficiency along with the junction temperature does not need to be tested; the device has low manufacturing cost, easy construction, simple method and good stability.

Description

Measuring device and measuring method for thermal relaxation time of semiconductor laser

technical field

The invention relates to a semiconductor laser, in particular to a test device and a test method for the thermal relaxation time of the semiconductor laser.

Background technique

The thermal characteristics of semiconductor lasers are an important issue in practical applications. High thermal resistance will lead to a high temperature rise in the active region of the laser, which will lead to an increase in the threshold current of the laser, a decrease in slope efficiency, a decrease in output power, and more seriously, affect the life of the device. In addition to thermal resistance, another thermal characteristic parameter of semiconductor lasers is thermal relaxation time. For semiconductor lasers in the pulse working state, the thermal relaxation time parameter is a very important parameter.

When a square wave current is applied to a semiconductor laser, the junction temperature of the laser rises gradually within the pulse, and after a period of time, the junction temperature reaches a steady-state value. The junction temperature change can be expressed as:

T＝T ₀ +R _th P[1-exp(-Δt/τ)] (1)

Where R _th is the thermal resistance of the laser, P is the injected heat flow, τ is the thermal relaxation time, and T ₀ is the junction temperature of the laser when no current is injected.

The thermal relaxation time reflects how quickly the junction temperature of a laser rises. For some lasers working in short pulses, if the thermal relaxation time is large, the temperature rise in the pulse is very small; if the thermal relaxation time is small, the laser junction temperature will reach a steady state value in a short time.

Existing test protocols for thermal relaxation times are:

In the prior art [1] (H.I.Abdelkader, H.HHausien, and J.D.Martin.Temperature rise and thermal rise-time measurement of a semiconductor laser diode.Rev.Sci.Instrum.63(3), March 1992:2004-2007) , H.I.Abdelkader studied the relationship between the threshold current and slope efficiency of semiconductor lasers as a function of junction temperature. By testing the laser light power changes at different pulse times under pulsed operation, the junction temperature rise at different times was obtained, and the thermal relaxation time was calculated. . However, the optical power value of the laser is relatively small under short pulses, and it is difficult to accurately measure the change of the optical power of the laser at different times, requiring more sophisticated equipment. Prior technology [2] (M.Voss, C.Lier, U.Menzel, A.Barwolff, and T.Elsaesser. Time-resolved emission studies of GaAs/AlGaAs laser diode arrays on different heat sinks.J.Appl.phys.79 (2).15 January 1996:1170-1172), M.Voss et.al. obtained the dynamic thermal characteristics of the laser by setting an optical switch on the CCD of the receiving device of the spectrometer, and then testing the spectra of different switching times. This technology uses optical switches for pulsed optical signals, which requires precise control of switching time, and the requirements for optical signal control are too high.

Contents of the invention

The present invention overcomes the above-mentioned deficiencies in the prior art, and provides a measurement device and a test method thereof for the thermal relaxation time of a semiconductor laser,

Technical solution of the present invention is as follows:

A device for measuring the thermal relaxation time of a semiconductor laser, the device is composed of: a pulse power supply, the output terminal of the pulse power supply is connected to the semiconductor laser, and along the laser forward direction of the semiconductor laser is a collimation system, a spectrometer, a photoelectric The multiplier tube is located at the output slit of the spectrometer, the output end of the photomultiplier tube is connected to the input end of the Boxcar integrator, the synchronous output end of the pulse power supply is connected to the trigger input end of the Boxcar integrator through a delay circuit, and the computer input The terminal data acquisition card is connected to the output terminal of the Boxcar integrator.

The test method of the thermal relaxation time of semiconductor laser of the present invention is characterized in that the method comprises the following steps:

① First set the parameters of the Boxcar integrator: the sampling pulse signal T _g is 0.5us, and the scanning time T _s is 150s; secondly, set the delay time of the delay circuit to no more than 5ms; the slit width of the spectrometer is 10μm-40μm;

② Turn on the laser pulse power supply, fix the scanning wavelength λ _s1 of the spectrometer, the sampling pulse signal generated by the Boxcar integrator scans the electrical signal converted from the optical power signal by the photomultiplier tube, and the computer collects the output of the Boxcar integrator to obtain the electrical signal data I ₁ ... ...1 _i ..., from a series of electrical signal data I _i and the corresponding time t to obtain the time t= _um1 of the electrical signal peak value;

③ Change the scanning wavelength λ _si (i=2, 3....15) of the spectrometer, and repeat the second step to obtain a series of electrical signal peak appearance times u _m1 (i=2, 3....15).

④ Use the following formula to calculate τ ₁ from the scanning wavelength λ _si and the peak time u _m1 , and then obtain the thermal relaxation time parameter value τ of the laser on average:

$\mathrm{<span\; class="notranslate">\; \&tau;</span>}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span>\frac{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}}{\mathrm{<span\; class="notranslate">\; ln</span>}<span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\frac{{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}_{\mathrm{<span\; class="notranslate">\; P</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; )</span>}{{{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}_{\mathrm{<span\; class="notranslate">\; T</span>}}}^{<span\; class="notranslate">\; \&prime;</span>}{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; the\; th</span>}}\mathrm{<span\; class="notranslate">\; P</span>}}<span\; class="notranslate">\; ]</span>}$

In the formula: λ _s is the fixed scanning wavelength value of the spectrometer, u _m is the appearance time of the corresponding optical power peak, λ _p (T ₀ ) is the initial peak wavelength, and λ _T ′ is the spectral temperature coefficient.

The delay time of the delay circuit should be 0.2ms.

The slit width is 30 μm.

Compared with other test methods, the present invention has the advantages of: no need to test the relationship between laser threshold current and slope efficiency with junction temperature; the use of electric switches is easier to control than optical switches, the cost of the entire experimental device is low, easy to build, and the method is simple , Good stability.

Description of drawings

Fig. 1 is a structural schematic diagram of the device of the present invention.

Fig. 2 is a graph showing the relationship between the scanning wavelength and the peak time of optical power obtained from the test results.

In Figure 1: 1-semiconductor laser, 2-pulse power supply, 3-delay circuit, 4-collimation system, 5-spectrometer, 6-photomultiplier tube, 7-Boxcar integrator, 8-computer

Detailed ways

The present invention will be further described below in conjunction with embodiment.

Please refer to Figure 1 first. Fig. 1 is a schematic structural diagram of an embodiment of the device of the present invention. As can be seen from the figure, the test device of the thermal relaxation time of the semiconductor laser of the present invention is characterized in that the composition of the device is: a pulse power supply 2, the output terminal of the pulse power supply 2 is connected to the semiconductor laser 1, along the laser beam of the semiconductor laser 1 The forward direction is the collimation system 4 and the spectrometer 5 successively, the photomultiplier tube 6 is positioned at the output slit of the spectrometer 5, the output terminal of the photomultiplier tube 6 is connected to the input end of the Boxcar integrator 7, and the pulse power supply 2 of the The synchronization output end is connected to the trigger input end of the Boxcar integrator 7 through the delay circuit 3, and the data acquisition card at the input end of the computer 8 is connected to the output end of the Boxcar integrator 7.

Utilize the device described in Fig. 1 to carry out the test method of the thermal relaxation time of semiconductor laser, comprise the following steps:

① First set the parameters of the Boxcar integrator 7: the sampling pulse signal T _g is 0.5us, and the scanning time T _s is 150s; secondly, set the delay time of the delay circuit 3 to 0.2ms. The slit width of the spectrometer 5 is 1 and the slit width is 30 μm;

② Turn on the pulse power supply 2 of the laser, fix the spectrometer 5 to scan the wavelength λ _s1 , the sampling pulse signal generated by the Boxcar integrator 7 scans the electrical signal converted by the photomultiplier tube 6 from the optical power signal, and the computer 8 collects the output of the Boxcar integrator 7 to obtain Electrical signal data I ₁ ... 1 _i ..., from a series of electrical signal data I _i and the corresponding time t to obtain the time t= _um1 of the electrical signal peak value;

③ Change the scanning wavelength λ _si (i=2, 3....15) of the spectrometer 5, repeat the second step process, and obtain a series of electrical signal peak time u _mi (i=2, 3....15) .

④ Use the following formula to obtain τ ₁ from the scanning wavelength λ _si and the peak time u _mi , and then obtain the thermal relaxation time parameter value τ of the laser on average:

$\mathrm{<span\; class="notranslate">\; \&tau;</span>}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span>\frac{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}}{\mathrm{<span\; class="notranslate">\; ln</span>}<span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\frac{{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}_{\mathrm{<span\; class="notranslate">\; P</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; )</span>}{{{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}_{\mathrm{<span\; class="notranslate">\; T</span>}}}^{<span\; class="notranslate">\; \&prime;</span>}{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; the\; th</span>}}\mathrm{<span\; class="notranslate">\; P</span>}}<span\; class="notranslate">\; ]</span>}$

In the formula: λ _s is the fixed scanning wavelength value of the spectrometer, u _m is the appearance time of the corresponding optical power peak, λ _p (T ₀ ) is the initial peak wavelength, and λ _T ′ is the spectral temperature coefficient.

The peak time of the optical power signal is the time required from the injection of the current pulse to the appearance of the peak optical power of the laser. When collecting the output data of the Boxcar integrator 7, the sampling pulse signal needs to be collected at the same time. It is set in the experiment that when the sampling pulse signal is collected, the output signal of the Boxcar integrator 7 is started to be collected. Therefore, each acquisition of the output signal of the Boxcar integrator 7 starts at the same moment. During the experiment, because the sampling pulse width is 0.5μs, and the acquisition rate of the data acquisition card is up to 40k/s, it is not easy to sample. Therefore, the sampling pulse signal is expanded into a synchronous signal with a width of 250 μs, which is sent to the computer 8 for sampling. When the rising edge of the signal is collected, the data acquisition card starts to collect the output signal of the Boxcar integrator 7 .

Fig. 2 is a relation diagram of fixed wavelength λ _s and average peak time u _m . By (3), when $\frac{{\mathrm{\&lambda;}}_{\mathrm{the\; s}}-{\mathrm{\&lambda;}}_P\left(T_0\right)}{{\mathrm{\&lambda;}}_T^{\&prime;}{R}_{\mathrm{the\; th}}P}<<1$ When , u _m and λ _s change linearly, formula (3) is written as: $\mathrm{\&tau;}=-\frac{u_m}{\frac{{\mathrm{\&lambda;}}_{\mathrm{the\; s}}-{\mathrm{\&lambda;}}_P\left(T_0\right)}{{{\mathrm{\&lambda;}}_T}^{\&prime;}{R}_{\mathrm{the\; th}}P}}.$ Therefore, the thermal relaxation time value of the laser can be calculated to be 390 μs from the slope of the fitting curve in Figure (2).

Claims (2)

1. the proving installation of the thermal relaxation time of a semiconductor laser, the formation that it is characterized in that this device is: a pulse power (2), the output termination semiconductor laser (1) of this pulse power (2), laser working direction along this semiconductor laser (1) is colimated light system (4) and spectrometer (5) successively, photomultiplier (6) is positioned at the output slit of described spectrometer (5), the input end of the output termination Boxcar integrator (7) of photomultiplier (6), the synchronous output end of the described pulse power (2) is through the triggering input end of delay circuit (3) connection Boxcar integrator (7), and computing machine (8) input end data collecting card connects Boxcar integrator (7) output terminal.

2. utilize the described device of claim 1 to carry out the method for testing of the thermal relaxation time of semiconductor laser, it is characterized in that this method comprises the following steps:

1. at first set the parameter of Boxcar integrator (7): sample-pulse signal T _gBe 0.5us, sweep time T _sBe 150s; Next delay time of setting delay circuit (3) is no more than 0.2ms; The slit width of spectrometer (5) is 30 μ m;

2. open laser pulse power supply (2), fixed light spectrometer (5) scanning wavelength λ _S1, the sample-pulse signal scanning photomultiplier (6) that Boxcar integrator (7) produces is by the optical power signals signals converted, and computing machine (8) is exported Boxcar integrator (7) and is gathered, and obtains electrical signal data I ₁L _i, from the series of electrical signals data I _iAnd corresponding time t obtains the time t=u that electrical signal peak occurs _M1

3. change the scanning wavelength λ s of spectrometer (5) ₁(i=2 3....15), repeats the second step process, obtains series of electrical signals peak value time of occurrence u _M1(i=2,3....15);

4. with scanning wavelength λ _S1With peak value time of occurrence u _M1Utilize following formula to obtain τ _i, on average obtain the thermal relaxation time value of consult volume τ of this laser instrument again:

$\mathrm{\&tau;}=-\frac{u_m}{\ln [1-\frac{{\mathrm{\&lambda;}}_s-{\mathrm{\&lambda;}}_P\left(T_0\right)}{{{\mathrm{\&lambda;}}_T}^{\&prime;}{R}_{\mathrm{th}}P}]}$

In the formula: λ _sBe the fixing scanning wavelength value of spectrometer, u _mBe corresponding luminous power peak value time of occurrence, λ _p(T ₀) be the initial spike wavelength, λ _T' be the spectroscopic temperature coefficient.

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