JP2006310665A - Signal-detecting device for semiconductor laser element and input/output characteristics detecting device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide, at low cost, an input/output characteristics detecting device which can set a plurality of sampling times in a single pulse, with arbitrary timing and measure the input/output characteristics of a semiconductor laser element at each sampling times. <P>SOLUTION: Detecting circuits 30 and 50 for a pulse signal outputted from the semiconductor laser element comprise amplifiers 32 and 52 for the pulse signal, A/D converters 34 and 54, which digitally convert amplified pulse signals, and latch circuits 36 and 56 constituted of three-stage latch ICs. Digital signals corresponding to the pulse signals are inputted to the latch circuits 36 and 56, and one latch timing signal each is input to respective latches IC of three stages, during one pulse of the pulse signal by a timing circuit 40 at points t1, t2, and t3 of time, in the order, from the rising point t0 of time to detect digital signals, corresponding to the crest values of the pulse signals at the points t1, t2, and t3 of the times (sampling times), when latch timing signals are inputted. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a pulse-driven semiconductor laser element signal detection apparatus and an input / output characteristic detection apparatus using the same.

  In recent years, as one of typical photoelectronic devices, a semiconductor laser element has been used in many fields. For example, in the field of an optical disk drive, a pulsed semiconductor laser element is used as a light source for writing. Yes. In this field, as the demand for increasing the writing speed is high, semiconductor laser elements are increasing in output year by year. Therefore, a semiconductor laser element capable of stably oscillating a laser even at a high driving current is provided. It is necessary to provide.

  However, in some semiconductor laser devices, linearity is disturbed on the graph showing the optical output characteristics (input / output characteristics) with respect to the driving current in the high current region, or the rise of the pulsed light output during pulse driving is insufficient. In some cases, the flatness of the pulse waveform is lost, such as overshoot. Such a phenomenon is called a kink phenomenon, which is caused by crystal defects or stacking errors of the semiconductor thin film during manufacturing, and the oscillation of the transverse mode becomes unstable. It cannot be used as a light source. Therefore, when manufacturing semiconductor laser devices, screening is performed by measuring the input / output characteristics under the driving conditions in accordance with the actual usage conditions for all manufactured semiconductor laser devices, and the above-described kinks are generated. The semiconductor laser is removed.

  As shown in FIG. 6, the semiconductor laser input / output characteristic detection apparatus used for the screening has a predetermined pulse width and repetition period from the current pulse circuit 100, and the peak value increases to a predetermined maximum value. The current pulse train signal to be input is input to the semiconductor laser 102 which is the inspection target element and is pulse-driven, and the peak value of the driving current extracted from the semiconductor laser 102 and the pulsed light emitted from the semiconductor laser element 102 are converted into photoelectric conversion means 104. The input / output characteristics of the semiconductor laser 102 are detected by detecting the peak value of the electric pulse signal obtained by the conversion by the above.

  Conventionally, sample hold circuits 106 and 106 have been used as detection circuits for detecting the peak value of the drive current and the peak value of the electric pulse signal (see, for example, Patent Document 1). The sample hold circuit 106 includes a relay 108 that cuts off an input drive current or electric pulse signal and a capacitor 110 that is charged by the input signal. The relay 108 is set to OPEN at an arbitrary timing of the input signal to be detected. Thus, the peak value of the input signal at that time (sample time) is held, and thereby the held peak value can be measured.

However, when the sample hold circuit 106 is used as the detection circuit for detecting the peak value of the pulsed input signal in the input / output characteristic detection apparatus as described above, there are the following problems. That is, in order to detect the waveform flatness of the pulsed light output from the semiconductor laser element 102 during pulse driving, a plurality of N sample times are set in one pulse of the pulsed light, and the input / output characteristics at each sample time are set. Is detected, a plurality of N pulse current pulse train signals having the same peak value are input to the semiconductor laser element 102, and the drive current and electric pulse signal from the semiconductor laser 102 are relayed to the relay 108 of the sample hold circuit 106 each time. It is necessary to repeat the measurement N times a plurality of times at different timings, which requires N times as a problem. In particular, in the current mass production process in which input / output characteristic inspection is performed over the entire number of manufactured semiconductor laser elements, it takes a lot of time, which is a problem.
Japanese Patent Laid-Open No. 2004-200388

  The present invention has been made in view of the above problems, and by setting a plurality of N sample times at an arbitrary timing within one pulse without increasing the detection time, the input / output characteristics at each sample time are set. An object of the present invention is to provide an input / output characteristic detection device for a semiconductor laser element capable of detecting the above at low cost.

  The invention according to claim 1 is a signal detection device for a semiconductor laser element that outputs pulsed light based on a current pulse train signal whose peak value increases stepwise with a constant period. A current detection circuit for detecting a peak value at a predetermined sample time in the pulse, wherein the current detection circuit is an A / D converter and an N stage to which a latch timing signal is input (where N> 1 integer) The latch timing signal is set so that the sampling time in the one pulse becomes longer in order, and each latch timing signal is supplied to the N-stage latch means. By inputting each, N sample times are set in one pulse of the drive current, and each wave height at each sample time is set. A signal detecting apparatus for a semiconductor laser device characterized by detecting a.

  According to a second aspect of the present invention, there is provided a signal detecting device for a semiconductor laser element that outputs a pulsed light based on a current pulse train signal whose peak value increases stepwise with a constant period, and an electric signal converted from the pulsed light by a photoelectric conversion means. It has a photodetection circuit for detecting a peak value at a predetermined sample time in one pulse in the pulse signal, and the photodetection circuit has A / D conversion means and N stages (however, N The latch timing signal is set to N so that the sampling time in the one pulse becomes longer in order, and each of the N stages of latch means has each latch timing signal. By inputting the latch timing signal, N sample times are set in one pulse of the electric pulse signal, and each sample time is set. A signal detecting apparatus for a semiconductor laser device characterized by detecting the peak value of Rusorezore.

  According to a third aspect of the present invention, a semiconductor laser element is driven by inputting a current pulse train signal whose peak value increases stepwise with a constant period, and the peak value of the driving current of the semiconductor laser element is calculated from the semiconductor laser element. A semiconductor laser device for detecting a change in the peak value of a pulsed light relative to a change in the peak value of a drive current by detecting the peak value of an electric pulse signal obtained by converting the emitted pulsed light by a photoelectric conversion means. In the input / output detection apparatus, a current detection circuit for detecting a peak value at a predetermined sample time in one pulse in the drive current extracted from the semiconductor laser element, and a wave at a predetermined sample time in one pulse in the electric pulse signal A photodetection circuit for detecting a high value, wherein the current detection circuit is configured to receive an A / D conversion unit and an N input with a first latch timing signal; (Where N> 1 is an integer) having a first latch circuit, and the number of the first latch timing signals is N so that the sampling time in one pulse of the drive current becomes longer in order. The first latch timing signals are respectively input to the N-stage latch means in the first latch circuit, so that N sample times are set in one pulse of the drive current. Each peak value is detected, and the light detection circuit includes an A / D conversion unit and a second latch circuit including an N-stage latch unit to which a second latch timing signal is input. N latch timing signals are set at the same timing as the respective sample times of the first latch timing signals, and each latch timing signal is set in each of the N stages of latch means in the second latch circuit. 2 latch timing signals are respectively input, N sample times are set in one pulse of the electric pulse signal, and a peak value at each sample time is detected. This is an input / output characteristic detection device.

  According to a fourth aspect of the present invention, the electric pulse signal corresponding to a change in the peak value of the driving current is based on the peak value of the driving current and the peak value of the electric pulse signal detected at the same sampling time in one pulse. 4. The input / output characteristic detecting device for a semiconductor laser device according to claim 3, wherein a change in the crest value of is detected.

  The invention according to claim 5 includes a crest value control means for varying a crest value of the current pulse train signal, and based on a deviation between a target crest value of the current pulse train signal and a crest value detected by the current detection circuit, 5. The semiconductor laser element according to claim 3, wherein a peak value of a current pulse train signal input to the semiconductor laser element is set to a predetermined target peak value by feedback compensation of a peak value control means. This is an input / output characteristic detection device.

  The invention according to claim 6 is characterized in that the integer N is 3 or more, and the interval of each sample time of the first latch timing signal is set to be equal. An input / output characteristic detection apparatus for a semiconductor laser device according to claim 1.

  According to the present invention, input / output characteristics of a semiconductor laser element at a plurality of sample times set at arbitrary timings in one pulse can be measured at high speed without increasing the cost.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a block circuit diagram of an input / output characteristic detection device 10 for a semiconductor laser device 1 according to the present embodiment. FIG. 2 is a graph showing various electrical signals in a current pulse train signal generation circuit 20 of the block circuit of the device 10. 3 is a graph showing various signals in the detection circuits 30 and 50 of the block circuit of the apparatus 10, and FIG. 4 is a graph showing input / output characteristics detected by the apparatus 10.

  As shown in FIG. 1, this input / output characteristic detection device 10 is a device for detecting a change in optical output with respect to a change in drive current of a semiconductor laser element 1 during pulse driving, and is a semiconductor laser to be inspected. A current pulse train signal generation circuit 20 that generates a current pulse train signal input to the element 1, a current detection circuit 30 that detects a drive current extracted from the semiconductor laser element 1 that has been operated in response to the current pulse train signal, and a current pulse train signal The light detection circuit 50 receives the pulsed light emitted from the semiconductor laser element 1 and the main processor 12 controls the circuits 20, 30, and 50 according to a predetermined operation program.

  The current pulse train signal generation circuit 20 includes a staircase waveform voltage generation circuit 22 and a drive circuit 24. The staircase waveform voltage generation circuit 22 that receives the input of the voltage generation command from the main processor 12 is shown in FIG. As shown, a reference voltage signal Vref whose peak value increases stepwise from 0 V to a predetermined maximum value (eg, 10 V) with a constant period τc (eg, τc = 1 ms) is generated and input to the drive circuit 24. .

  In the drive circuit 24 to which the reference voltage signal Vref is input, the voltage-current conversion circuit 26 converts the reference voltage signal Vref into a current signal. The converted current signal is subjected to ON / OFF control of the switch means 28 configured using a high-speed switching transistor or the like, so that the pulse width Pw (for example, 20 ns) and the repetition period as shown in FIG. It is shaped into a current pulse train signal having Pt (for example, 40 ns) and the peak value increasing to a predetermined maximum value. The switch means 28 is controlled by ON / OFF switching operation timing pulses sent from a pulse generator (not shown) that operates in response to a pulse width setting command from the main processor 12.

  The current pulse train signal generated in the current pulse train signal generation circuit 20 is input to the semiconductor laser element 1 to be inspected, so that the semiconductor laser element 1 is driven and the light intensity and pulse width corresponding to the peak value of the drive current are obtained. The pulse light having The pulse current value flowing through the semiconductor laser element 1 operated in this way, that is, the peak value of the drive current is detected by the current detection circuit 30.

  The current detection circuit 30 includes an amplifier 32, an A / D converter 34, and a latch circuit 36, and amplifies and digitally converts the drive current extracted from the semiconductor laser element 1 via the amplifier 32 and the A / D converter 34. By inputting this to a latch circuit 36 composed of a three-stage latch IC, a digital signal corresponding to the peak value of the drive current input to each latch IC is detected.

  Specifically, as shown in FIG. 3, the drive current for one pulse extracted from the semiconductor laser element 1 input to the A / D converter 34 is digital at the rising edge of the conversion clock of the A / D converter 34. Each time it is converted into a signal, it is input to each of the three stages of latch ICs of the latch circuit 36 disposed at the subsequent stage of the A / D converter 34. The latch circuit 36 receives a latch operation command from the main processor 12, and from the timing circuit 40, in one pulse of the driving current, the time from the rising time t 0 of the pulse is different, and the three times t 1, which become longer in order, Latch timing signals are output at t2 and t3, and three latch timing signals set at different times t1, t2 and t3 are input to each of the three stages of latch ICs in the latch circuit 36, respectively. Each of the three stages of latch ICs operates according to the latch timing signal received, and detects a digital signal corresponding to the peak value of the drive current at the time when the latch timing signal is input. That is, the three times t1, t2, and t3 set during one pulse are sample times for detecting the peak value of the drive current during one pulse. Note that in the A / D converter 34, there may be a conversion time lag of a period corresponding to several clocks (for example, 6 clocks) from the input of the drive current to the output of the digital conversion result. . In such a case, the latch timing signal in FIG. 3 may be set to a time delayed by the conversion time lag (for example, a period corresponding to 6 clocks).

  The crest values of the drive current at the three sample times t1, t2, and t3 detected by the latch circuit 36 are output from the current detection circuit 30 and transferred to the main processor 12.

  The intensity of the pulsed light output from the semiconductor laser element 1, that is, the peak value of the pulsed light is a photoelectric conversion means 60 using a light receiving element such as a photodiode disposed in the vicinity of the semiconductor laser element 1. Is converted into an electric pulse signal, and the peak value of the electric pulse signal is detected by the optical output detection circuit 50.

  The light detection circuit 50 has the same configuration and operation as the current detection circuit 30 except that an electric pulse signal corresponding to the pulsed light emitted from the semiconductor laser element 1 is input. That is, the photodetection circuit 50 includes an amplifier 52, an A / D converter 54, and a latch circuit 56, and amplifies and digitally converts an electrical pulse signal corresponding to the pulsed light via the amplifier 52 and the A / D converter 54. Then, the data is output to a latch circuit 56 composed of a three-stage latch IC. In the latch circuit 56 to which a digital signal corresponding to the electric pulse signal is input, the timing from the timing t40 when the pulse of the electric pulse signal rises to the latch circuit 36 of the current detection circuit 30 is input. Three latch timing signals set at the same time as the timings t1, t2, and t3 set in the timing signal are respectively input to the three stages of latch ICs in the latch circuit 56. That is, the three latch timing signals in the photodetection circuit 50 are set to the same timing as the respective sample times t1, t2, and t3 of the latch timing signal in the current detection circuit 30. Each of the three stages of latch ICs in the latch circuit 56 operates in accordance with the latch timing signal received, and corresponds to the peak value of the current pulse signal at times (sample times) t1, t2, and t3 when the latch timing signal is input. Detected digital signal. The peak values of the pulsed light detected at the three sample times detected by the latch circuit 56 are output from the photodetection circuit 50 and transferred to the main processor 12.

  Note that the latch circuits 36 and 56 of the current detection circuit 50 and the light detection circuit 50 may be configured by a CPLD (Complex Programmable Logic Device) instead of the three-stage latch IC.

  Then, detection of the crest value of the driving current and the crest value of the pulsed light of the semiconductor laser element 1 corresponding to all the current pulses having the crest value of the current pulse train signal output from the current pulse train signal generation circuit 20 is performed. Thus, as shown in FIG. 4, it is possible to detect the optical output characteristics with respect to the injection current of the semiconductor laser device 1 at the three sample times t1 to t3 set in one pulse.

  In the present embodiment, three sample times are set. However, the present invention is not limited to this, and the latch ICs in both the latch circuits 36 and 56 of the current detection circuit 30 and the photodetection circuit 50 are arranged in N stages. (An integer of N> 1) Preferably, it is composed of three or more stages, and N latch timing signals may be set, thereby detecting input / output characteristics at different N sample times in one pulse. be able to.

  Further, in this embodiment, when three or more different sample times are set in one pulse, it is preferable to set each sample time at equal intervals. It is possible to detect a semiconductor laser element in which the flatness of the pulse waveform such as insufficient rise or overshoot of the pulsed light output from 1 is lost.

  As described above, in the apparatus according to the present embodiment, each of the current detection circuit and the light detection circuit is configured by an A / D converter and a latch circuit including an N-stage latch IC, and A / D conversion is performed. By setting N latch timings for sampling the digital signal output from the detector, N sample times are set in one pulse of the signal input to each detection circuit, and each wave at each sample time is set. A high value can be detected at a time, and in order to detect input / output characteristics at different N sample times during one pulse in a pulse-driven semiconductor laser element, the peak value of the drive current and the pulse light It is not necessary to repeat the measurement of the peak value of N times, and the detection time does not increase. Therefore, in the mass production process, such input / output characteristics at a plurality of sample times can be detected practically, and the flatness of the pulse waveform of the pulsed light output from the semiconductor laser element 1 is lost. More reliable screening can be performed by detecting a semiconductor laser element.

  In addition, according to the present invention, since the peak value is detected by an inexpensive latch IC, even when the input / output characteristics at the N sample times are detected, it is configured by N latch ICs. Can be manufactured at low cost.

  Furthermore, since the peak value sampled by the latch IC is output almost simultaneously with the input of the latch timing signal, high-speed measurement is possible.

(Second Embodiment)
Next, a second embodiment of the present invention will be described with reference to FIG. The second embodiment relates to a semiconductor laser element input / output characteristic detection apparatus, and the same components as those in the first embodiment are denoted by the same reference numerals and description thereof is omitted.

  Compared with the first embodiment, the second embodiment is configured to perform feedback compensation so that the peak value of the drive current extracted from the semiconductor laser element becomes a predetermined target peak value, that is, a comparator that is a peak value control means. The difference is that 70 is provided.

  As shown in FIG. 5, the comparator 70 has one input terminal connected to the output terminal of the staircase waveform voltage generation circuit 22, and the other input terminal connected to the output terminal of the current detection circuit 30 via the D / A converter 72. Thus, the reference voltage signal Vref having a peak value corresponding to the target peak value A of the current pulse train signal is input to one input terminal, and the semiconductor laser element 1 detected by the current detection circuit 30 is input to the other input terminal. The peak value of the drive current is input. As a result, the comparator 70 calculates a deviation between the target peak value A and the peak value of the driving current of the semiconductor laser device 1, and a signal indicating this deviation is input to the driving circuit 24. A current pulse train signal having a peak value corresponding to the target peak value A is output from the current conversion circuit 26.

  In the input / output characteristic detection apparatus of the present embodiment, for example, when a current pulse train signal having the same peak value is input, and the input / output characteristics are detected based on the average values of the corresponding drive current and pulse light peak values. Even when a plurality of sample times are set in one pulse of the drive current and pulsed light, there is no need to change the sample times a plurality of times and repeat the measurement, and the detection time does not increase. Further, since the drive current is feedback compensated so as to be the target peak value A by the comparator 70, the input / output characteristics can be accurately detected based on the average value as described above.

1 is a block circuit diagram of an input / output detection apparatus for a semiconductor laser device according to a first embodiment of the present invention. 2 is a graph showing various electric signals in a current pulse train signal generation circuit of the block circuit of FIG. 1. It is a graph which shows the various signals in the detection circuit of the block circuit of FIG. It is a graph which shows the input-output characteristic detected by the same apparatus. It is a block circuit diagram of the input / output detection apparatus of the semiconductor laser element concerning the 2nd Embodiment of this invention. It is a block circuit diagram of the conventional input / output detection apparatus of a semiconductor laser element.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Semiconductor laser element 10 ... Input / output characteristic detection apparatus 20 ... Current pulse train signal generation circuit 30 ... Current detection circuit 32 ... Amplifier 34 ... A / D converter 36 ... Latch circuit 40 ... Timing circuit 50 ... Optical output detection circuit 52 ... Amplifier 54 ... A / D converter 56 ... Latch circuit 60 ... Photoelectric conversion means 70 ... Comparator t1, t2, t3 ... Sample time

Claims (6)

In a signal detection device for a semiconductor laser element that outputs pulsed light based on a current pulse train signal whose peak value increases stepwise with a constant period,
A current detection circuit for detecting a peak value at a predetermined sample time within one pulse in the drive current extracted from the semiconductor laser element;
The current detection circuit includes an A / D conversion unit and a latch circuit including an N-stage (where N> 1 integer) latch unit to which a latch timing signal is input,
The latch timing signals are set to N so that the sample times in the one pulse become longer in order,
Each of the latch timing signals is input to the N-stage latch means, so that N sample times are set in one pulse of the drive current, and each peak value at each sample time is detected. A signal detection device for a semiconductor laser element. In a signal detection device for a semiconductor laser element that outputs pulsed light based on a current pulse train signal whose peak value increases stepwise with a constant period,
A light detection circuit for detecting a peak value at a predetermined sample time in one pulse in the electric pulse signal converted from the pulsed light by the photoelectric conversion means;
The photodetection circuit includes A / D conversion means and a latch circuit including N-stage (where N> 1 integer) latch means to which a latch timing signal is input,
The latch timing signals are set to N so that the sample times in the one pulse become longer in order,
Each of the latch timing signals is input to the N-stage latch means, so that N sample times are set in one pulse of the electric pulse signal, and each peak value at each sample time is detected. A signal detection device for a semiconductor laser element. A semiconductor laser element is driven by inputting a current pulse train signal whose peak value increases stepwise with a constant period, and the peak value of the driving current of the semiconductor laser element and the pulsed light emitted from the semiconductor laser element are photoelectrically converted. In the input / output detection device of the semiconductor laser element for detecting the change in the peak value of the pulsed light relative to the change in the peak value of the drive current by detecting the peak value of the electric pulse signal obtained by conversion by means,
A current detection circuit for detecting a crest value at a predetermined sample time within one pulse in the drive current extracted from the semiconductor laser element, and a light detection for detecting a crest value at a predetermined sample time within one pulse in the electric pulse signal. Have a circuit,
The current detection circuit includes an A / D conversion unit and a first latch circuit including an N-stage (where N> 1 integer) latch unit to which the first latch timing signal is input,
The number of the first latch timing signals is set so that the sampling time in one pulse of the driving current becomes longer in order,
Each of the first latch timing signals is input to the N-stage latch means in the first latch circuit, so that N sample times are set in one pulse of the drive current, and each wave at each sample time is set. Detect highs,
The photodetection circuit includes an A / D conversion unit and a second latch circuit including an N-stage latch unit to which a second latch timing signal is input.
N second latch timing signals are set at the same timing as the respective sample times of the first latch timing signals,
Each of the second latch timing signals is input to the N-stage latch means in the second latch circuit, so that N sample times are set in one pulse of the electric pulse signal. Detect the peak value,
An input / output characteristic detection apparatus for a semiconductor laser device. Based on the peak value of the driving current and the peak value of the electric pulse signal detected at the same sampling time in one pulse, a change in the peak value of the electric pulse signal with respect to a change in the peak value of the driving current is detected. The input / output characteristic detection device for a semiconductor laser element according to claim 3. Crest value control means for varying the crest value of the current pulse train signal,
Based on the deviation between the target peak value of the current pulse train signal and the peak value detected by the current detection circuit, the peak value of the current pulse train signal input to the semiconductor laser element is obtained by feedback compensation of the peak value control means. The input / output characteristic detection device for a semiconductor laser element according to claim 3 or 4, wherein the input / output characteristic detection device is set to a predetermined target peak value. 6. The semiconductor laser device according to claim 3, wherein the integer N is equal to or greater than 3, and the interval between the sampling times of the first latch timing signal is set to be equal. Input / output characteristic detector.

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