JP2009026889A - Semiconductor laser device and method for avoiding shut-down of operation of semiconductor laser device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a semiconductor laser device for avoiding the shut-down of operation caused by the generation of a failure such as a short circuit or an opening without shortening an operation life span of the device, and also to provide a method for avoiding the shut-down of the operation of the semiconductor laser device. <P>SOLUTION: A drive current to which a superimposed alternate current generated by a superimposed alternate current element generator 3 is superimposed is made to flow to a semiconductor laser 1 of the semiconductor laser device, and thereby a synchronization detecting circuit 4 detects a voltage signal synchronized with a frequency of the superimposed alternate current. A detection signal comparator 5 compares a differential resistance value of the semiconductor laser 1 calculated from the detected voltage signal with a preset failure determination differential resistance value, determines the occurrence of a failure when the differential resistance value of the semiconductor laser 1 is lower than the failure determination differential resistance value, and sends a switching signal to a current bypass control unit 6. The current bypass control unit 6 bypasses a drive current supplied to the semiconductor laser 1 based on the switching signal not to allow a current to flow to the semiconductor laser 1. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a semiconductor laser device used for a light source for exciting a YAG laser, and more particularly to a semiconductor laser device capable of avoiding an operation stop due to a failure such as a short circuit or an open, and such an operation stop avoidance method.

It is known that a semiconductor laser used as a light source for exciting a YAG laser has the following two types of degradation modes that cause a failure when operated for a long period of time.
Degradation 1 ... Slow degradation that appears as a gradual decrease in output.
Degradation 2 ... Opening of the semiconductor laser due to short circuit or solder melting
With rapid deterioration.

  With respect to the degradation 1, by selecting a device by screening and selecting an appropriate operating condition, a lifetime (for example, 10,000 hours or more) that does not cause a practical problem with respect to the lifetime of the semiconductor laser can be obtained. In fact, it is known that it operates as expected even when applied to an actual YAG laser.

  On the other hand, the failure due to degradation 2 is difficult to predict when it occurs (because it is a sudden or accidental failure), and the degradation is so rapid that the entire YAG laser system operates without any sign. There is a problem that falls into suspension.

In the YAG laser, an array type is generally used as a pumping semiconductor laser, and a YAG rod is optically pumped by flowing a large current of several tens of amperes through the semiconductor laser. In order to construct a YAG laser having an output of several hundred to several kilowatts, several tens to several hundred semiconductor lasers for excitation are required. In order to simultaneously turn on such a large number of high-power semiconductor laser arrays, practically, semiconductor lasers are connected in series in units of at least several tens, and these are controlled by one DC power source. The advantages of serializing semiconductor lasers are the following two points.
Advantage 1 ... The current capacity of the power supply is only one semiconductor laser,
The power supply size is within a practical range.
Advantage 2: Simplified wiring of large capacity.

On the other hand, the disadvantages of serialization are the following two points.
Disadvantages 1 ... If one fails, the whole will stop.
Disadvantage 2 ... The operating state of each semiconductor laser cannot be managed.

In particular, when an open failure occurs due to deterioration 2, the system stops due to demerit 1. The following two points can be considered as measures for preventing such a system stoppage.
Countermeasure 1 ... Switch to the bypass circuit instantaneously when an open failure occurs.
Countermeasure 2 ... It is considered that failure due to degradation 2 does not occur during the lifetime due to degradation 1
Therefore, the semiconductor laser is kept in the state of degradation 1.

  Since it is difficult to implement Measure 2 with the current semiconductor laser, Measure 1 is implemented to prevent the YAG laser system from stopping (for example, see Patent Document 1).

  In addition, since there are only one or two failures due to the degradation 2 during the periodic inspection period of the YAG laser system, it is possible to avoid stopping the system if the failed semiconductor laser is bypassed. The detection of the failure for the measure 1 uses, for example, an open failure of the semiconductor laser package (see, for example, Patent Document 2).

JP 59-103565 A JP 59-113768

  However, the conventional technique has the following problems. Since the semiconductor laser used in the YAG laser system is not a sealed structure, when a short circuit / open failure occurs, surrounding components are soiled and the atmosphere is deteriorated. Therefore, when a short circuit / open failure occurs, even if an attempt is made to prevent the system from being stopped by bypass as in the prior art, the deterioration of the pumping optical system and the surrounding semiconductor laser progresses quickly due to the contamination of surrounding parts, and the YAG laser system There was a problem that the whole lifetime was shortened.

  The present invention has been made in view of the above, and a semiconductor laser device capable of avoiding an operation stop due to occurrence of a short circuit / open failure without shortening the device life and avoiding an operation stop of the semiconductor laser device The purpose is to obtain a method.

  In order to solve the above-described problems and achieve the object, a semiconductor laser device according to the present invention includes a semiconductor laser, a power supply unit that supplies a driving current to the semiconductor laser, and the driving current to the semiconductor laser. A current bypass control unit capable of bypassing and flowing, and detecting a physical quantity that changes in accordance with the amount of non-radiative recombination components at the time of driving the semiconductor laser, and about the value of the detected physical quantity and the physical quantity A physical quantity detection comparison that compares a failure determination reference value as a failure determination reference of the semiconductor laser set in advance and sends a switching signal to the current bypass control unit when it is determined that the failure is based on the comparison result And the current bypass control unit causes the drive current to bypass the semiconductor laser and flow based on the switching signal. That.

  In the present invention, a physical quantity that changes in accordance with the amount of non-radiative recombination component at the time of driving the semiconductor laser is detected, and the value of the detected physical quantity and a failure determination reference value as a predetermined failure determination reference are obtained. In comparison, if a failure is determined based on the comparison result, the drive current supplied to the semiconductor laser is bypassed and the current is prevented from flowing to the semiconductor laser. In other words, based on the detected value of the physical quantity that changes according to the amount of non-radiative recombination components, the occurrence of a short-circuit or open failure in a semiconductor laser is determined and predicted before the actual failure occurs, and the drive current is supplied to the semiconductor laser. By detouring the flow, it is possible to prevent the operation of the apparatus from being stopped and to prevent the surrounding parts from being contaminated due to actual failure.

  Therefore, when this semiconductor laser device is used in a laser system for laser excitation, etc., if the semiconductor laser determined to be faulty is replaced, other components can be used as they are, and the gradual deterioration that appears as a gradual decrease in output. It is possible to continue to use the laser system until the specified semiconductor laser lifetime. In this way, a laser system that is almost maintenance-free can be constructed, and continuous operation in the factory line can be handled.

  Embodiments of a semiconductor laser device and an operation stop avoidance method of the semiconductor laser device according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Of the physical quantities that can predict the failure of the semiconductor laser, the following four points can be listed as those that can be easily monitored.
(1) Change in differential resistance value at operating point of semiconductor laser (2) Change in forward ON voltage value of semiconductor laser (3) Change in reverse current-reverse voltage characteristic of semiconductor laser (4) Change in optical output of semiconductor laser

  An embodiment for predicting a failure using these four physical quantities will be described below.

Embodiment 1 FIG.
FIG. 1 is a diagram showing the variation of the differential resistance value when the semiconductor laser is deteriorated, and FIG. 2 is a block diagram for explaining the configuration and operation of the semiconductor laser device according to the present embodiment.

  In FIG. 1, the horizontal axis represents the operating current applied to the semiconductor laser, and the vertical axis represents the differential resistance value or the optical output. The differential resistance value is displayed on the left vertical axis, and the optical output is displayed on the right vertical axis. In the figure, P1 indicates the relationship between the operating current and the optical output before the semiconductor laser is degraded (dotted line), and P2 indicates the relationship between the operating current and the optical output after the semiconductor laser is degraded (solid line). ). As indicated by P1 and P2, in the semiconductor laser, when the current value exceeds the oscillation threshold value (Th1 before deterioration, Th2 after deterioration), optical output is generated and laser oscillation occurs. DR1 indicates the relationship between the operating current and the differential resistance value before degradation of the semiconductor laser (dotted line), and DR2 indicates the relationship between the operating current and the differential resistance value after degradation of the semiconductor laser (solid line). ). As will be described later, the differential resistance is defined as a ratio of a change in voltage with respect to a minute change in current.

  As shown in FIG. 1, the differential resistance value of the semiconductor laser is constant in a region where the operating current is larger than the oscillation threshold value. When the semiconductor laser deteriorates, the current-light conversion efficiency decreases, the oscillation threshold current increases, and the non-light emitting recombination current component increases. Therefore, the differential resistance value at the time of laser oscillation decreases after the deterioration as compared with before the deterioration (changes from the dotted line (DR1) to the solid line (DR2) in FIG. 1). That is, if the differential resistance value is monitored, it is possible to predict the occurrence of a semiconductor laser failure.

The differential resistance value is monitored by, for example, an LD (laser diode) as a semiconductor laser that drives a minute component (preferably 10% or less of the LD drive current) and a relatively high frequency AC component during its operation. This can be realized by superimposing the current. The differential resistance value Rd can be obtained by the following equation (1) using the current amplitude ΔId of the alternating current component to be superimposed and the voltage amplitude ΔVd of the alternating current component to be superimposed.
Rd = ΔVd / ΔId (1)

  Therefore, it is possible to substantially know the differential resistance value by superimposing an AC component signal in which one of ΔId and ΔVd is known on the drive current and monitoring the other. This method can be applied, for example, in the case of DC operation or when the semiconductor laser is driven by ON / OFF operation at a frequency sufficiently lower than the AC component to be superimposed, and is monitored in a state where the semiconductor laser is actually oscillating. can do. Furthermore, if only a signal synchronized with the frequency of the superimposed AC component is selectively monitored using a PLL (Phase Locked Loop) or the like, malfunction due to noise can be prevented.

  Further, even if the operating point of the semiconductor laser is changed because the laser output is changed in applications such as pumping of YAG laser, as shown in FIG. 1, the differential resistance against the operating current exceeding the oscillation threshold of the semiconductor laser is shown. Since the value is almost constant, failure prediction is possible without changing the failure determination value for determining failure.

  The semiconductor laser device according to the present embodiment performs switching from the semiconductor laser to the bypass circuit before the occurrence of a failure by monitoring the differential resistance value of the semiconductor laser using such a method. As shown in FIG. 2, the semiconductor laser device according to the present embodiment includes a semiconductor laser 1, a control power supply 2 capable of supplying a drive current to the semiconductor laser 1 and controlling the amount of current, and being superimposed on the drive current. A superimposed alternating current component generator 3 that generates a superimposed alternating current component, a synchronization detection circuit 4 that detects a voltage signal synchronized with the superimposed alternating current component from the semiconductor laser 1, a detection result of the synchronous detection circuit 4, and a failure determination value And a current bypass control unit 6 capable of switching the current supplied to the semiconductor laser 1 to a bypass circuit based on the comparison result of the detection signal comparison unit 5. Yes. In the present embodiment, the superimposed alternating current component generator 3, the synchronization detection circuit 4, and the detection signal comparison unit 5 detect a physical quantity that changes according to the amount of non-radiative recombination components when the semiconductor laser 1 is driven. When the detected physical quantity value is compared with a failure determination reference value as a failure determination reference of the semiconductor laser 1 set in advance for the physical quantity, and a failure is determined based on the comparison result, A physical quantity detection / comparison unit that sends a switching signal to the bypass control unit 6 is configured. Note that the value of the physical quantity in the present embodiment is the differential resistance value of the semiconductor laser 1.

  The semiconductor laser 1 is connected to a control power source 2 via a current bypass control unit 6, and a drive current is supplied from the control power source 2. In addition to the current component for driving the laser generated by the control power source 2, the drive current includes a frequency different from the drive current generated by the superimposed AC component generator 3 (for example, higher than the frequency of the drive current, AC component with a constant amplitude ΔId is superimposed. The amplitude ΔId is desirably 10% or less of the amplitude of the drive current, for example. Further, the semiconductor laser 1 is connected to the synchronization detection circuit 4 through a signal line, and only the voltage signal synchronized with the signal frequency component of the superimposed AC component generator 3 from the voltage across the semiconductor laser 1 is detected by the synchronization detection circuit 4. Is detected.

  Here, the voltage signal amplitude ΔVd detected by the synchronization detection circuit 4 is a reference voltage amplitude value ΔVdj (that is, Rdj × ΔId) corresponding to the failure determination differential resistance value Rdj predetermined by the detection signal comparison unit 5. Compared with At this time, if ΔVdj> ΔVd, a switching signal to the bypass circuit is output from the detection signal comparison unit 5 to the current bypass control unit 6, the semiconductor laser determined to be faulty is bypassed, and the current is supplied to the semiconductor laser. No longer flows. The failure determination by comparing the voltage signal amplitude ΔVd and the reference voltage amplitude value ΔVdj is that the differential resistance value of the semiconductor laser 1 calculated from the voltage signal amplitude ΔVd and the amplitude ΔId and the failure determination differential resistance value Rdj. Is determined to be a failure, and when the differential resistance value of the semiconductor laser 1 falls below the failure determination differential resistance value Rdj, a failure is determined.

  The semiconductor laser 1 is, for example, an array type semiconductor laser used as a light source for exciting a YAG laser, and the bypass circuit is controlled by a current bypass control unit 6 so that a number of semiconductor lasers (or LD) can be individually bypassed to control the path of the drive current.

  In addition, when the semiconductor laser itself is turned on / off at a relatively high frequency, the driving current of the semiconductor laser is known, so if the peak voltage of each semiconductor laser is monitored at that driving frequency, the change in the peak voltage value Thus, the failure determination can be performed in the same manner as in the case where the AC component described above is superimposed. In this case, the superimposed alternating current component generator 3 of FIG. 2 is used for controlling the drive current, rather than superimposing a small alternating current component on the drive current.

If the differential resistance value Rdj for failure determination is determined, it is determined that a failure occurs when the differential resistance value of the semiconductor laser enters the hatched region of FIG. 1, and the bypass circuit can be operated immediately before the actual short circuit / opening. . The differential resistance value Rdj for failure determination can be determined from the characteristic distribution of the semiconductor laser to be applied. For example, in the population of the entire semiconductor laser actually used in a YAG laser device or the like, assuming that the average value and the variance value of the differential resistance values are the average value Rda and the variance value σRd, Rdj can be calculated by the following formula (2). .
Rdj = (Rda−A · σRd) × B (2)
However, A and B are parameters. If parameters A and B in Equation (2) are appropriately determined according to the characteristics of the semiconductor laser device to be applied, a short circuit / open failure can be predicted and switched to a bypass circuit before the failure occurs.

  According to the present embodiment, it is predicted that a failure has occurred due to rapid deterioration accompanying short circuit / opening of the semiconductor laser, and the operation is stopped by operating the bypass circuit at a stage before the failure due to short circuiting / opening, etc. In addition to avoiding this, it is possible to prevent contamination of surrounding parts due to actual occurrence of a failure.

  Therefore, when this semiconductor laser device is used for pumping YAG laser, etc., if the semiconductor laser determined to be faulty is replaced, other parts can be used as they are. It is possible to continue to use the laser system (laser such as YAG laser and laser system including this semiconductor laser device) until the lifetime of the semiconductor laser. Thus, by predicting a short circuit / open state and switching to the bypass circuit, it is possible to construct a substantially maintenance-free laser system and to cope with continuous operation in the factory line.

Embodiment 2. FIG.
FIG. 3 is a diagram showing fluctuations in the ON voltage value when the semiconductor laser deteriorates, and FIG. 4 is a block diagram for explaining the configuration and operation of the semiconductor laser device according to the present embodiment.

  In FIG. 3, the horizontal axis represents the operating current applied to the semiconductor laser, and the vertical axis represents the operating voltage value. In the figure, V1 indicates the relationship between the operating current and the operating voltage before deterioration of the semiconductor laser (dotted line), and V2 indicates the relationship between the operating current and the operating voltage after deterioration of the semiconductor laser (solid line). ).

  Since the semiconductor laser is a kind of diode, the forward current-voltage characteristic is generally as shown in FIG. The ON voltage of the diode is determined by the semiconductor laser material, layer structure, doping amount, and the like. When the semiconductor laser is deteriorated, the pN junction of the diode is microscopically destroyed by crystal defects, and non-radiative recombination centers are generated. Accordingly, the carrier diffusion length is shortened and the reverse saturation current density is increased, so that the ON voltage of the semiconductor laser is lowered. Therefore, it is possible to predict a failure by monitoring the ON voltage of the semiconductor laser.

  The simplest method for evaluating the ON voltage of the diode is to measure the voltage when a current of about 1/100 of the operating condition is passed. For example, ifo may be set as the measurement current, and the potential difference between both ends of the semiconductor laser at that time may be simply defined as the ON voltage Vfo. The timing of monitoring by this method is limited to when the apparatus is started up or when the semiconductor laser is turned off by an ON / OFF operation or the like. However, there is an advantage that measurement is simple and easy to apply to an actual apparatus. In the example of FIG. 3, the semiconductor laser that initially had the ON voltage Vfo1 deteriorated, and the ON voltage decreased to Vfo2.

  The semiconductor laser device according to the present embodiment switches from the semiconductor laser to the bypass circuit before the occurrence of the failure by the ON voltage monitor of the semiconductor laser using such a method. As shown in FIG. 4, the semiconductor laser device according to the present embodiment includes a semiconductor laser 1, a control power supply 2, a current bypass control unit 6, a voltage monitor circuit 9, and a voltage comparison unit 10. ing. Further, in the present embodiment, the voltage monitor circuit 9 and the voltage comparison unit 10 detect a physical quantity that changes in accordance with the amount of non-radiative recombination component when the semiconductor laser 1 is driven, and the value of the detected physical quantity and When the physical quantity is compared with a failure determination reference value as a failure determination reference of the semiconductor laser 1 set in advance for the physical quantity, and a failure is determined based on the comparison result, a switching signal is sent to the current bypass control unit 6. The physical quantity detection / comparison unit is configured. Note that the value of the physical quantity in the present embodiment is the voltage value at both ends when a current for voltage measurement is passed through the semiconductor laser 1 in the forward direction.

  In the semiconductor laser 1, a drive current flows while being connected to the control power supply 2 by the current bypass control unit 6. Further, a signal line is connected from the semiconductor laser 1 to the voltage monitor circuit 9 so that the voltage applied to the semiconductor laser 1 can be monitored. At the time of monitoring, a constant current Ifo as a measurement current is injected into the semiconductor laser 1, the voltage value is measured by the voltage monitor circuit 9, and the measurement result is obtained by the voltage comparison unit 10 as a reference voltage value Vfoj for failure determination. Compared with Here, if Vfo <Vfoj, a switching signal to the bypass circuit is output from the voltage comparison unit 10 to the current bypass control unit 6, the semiconductor laser 1 determined to be faulty is bypassed, and a current is supplied to the semiconductor laser. No longer flows.

If the failure determination ON voltage value Vfoj is determined, it is determined that a failure occurs when Vfo enters the hatched region of FIG. 3, and the bypass circuit can be operated immediately before short-circuiting / opening. The failure determination ON voltage value Vfoj can be determined from the characteristic distribution of the semiconductor laser to be applied. For example, in an entire population of semiconductor lasers actually used in a YAG laser device or the like, assuming that the average value and dispersion value of the ON voltage value are the average value Vfoa and the dispersion value σVfo, Vfoj can be calculated by the following equation (3). .
Vfoj = (Vfoa−C · σVfo) × D (3)

  However, C and D are parameters. If the parameters C and D in Equation (3) are appropriately determined according to the characteristics of the semiconductor laser device to be applied, a short circuit / open failure can be predicted and switched to a bypass circuit before the failure occurs.

  This embodiment has the same effect as that of the first embodiment, predicts the occurrence of a failure due to a rapid deterioration accompanying a short circuit / opening of a semiconductor laser, and the bypass circuit in a stage before the occurrence of a failure due to a short circuit / opening, etc. By operating the, it is possible to prevent the operation from being stopped and to prevent the surrounding parts from being contaminated due to actual failure.

Embodiment 3 FIG.
FIG. 5 is a diagram showing fluctuations in the reverse voltage value when the semiconductor laser is deteriorated, and FIG. 6 is a block diagram for explaining the configuration and operation of the semiconductor laser device according to the present embodiment.

  In FIG. 5, the horizontal axis represents the reverse current applied to the semiconductor laser, and the vertical axis represents the reverse voltage. In the figure, V1 indicates the relationship between the reverse current and the reverse voltage before the semiconductor laser deteriorates (dotted line), and V2 indicates the relationship between the reverse current and the reverse voltage after the semiconductor laser deteriorates. (Solid line).

  Since the semiconductor laser is a kind of diode, the reverse current-voltage characteristic is generally as shown in FIG. The reverse saturation current of the diode is determined by the material of the semiconductor laser, the layer structure, the doping amount, and the like. When the semiconductor laser is deteriorated, the pN junction of the diode is microscopically destroyed by crystal defects, and non-radiative recombination centers are generated. Therefore, since the carrier diffusion length is shortened and the reverse saturation current density is increased, the voltage for supplying a constant reverse current to the semiconductor laser is lowered. Therefore, it is possible to predict a failure by monitoring the reverse voltage of the semiconductor laser.

  The reverse voltage of the diode is generally evaluated by passing a small current of, for example, several tens to several hundreds of μA with a constant current source. For example, Ir may be set as the measurement current, and the potential difference between both ends of the semiconductor laser at that time may be simply defined as the reverse voltage Vr. The timing of monitoring by this method is limited to when the apparatus is started up or when the semiconductor laser is turned off by an ON / OFF operation or the like. This evaluation requires a current source for the reverse current, but has an advantage of good sensitivity because it can directly monitor the reverse saturation current fluctuation. In the example of FIG. 5, the semiconductor laser whose reverse voltage value was initially Vr1 deteriorated, and the reverse voltage value decreased to Vr2. The precaution of this method is that Vr1 may become a very large voltage depending on the set value of Ir. Therefore, a voltage limit value must be provided so as not to destroy the semiconductor laser with respect to a current source for passing a minute current. Don't be.

  The semiconductor laser device according to the present embodiment switches from the semiconductor laser to the bypass circuit before the occurrence of the failure by the reverse voltage monitor of the semiconductor laser using the above-described method. As shown in FIG. 6, the semiconductor laser device according to the present embodiment includes a semiconductor laser 1, a control power source 13, a reverse constant current source 14, a voltage monitor circuit 9, a voltage comparison unit 10, a bypass, and the like. And a control unit 6. The reverse constant current source 14 is a current supply unit that supplies a small constant current in the reverse direction to the semiconductor laser 1. Further, in the present embodiment, the reverse direction constant current source 14, the voltage monitor circuit 9, and the voltage comparison unit 10 detect a physical quantity that changes in accordance with the amount of non-radiative recombination components when the semiconductor laser 1 is driven. When the detected physical quantity value is compared with a failure determination reference value as a failure determination reference of the semiconductor laser 1 set in advance for the physical quantity, and a failure is determined based on the comparison result, current bypass control is performed. A physical quantity detection / comparison unit that sends a switching signal to the unit 6 is configured. Note that the value of the physical quantity in the present embodiment is the voltage value at both ends when a current for voltage measurement is passed through the semiconductor laser 1 in the reverse direction.

  In the semiconductor laser 1, a drive current flows while being connected to the control power supply 13 by the current bypass control unit 6. Further, a signal line is connected from the semiconductor laser 1 to the voltage monitor circuit 9 so that the voltage applied to the semiconductor laser 1 can be monitored. At the time of monitoring, an instruction from the control power supply 13 is received, a backward current Ir is injected from the backward constant current source 14 into the semiconductor laser 1, the backward voltage value Vr is measured by the voltage monitor circuit 9, and the measured backward direction is measured. The voltage value Vr is compared with a reference voltage value Vrj for failure determination by the voltage comparison unit 10. Here, if Vr <Vrj, a switching signal to the bypass circuit is output from the voltage comparison unit 16 to the current bypass control unit 6, and the semiconductor laser 1 determined to be faulty is bypassed, and a current is supplied to the semiconductor laser. No longer flows.

  The reverse current-voltage characteristic can also be used as a monitoring method using the reverse current value Ir while the measurement voltage value Vr is constant. In this case, it is possible to predict a failure by increasing the reverse current due to deterioration. When monitoring the reverse current, it is necessary to provide a current limit so that the semiconductor laser does not carry more current than necessary.

If the failure determination reverse voltage value Vrj is determined, it is determined that a failure occurs when Vr enters the hatched region of FIG. 5, and the bypass circuit can be operated immediately before short-circuiting and opening. The failure determination reverse voltage value Vrj can be determined from the characteristic distribution of the semiconductor laser to be applied. For example, assuming that the average value and the dispersion value of the reverse voltage value are the average value Vra and the dispersion value σVr in the population of the entire semiconductor laser actually used in the YAG laser device, Vrj is calculated by the following formula (4). it can.
Vrj = (Vra−E · σVr) × F (4)

  However, E and F are parameters. If the parameters E and F in Equation (4) are appropriately determined according to the characteristics of the semiconductor laser device to be applied, a short circuit / open failure can be predicted and switched to a bypass circuit before the failure occurs.

  This embodiment has the same effect as that of the first embodiment, predicts the occurrence of a failure due to a rapid deterioration accompanying a short circuit / opening of a semiconductor laser, and the bypass circuit in a stage before the occurrence of a failure due to a short circuit / opening, etc. By operating the, it is possible to prevent the operation from being stopped and to prevent the surrounding parts from being contaminated due to actual failure.

Embodiment 4 FIG.
When the semiconductor laser is deteriorated, non-radiative recombination centers are formed as described above, so that the light output at the same current is reduced as compared with that before the deterioration. If many semiconductor lasers connected in series, such as YAG laser devices, have deteriorated in particular, the light output of only those products will be lower than the surroundings. By individually monitoring and comparing the light output, it is possible to predict degradation. Note that the gradual deterioration of the semiconductor laser can be detected by an output monitor such as a YAG laser, but in order to predict a short circuit / open failure, monitoring of the output of the individual semiconductor laser is essential.

  As an optical output monitoring method, for example, a method of installing a monitoring photodiode on the high reflectance coating side of a semiconductor laser is widely used. This method can be used in the same manner even when the semiconductor laser is an array type, and various types of photodiodes such as a CCD and a linear array type can be applied as well as a single element. Further, since the optical output can be monitored during the operation of the semiconductor laser, there is an advantage that the monitoring timing is not limited.

  The semiconductor laser device according to the present embodiment performs switching from the semiconductor laser to the bypass circuit before the occurrence of the failure by the optical output monitor of the semiconductor laser using such a technique. FIG. 7 is a block diagram for explaining the configuration and operation of the semiconductor laser device according to the present embodiment. The semiconductor laser device according to the present embodiment includes a semiconductor laser 1, a control power supply 2, a current bypass control unit 6, a monitoring photodiode 20, and an output current comparison unit 21. Further, in the present embodiment, the monitoring photodiode 20 and the output current comparison unit 21 detect a physical quantity that changes in accordance with the amount of non-radiative recombination component when the semiconductor laser 1 is driven, and the detected physical quantity The value is compared with a failure determination reference value as a failure determination criterion of the semiconductor laser 1 set in advance for the physical quantity, and when it is determined that there is a failure based on this comparison result, a switching signal is sent to the current bypass control unit 6 Is configured as a physical quantity detection / comparison unit. The value of the physical quantity in the present embodiment is an output current value corresponding to the optical output of the semiconductor laser 1 by the monitoring photodiode 20.

  In the semiconductor laser 1, a drive current flows while being connected to the control power supply 2 by the current bypass control unit 6. The optical output of the semiconductor laser is monitored by a monitoring photodiode 20 as an optical output monitoring unit. When a large number of semiconductor lasers are connected in series, such as when used in a YAG laser system, the monitoring photodiode 20 individually monitors the optical output of each semiconductor laser.

  Further, a signal line is connected from the monitoring photodiode 20 to the output current comparison unit 21, and the output Po of the semiconductor laser can be monitored by the output current Ipd of the monitoring photodiode 20. The output current Ipd of the monitoring photodiode 20 is compared with a reference current value Ipdj as a failure determination current value by the output current comparison unit 21. Here, if Ipd <Ipdj, a switching signal to the bypass circuit is output from the output current comparison unit 21 to the current bypass control unit 6, and the semiconductor laser 1 determined to be faulty is bypassed, Current stops flowing.

  This embodiment has the same effect as that of the first embodiment, predicts the occurrence of a failure due to a rapid deterioration accompanying a short circuit / opening of a semiconductor laser, and the bypass circuit in a stage before the occurrence of a failure due to a short circuit / opening, etc. By operating the, it is possible to prevent the operation from being stopped and to prevent the surrounding parts from being contaminated due to actual failure.

  In addition, by using this embodiment in combination with the matrix wiring described in the fifth embodiment, it is suitably used for the purpose of identifying and predicting a deteriorated product among a large number of connected semiconductor lasers. .

Embodiment 5 FIG.
For semiconductor laser devices in which many semiconductor lasers such as those for YAG laser excitation are connected in series, in order to operate the bypass circuit effectively, individual semiconductor lasers are identified and monitored, and those for which deterioration is predicted Switching to the bypass circuit. Such sensing wiring increases in proportion to the number of semiconductor lasers used, and switching is complicated. Therefore, a specific semiconductor laser can be easily designated and monitored by forming the sensing wiring in an M × N matrix (M and N are positive integers), for example. Since it is not always necessary to monitor all of the semiconductor lasers at the same time, they may be monitored in order by addressing the M × N matrix. The monitor control generally uses a microcomputer / sequencer, but such an addressing method has an advantage of good matching with a method using a microcomputer or a sequencer. The operation designation of the bypass circuit may be performed by the same M × N matrix wiring.

  FIG. 8 is a schematic diagram illustrating the semiconductor laser identification device according to the present embodiment, and particularly illustrates an example of sensing wiring. The semiconductor laser identification device using the matrix wiring includes an Mch (M channel) switch 23 and an Nch (N channel) switch 24, and each intersection of M wirings and N wirings drawn from these switches. The semiconductor laser 25 or the photodiode 26 is connected to each switching element. The semiconductor laser 25 or the photodiode 26 is designated by an address (i, j) of an M × N matrix. Here, i and j are integers satisfying 1 ≦ i ≦ M and 1 ≦ j ≦ N, and M and N may be set appropriately for the number of semiconductor lasers used in the apparatus and the connection method. By using such a semiconductor laser identification device, the optical output of the semiconductor laser is individually monitored, and the semiconductor laser that has failed using the failure determination method described in the fourth embodiment is assigned to the address (i, j) can be specified.

  In the first to fourth embodiments, when the semiconductor laser is configured by connecting a plurality of semiconductor lasers in series, by applying this embodiment, wiring is simplified, and a detection circuit or Since only one control circuit is required, cost reduction and improved reliability can be realized.

  As described above, the semiconductor laser device according to the present invention is useful as a semiconductor laser device for excitation used in a YAG laser system or the like.

It is a figure which shows the fluctuation | variation of the differential resistance value at the time of semiconductor laser degradation. 1 is a block diagram for explaining a configuration and operation of a semiconductor laser device according to a first embodiment; It is a figure which shows the fluctuation | variation of the ON voltage value at the time of semiconductor laser degradation. 6 is a block diagram for explaining the configuration and operation of a semiconductor laser device according to a second embodiment; FIG. It is a figure which shows the fluctuation | variation of the reverse voltage value at the time of semiconductor laser deterioration. FIG. 6 is a block diagram for explaining a configuration and operation of a semiconductor laser device according to a third embodiment; FIG. 6 is a block diagram for explaining a configuration and operation of a semiconductor laser device according to a fourth embodiment; It is a schematic diagram which shows the semiconductor laser identification device in Embodiment 5, and is a figure which shows an example of the wiring for sensing especially.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Semiconductor laser 2, 13 Control power supply 3 Superposition alternating current component generator 4 Synchronization detection circuit 5 Detection signal comparison part 6 Current bypass control part 9 Voltage monitor circuit 10 Voltage comparison part 14 Reverse direction constant current source 20 Monitor photodiode 21 Output current Comparison unit 23 Mch switch 24 Nch switch 25 Semiconductor laser 26 Photodiode

Claims (11)

A semiconductor laser;
A power supply for supplying a drive current to the semiconductor laser;
A current bypass control unit capable of flowing the drive current by bypassing the semiconductor laser;
A physical quantity that changes in accordance with the amount of non-radiative recombination components at the time of driving the semiconductor laser is detected, and the value of the detected physical quantity and failure determination as a failure determination criterion of the semiconductor laser set in advance for the physical quantity are detected. When comparing with a reference value and determining a failure based on the comparison result, a physical quantity detection comparator that sends a switching signal to the current bypass controller;
With
The semiconductor laser device, wherein the current bypass control unit causes the drive current to bypass the semiconductor laser based on the switching signal. The physical quantity detection comparing unit is
A superimposed alternating current component generator that generates a superimposed alternating current that is superimposed on the drive current and has a frequency different from that of the drive current;
A synchronization detector for detecting a voltage signal synchronized with the frequency of the superimposed alternating current from the semiconductor laser to which the driving current on which the superimposed alternating current is superimposed is supplied;
The differential resistance value of the semiconductor laser as the value of the physical quantity calculated from the voltage signal detected by the synchronization detection unit and the superimposed alternating current, and the failure as a preset failure determination criterion of the semiconductor laser A detection signal comparison unit that compares a determination differential resistance value, determines that a failure occurs when the differential resistance value of the semiconductor laser is lower than the failure determination differential resistance value, and sends a switching signal to the current bypass control unit When,
The semiconductor laser device according to claim 1, comprising: The physical quantity detection comparing unit is
A voltage monitoring unit for measuring a voltage across the semiconductor laser when a voltage measurement current is passed in the forward direction to the semiconductor laser;
The voltage value as the physical quantity value measured by the voltage monitor unit is compared with a failure determination forward voltage value as a failure determination criterion of the semiconductor laser set in advance, and the measured voltage value is A voltage comparison unit that determines a failure when the voltage falls below the failure determination forward voltage value, and sends a switching signal to the current bypass control unit;
The semiconductor laser device according to claim 1, comprising: The physical quantity detection comparing unit is
A reverse current supply unit for supplying a voltage measurement current in the reverse direction to the semiconductor laser;
A voltage monitoring unit for measuring a voltage across the semiconductor laser when the current for voltage measurement supplied from the reverse current supply unit is supplied to the semiconductor laser;
The voltage value as the physical quantity value measured by the voltage monitor unit is compared with a failure determination reverse voltage value as a failure determination criterion of the semiconductor laser set in advance, and the measured voltage value is A voltage comparison unit that determines a failure when the failure determination reverse voltage value falls below, and sends a switching signal to the current bypass control unit;
The semiconductor laser device according to claim 1, comprising: The physical quantity detection comparing unit is
An optical output monitor for monitoring the optical output of the semiconductor laser to which the drive current is supplied;
The output current value as the value of the physical quantity output from the light output monitor unit corresponding to the monitored light output is compared with a failure determination current value as a failure determination criterion of the semiconductor laser set in advance. An output current comparison unit that determines a failure when the output current value is lower than the failure determination current value, and sends a switching signal to the current bypass control unit;
The semiconductor laser device according to claim 1, comprising: In a configuration in which a plurality of semiconductor lasers connected in series is provided, the semiconductor laser further includes a matrix wiring arranged in a matrix for monitoring each semiconductor laser,
6. The semiconductor laser according to claim 1, wherein a faulty semiconductor laser is identified from the plurality of semiconductor lasers by designating intersections of the matrix wirings. apparatus. Stopping the operation of the semiconductor laser device, comprising: a semiconductor laser; a power supply unit that supplies a driving current to the semiconductor laser; and a current bypass control unit that allows the driving current to bypass the semiconductor laser. It is a workaround of
A physical quantity that changes in accordance with the amount of non-radiative recombination components at the time of driving the semiconductor laser is detected, and the value of the detected physical quantity and failure determination as a failure determination criterion of the semiconductor laser set in advance for the physical quantity are detected. When comparing with a reference value and determining a failure based on the comparison result, a physical quantity detection comparing step of sending a switching signal to the current bypass control unit;
A current bypass step in which the current bypass control unit bypasses the drive current with respect to the semiconductor laser based on the switching signal; and
An operation stop avoidance method for a semiconductor laser device, comprising: The physical quantity detection comparison step includes:
Superimposing a superimposed alternating current having a frequency different from that of the drive current on the drive current supplied from the power supply unit to the semiconductor laser;
Detecting a voltage signal synchronized with the frequency of the superimposed alternating current from the semiconductor laser supplied with the drive current on which the superimposed alternating current is superimposed;
The differential resistance value of the semiconductor laser is calculated from the detected voltage signal and the superimposed alternating current, the differential resistance value of the semiconductor laser as the value of the physical quantity, and a preset failure determination criterion for the semiconductor laser Comparing with a failure determination differential resistance value as, and determining a failure when the differential resistance value of the semiconductor laser is lower than the failure determination differential resistance value, and sending a switching signal to the current bypass control unit When,
The method of avoiding the operation stop of the semiconductor laser device according to claim 7, comprising: The physical quantity detection comparison step includes:
Measuring a voltage across the semiconductor laser when a voltage measurement current is passed in the forward direction;
The measured voltage value as the physical quantity value is compared with a failure determination forward voltage value as a failure determination criterion of the semiconductor laser set in advance, and the measured voltage value is the failure determination forward direction. Determining a failure when the voltage value falls below the voltage value, and sending a switching signal to the current bypass control unit;
The method of avoiding the operation stop of the semiconductor laser device according to claim 7, comprising: The physical quantity detection comparison step includes:
Supplying a voltage measurement current in a reverse direction to the semiconductor laser, and measuring a voltage across the semiconductor laser;
The measured voltage value as the physical quantity value is compared with a failure determination reverse voltage value as a failure determination criterion of the semiconductor laser set in advance, and the measured voltage value is the failure determination reverse direction. Determining a failure when the voltage value falls below the voltage value, and sending a switching signal to the current bypass control unit;
The method of avoiding the operation stop of the semiconductor laser device according to claim 7, comprising: The physical quantity detection comparison step includes:
Monitoring the optical output of the semiconductor laser to which the drive current is supplied from the power supply unit;
An output current value as a value of the physical quantity corresponding to the monitored optical output is compared with a failure determination current value as a failure determination criterion of the semiconductor laser set in advance, and the output current value is determined as the failure determination. Determining a failure when the current value is lower than the current value, and sending a switching signal to the current bypass control unit;
The method of avoiding the operation stop of the semiconductor laser device according to claim 7, comprising:

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