WO2016139978A1

WO2016139978A1 - Control device, light source device, laser light-emitting device, and control method

Info

Publication number: WO2016139978A1
Application number: PCT/JP2016/051329
Authority: WO
Inventors: 和田　成司
Original assignee: ソニー株式会社
Priority date: 2015-03-02
Filing date: 2016-01-18
Publication date: 2016-09-09

Abstract

[Problem] To provide a control device capable of bringing the time of light emission closer to the time of an input pulse by making the slope of a rising edge steeper, by combining a voltage drive control system with a current drive control system. [Solution] A control device is provided with: a current drive unit that outputs, to a laser that emits light in accordance with a current, a current that is set in accordance with a first pulse; and a voltage drive unit that, in a period in the pulse width of the first pulse, including a period in which the current output by the current drive unit rises, outputs a current to the laser on the basis of a voltage that is set in accordance with a second pulse having a shorter pulse width than the pulse width of the first pulse.

Description

Control device, light source device, laser light generation device, and control method

The present disclosure relates to a control device, a light source device, a laser light generation device, and a control method.

When a semiconductor light emitting device such as a semiconductor laser is pulse-modulated or driven by PWM (Pulse Width Modulation) for heat dissipation, a current is supplied from the laser driving device to the semiconductor laser to emit light. There is a current drive control system. However, in the current drive control method, the current increase rate does not increase to a certain degree due to the low current increase rate derived from the high output impedance of the current source, and the substantial emission time of the semiconductor laser is the pulse width of the input pulse. Shorter than the time.

Therefore, for example, as disclosed in Patent Document 1, in order to sharpen the dull rise of the pulse emission of the laser, the edge is emphasized by inputting a pulse having a pulse width shorter than the pulse width of the input pulse. There is a technique for bringing the light emission time closer to the pulse width time of the input pulse.

Japanese Patent No. 4398331

However, Patent Document 1 discloses a technique in which an input pulse and a pulse having a pulse width shorter than the pulse width of the input pulse are generated by a current source. As described above, the current drive control method does not increase the current increase rate to a certain extent, so that the current drive control method alone has a limit in bringing the laser light emission time closer to the input pulse time.

Therefore, in the present disclosure, a novel and improved control device capable of bringing the emission time of the laser light closer to the time of the input pulse by combining the current drive control method with the voltage drive control method to make the rising slope steep. , A light source device, a laser beam generator, and a control method are proposed.

According to the present disclosure, a current driving unit that outputs a current set according to a first pulse to a laser that emits light according to a current, and the current driving unit in the pulse width of the first pulse A voltage driver that outputs current to the laser based on a voltage set in accordance with a second pulse having a pulse width shorter than the pulse width of the first pulse in a period including a period in which an output current rises And a control device is provided.

Further, according to the present disclosure, a light source device including the control device is provided.

According to the present disclosure, there is provided a laser light generation device including the light source device.

According to the present disclosure, a current set according to the first pulse is output to a laser that emits light according to the current, and the first pulse in the pulse width of the first pulse is output. And outputting a current to the laser based on a voltage set according to a second pulse having a pulse width shorter than the pulse width of the first pulse in a period including a period in which a current output correspondingly rises. And a control method is provided.

As described above, according to the present disclosure, the current drive control method is combined with the voltage drive control method to make the rising slope steep so that the laser light emission time can be made closer to the input pulse time. In addition, an improved control device, light source device, laser light generation device, and control method can be provided.

Note that the above effects are not necessarily limited, and any of the effects shown in the present specification, or other effects that can be grasped from the present specification, together with or in place of the above effects. May be played.

It is the block diagram which showed an example of the schematic structure of the laser beam generator which concerns on embodiment of this indication. It is explanatory drawing which shows the function structural example of the SOA driver 40 of the laser beam generator 1 which concerns on this embodiment. 3 is an explanatory diagram illustrating a specific circuit configuration example of a current driving unit and a voltage driving unit 103. FIG. It is explanatory drawing which shows the equivalent circuit of semiconductor light-emitting device LD. It is explanatory drawing which shows the example of the relationship of a pulse, a drive voltage, and a drive current with a graph. It is explanatory drawing which shows the example of the relationship of a pulse, a drive voltage, and a drive current with a graph. It is explanatory drawing which shows the example of the relationship of a pulse, a drive voltage, and a drive current with a graph. It is explanatory drawing which shows the example of the relationship of a pulse, a drive voltage, and a drive current with a graph. It is explanatory drawing which shows the example of the waveform of the output current to the semiconductor light-emitting device in the case of only current drive. It is explanatory drawing which shows the example of the waveform of the output current to the semiconductor light-emitting device in the case of only voltage drive. It is explanatory drawing which shows the example of the waveform of the output current to the semiconductor light-emitting device at the time of combining current drive and voltage drive. 3 is an explanatory diagram illustrating a specific circuit configuration example of a current driving unit and a voltage driving unit 103. FIG.

Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In addition, in this specification and drawing, about the component which has the substantially same function structure, duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol.

The description will be made in the following order.
1. One Embodiment of the Present Disclosure 1.1. Configuration of laser light generator 1.2. 1. Configuration of control device Summary

<1. One Embodiment of the Present Disclosure>
[1.1. Configuration of laser light generator]
First, with reference to FIG. 1, the structure of the laser beam generator which concerns on embodiment of this indication is demonstrated. FIG. 1 is a configuration diagram illustrating an example of a schematic configuration of a laser beam generator according to an embodiment of the present disclosure.

As shown in FIG. 1, a laser beam generator 1 according to this embodiment includes a light source unit 10, a wavelength conversion optical system 20, a controller 30, an adder 31, an SOA (Semiconductor Optical Amplifier) driver 40, and the like. including.

The light source unit 10 uses a pulse laser, and has a MOPA (Master) that includes a laser (Mode Locked Laser Diode (hereinafter referred to as MLLD)) having a resonator and a semiconductor optical amplifier (SOA). It is an Oscillator Power Amplifier type light source.

The light source unit 10 includes an MLLD (mode-locked laser) unit 11,

lenses

121, 127 and 129, a mirror 123, an isolator 125, and an optical amplifier unit (SOA unit) 131. The MLLD unit 11 corresponds to a laser (MLLD) including a resonator.

The operation of the light source unit 10 is controlled by the control unit 30. The control unit 30 includes an oscillator 301, an isolator 303, a photodetector 305, a band pass filter 307, a mixer 309, a drive signal generation unit 311, and a servo control driver 313. Hereinafter, the configuration of the light source unit 10 will be described together with the configuration of the oscillator 301 in the configuration of the control unit 30. Other configurations of the control unit 30 will be described later separately.

The signal of frequency f _M output from the oscillator 301 is supplied to the adder 31 and the mixer 309.

The adder 31, to the signal of the frequency _{f M} which is supplied from the oscillator 301, by adding a direct current component (DC Current) having a predetermined output (amplitude), the signal of the frequency _{f M} of the DC component is added The modulated signal is supplied to the MLLD unit 11.

The MLLD unit 11 includes a laser light source 111, a lens 113, and a diffraction grating 115.

The laser light source 111 outputs laser light and can be constituted by various lasers. In the MLLD unit 11 according to the present embodiment, for example, a semiconductor laser is used as the laser light source 111.

Laser light emitted from the laser light source 111 is guided to the diffraction grating 115 through the lens 113. A resonator (spatial resonator) is formed between the mirror on the rear end face of the laser light source 111 and the diffraction grating 115, and the frequency f _{MLLD of the} laser light is determined by the optical path length Lc of the resonator. Specifically, the frequency f _MLLD is determined as f _MLLD = 2Lc / C based on the optical path length 2Lc in the MLLD unit 11 and the light velocity C.

The laser light source 111 is supplied with a modulation signal obtained by adding a direct current component to the signal of the frequency f _M supplied from the oscillator 301 by the adder 31. The laser beam having the frequency f _MLLD in the MLLD unit 11 is phase-modulated by the supplied modulation signal having the frequency f _M.

For modulation of the laser beam having the frequency f _MLLD , for example, a phase modulator composed of an EO (electro-optic) element or an AO (acousto-optic) element may be used. In this case, the phase modulator modulates the laser beam having the frequency f _{MLLD with} the supplied modulation signal having the frequency f _M.

As another example, the laser light source 111 may be directly driven by using the modulation signal having the frequency f _M as a drive signal, so that the laser light modulated at the frequency f _M is emitted from the laser light source 111.

Moreover, the laser light source 111 may include a saturable absorber mirror (SAM) as a rear end face mirror. The supersaturated absorption mirror is mainly composed of a distributed Bragg reflector (DBR) and a saturable absorber. A specific example is a semiconductor saturable absorber mirror (SESAM).

The semiconductor saturable absorption mirror converts the laser light emitted from the laser light source 111 into laser light having a shorter pulse width and higher energy than the laser light by generating a Q-switch mode lock by a saturable absorption mechanism.

The diffraction grating 115 reflects a part of the incident laser light having a predetermined frequency (that is, the frequency f _MLLD ) so as to be emitted to the outside of the MLLD unit 11 and directs the other part toward the laser light source 111. To reflect. In addition, the diffraction grating 115 reflects light having a different frequency from the frequency f _MLLD toward the outside of the MLLD unit 11 and a direction different from the laser light source 111. With such a configuration, with light of a frequency _{f MLLD} resonates inside the MLLD portion 11, and only light of the frequency _{f MLLD} is emitted to the outside of the MLLD portion 11. If the above-described configuration can be realized, the diffraction grating 115 may be replaced with another configuration. As a specific example, instead of the diffraction grating 115, a configuration in which a bandpass filter (BPF) and a half mirror are combined may be provided. Further, hereinafter, the laser light emitted from the MLLD unit 11, that is, the laser light obtained by modulating the light with the frequency f _MLLD by the modulation signal with the frequency f _M may be referred to as “laser light L1”.

The laser beam L1 emitted from the MLLD unit 11 is guided to the isolator 125 through the lens 121 and the mirror 123, passes through the isolator 125, and enters the optical amplifier unit (SOA unit) 131 through the lens 127. If the laser beam L1 emitted from the MLLD unit 11 can be guided to the optical amplifier unit (SOA unit) 131 via the isolator 125, the configuration of the optical system arranged in the optical path is a lens. Needless to say, it is not limited to 121 and the mirror 123.

The isolator 125 is interposed between the MLLD unit 11 and the optical amplifier unit (SOA unit) 131, and transmits the laser light L1 from the MLLD unit 11 toward the optical amplifier unit (SOA unit) 131. Further, the isolator 125 blocks the reflected light (leakage light) from the optical amplifier unit (SOA unit) 131 and the emitted light from the inside of the optical amplifier unit (SOA unit), so that the reflected light and the optical amplifier unit (SOA unit) are blocked. Part) The outgoing light from the inside is prevented from entering the MLLD part 11.

The optical amplifier unit (SOA unit) 131 is composed of, for example, a semiconductor optical amplifier. The optical amplifier section (SOA section) 131 functions as an optical modulation section that amplifies and modulates the incident laser light (that is, the laser light L1 emitted from the MLLD section 11), and is disposed at the subsequent stage of the isolator 125.

The laser output from the MLLD unit 11 is amplified by the optical amplifier unit 131 because its power is relatively small.

The optical amplifier 131 is a small and low-cost optical amplifier, and can be used as an optical gate and an optical switch for turning light on and off. In the present embodiment, the laser light L1 emitted from the MLLD unit 11 is modulated by turning on / off the optical amplifier unit 131.

The operation of the optical amplifier unit 131 is controlled by the SOA driver 40. Specifically, the optical amplifier unit (SOA unit) 131 amplifies the laser beam L1 according to the magnitude of the control current (direct current) supplied from the SOA driver 40. Further, the optical amplifier unit 131 performs intermittent driving with a control current having a pulse waveform at the time of amplification, thereby turning on / off the laser light L1 at a predetermined period, thereby intermittent laser light, that is, pulse laser light. L2 is output.

At this time, the SOA driver 40 intermittently drives the optical amplifier unit (SOA unit) 131 based on the SOA drive signal having the frequency f _SOA . That is, the optical amplifier unit (SOA unit) 131 modulates the laser beam L1 by turning on and off the laser beam L1 at the frequency f _SOA , and outputs the modulated pulsed laser beam L2.

The frequency f _{SOA of the} control current is determined so as to avoid interference with a band in which a servo control driver 313 described later servo-controls the optical path length of the resonator 21.

The pulsed laser light L2 emitted from the optical amplifier unit (SOA unit) 131 is guided to the isolator 303 of the control unit 30 described later through the lens 129, passes through the isolator 303, and enters the wavelength conversion optical system 20. To do.

Next, each configuration of the wavelength conversion optical system 20 will be described. The wavelength conversion optical system 20 includes a resonator 21,

relay lenses

221 and 223, and mirrors 225 and 227.

The pulsed laser light L2 output from the light source unit 10 is incident on the inside of the resonator 21 from the input coupler 201 through an isolator 303 of the control unit 30 described later,

relay lenses

221 and 223, and mirrors 225 and 227. . If the pulsed laser light L2 emitted from the light source unit 10 can be guided into the resonator 21 through the isolator 303, the configuration of the optical system disposed in the optical path is the relay lens 221. And 223 and the

mirrors

225 and 227 are not limited.

The resonator 21 is a so-called optical parametric oscillator (OPO), which resonates the pulse laser beam L2 from the light source unit 10 inside, converts the wavelength of the laser beam L2, and converts the wavelength. The pulsed laser beam L4 is output. The detailed configuration of the resonator 21 will be described below. Hereinafter, the pulse laser light incident on the resonator 21 may be referred to as “excitation laser light”, and the pulse laser light whose wavelength is converted and output from the resonator 21 may be referred to as “OPO laser light”. Further, when the excitation laser light resonating in the resonator 21 is distinguished from the pulse laser light L2 before entering the resonator 21, “excitation laser light L3” or “pulse laser light L3” is used. May be described.

The resonator 21 includes an input coupler 201, mirrors 203, 205, and 207, a dichroic mirror 209, an output coupler 211, and a nonlinear optical element 213. The input coupler 201 and the output coupler 211 are generally partial reflectors (partial reflectors) having a transmittance of several percent.

Further, a nonlinear optical element 213 is disposed between the mirror 203 and the mirror 205.

The nonlinear optical element 213 includes, for example, KTP (KTiOPO ₄ ), LN (LiNbO ₃ ), QPMLN (pseudo phase matching LN), BBO (β-BaB ₂ O ₄ ), LBO (LiB ₃ O ₄ ), KN (KNbO ₃ ). ) Etc. are used.

As an example, the nonlinear optical element 213 converts input laser light (that is, excitation laser light L3) into two wavelengths. Then, at least one of the two converted wavelengths (for example, a long wavelength) laser light resonates in the resonator 21 as the OPO laser light L4, and is output from the output coupler 211 to the outside of the resonator 21. Will be output.

A dichroic mirror 209 is disposed between the input coupler 201 and the mirror 203. Of the light reflected toward the input coupler 201 by the mirror 203, the dichroic mirror 209 transmits the excitation laser light L3 toward the input coupler 201 and reflects the OPO laser light L4 toward the output coupler 211. With such a configuration, the resonator 21 according to the present embodiment is guided through the resonator 21 through optical paths in which the excitation laser light L3 and the OPO laser light L4 are different. The details of the optical paths of the excitation laser light L3 and the OPO laser light L4 in the resonator 21 will be described below.

First, focus on the optical path of the excitation laser beam L3. The excitation laser light L3 incident on the resonator from the input coupler 201 passes through the dichroic mirror 209, reaches the mirror 207 via the mirror 203, the nonlinear optical element 213, and the mirror 205, and is reflected by the mirror 207. .

Further, the excitation laser light L3 reflected by the mirror 207 is guided to the dichroic mirror 209 through the mirror 205, the nonlinear optical element 213, and the mirror 203, passes through the dichroic mirror 209, and is guided to the input coupler 201. Is done.

The input coupler 201 reflects a part of the guided excitation laser beam L3 and emits the other part to the outside of the resonator 21. As described above, the excitation laser light L3 incident on the resonator 21 is repeatedly reflected between the input coupler 201 and the mirror 207. That is, the optical path between the input coupler 201 and the mirror 207 corresponds to the optical path length of the excitation laser light L3 in the resonator 21 (in other words, the resonator length), and the optical path length is the resonance of the excitation laser light L3. By adjusting according to the conditions, the excitation laser light L3 resonates in the resonator 21. Thus, the light density can be increased by resonating light repeatedly in the resonator. Raising the light density in this way is called pumping, and when it is raised, the other light is called pump light. This is an effective method for exceeding the threshold when the output of the excitation light is lower than the threshold of the nonlinear element.

Further, the excitation laser light emitted from the input coupler 201 to the outside of the resonator 21 is guided toward the photodetector 305 by the isolator 303 as reflected light from the resonator 21 and detected by the photodetector 305. Is done.

Next, attention is focused on the optical path of the OPO laser beam L4. The excitation laser light L3 wavelength-converted by the nonlinear optical element 213, that is, the OPO laser light L4 reaches the mirror 207 via the mirror 205 and is reflected by the mirror 207.

Further, the OPO laser light L4 reflected by the mirror 207 is guided to the dichroic mirror 209 via the mirror 205, the nonlinear optical element 213, and the mirror 203, reflected by the dichroic mirror 209, and then output to the output coupler 211. Light is guided.

The output coupler 211 reflects a part of the guided OPO laser beam L4 and emits the other part to the outside of the resonator 21. As described above, the OPO laser light L 4 incident on the resonator 21 is repeatedly reflected between the output coupler 211 and the mirror 207. That is, the optical path between the output coupler 211 and the mirror 207 corresponds to the optical path length of the OPO laser light L4 in the resonator 21 (in other words, the resonator length), and the optical path length is the same as that of the OPO laser light L4. By adjusting according to the resonance condition, the OPO laser beam L4 resonates in the resonator 21.

Next, an operation related to adjustment of the optical path lengths of the excitation laser beam L3 and the OPO laser beam L4 in the resonator 21 will be described. In the resonator 21 according to the present embodiment, the mirror 207 is configured to be adjustable in position along the optical axis direction of the excitation laser light L3 and the OPO laser light L4 incident on the mirror 207. Similarly, the output coupler 211 is configured such that the position can be adjusted along the optical axis direction of the OPO laser light L4 incident on the output coupler 211.

That is, the optical path length of each of the excitation laser light L3 and the OPO laser light L4 is adjusted by adjusting the position of the mirror 207, and the optical path length of the OPO laser light L4 is adjusted by adjusting the position of the output coupler 211. Is adjusted. Therefore, for example, the position of the mirror 207 may be adjusted so as to satisfy the resonance condition of the excitation laser beam L3, and then the position of the output coupler 211 may be adjusted so as to satisfy the resonance condition of the OPO laser beam L4. . By adjusting the positions of the mirror 207 and the output coupler 211 in this order, the optical path length can be controlled so as to satisfy the resonance condition for each of the excitation laser light L3 and the OPO laser light L4.

The positions of the mirror 207 and the output coupler 211 are adjusted by an actuator device such as an electromagnetic actuator (VCM: Voice Coil Motor) or a piezoelectric element configuration, for example. The operation of the actuator device for adjusting the positions of the mirror 207 and the output coupler 211 is controlled by a servo control driver 313 described later.

Next, each configuration of the control unit 30 will be described.

The isolator 303 is interposed between the optical amplifier unit (SOA unit) 131 and the resonator 21, and transmits the pulsed laser light L2 output from the optical amplifier unit (SOA unit) 131 toward the resonator 21.

Further, a part of the excitation laser light L3 transmitted through the input coupler 201 of the resonator 21 and emitted to the outside of the resonator 21, that is, the reflected light from the resonator 21, is reflected by the

mirrors

227 and 225 and the relay lens 223. And 221 and guided to the isolator 303. The isolator 303 reflects the reflected light from the resonator 21 toward the photodetector 305 disposed in a different direction from the optical amplifier unit (SOA unit) 131, so that the reflected light is reflected in the optical amplifier unit (SOA unit). Part) 131 is prevented from entering.

The photodetector 305 is made of, for example, a PD (Photo Detector). The photodetector 305 detects the reflected light from the resonator 21 guided through the isolator 303. The photodetector 305 outputs the detection result of the reflected light from the resonator 21 to the bandpass filter 307 as a reflected signal.

Bandpass filter 307, towards a signal in a band corresponding to the modulation frequency f _M of the excitation laser beam L3 to the mixer 309 is passed through, to cut off the signal other than the band. As a result, among the signals based on the detection result of the photodetector 305, the signal based on the reflected light from the resonator 21 (that is, the excitation laser light L 3 leaking from the resonator 21) passes through the bandpass filter 307. A signal that is input to the mixer 309 and is based on other light due to disturbance or the like is blocked by the bandpass filter 307.

The mixer 309 _multiplies the signal of the frequency f _M supplied from the oscillator 301 by the reflected signal based on the reflected light from the resonator 21 to generate an error signal of the resonator length, and the generated error signal is Output to the drive signal generator 311. The error signal generated at this time corresponds to an error signal in a so-called PDH (Pound-Drever-Hall) method, and the optical path length of the excitation laser light L3 in the resonator 21 and the resonance condition of the excitation laser light L3 are determined. The deviation from the optical path length to be filled is shown.

The drive signal generation unit 311 includes a low-pass filter, a synchronous detection circuit synchronized with intermittent light emission, and a phase compensation unit. The error signal output from the mixer 309 is supplied with a high-frequency component (that is, noise) from the low-pass filter of the drive signal generation unit 311 and supplied to the synchronous detection circuit.

The synchronous detection circuit of the drive signal generation unit 311 synchronously detects the error signal from which noise has been removed by the low-pass filter based on the S / H signal synchronized with intermittent light emission. Then, the synchronous detection circuit outputs an error signal synchronously detected based on the S / H signal (hereinafter, sometimes referred to as “S / H output”) to the phase compensation unit.

The phase compensation unit of the drive signal generation unit 311 performs phase compensation by matching the S / H output supplied from the synchronous detection circuit with the characteristics of the VCM, and sends the signal output whose phase is compensated to the servo control driver 313 as a drive signal. Supply.

The servo control driver 313 adjusts the position of the mirror 207 by driving the actuator device based on the drive signal supplied from the drive signal generation unit 311. At this time, the drive signal is generated based on an error signal indicating a deviation between the optical path length of the excitation laser light L3 in the resonator 21 and the optical path length satisfying the resonance condition of the excitation laser light L3. Therefore, the servo control driver 313 controls the position of the mirror 207 based on the drive signal supplied from the drive signal generation unit 311, so that the optical path length of the excitation laser light L 3 in the resonator 21 is servo-controlled.

When the optical path length of the excitation laser beam L3 in the resonator 21 is controlled, that is, when the position of the mirror 207 varies, the optical path length of the OPO laser beam L4 in the resonator 21 also varies. Become. Therefore, when the servo control driver 313 controls the position of the mirror 207, the servo control driver 313 adjusts the position of the output coupler 211 according to the control amount of the position of the mirror 207, thereby adjusting the optical path length of the OPO laser light L4. Needless to say, it may be controlled together.

The configuration of the laser beam generator 1 according to the present embodiment has been described above with reference to FIG.

In the laser light generator 1 configured as shown in FIG. 1, if the light emission time of the laser light can be brought close to the pulse width of the input pulse input to the SOA driver 40, the light emission efficiency is improved. However, since the current increase rate does not increase to some extent in the current drive control method, the current drive control method alone has a limit in bringing the laser light emission time closer to the pulse width time of the input pulse.

Therefore, the inventor of the present invention diligently studied a technique capable of making the laser light emission time closer to the time of the pulse width of the input pulse. As a result, the present inventor makes the laser light emission time closer to the pulse width time of the input pulse by combining the current drive control method with the voltage drive control method to make the rising slope of the laser light emission steep. The SOA driver 40 that can be used has been devised.

Next, a functional configuration example of the SOA driver 40 of the laser beam generator 1 according to the present embodiment will be described.

FIG. 2 is an explanatory diagram showing a functional configuration example of the SOA driver 40 of the laser light generating apparatus 1 according to the present embodiment. As shown in FIG. 2, the SOA driver 40 includes a signal shaping unit 101, a current driving unit 102, a voltage driving unit 103, and a combining unit 104.

The signal shaping unit 101 outputs the input pulse input to the SOA driver 40 to the current driving unit 102 as a pulse V1, and shapes the input pulse to output it to the voltage driving unit 103 as a pulse V2.

The signal shaping unit 101 generates the pulse V2 so that the pulse width of the pulse V2 is narrower than the pulse width of the pulse V1. The pulse V1 output from the signal shaping unit 101 to the voltage driving unit 102 is a pulse for setting the light emission amount of the laser light of the light source unit 10, and the laser light of the light source unit 10 is emitted during the period of the pulse width of the pulse V1. To do. The pulse V <b> 2 output from the signal shaping unit 101 to the voltage driving unit 103 is a pulse for making the rising slope of the laser light emission of the light source unit 10 steep.

The current driving unit 102 outputs a current based on the pulse V1 sent from the signal shaping unit 101. The current output from the current driving unit 102 based on the pulse V <b> 1 is supplied to the combining unit 104. The voltage driver 103 outputs a current based on the pulse V <b> 2 sent from the signal shaping unit 101. The current output from the voltage driving unit 103 based on the pulse V <b> 2 is supplied to the combining unit 104. Specific circuit configuration examples of the current driver 102 and the voltage driver 103 will be described in detail later.

Further, as will be described later, the current output from the voltage driver 103 based on the pulse V2 is output in a section including the rising section of the current output from the current driver 102 based on the pulse V1. The voltage driver 103 outputs a current based on the pulse V2 in a section including a section where the current output from the current driver 102 is output based on the pulse V1, so that the current driver 102 changes to the pulse V1. Based on this, it is possible to compensate for the rise of the output current.

The combining unit 104 combines the current output from the current driving unit 102 and the current output from the voltage driving unit 103. When the combining unit 104 combines the current output from the current driving unit 102 and the current output from the voltage driving unit 103, the combining unit 104 outputs the combined current to the light source unit 10. The light source unit 10 drives the semiconductor light emitting element based on the current output from the combining unit 104, so that the light emission unit has a steep rise in light emission over the time of the pulse width of the input pulse and the light emission amount is substantially constant. Realize light emission.

Subsequently, specific circuit configuration examples of the current driving unit 102 and the voltage driving unit 103 will be described. FIG. 3 is an explanatory diagram illustrating a specific circuit configuration example of the current driving unit 102 and the voltage driving unit 103.

As shown in FIG. 3, the current driver 102 includes an amplifier AMPA and resistors RS1, RF1, RS2, RF2, and R1.

In the current driving unit 102 shown in FIG. 3, the resistor RS1 and the resistor RF1 are connected in series, and the resistor RS2 and the resistor RF2 are connected in series. The resistor RS1 and the resistor RF1 are connected to the inverting input terminal of the amplifier AMPA, and the resistor RS2 and the resistor RF2 are connected to the non-inverting input terminal of the amplifier AMPA. The side of the resistor RS1 not connected to the inverting input terminal of the amplifier AMPA is connected to the ground, and the side of the resistor RS2 not connected to the non-inverting input terminal of the amplifier AMPA is connected to the terminal to which the pulse V1 is input. Is done. The resistor R1 is provided between the output terminal of the amplifier AMPA and the side of the resistor RF2 that is not connected to the non-inverting input terminal of the amplifier AMPA.

As shown in FIG. 3, the voltage driving unit 103 includes an amplifier AMPB and resistors RV1 and RV2.

In the voltage driver 103 shown in FIG. 3, the resistor RV1 is provided between the inverting input terminal of the amplifier AMPB and the ground. The resistor RV2 is provided between the inverting input terminal of the amplifier AMPB and the output terminal of the amplifier AMPB. The non-inverting input terminal of the amplifier AMPB is connected to a terminal to which the pulse V2 is input.

FIG. 3 also shows the diodes D1, D2, and D3 and the semiconductor light emitting element LD. The diodes D1 and D2 can function as an example of the combining unit 104 in FIG. In addition, the diodes D1, D2, and D3 can function as protective elements that prevent reverse current flow, but the diodes D1, D2, and D3 are not necessarily provided.

The current Io output from the current driving unit 102 can be expressed by the following formula 1. In the following Equation 1, Rf is the resistance value of the resistors RF1 and RF2, and Rs is the resistance value of the resistors RS1 and RS2. Therefore, the resistors RF1 and RF2 have the same resistance value, and the resistors RS1 and RS2 are the same. It has a resistance value. In Equation 1, V1 is a voltage value supplied by the pulse V1.

Io = (Rf / Rs) * (V1 / R1) (Formula 1)

Further, the voltage Vo output from the voltage driving unit 103 can be expressed by Equation 2 below. In Equation 2 below, RV1 and RV2 are resistance values of the resistors RV1 and RV2, respectively. In Equation 2, V2 is a voltage value supplied by the pulse V2.

Vo = (RV1 + RV2) / RV1 * V2 (Equation 2)

The light emission amount of the semiconductor light emitting element LD is a function of the drive current, and the light emission amount of the semiconductor light emitting element LD increases as the drive current increases. Hereinafter, using an equivalent circuit of the semiconductor light emitting element LD, it will be described that the light emission amount of the semiconductor light emitting element LD increases as the drive current increases.

FIG. 4 is an explanatory diagram showing an equivalent circuit of the semiconductor light emitting element LD. The semiconductor light emitting element LD can be represented by a predetermined equivalent inductance L, equivalent capacitance C, and equivalent resistance R, as shown in FIG.

The equivalent inductance L is the total value of the inductance of the package lead and gold wire and the wiring inductance between the light emitting unit 10 and the current driving unit 102, and the equivalent capacitance C is the parasitic capacitance of the submount and lead lead insulating part and the light emitting unit 10 The total wiring capacitance between the current driving unit 102 and the voltage driving unit 103, and the equivalent resistance R represent IV characteristics (differential resistance) at or above the threshold current of the semiconductor laser. The values of L, C, and R vary depending on the type of semiconductor laser, and the frequency characteristics of the semiconductor laser alone are determined by the equivalent inductance L, equivalent capacitance C, and equivalent resistance R.

The equivalent resistance R can be obtained from Equation 3 using terminal voltages V1 and V2 of the light emitting element at two drive current values I1 and I2 having different values.
R = (V2-V1) / (I2-I1) (Equation 3)

Further, the equivalent inductance L is obtained by the following

formulas

4 and 5 from the drive voltage value V3 of the semiconductor light emitting element LD and the current value I3 after the drive time t3 has elapsed.
V = L * dI / dt (equation 4)
L = (V3-R * I3) / (I3 / t3) (Equation 5)

An example of the relationship between the pulse V1, the drive voltage Vo, and the drive current Io is shown. 5 and 6 are explanatory diagrams illustrating an example of the relationship among the pulse V1, the drive voltage Vo, and the drive current Io. FIG. 5 shows the relationship when the drive current Io is 4.0 A, and FIG. 6 shows the relationship when the drive current Io is 6.0 A. 5 and 6, when the drive current Io is 4.0 A, the drive voltage Vo is 4.45 [V], and when the drive current Io is 6.0 A, the drive voltage Vo is 5.0 [V]. . Therefore, the equivalent resistance R is
R = (5.0 [V] -4.45 [V]) / (6.0 [A] -4.0 [A])
= 0.275 [Ω]
Is required.

FIGS. 7 and 8 are explanatory diagrams illustrating an example of the relationship between the pulse V2, the drive voltage Vo, and the drive current Io. FIG. 7 shows the relationship when the drive voltage Vo is 8.5V, and FIG. 8 shows the relationship when the drive voltage Vo is 13V.

When the drive voltage Vo was 8.5V, the time for the drive current Io to rise from 0A to 4A was 174 ns. Therefore, the equivalent inductance L is
L = (8.5 [V] −R [Ω] * 4 [A]) / (4 [A] / 174 [ns])
= (8.5 [V] -0.275 [Ω] * 4 [A]) / (4 [A] / 174 [ns])
= 0.32 [uH]
Is required.

When the drive voltage Vo was 13 V, the time for the drive current Io to rise from 0 A to 4 A was 94 ns. Therefore, the equivalent inductance L is
L = (13 [V] −R [Ω] * 4 [A]) / (4 [A] / 94 [ns])
= (13 [V] -0.275 [Ω] * 4 [A]) / (4 [A] / 94 [ns])
= 0.28 [uH]
Is required.

There is a relationship in which the current increase rate dI / dt of the semiconductor light emitting element LD is proportional to the driving voltage of the voltage driving unit 103 due to the equivalent resistance and equivalent inductance of the semiconductor light emitting element LD obtained from

Equations

4 and 5 and FIGS. Accordingly, the driving voltage of the voltage driving unit 103 is determined based on the equivalent inductance component of the conductor light emitting element LD, and increasing the driving voltage of the voltage driving unit 103 shortens the time required for the light emitting rise of the semiconductor light emitting element LD. Can do.

The effect of the SOA driver 40 having the configuration shown in FIGS. 2 and 3 will be described with reference to FIGS.

FIG. 9 is an explanatory diagram showing an example of a waveform of the output current Io to the semiconductor light emitting element LD when only current driving is performed by the current driving unit 102. FIG. 10 is an explanatory diagram showing an example of the waveform of the output current Io to the semiconductor light emitting element LD when only voltage driving is performed by the voltage driving unit 103. FIG. 11 is an explanatory diagram showing an example of the waveform of the output current Io to the semiconductor light emitting element LD when the current driving by the current driving unit 102 and the voltage driving by the voltage driving unit 103 are combined.

As shown in FIG. 9, in the case of only current driving by the current driving unit 102, the time until the output current Io reaches a predetermined value (6A in the example of FIG. 9) is 200 ns. As shown in FIG. 10, in the case of only voltage driving by the voltage driving unit 103, the time until the output current Io reaches a predetermined value (6A in the example of FIG. 10) is 145 ns, and only in current driving. Although shorter, the output current Io decreases again after the output current Io reaches a predetermined value.

As shown in FIG. 11, when current driving by the current driving unit 102 and voltage driving by the voltage driving unit 103 are combined, the output current Io reaches a predetermined value (6A in the example of FIG. 11). The time until the time is 120 ns, which is even shorter than the case of only voltage driving, and since current driving and voltage driving are combined, even after the output current Io reaches a predetermined value (6A in the example of FIG. 10). Continue to maintain a predetermined value.

As described above, the SOA driver 40 having the configuration shown in FIGS. 2 and 3 can shorten the time until the output current Io reaches a predetermined value as compared with the case of only current driving. It becomes possible.

(Modification)
FIG. 12 is an explanatory diagram illustrating a specific circuit configuration example of the SOA driver 40. FIG. 12 shows a configuration in which a current mirror circuit 105 is inserted after the current driver 102 and a current from the current mirror circuit 105 is output to the semiconductor light emitting element LD.

The current mirror circuit 105 is an example of a current amplification unit of the present disclosure. As shown in FIG. 12, the current mirror circuit 105 includes transistors TR1 and TR2, and the output current from the current driver 102 can be amplified by appropriately selecting the transistors TR1 and TR2.

Therefore, by inserting the current mirror circuit 105 in the subsequent stage of the current driving unit 102, a large current can flow through the semiconductor light emitting element LD even when the output current from the current driving unit 102 is small. Further, by inserting the current mirror circuit 105 at the subsequent stage of the current driving unit 102, the resistance R1 of the current driving unit 102 and the internal parasitic inductance components existing in the elements such as the transistors TR1 and TR2 are fixed on the substrate and minimized. Thus, the current driver 102 can be stabilized.

<2. Summary>
As described above, according to an embodiment of the present disclosure, by combining the current driving by the current driving unit 102 and the voltage driving by the voltage driving unit 103, the light emission time of the semiconductor light emitting element LD is set to the pulse width of the input pulse. An SOA driver 40 that can be brought close to is provided.

When a semiconductor light emitting element LD such as a semiconductor laser is subjected to pulse modulation operation or PWM driving for heat dissipation, the current drive control method alone is caused by the low current increase rate derived from the high output impedance of the current source. The current increase rate does not become higher than a certain level. Therefore, in the case of only the current control driving method, the substantial light emission time of the semiconductor light emitting element LD is shorter than the time of the pulse width of the input pulse.

In the present embodiment, by providing not only the current driver 102 but also the voltage driver 103, the current increase rate of the semiconductor light emitting element LD as a load is increased in proportion to the drive voltage from the voltage driver 103. Can do. By providing not only the current driving unit 102 but also the voltage driving unit 103, the light emission of the semiconductor light emitting element LD starts earlier, so that the light emission time can be extended in a direction closer to the time of the pulse width of the input pulse.

In the present embodiment, the parasitic component of the semiconductor light emitting element LD and the inductance component of the transmission path are controlled, thereby enabling high-speed light emission startup during pulse modulation operation or pulse driving for heat dissipation.

Further, in the present embodiment, in the SOA high power intermittent drive of the short pulse laser light source, the parasitic inductance component that cannot be ignored due to the low internal resistance associated with the high power element is positively controlled to reach the light emission timing in the steady state. Light emission duty can be increased by advancing time.

In the above-described embodiment, the SOA driver 40 is an example of the control device of the present disclosure, the configuration in which the light source unit 10 is added to the SOA driver 40 is an example of the light source device of the present disclosure, and the laser light generator 1 is the main device. It is an example of the laser beam generator of an indication.

The preferred embodiments of the present disclosure have been described in detail above with reference to the accompanying drawings, but the technical scope of the present disclosure is not limited to such examples. It is obvious that a person having ordinary knowledge in the technical field of the present disclosure can come up with various changes or modifications within the scope of the technical idea described in the claims. Of course, it is understood that it belongs to the technical scope of the present disclosure.

In addition, the effects described in this specification are merely illustrative or illustrative, and are not limited. That is, the technology according to the present disclosure can exhibit other effects that are apparent to those skilled in the art from the description of the present specification in addition to or instead of the above effects.

The following configurations also belong to the technical scope of the present disclosure.
(1)
A current driver that outputs a current set according to the first pulse for a laser that emits light according to the current;
In the period including the period in which the current output from the current driver rises in the pulse width of the first pulse, the first pulse is set according to the second pulse having a pulse width shorter than the pulse width of the first pulse. A voltage driver that outputs a current to the laser based on a voltage;
A control device comprising:
(2)
The control device according to (1), wherein the voltage set by the voltage driving unit is determined based on an equivalent inductance component of the laser.
(3)
The control device according to (1) or (2), further including a current amplifying unit that amplifies a current output from the current driving unit and outputs the current to the laser.
(4)
Any of (1) to (3), further comprising: a signal shaping unit that generates the first pulse output from the input pulse to the current driver and the second pulse output to the voltage driver. A control device according to claim 1.
(5)
The control device according to any one of (1) to (4), wherein the laser is an intermittently driven laser.
(6)
A light source device comprising the control device according to any one of (1) to (5).
(7)
A laser beam generator comprising the light source device according to (6).
(8)
Outputting a current set according to the first pulse to a laser emitting according to the current;
In response to a second pulse having a pulse width shorter than the pulse width of the first pulse in a period including a period in which a current output in response to the first pulse rises in the pulse width of the first pulse. Outputting current to the laser based on the voltage set by
Including a control method.

1: Laser light generator 10: Light source unit 11: MLLD unit 20: Wavelength conversion optical system 21: Resonator 30: Control unit 31: Adder 40: SOA driver 111: Laser light source 113: Lens 115: Diffraction grating 121: Lens 123: Mirror 125: Isolator 127: Lens 129: Lens 131: Optical amplifier unit 201: Input coupler 203: Mirror 205: Mirror 207: Mirror 209: Dichroic mirror 211: Output coupler 213: Nonlinear optical element 221: Relay lens 223 : Relay lens 225: Mirror 227: Mirror 301: Oscillator 303: Isolator 305: Optical detector 307: Band pass filter 309: Mixer 311 Drive signal generation unit 313: servo control driver

Claims

A current driver that outputs a current set according to the first pulse for a laser that emits light according to the current;
In the period including the period in which the current output from the current driver rises in the pulse width of the first pulse, the first pulse is set according to the second pulse having a pulse width shorter than the pulse width of the first pulse. A voltage driver that outputs a current to the laser based on a voltage;
A control device comprising:
The control device according to claim 1, wherein the voltage set by the voltage driving unit is determined based on an equivalent inductance component of the laser.
The control device according to claim 1, further comprising a current amplifying unit that amplifies a current output from the current driving unit and outputs the amplified current to the laser.
2. The control device according to claim 1, further comprising a signal shaping unit that generates the first pulse output from the input pulse to the current drive unit and the second pulse output to the voltage drive unit.
The control device according to claim 1, wherein the laser is an intermittently driven laser.
A light source device comprising the control device according to claim 1.
A laser light generator comprising the light source device according to claim 6.
Outputting a current set according to the first pulse to a laser emitting according to the current;
In response to a second pulse having a pulse width shorter than the pulse width of the first pulse in a period including a period in which a current output in response to the first pulse rises in the pulse width of the first pulse. Outputting current to the laser based on the voltage set by
Including a control method.