WO2015098321A1 - 制御装置、制御方法、及びプログラム - Google Patents
制御装置、制御方法、及びプログラム Download PDFInfo
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- WO2015098321A1 WO2015098321A1 PCT/JP2014/079817 JP2014079817W WO2015098321A1 WO 2015098321 A1 WO2015098321 A1 WO 2015098321A1 JP 2014079817 W JP2014079817 W JP 2014079817W WO 2015098321 A1 WO2015098321 A1 WO 2015098321A1
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- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/35—Non-linear optics
- G02F1/353—Frequency conversion, i.e. wherein a light beam is generated with frequency components different from those of the incident light beams
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B26/00—Optical devices or arrangements for the control of light using movable or deformable optical elements
-
- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/35—Non-linear optics
- G02F1/3501—Constructional details or arrangements of non-linear optical devices, e.g. shape of non-linear crystals
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/005—Optical devices external to the laser cavity, specially adapted for lasers, e.g. for homogenisation of the beam or for manipulating laser pulses, e.g. pulse shaping
- H01S3/0092—Nonlinear frequency conversion, e.g. second harmonic generation [SHG] or sum- or difference-frequency generation outside the laser cavity
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- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/35—Non-linear optics
- G02F1/3501—Constructional details or arrangements of non-linear optical devices, e.g. shape of non-linear crystals
- G02F1/3503—Structural association of optical elements, e.g. lenses, with the non-linear optical device
-
- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F2203/00—Function characteristic
- G02F2203/15—Function characteristic involving resonance effects, e.g. resonantly enhanced interaction
Definitions
- the present disclosure relates to a control device, a control method, and a program.
- a nonlinear optical element is disposed between at least a pair of opposing mirrors constituting the resonator, and a fundamental laser beam is incident on the resonator, The laser beam is passed through the nonlinear element.
- the distance between the mirrors that is, the optical path length in the resonator
- the laser beam resonates in the resonator and laser oscillation occurs. Arise.
- Patent Document 1 discloses an example of a laser beam generator using a resonator as described above.
- the laser light generating device according to Patent Document 1 is configured so that the position of a mirror constituting the resonator can be moved in the optical axis direction, and an error signal proportional to the deviation of the resonator length with respect to the incident laser light of the resonator. Based on this, the position of the mirror is servo controlled.
- the optical path length of the resonator is automatically controlled so that the incident laser light satisfies the condition of resonating in the resonator, and the resonator Resonant operation with respect to incident laser light is stabilized.
- a laser light source that oscillates in multimode such as a semiconductor laser
- a laser light source that oscillates in this way combine the laser light source with an external resonator, adjust the resonator length of the external resonator, and resonate in a desired mode. It may be used as a light source with close characteristics.
- the influence of leakage light from the resonator may differ depending on the mode, and the intensity of the laser light output from the resonator may differ depending on the mode. is there. In such a case, it is possible to obtain a laser beam with higher intensity by resonating in a mode capable of efficiently resonating with less leakage light from the resonator.
- the optical path length of the resonator is not always controlled so as to resonate in the mode in which the intensity of the laser beam is maximum, and in such a case, the performance of the laser light source cannot be fully utilized. There are a lot of possibilities.
- a new and improved control device, control method, and program capable of controlling the optical path length of the resonator so as to resonate in a mode capable of obtaining a laser beam with higher intensity. Propose.
- the present disclosure includes at least a pair of reflecting portions and a nonlinear optical crystal, and resonates incident laser light, thereby converting the wavelength of the laser light, and resonance of the incident laser light.
- the driving unit that moves at least one of the pair of reflecting units in the optical axis direction and the detection result of the reflected light from the resonator in the resonator having a plurality of modes that satisfy the conditions
- the laser beam incident on the device is changed to a state in which the laser beam resonates in a second mode different from the first mode from a state in which the laser beam resonates in the first mode among the plurality of modes.
- a control device including a control unit that controls the optical path length of the resonator by moving the at least one reflection unit.
- the drive unit includes at least a pair of reflection units and a nonlinear optical crystal, and resonates the incident laser beam to convert the wavelength of the laser beam, and In a resonator in which a plurality of modes satisfying the resonance condition of the incident laser beam exist, at least one of the pair of reflecting portions is moved in the optical axis direction, and the processor reflects the reflected light from the resonator. Based on the detection result, the laser beam incident on the resonator transitions from a state in which the laser beam resonates in the first mode to a state in which the laser beam resonates in a second mode different from the first mode.
- a control method including controlling the optical path length of the resonator by moving the at least one reflection unit to the drive unit.
- the computer includes at least a pair of reflecting portions and a nonlinear optical crystal, and resonates the incident laser light to convert the wavelength of the laser light, and the incident
- the step of moving at least one of the pair of reflecting portions in the optical axis direction of the resonator having a plurality of modes satisfying the resonance condition of the laser beam, and the detection result of the reflected light from the resonator Based on this, the laser beam incident on the resonator is changed from a state of resonating in the first mode among the plurality of modes to a state of resonating in a second mode different from the first mode. Moving the at least one reflecting portion to control the optical path length of the resonator.
- the optical path length of the resonator so as to resonate in a mode capable of obtaining a laser beam with higher intensity.
- 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.
- a laser beam generator 1 includes an oscillator 11, a light source unit 50, mirrors 501 and 503, a resonator 20, an isolator 40, a photodetector 41, and a drive.
- the unit 30 and the control unit 10 are included.
- the light source unit 50 includes a laser light source 51, a phase modulator 52, and a driver (drive circuit) 53.
- the laser light source 51 outputs laser light and can be constituted by various lasers.
- a laser light source 51 that uses multimode oscillation such as a semiconductor laser is used.
- the phase modulator 52 includes, for example, an EO (electro-optic) element or an AO (acousto-optic) element.
- the phase modulator 52 is supplied with a modulation signal having a frequency fm from the oscillator 11 by a driver 53.
- the phase modulator 52 modulates the laser light from the laser light source 51 by the modulation signal supplied from the driver 53, and emits the modulated laser light L1 to the outside.
- the phase modulator 52 may be configured to output the laser light from the laser light source 51 as pulsed laser light by being intermittently driven based on the control from the driver 53.
- the configuration of the light source unit 50 described above is merely an example, and is not necessarily limited to the configuration described above.
- the driver 53 directly drives the laser light source 51 based on the modulation signal without providing the phase modulator 52, thereby emitting the modulated laser light L1. It is good also as a structure.
- the laser light L1 emitted from the light source unit 50 is guided to the isolator 40 through the mirrors 501 and 503, passes through the isolator 40, and enters the inside of the resonator 20 from the input coupler 201. If the laser light L1 emitted from the light source unit 50 can be guided into the resonator 20 through the isolator 40, the configuration of the optical system arranged in the optical path is mirrors 501 and 503. Needless to say, it is not limited to.
- the isolator 40 is interposed between the light source unit 50 and the resonator 20, and transmits the laser light L1 from the light source unit 50 toward the resonator 20. Further, the isolator 40 reflects the reflected light (leakage light) L3 from the resonator 20 toward the photodetector 41 arranged in a direction different from the light source unit 50, so that the reflected light L3 is reflected in the light source unit. 50 is prevented from entering.
- the light detector 41 is composed of, for example, a PD (Photo Detector).
- the photodetector 41 detects the reflected light L3 from the resonator 20 guided through the isolator 40.
- the reflected light L3 detected by the photodetector 41 is synchronously detected by the control unit 10 described later.
- the resonator 20 is a so-called optical parametric oscillator (OPO), which resonates the laser light L1 from the light source unit 50 inside, converts the wavelength of the laser light L1, and converts the wavelength.
- the laser beam L2 is output.
- the laser light incident on the resonator 20 may be referred to as “excitation laser light”, and the laser light whose wavelength is converted and output from the resonator 20 may be referred to as “OPO laser light”.
- the resonator 20 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.
- 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 ( ⁇ -BaB 2 O 4 ), LBO (LiB 3 O 4 ), KN (KNbO 3 ). ) Etc. are used.
- the nonlinear optical element 213 converts input laser light (that is, excitation laser light L1) into two wavelengths. Then, laser light having at least one of the two converted wavelengths (for example, long wavelength) resonates in the resonator 20 as the OPO laser light L2, and is output from the output coupler 211 to the outside of the resonator 20. 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 L1 toward the input coupler 201 and reflects the OPO laser light L2 toward the output coupler 211. With such a configuration, in the resonator 20 according to the present embodiment, the excitation laser light L1 and the OPO laser light L2 are guided through the resonator 20 through different optical paths. The details of the optical paths of the excitation laser beam L1 and the OPO laser beam L2 in the resonator 20 will be described below.
- the excitation laser light L1 incident on the inside of 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. .
- the excitation laser light L 1 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, transmitted through the dichroic mirror 209, and guided to the input coupler 201. Is done.
- the input coupler 201 reflects a part of the guided excitation laser light L1 and emits the other part to the outside of the resonator 20.
- the excitation laser light L 1 incident in the resonator 20 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 L1 in the resonator 20 (in other words, the resonator length), and the optical path length is the resonance of the excitation laser light L1.
- the excitation laser light L1 resonates in the resonator 20.
- the excitation laser light emitted from the input coupler 201 to the outside of the resonator 20 is guided as light reflected from the resonator 20 toward the photodetector 41 by the isolator 40 and detected by the photodetector 41. Is done.
- the OPO laser light L 2 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, reflected by the dichroic mirror 209, and output to the output coupler 211. Light is guided.
- the output coupler 211 reflects a part of the guided OPO laser beam L2 and emits the other part to the outside of the resonator 20.
- the OPO laser light L 2 incident on the resonator 20 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 L2 in the resonator 20 (in other words, the resonator length), and the optical path length is the optical path length of the OPO laser light L2.
- the OPO laser light L2 resonates in the resonator 20.
- the mirror 207 adjusts the position along the optical axis direction of the excitation laser light L1 and the OPO laser light L2 incident on the mirror 207 by driving a driving unit 30 described later. It is configured to be possible.
- the output coupler 211 is configured to be capable of adjusting the position along the optical axis direction of the OPO laser light L2 incident on the output coupler 211 by driving the drive unit 30.
- the optical path length of each of the excitation laser beam L1 and the OPO laser beam L2 is adjusted by adjusting the position of the mirror 207, and the optical path length of the OPO laser beam L2 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 light L1, and then the position of the output coupler 211 may be adjusted so as to satisfy the resonance condition of the OPO laser light L2. . 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 L1 and the OPO laser light L2.
- the drive unit 30 includes an actuator device such as an electromagnetic actuator (VCM: Voice Coil Motor) or a piezoelectric element configuration.
- VCM Voice Coil Motor
- a piezoelectric element configuration In the following description, it is assumed that an electromagnetic actuator is used as the drive unit 30.
- the drive unit 30 adjusts the positions of the mirror 207 and the output coupler 211 based on control by the control unit 10 described later (that is, a control signal supplied from the control unit 10). Needless to say, the drive unit 30 may be provided for each of the mirror 207 and the output coupler 211.
- the control unit 10 controls the positions of the mirror 207 and the output coupler 211 by controlling the operation of the driving unit 30. Accordingly, the control unit 10 controls the optical path lengths of the excitation laser light L1 and the OPO laser light L2 in the resonator 20.
- control unit 10 servo-controls the optical path length of the excitation laser light L1 so that at least the optical path length of the excitation laser light L1 in the resonator 20 satisfies the resonance condition of the excitation laser light L1.
- control unit 10 detects the reflected light L3 from the resonator 20 detected by the photodetector 41 based on the signal of the frequency fm supplied from the oscillator 11 and performs synchronous detection by sample and hold. By doing so, a reflected signal is obtained.
- the control unit 10 Based on the acquired reflection signal, the control unit 10 generates an error signal indicating a deviation between the optical path length of the excitation laser light L1 in the resonator 20 and the optical path length satisfying the resonance condition of the excitation laser light L1, for example, And PDH (Pound-Drever-Hall) method. Needless to say, if the error signal can be generated, the method is not limited to the PDH method.
- the controller 10 uses the generated error signal as a pull-in signal for servo-controlling the optical path length of the excitation laser light L1, and servo-controls the optical path length of the excitation laser light L1. Specifically, the control unit 10 generates a drive signal for controlling the drive unit 30 based on the generated error signal, and causes the drive unit 30 to adjust the position of the mirror 207 using the drive signal, thereby Servo-control the optical path length of the excitation laser beam L1.
- the control unit 10 may be configured by a control unit such as a BPU (Basic Processing Unit) or a CPU (Central Processing Unit). Further, the control unit 10 may include a storage such as a RAM (Random Access Memory) or a ROM (Read Only Memory) for recording data and programs for performing the control described above.
- a control unit such as a BPU (Basic Processing Unit) or a CPU (Central Processing Unit).
- the control unit 10 may include a storage such as a RAM (Random Access Memory) or a ROM (Read Only Memory) for recording data and programs for performing the control described above.
- control unit 10 and the drive unit 30 may be configured to be externally attached to the laser light generation device 1 as the external configuration of the laser light generation device 1.
- a device including the control unit 10 and the drive unit 30 corresponds to an example of a “control device”.
- FIG. 2 is an explanatory diagram for explaining servo pull-in when a laser light source that oscillates in a multimode is used.
- reference numeral g11 indicates the position of the mirror 207, and the optical path length of the excitation laser light L1 in the resonator 20 is determined according to the position of the mirror 207.
- Reference numeral g21 indicates a reflected signal (in other words, a signal indicating the level of the reflected light L3) obtained corresponding to each position of the mirror 207 indicated by the reference numeral g11.
- Reference sign g31 indicates an error signal based on the reflected signal g21.
- the resonator 20 When the optical path length of the excitation laser light L1 in the resonator 20 satisfies the resonance condition of the excitation laser light L1, that is, when the optical path length is an integral multiple of the wavelength of the excitation laser light L1, the resonator The level (intensity) of the reflected light from 20 decreases. Therefore, when a laser light source that oscillates in a multimode is used, as shown in FIG. 2, there are a plurality of positions of the mirror 207 where the level of reflected light decreases, that is, a mode (optical path length). In contrast, an error signal is generated.
- the level of reflected light corresponding to each mode tends to be different depending on the mode, and the mode with a lower level of this reflected light has less leakage light from the resonator 20, A high-power OPO laser beam L2 can be obtained. Therefore, as indicated by the range g13 in FIG. 2, it is more desirable to adjust the position of the mirror 207 so that the reflected signal (that is, the level of the reflected light L3) is in the lowest mode.
- Control unit according to comparative example> Next, the conventional laser beam generator is used as a comparative example, and the servo pull-in method by the control unit according to the comparative example is described to organize the problems of the laser beam generator 1 according to the present embodiment.
- FIG. 3 is a block diagram illustrating an example of a functional configuration of the control unit 10w according to the comparative example.
- the control unit 10w includes an error signal generation unit 101, level detection units 103 and 105, a servo control unit 107, a switch 109, a phase compensation unit 111, and a VCM driver 113. Including.
- the error signal generator 101 reflects the reflected light L3 from the resonator 20 detected by the photodetector 41 by synchronous detection by sample and hold based on the signal of the frequency fm supplied from the oscillator 11. Get a signal. Based on the acquired reflection signal, the error signal generation unit 101 generates an error signal indicating a deviation between the optical path length of the excitation laser light L1 in the resonator 20 and the optical path length satisfying the resonance condition of the excitation laser light L1. Generate.
- the PDH method may be used for generating the error signal.
- the sideband fc ⁇ fm is established by the phase modulation by the phase modulator 52.
- the error signal generation unit 101 obtains an erroneous calculation signal by detecting beats with the frequencies fc and fc ⁇ fm for the supplied reflected light L3.
- the error signal generation unit 101 generates an error signal based on the reflection signal obtained by synchronously detecting the reflected light L3, and the generated error signal is sequentially transmitted to the level detection unit 105 and the switch 109. Output.
- the level detection unit 103 sequentially acquires the detection result of the reflected light L3 from the resonator 20 at a predetermined sampling rate (for example, the frequency fm supplied from the oscillator 11) from the photodetector 41. Note that the level detection unit 103 may acquire the reflection signal synchronously detected by the sample and hold based on the signal of the frequency fm supplied from the oscillator 11 as the detection result of the detection result of the reflected light L3. .
- the level detection part 103 detects the level of the reflected light L3 based on the acquired detection result.
- the level of the reflected light L3 detected is such that the optical path length of the excitation laser light L1 in the resonator 20 satisfies the resonance condition of the excitation laser light L1 as the mirror position moves. It varies depending on whether or not it is satisfied.
- the level detection unit 103 outputs a signal indicating the level detection result to the servo control unit 107 when the level of the detected reflected light L3 falls below a predetermined threshold.
- the level detection unit 105 sequentially acquires the generated error signal from the error signal generation unit 101. Then, the level detection unit 105 detects the zero cross level of the acquired error signal, and based on the detection timing of the zero cross level, the resonator length of the resonator 20 corresponding to each mode (that is, the excitation laser in the resonator 20). A servo trigger indicating the timing for starting servo control of the optical path length of the light L1 is generated. The level detection unit 105 sequentially outputs the generated servo trigger to the servo control unit 107.
- Servo control unit 107 sequentially acquires servo trigger pulses from level detection unit 105. Then, when the servo control unit 107 acquires a signal indicating the detection result of the level of the reflected light L3 from the level detection unit 103, a signal indicating the start of the servo based on the servo trigger pulse supplied at the timing of acquiring the signal. Is supplied to the switch 109.
- the switch 109 is configured to be able to switch the connection relationship between the error signal generation unit 101 provided in the previous stage and the phase compensation unit 111 provided in the subsequent stage based on a signal supplied from the servo control unit 107. Yes. Specifically, the switch 109 is turned on when a signal indicating the start of servo is supplied from the servo control unit 107, and connects the error signal generation unit 101 and the phase compensation unit 111. As a result, the error signal output from the error signal generation unit 101 is supplied to the phase compensation unit 111.
- the phase compensation unit 111 is supplied with an error signal from the error signal generation unit 101 when the switch 109 is turned on.
- the phase compensation unit 111 compensates the phase of the error signal from the error signal generation unit 101 and supplies the error signal whose phase has been compensated to the VCM driver 113.
- the VCM driver 113 drives the drive unit 30 based on the error signal supplied from the phase compensation unit 111 to perform servo pull-in (that is, adjustment of the position of the mirror 207).
- FIG. 4 is an explanatory diagram for explaining an example of a servo pull-in operation by the control unit 10w according to the comparative example.
- reference numerals g11, g21, g31, and g13 in FIG. 4 are respectively in the range g13 in which the detection result of the position g11 of the mirror 207, the reflected signal g21, the error signal g31, and the reflected light L3 is the lowest in FIG. It corresponds.
- the controller 10w controls the optical path length of the excitation laser light L1 in the resonator 20 by causing the driving unit 30 to adjust the position of the mirror 207 in the resonator 20, and from the resonator 20 corresponding to the optical path length.
- the detection result of the reflected light L3 is obtained from the photodetector 41.
- the error signal generation unit 101 of the control unit 10w synchronously detects the reflected light L3 from the resonator 20 detected by the photodetector 41 to obtain a reflected signal g21.
- the error signal generation unit 101 generates an error signal g31 based on the acquired reflection signal.
- the level detection unit 105 sequentially acquires the generated error signal g31 from the error signal generation unit 101, detects the zero cross level of the error signal g31, and generates the servo trigger g51 based on the detection timing of the zero cross level.
- the level detection unit 105 sequentially outputs the generated servo trigger g51 to the servo control unit 107.
- the level detection unit 103 sequentially acquires and detects the detection result of the reflected light L3 from the resonator 20 at a predetermined sampling rate (for example, the frequency fm supplied from the oscillator 11) from the photodetector 41.
- the level of the reflected light L3 is compared with the threshold value g25.
- the threshold value g25 is determined in advance according to the output of the laser beam L1 output from the light source unit 50 and the characteristics of the resonator 20. As a specific example, the threshold value g25 is determined based on the minimum value of the reflected light L3 obtained as a result of the measurement by measuring the level of the reflected light L3 from the resonator 20 beforehand through experiments or the like. That's fine.
- the level detection unit 103 outputs a signal g41 indicating the level detection result to the servo control unit 107 at a timing when the level of the detected reflected light L3 falls below a predetermined threshold value g25.
- the servo control unit 107 indicates the start of servo based on the servo trigger pulse g51 sequentially supplied from the level detection unit 105 and the signal g41 indicating the detection result of the level of the reflected light L3 supplied from the level detection unit 103.
- the signal g61 is supplied to the switch 109.
- the servo control unit 107 receives the signal g41 from the level detection unit 103, the servo trigger g51 supplied at the timing of receiving the signal g41 (the timing at which the signal g41 is turned on).
- the signal g61 indicating the start of the servo is supplied to the switch 109 using the rising edge of.
- the switch 109 When the signal g61 indicating the start of servo is supplied to the switch 109, the switch 109 is turned on, and the error signal output from the error signal generator 101 is supplied to the phase compensator 111.
- the phase compensation unit 111 is supplied with the error signal from the error signal generation unit 101, compensates the phase of the error signal, and sends the error signal whose phase is compensated to the VCM driver 113. Supply.
- the VCM driver 113 drives the drive unit 30 based on the error signal supplied from the phase compensation unit 111 to perform servo pull-in (that is, adjustment of the position of the mirror 207). That is, the position of the mirror 207 is adjusted by the drive unit 30 so that the optical path length of the excitation laser light L1 in the resonator 20 becomes a mode corresponding to the timing at which the servo is started, as indicated by reference numeral g15 in FIG. Is adjusted.
- the mode of the resonator 20 is locked in accordance with the servo control of the optical path length of the excitation laser light L1 by the VCM driver 113, the level of the reflected light L3 becomes constant as indicated by reference numeral g23 in FIG.
- the error signal is also stabilized as indicated by reference numeral g33.
- the threshold value g25 is obtained by prior measurement in order to reliably perform the servo pull-in. In many cases, the value is set higher than the minimum value of the reflected light L3.
- the mode for operating the laser light generator is the level of the reflected light L3. Is often different from the mode g27 that minimizes. That is, the laser beam generator to which the control unit 10w according to the comparative example is applied may not operate in the mode g27 in which the level of the reflected light L3 is minimized, that is, in the mode in which the output of the OPO laser beam L2 is maximized. In some cases, the laser light source performance could not be fully utilized.
- the laser beam generator according to the present embodiment resonates in a mode in which higher intensity laser beam can be obtained, that is, a mode in which reflected light (leakage light) from the resonator 20 is minimized.
- the purpose is to enable control of the optical path length of the resonator.
- the laser beam generator 1 according to the present embodiment will be described with particular attention to the configuration of the control unit 10.
- FIG. 5 is a block diagram illustrating an example of a functional configuration of the control unit 10 according to the present embodiment.
- the control unit 10 includes an error signal generation unit 101, level detection units 103 and 105, a switch 109, a servo control unit 121, a jump pulse generation unit 123, and a switch. 125, a phase compensation unit 111, and a VCM driver 113.
- the error signal generation unit 101, the level detection units 103 and 105, the switch 109, the phase compensation unit 111, and the VCM driver 113 are the same as the control unit 10w according to the comparative example described above (see FIG. 3). Therefore, detailed description is omitted and only an outline is described.
- the error signal generation unit 101 acquires a reflected signal by synchronously detecting the reflected light L3 from the resonator 20 detected by the photodetector 41, and generates an error signal based on the acquired reflected signal.
- the error signal generation unit 101 sequentially outputs the generated error signal to the level detection unit 105 and the switch 109.
- the level detection unit 103 sequentially acquires the detection result of the reflected light L3 from the resonator 20 from the photodetector 41, and detects the level of the reflected light L3 based on the acquired detection result.
- the level detection unit 103 outputs a signal indicating the detection result of the level to the servo control unit 107 at a timing when the level of the detected reflected light L3 falls below a predetermined threshold.
- the level detection unit 105 sequentially acquires the generated error signal from the error signal generation unit 101, detects the zero cross level of the error signal, and generates a servo trigger based on the detection timing of the zero cross level. Then, the level detection unit 105 sequentially outputs the generated servo trigger to the servo control unit 107.
- the switch 109 is interposed between the error signal generation unit 101 and the switch 125, and is configured to be able to switch the connection relationship between the error signal generation unit 101 and the switch 125 based on a signal supplied from the servo control unit 107.
- the switch 109 is turned on when a signal indicating the start of servo is supplied from the servo control unit 107, and connects the error signal generation unit 101 and the switch 125.
- the error signal output from the error signal generation unit 101 is supplied to the switch 125.
- the operation so far is the same as that of the control unit 10w according to the comparative example described above.
- the switch 125 has terminals 125a to 125c.
- the terminal 125 a is connected to the signal line from the switch 109, and the terminal 125 b is connected to the signal line from the jump pulse generation unit 123.
- the terminal 125c is connected to the signal line from the phase compensation unit 111.
- the switch 125 is configured to be switchable so that the terminal 125c is connected to one of the terminals 125a and 125b. That is, the switch 125 can switch between a state in which the switch 109 and the phase compensation unit 111 are connected and a state in which the jump pulse generation unit 123 and the phase compensation unit 111 are connected. Switching of the switch 125 is controlled by a jump timing signal supplied from the servo control unit 121.
- the switch 109 When the switch 109 is in the ON state, the error signal from the error signal generation unit 101 is supplied to the terminal 125a. That is, when the switch 125 is switched so that the terminals 125a and 125c are connected, the error signal from the error signal generation unit 101 is supplied to the phase compensation unit 111 via the switch 109. Become.
- a jump pulse is supplied from the jump pulse generator 123 to the terminal 125b. That is, when the switch 125 is switched so that the terminal 125 b and the terminal 125 c are connected, the jump pulse from the jump pulse generation unit 123 is supplied to the phase compensation unit 111. The details of the jump pulse will be described later separately.
- the servo control unit 121 sequentially acquires servo trigger pulses from the level detection unit 105. Then, when the servo control unit 121 acquires a signal indicating the detection result of the level of the reflected light L3 from the level detection unit 103, a signal indicating the start of the servo based on the servo trigger pulse supplied at the timing of acquiring the signal. Is supplied to the switch 109. At this time, the servo control unit 121 supplies a control signal to the switch 125 so that the terminal 125a and the terminal 125c of the switch 125 are connected.
- the switch 109 is turned on, the terminals 125a and 125c of the switch 125 are connected, and the error signal from the error signal generation unit 101 is supplied to the phase compensation unit 111 via the switch 109 and the switch 125. .
- phase compensation of the error signal is performed by the phase compensation unit 111, and the servo is pulled in by the VCM driver 113 driving the drive unit 30 based on the error signal whose phase is compensated.
- the control relating to the initial pull-in of the servo described above is the same as the servo pull-in control based on the comparison between the level of the reflected light L3 and the threshold value g25 shown in FIG.
- the servo pull-in control based on the comparison between the level of the reflected light L3 and the threshold value g25 may be referred to as “initial pull-in”.
- the servo control unit 121 changes the optical path length of the excitation laser light L1 in the resonator 20 so that the set mode is sequentially switched to another mode different from the mode.
- the servo control unit 121 causes the jump pulse generation unit 123 to generate a jump pulse for adjusting the position of the mirror 207 so as to jump between the modes and supply the jump pulse to the terminal 125b of the switch 125.
- mode jump the operation of adjusting the position of the mirror 207 so as to jump between modes.
- the servo control unit 121 synchronizes with the timing when the jump pulse generation unit 123 supplies the jump pulse to the terminal 125b, and a control signal for switching the switch 125 so that the terminal 125b and the terminal 125c are connected (hereinafter referred to as the control signal). Then, it may be referred to as “jump timing signal”) is supplied to the switch 125.
- the VCM driver 113 temporarily stops the servo control of the optical path length of the excitation laser beam L1 in the resonator 20 so that the set mode transitions to another mode while the servo control is stopped. In addition, the optical path length is controlled.
- the servo control unit 121 sequentially switches the mode, and acquires the detection result of the level of the reflected light L3 from the level detection unit 103 for each switched mode. Then, the servo control unit 121 specifies a mode that minimizes the level of the reflected light L3 based on the detection result of the level of the reflected light L3 acquired for each mode, and resonates in the specified mode. 20 controls the optical path length of the excitation laser beam L1. For details of the operation related to the mode jump and the operation related to specifying the mode in which the level of the reflected light L3 is minimized as described above, see [4.2. Servo pull-in operation] will be separately described later.
- the optical path length of the excitation laser beam L1 in the resonator 20 is controlled, that is, when the position of the mirror 207 varies, the optical path length of the OPO laser beam L2 in the resonator 20 also varies. Become. Therefore, when the position of the mirror 207 is controlled, the servo control unit 121 adjusts the position of the output coupler 211 in accordance with the control amount of the position of the mirror 207, thereby adjusting the optical path length of the OPO laser light L2. Needless to say, it may be controlled together.
- control unit 10 The functional configuration of the control unit 10 according to the present embodiment has been described above with reference to FIG.
- reference sign g31 indicates an error signal generated by synchronous detection of the reflected light L3 from the resonator 20 by the error signal generation unit 101.
- the VCM driver 113 can servo-control the optical path length of the excitation laser beam L1 by adjusting the position of the mirror 207 using the error signal as a drive signal.
- the reference symbol g71 indicates a jump pulse generated by the jump pulse generation unit 123.
- the jump pulse g71 is composed of a kick pulse g711 and a brake pulse g713.
- the kick pulse g711 is a drive signal for moving the position of the mirror 207 by a predetermined distance.
- the distance that the mirror 207 moves by the kick pulse g711 is determined by the amplitude Vk and the pulse width Tk of the kick pulse g711 and the characteristics of the VCM driver 113 and the drive unit 30. Therefore, for example, by investigating the relationship between the amplitude Vk and pulse width Tk of the kick pulse g711 and the control amount of the position of the mirror 207 by the VCM driver 113 and the drive unit 30 in advance, Vk and pulse width Tk may be determined.
- the direction of the amplitude Vk of the kick pulse g711, that is, the direction in which the mirror 207 moves is controlled by positive and negative.
- the position of the mirror 207 is controlled so as to move in the direction of extending the optical path length along the optical axis direction of the excitation laser light L1 in the resonator 20.
- the amplitude Vk is negative
- the position of the mirror 207 is controlled so as to move in the direction of shortening the optical path length.
- the direction in which the optical path length of the excitation laser beam L1 in the resonator 20 is extended is sometimes referred to as “+ (plus) direction”, and the direction in which the optical path length is shortened is sometimes referred to as “ ⁇ (minus) direction”. .
- the brake pulse g713 is a signal for braking in the direction opposite to the moving direction of the mirror 207 in order to stop the mirror 207 moved by the kick pulse g711. Therefore, the brake pulse g713 is formed as a signal whose polarity is reversed from that of the kick pulse g711.
- the amount of load for braking the moving mirror 207 by the brake pulse g713 is determined by the amplitude Vb and the pulse width Tb of the brake pulse g713 and the characteristics of the VCM driver 113 and the drive unit 30. Therefore, similarly to the kick pulse g711, the relationship between the amplitude Vb and the pulse width Tb and the control amount of the mirror 207 by the VCM driver 113 and the drive unit 30 is investigated in advance, and the amplitude Vb is based on the investigation result. And the pulse width Tb may be determined.
- the jump pulse g71 composed of the kick pulse g711 and the brake pulse g713 is used as a drive signal for adjusting the position of the mirror 207, whereby the position of the mirror 207 is set in a predetermined direction by a predetermined distance. It becomes possible to move only intermittently.
- the jump pulse generator 123 has amplitudes Vk and Vb so that the moving distance of the mirror 207 is an integral multiple of 1 ⁇ 2 wavelength of the excitation laser light L1 along the optical axis direction of the excitation laser light L1.
- the jump pulse g71 is generated by adjusting the pulse widths Tk and Tb.
- the optical path length of the excitation laser light L1 in the resonator 20 is one wavelength of the excitation laser light L1. Will change. Therefore, by controlling the position of the mirror 207 based on the jump pulse g71 generated as described above, the position of the mirror 207 is adjusted so as to jump between modes.
- Reference numeral g73 indicates a jump timing signal for the servo control unit 121 to switch the switch 125.
- the switch 125 When the jump timing signal g73 is turned off, the switch 125 is switched so that the terminals 125a and 125c of the switch 125 are connected. That is, in this case, the error signal g31 generated by the error signal generation unit 101 is supplied as a drive signal to the VCM driver 113 via the switch 109, the switch 125, and the phase compensation unit 111.
- the switch 125 is switched so that the terminal 125b and the terminal 125c of the switch 125 are connected. Therefore, in this case, the jump pulse g71 generated by the jump pulse generator 123 is supplied as a drive signal to the VCM driver 113 via the switch 125 and the phase compensator 111.
- the servo control unit 121 supplies the jump timing signal g73 to the switch 125 in synchronization with the timing at which the jump pulse generation unit 123 supplies the jump pulse to the terminal 125b. Specifically, in the example shown in FIG. 6, the servo control unit 121 controls the jump timing signal g73 to be turned on in synchronization with the timing t1 when the kick pulse g711 rises. Further, the servo control unit 121 controls the jump timing signal g73 to be in an OFF state in synchronization with the timing t2 when the brake pulse g713 rises.
- the drive signal indicated by reference numeral g75 that is, the drive signal in which the error signal g31 and the jump pulse g71 are combined is supplied to the VCM driver 113 in time series.
- the VCM driver 113 causes the drive unit 30 to control the position of the mirror 207 based on the drive signal g75, and when performing mode jump, temporarily stops servo control based on the error signal g31 and completes the mode jump. Servo control is resumed later. With such a configuration, the mode jump is smoothly performed according to the control unit 10 according to the present embodiment.
- FIG. 7 is an explanatory diagram for explaining an example of a servo pull-in operation by the control unit 10 according to the present embodiment.
- the control unit 10 compares the level of the reflected light L3 (in other words, the reflected signal g21) from the resonator 20 detected by the photodetector 41 with the threshold value g25, and the level of the reflected light L3 is equal to the predetermined threshold value g25.
- Servo pull-in that is, initial pull-in
- the position of the mirror 207 is adjusted to a position corresponding to the mode indicated by the reference symbol i in FIG.
- the control unit 10 When the servo initial pull-in is completed, the control unit 10 first sets the position of the mirror 207 so that the mode is sequentially switched in a predetermined direction (that is, mode jump) as indicated by reference numeral g81. Control. For example, in the example illustrated in FIG. 7, the control unit 10 controls the position of the mirror 207 so as to sequentially jump to adjacent modes. And the control part 10 acquires the level of the reflected light L3 about each mode switched.
- control unit 10 sequentially jumps from mode i to mode i + 1, i + 2,..., I + 6, starting from mode i immediately after the initial pull-in, as indicated by reference numeral g81.
- the position of the mirror 207 is controlled.
- control unit 10 compares the levels of the reflected light L3 before and after the mode jump while sequentially performing the mode jump, and specifies the mode in which the level of the reflected light L3 is the lowest.
- FIG. 8 is an explanatory diagram for explaining an example of the servo pull-in operation by the control unit according to the embodiment, and shows a change in the level of the reflected light L3 accompanying the mode jump in the example shown in FIG.
- the horizontal axis represents time t
- the vertical axis represents the level of the reflected light L3.
- Reference numeral t11 indicates the timing immediately after the initial pull-in of the servo. That is, at the timing t11, the position of the mirror 207 is adjusted to a position corresponding to the mode i.
- the control unit 10 changes the level of the reflected light L3 between the modes i + 2 and i + 3 and between the modes i + 3 and i + 4 based on the comparison result of the level of the reflected light L3 with the mode i + 3 as a boundary. A change from (minus) to + (plus) is detected. Thereby, the control unit 10 sets the mode i + 3 as an optimum point, that is, a mode in which the level of the reflected light L3 is minimized.
- the control unit 10 controls the position of the mirror 207 so as to jump from the optimum point by the predetermined number of modes, and acquires the level of the reflected light L3 in each mode. For example, in the case of the example shown in FIG. 7, the control unit 10 controls the position of the mirror 207 so as to make a mode jump for three modes (that is, to make a mode jump to mode i + 6) based on the mode i + 3. is doing.
- control part 10 compares the level of the reflected light L3 in each acquired mode with the level of the reflected light L3 in an optimal point.
- the level of the reflected light L3 in the mode i + 3 set at the optimum point is lower than the level of the reflected light L3 in any of the modes i + 4 to i + 6.
- the control unit 10 moves the mirror 207 to the position corresponding to the optimum point, and completes the operation related to the servo pull-in.
- the control unit 10 controls the position of the mirror 207 so that the mode jumps from the mode i + 6 to the mode i + 3 set to the optimum point, as indicated by reference numeral g83. .
- the position of the mirror 207 is at the optimum point where the mode changes and the level of the reflected light L3 becomes the minimum, that is, the position corresponding to the mode i + 3. Is adjusted.
- control unit 10 may search for the optimum point again.
- FIG. 9 is a flowchart showing a flow of a series of operations of the control unit 10 according to the present embodiment.
- Step S10 When the laser light generator 1 starts operation, the control unit 10 sequentially switches modes, acquires the detection result of the level of the reflected light L3 for each switched mode, and sets the level of the reflected light L3 to the minimum. Specify the mode. Then, the control unit 10 pulls in the servo so that the excitation laser light L1 resonates in the specified mode. Details of the operation related to servo pull-in will be described later.
- Step S20 When the servo pull-in is completed, the control unit 10 acquires the detection result of the reflected light L3 from the resonator 20 from the light detector 41, and the servo control operates normally based on the level of the reflected light L3. It is determined whether or not.
- the control unit 10 can determine whether the servo control is operating normally. That is, when the optical path length of the excitation laser L1 in the resonator 20 satisfies the resonance condition of the excitation laser L1, the reflected light L3 For example, the level is lowered as shown in FIG. On the other hand, when the optical path length of the excitation laser L1 in the resonator 20 does not satisfy the resonance condition of the excitation laser L1, the level of the reflected light L3 is higher than that when the resonance condition is satisfied. Become. Using such characteristics, the control unit 10 can determine whether the servo control is operating normally.
- step S20 When the servo control is not operating normally (step S20, NO), the control unit 10 executes the servo pull-in operation again.
- Step S30 and S40 When the servo control is operating normally (step S20, YES), the control unit 10 temporarily stops processing for a predetermined period (step S30), and the servo control is performed again after the period has elapsed. Check if it is operating normally. The control unit 10 continues the above operation until, for example, the operation of the laser beam generator 1 is stopped (NO in step S40). When the stop of the operation of the laser beam generator 1 is instructed (step S40, YES), the control unit 10 ends a series of processes related to the control of the optical path length of the excitation laser L1 in the resonator 20. To do.
- FIG. 10 is a flowchart showing a flow of a series of operations related to servo pull-in by the control unit 10 according to the present embodiment.
- Step S103 After controlling the position of the mirror 207 so as to jump between the modes, the control unit 10 acquires the detection result of the reflected light L3 after the mode jump from the photodetector 41, and reflects the reflected light L3 before and after the mode jump. Compare levels.
- Step S111 When the change in the level of the reflected light L3 is + (plus), that is, when the level of the reflected light L3 is higher after the mode jump than before the mode jump (step S103, YES), the control unit 10 The position of the mirror 207 is controlled so that the mode jumps in the ⁇ (minus) direction. If the position of the mirror 207 is controlled, the control unit 10 acquires the detection result of the reflected light L3 after the mode jump from the photodetector 41, and compares the level of the reflected light L3 before and after the mode jump.
- Step S112 As described above, as long as the change in the level of the reflected light L3 between before and after the mode jump is ⁇ (minus) (step S112, NO), the control unit 10 performs the mode jump in the ⁇ (minus) direction. The position of the mirror 207 is controlled.
- Step S114 When the optimum point is set, the control unit 10 controls the position of the mirror 207 so as to make a mode jump in the ⁇ (minus) direction by a predetermined number n of modes with the optimum point as a reference (step S115, NO). ).
- the control part 10 performs the process after step S102 anew, and specifies the mode in which the level of the reflected light L3 becomes the minimum value.
- Step S121 In step S103, even when the change in the level of the reflected light L3 between before and after the mode jump is ⁇ (minus) (NO in step S103), the basic control is different except that the control direction of the mirror 207 is different.
- the operation is the same as the operation shown in steps S111 to S117 described above.
- control unit 10 controls the position of the mirror 207 so as to make a mode jump in the + (plus) direction. If the position of the mirror 207 is controlled, the control unit 10 acquires the detection result of the reflected light L3 after the mode jump from the photodetector 41, and compares the level of the reflected light L3 before and after the mode jump.
- Step S122 As described above, the control unit 10 performs the mode jump in the + (plus) direction as long as the level change of the reflected light L3 between before and after the mode jump is ⁇ (minus) (NO in step S122). The position of the mirror 207 is controlled.
- Step S124 When the optimum point is set, the control unit 10 controls the position of the mirror 207 so as to make a mode jump in the + (plus) direction by a predetermined number n of modes with the optimum point as a reference (step S125, NO). ).
- the control part 10 performs the process after step S102 anew, and specifies the mode in which the level of the reflected light L3 becomes the minimum value.
- control unit 10 may be configured to constantly monitor whether the servo control is operating normally while the laser light generator 1 is activated.
- the control unit 10 controls the position of the mirror 207 by mode jump after the initial pull-in, but may control the position of the mirror 207 by mode jump without performing the initial pull-in. .
- the control unit 10 first controls the position of the mirror 207 so that the mode jumps by a plurality of modes, thereby narrowing down the mode range in which the level of the reflected light L3 is minimized. Then, the control unit 10 may specify the mode in which the level of the reflected light L3 is minimized by controlling the position of the mirror 207 so that the mode jump is performed in the narrowed range with a smaller number of modes.
- control unit 10 controls the position of the mirror 207 so that the modes are sequentially switched (that is, so that the mode jumps), and acquires the level of the reflected light L3 for each switched mode. Then, the control unit 10 compares the level of the reflected light L3 before and after the mode jump, and identifies the mode in which the level of the reflected light L3 is the lowest. With such a configuration, the control unit 10 according to the present embodiment can control the optical path length in the resonator 20 so as to resonate in a mode capable of outputting the OPO laser beam L2 having higher intensity. It becomes possible.
- the control unit 10 when performing the mode jump, temporarily stops the servo control based on the error signal, and resumes the servo control after the mode jump is completed. With such a configuration, the mode jump can be smoothly performed according to the control unit 10 according to the present embodiment.
- FIG. 11 is a diagram showing a configuration of a laser beam generator 1a according to a modification.
- the laser beam generator 1a according to the modification is different from the laser beam generator 1 according to the above-described embodiment (see FIG. 1) in that the position detectors 221 and 223 are provided. Therefore, hereinafter, description will be made by paying attention to the position detection units 221 and 223 and the control unit 10a, which are different from the laser light generation device 1 described above, and detailed description of other configurations will be omitted.
- the position detectors 221 and 223 are, for example, optical position sensors (PSD: Position Sensitive Detector).
- the position detection unit 221 detects the position of the mirror 207 that moves in the resonator 20 along the optical axis direction of the excitation laser L1 and the OPO laser L2.
- the position detection unit 221 notifies the control unit 10a of information indicating the detected position of the mirror 207. Thereby, the control unit 10a can recognize the position of the mirror 207 in the resonator 20.
- the position detector 223 detects the position of the output coupler 211 that moves in the resonator 20 along the optical axis direction of the OPO laser L2.
- the position detection unit 223 notifies the control unit 10a of information indicating the detected position of the output coupler 211. Thereby, the control unit 10a can recognize the position of the output coupler 211 in the resonator 20.
- control unit 10a is configured to sequentially switch the set mode to another mode different from the mode, and the optical path length of the excitation laser light L1 in the resonator 20 And the optimum point (that is, the mode in which the level of the reflected light L3 is minimized) is specified. Then, the control unit 10a adjusts the position of the mirror 207 so that the position corresponds to the identified optimum point.
- control unit 10a When the control unit 10a according to the modification adjusts the position of the mirror 207 to the position corresponding to the optimum point, the control unit 10a acquires the detection result of the position of the mirror 207 from the position detection unit 221 and indicates the detection result. Store information.
- FIG. 12 is an explanatory diagram for explaining an outline of the operation of the control unit 10a according to the modification.
- reference numeral g11 indicates the position of the mirror 207
- reference numeral g21 indicates a reflected signal (that is, the level of the reflected light L3) obtained corresponding to each position of the mirror 207 indicated by the reference numeral g11.
- Signal indicates a mode in which the level of the reflected light L3 is minimum, that is, an optimum point.
- the control unit 10a can recognize the position of the mirror 207 corresponding to the optimum point g27 based on the position information g81 indicated by the detection result of the position detection unit 221. Therefore, for example, even when the position of the mirror 207 changes due to a disturbance such as an impact on the resonator 20, the control unit 10a is based on the position information g81 stored in advance so that the position corresponds to the optimum point. The position of the mirror 207 can be adjusted.
- control unit 10a controls the position of the output coupler 211 so that the resonance condition of the OPO laser beam L2 is satisfied based on the position information stored in advance even when the position of the output coupler 211 changes due to disturbance. It becomes possible to do.
- the configuration of the laser beam generator 1a according to the modification has been described above with reference to FIGS.
- the control unit 10a can recognize the positions of the mirror 207 and the output coupler 211 in the resonator 20, the method is a method for recognizing based on the outputs of the optical position sensors such as the position detection units 221 and 223. It goes without saying that it is not limited.
- FIG. 13 is a flowchart showing a flow of a series of operations of the control unit 10a according to the modification.
- Step S10 When the laser light generator 1 starts operation, the control unit 10a sequentially switches modes, acquires the detection result of the level of the reflected light L3 for each switched mode, and sets the level of the reflected light L3 to the minimum. A mode (that is, an optimum point) is specified. Then, the control unit 10a performs servo pull-in so that the excitation laser light L1 resonates in the specified mode.
- the operation related to the servo pull-in is the same as that of the control unit 10 according to the above-described embodiment (FIGS. 9 and 10).
- Step S51 When the servo pull-in is completed, the control unit 10a acquires position information indicating the position of the mirror 207 from the position detection unit 221. Based on the position information, the control unit 10a can recognize the position of the mirror 207 corresponding to the mode (that is, the optimum point) in which the level of the reflected light L3 is minimized. The control unit 10a records the position information of the mirror 207 corresponding to the optimum point acquired from the position detection unit 221. At this time, the control unit 10a may acquire the position information of the output coupler 211 from the position detection unit 223 and store the position information.
- Step S20 the control unit 10 acquires the detection result of the reflected light L3 from the resonator 20 from the photodetector 41, and determines whether the servo control is operating normally based on the level of the reflected light L3. To do.
- Step S52 and S10 When the servo control is not operating normally (step S20, NO), the control unit 10 becomes a position corresponding to the optimum point based on the position information of the mirror 207 corresponding to the optimum point recorded in advance. Next, the position of the mirror 207 is controlled (step S52). At this time, the control unit 10a may control the position of the output coupler 211 based on the position information of the output coupler 211 recorded in advance. If the position of the mirror 207 is controlled based on the position information recorded in advance, the control unit 10 executes the servo pull-in operation again (step S10).
- Step S30 and S40 When the servo control is operating normally (step S20, YES), the control unit 10a temporarily stops processing for a predetermined period (step S30), and after the period elapses Check if the control is operating normally. The control unit 10a continues the above operation until, for example, the operation of the laser beam generator 1 is stopped (NO in step S40). When the stop of the operation of the laser beam generator 1 is instructed (step S40, YES), the control unit 10a ends a series of processes related to the control of the optical path length of the excitation laser L1 in the resonator 20. To do.
- the control unit 10a according to the modification can recognize the position of the mirror 207 corresponding to the optimum point g27 based on the position information indicated by the detection result of the position detection unit 221. Therefore, the control unit 10a, for example, even when the position of the mirror 207 is changed due to a disturbance such as an impact on the resonator 20, the mirror 10 so that the position corresponding to the optimum point is obtained based on the position information stored in advance. The position 207 can be adjusted.
- control unit 10a controls the position of the output coupler 211 so that the resonance condition of the OPO laser beam L2 is satisfied based on the position information stored in advance even when the position of the output coupler 211 changes due to disturbance. It becomes possible to do.
- the control unit 10a after adjusting the position of the mirror 207 based on the position information stored in advance, the control unit 10a according to the modification again specifies a mode in which the level of the reflected light L3 is minimized based on the operation related to the mode jump. You may fix it. Even in this case, since the mirror 207 moves to the vicinity of the position corresponding to the optimum point by controlling the position of the mirror 207 based on the position information, the control unit 10a is in a mode in which the level of the reflected light L3 is minimized. Can be immediately identified again.
- FIG. 14 is a diagram illustrating an example of a hardware configuration of the laser beam generator 1 according to the present embodiment.
- the laser light generator 1 includes a processor 901, a memory 903, a storage 905, a light source unit 907, an optical system unit 909, an operation device 911, and a display device 913.
- the processor 901 may be, for example, a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), a DSP (Digital Signal Processor), or a SoC (System on Chip), and executes various processes of the laser light generator 1.
- the processor 901 can be configured by, for example, an electronic circuit for executing various arithmetic processes. Note that the control unit 10 described above can be configured by the processor 901.
- the memory 903 includes RAM (Random Access Memory) and ROM (Read Only Memory), and stores programs and data executed by the processor 901.
- the storage 905 can include a storage medium such as a semiconductor memory or a hard disk. Note that the storage unit 66 described above can be configured by, for example, the memory 903 and the storage 905.
- the light source unit 907 is a unit for irradiating the excitation laser light L1, and corresponds to the light source unit 50 described above.
- the processor 901 controls the intensity and wavelength of the emitted excitation light.
- the optical system unit 909 is a unit for resonating the excitation laser light L1 emitted from the light source unit 907, converting the wavelength of the excitation laser light L1, and outputting the OPO laser light L2 whose wavelength has been converted.
- the optical system unit 909 corresponds to the resonator 20 and an optical system (for example, mirrors 501 and 503) for guiding the excitation laser light L1 to the resonator 20.
- the operation device 911 has a function of generating an input signal for a user to perform a desired operation.
- the operation device 911 may include an input unit for a user to input information, such as buttons and switches, and an input control circuit that generates an input signal based on an input by the user and supplies the input signal to the processor 901.
- the display device 913 is an example of an output device, and may be a display device such as a liquid crystal display (LCD) device, an organic EL (OLED: Organic Light Emitting Diode) display device, or the like.
- the display device 913 can provide information by displaying a screen to the user.
- the communication device 915 is a communication unit included in the laser light generator 1 and communicates with an external device via a network.
- the communication device 915 is an interface for wireless communication, and may include a communication antenna, an RF (Radio Frequency) circuit, a baseband processor, and the like.
- the communication device 915 has a function of performing various kinds of signal processing on a signal received from an external device, and can supply a digital signal generated from the received analog signal to the processor 901.
- the bus 917 connects the processor 901, the memory 903, the storage 905, the light source unit 907, the optical system unit 909, the operation device 911, the display device 913, and the communication device 915 to each other.
- the bus 917 may include a plurality of types of buses.
- a plurality of modes that include at least a pair of reflecting portions and a nonlinear optical crystal, convert the wavelength of the laser beam by resonating the incident laser beam, and satisfy the resonance condition of the incident laser beam.
- a drive unit that moves at least one of the pair of reflecting units in the optical axis direction in the resonator, Based on the detection result of the reflected light from the resonator, the laser light incident on the resonator resonates in the first mode of the plurality of modes, and a second different from the first mode.
- a control unit that controls the optical path length of the resonator by moving the at least one reflection unit to the drive unit so as to transition to a state of resonance in a mode;
- a control device comprising: (2) The control unit controls the optical path length of the resonator so as to transition to a state in which resonance occurs in at least one of the plurality of modes according to the detected level of the reflected light. The control device according to 1). (3) The control unit drives a jump pulse formed by a kick pulse for moving the at least one reflection unit by a predetermined distance and a brake pulse for stopping the reflection unit moved based on the kick pulse.
- the optical path length of the resonator is controlled so as to transition from a state resonating in the first mode to a state resonating in the second mode by supplying to the unit (1) or (2) The control device described in 1.
- the controller is When the optical path length of the resonator is controlled so that the optical path length of the resonator changes to a state of resonating in one mode of the plurality of modes based on the detection result of the reflected light, the reflecting unit Memorize the position information indicating the position of The control device according to any one of (1) to (3), wherein an optical path length of the resonator is controlled based on the stored position information.
- the control unit controls the optical path length of the resonator so that the laser light incident on the resonator resonates in a mode in which the level of the reflected light is minimum among the plurality of modes.
- the control device according to any one of 1) to (4).
- the control unit controls the optical path length of the resonator so that the modes are sequentially switched, acquires the level of the reflected light corresponding to each mode after switching, and the reflection corresponding to each acquired mode
- the control device according to (5) wherein a mode that minimizes the level of the reflected light is specified according to a light level.
- the controller is The optical path length of the resonator is controlled so that the mode is switched at least for each first unit larger than the distance between adjacent modes, and the level of the reflected light corresponding to each switched mode is acquired. In accordance with the level of the reflected light corresponding to each acquired mode, after identifying the first mode in which the level of the reflected light is minimum from the mode, In the vicinity of the first mode, the optical path length of the resonator is controlled so that the mode is switched every second unit smaller than the first unit, and the reflection corresponding to each switched mode is performed.
- control device wherein a level of the reflected light is acquired and a mode in which the level of the reflected light is minimized is determined according to the acquired level of the reflected light corresponding to each mode.
- the second mode is a mode adjacent to the first mode.
- the controller is Servo-control the optical path length so as to satisfy the resonance condition corresponding to the mode in which the optical path length of the resonator is set,
- the servo control is stopped, and after the transition of the state,
- the control device according to any one of (1) to (8), wherein the servo control is resumed with the second mode set as the set mode.
- the control unit generates an error signal indicating a deviation between the optical path length of the resonator and the optical path length satisfying the resonance condition of the incident laser light based on the detection result of the reflected light,
- the control device according to (9), wherein the optical path length of the resonator is servo-controlled based on an error signal.
- the drive unit includes at least a pair of reflection units and a nonlinear optical crystal, and resonates the incident laser beam to convert the wavelength of the laser beam, and the resonance condition of the incident laser beam is Moving at least one of the pair of reflecting portions in the direction of the optical axis in the resonator having a plurality of modes to be satisfied; and Based on the detection result of the reflected light from the resonator, the processor is different from the first mode from the state in which the laser light incident on the resonator resonates in the first mode of the plurality of modes. Controlling the optical path length of the resonator by moving the at least one reflection unit to the drive unit so as to transition to a state of resonance in the second mode; Including a control method.
- a plurality of modes that include at least a pair of reflecting portions and a nonlinear optical crystal, convert the wavelength of the laser beam by resonating the incident laser beam, and satisfy the resonance condition of the incident laser beam. Moving at least one of the pair of reflecting portions in the direction of the optical axis of the existing resonator; and Based on the detection result of the reflected light from the resonator, the laser light incident on the resonator resonates in the first mode of the plurality of modes, and a second different from the first mode. Controlling the optical path length of the resonator by moving the at least one reflecting portion so as to transition to a state of resonance in a mode; Including the program.
Abstract
Description
1.レーザー光発生装置の構成
2.サーボの引き込み
3.比較例に係る制御部
3.1.制御部の構成
3.2.サーボの引き込み動作
3.3.比較例に係るサーボの引き込み動作の課題
4.本実施形態に係る制御部
4.1.制御部の構成
4.2.サーボの引き込み動作
4.3.処理の流れ
4.4.作用効果
5.変形例
5.1.レーザー光発生装置の構成
5.2.処理の流れ
5.3.作用効果
6.ハードウェア構成
7.まとめ
まず、図1を参照して、本開示の実施形態に係るレーザー光発生装置の構成について説明する。図1は、本開示の実施形態に係るレーザー光発生装置の概略的な構成の一例を示した構成図である。
次に、本実施形態に係るレーザー光発生装置1の制御部10の詳細について説明するにあたり、まず、図2を参照しながら、レーザー光源51として、半導体レーザーのようにマルチモード発振するものを用いた場合のサーボの引き込みについて概要を説明する。図2は、マルチモード発振するレーザー光源を用いた場合のサーボの引き込みについて説明するための説明図である。
次に、従来のレーザー光発生装置を比較例として、当該比較例に係る制御部によるサーボの引き込み方法について説明することで、本実施形態に係るレーザー光発生装置1の課題について整理する。
まず、比較例に係る制御部10wの構成について、図3を参照しながら説明する。図3は、比較例に係る制御部10wの機能構成の一例を示したブロック図である。
次に、図4を参照しながら、比較例に係る制御部10wによるサーボの引き込み動作の詳細について説明する。図4は、比較例に係る制御部10wによるサーボの引き込み動作の一例について説明するための説明図である。なお、図4における参照符号g11、g21、g31、及びg13は、図2における、ミラー207の位置g11、反射信号g21、誤差信号g31、及び反射光L3の検出結果が最も低くなる範囲g13にそれぞれ対応している。
一方で、反射光L3のレベルと閾値g25との比較に基づきサーボの引き込みを行うタイミングを特定する場合には、サーボの引き込みを確実に行うために、閾値g25が、事前の測定により得られた反射光L3の最小値よりも高い値に設定される場合が少なくない。
[4.1.制御部の構成]
まず、図5を参照しながら、本実施形態に係る制御部10の構成について説明する。図5は、本実施形態に係る制御部10の機能構成の一例を示したブロック図である。
次に、モードジャンプに係る動作と、反射光L3のレベルが最小となるモードの特定に係る動作とについて、図6~図8を参照しながら説明する。
次に、図9及び図10を参照しながら、本実施形態に係る制御部10による、共振器20内における励起レーザーL1の光路長の制御に係る一連の動作について説明する。まず、図9を参照する。図9は、本実施形態に係る制御部10の一連の動作の流れを示したフローチャートである。
レーザー光発生装置1が動作を開始すると、制御部10は、モードを順次切り替えて、切り替えられたモードごとに、反射光L3のレベルの検出結果を取得し、当該反射光L3のレベルが最小となるモードを特定する。そして、制御部10は、励起レーザー光L1が特定したモードで共振するように、サーボの引き込みを行う。なお、サーボの引き込みに係る動作の詳細については、別途後述する。
サーボの引き込みが完了したら、制御部10は、光検出器41から、共振器20からの反射光L3の検出結果を取得し、当該反射光L3のレベルに基づき、サーボ制御が正常に動作しているか否かを判定する。
サーボ制御が正常に動作している場合には(ステップS20、YES)、制御部10は、あらかじめ決められた期間だけ一時的に処理を停止し(ステップS30)、当該期間経過後に再度サーボ制御が正常に動作しているか否かを確認する。制御部10は、以上のような動作を、例えば、レーザー光発生装置1の動作が停止するまで継続する(ステップS40、NO)。そして、レーザー光発生装置1の動作の停止が指示された場合には(ステップS40、YES)、制御部10は、共振器20内における励起レーザーL1の光路長の制御に係る一連の処理を終了する。
まず、制御部10は、光検出器41で検出された共振器20からの反射光L3のレベルを閾値g25と比較することで、サーボの初期引き込みを行う。これにより、ミラー207の位置が、例えば、図7に示す例におけるモードiの位置に調整される。なお、以降では、初期引き込み動作完了直後のモードをモード0(i=0)として説明する。
サーボの初期引き込みが完了したら、制御部10は、あらかじめ決められた方向にモードジャンプするように、ミラー207の位置を制御する。例えば、図10に示す例では、制御部10は、+(プラス)方向にモードジャンプするように(i=i+1)、ミラー207の位置を制御する。
モード間をジャンプするようにミラー207の位置を制御したら、制御部10は、モードジャンプ後における反射光L3の検出結果を光検出器41から取得し、当該モードジャンプの前後間で反射光L3のレベルを比較する。
反射光L3のレベルの変化が+(プラス)の場合、即ち、モードジャンプ前よりもモードジャンプ後の方が反射光L3のレベルが高かった場合には(ステップS103、YES)、制御部10は、-(マイナス)方向にモードジャンプするように、ミラー207の位置を制御する。ミラー207の位置を制御したら、制御部10は、モードジャンプ後における反射光L3の検出結果を光検出器41から取得し、当該モードジャンプの前後間で反射光L3のレベルを比較する。
以上のようにして、制御部10は、モードジャンプの前後間で反射光L3のレベルの変化が-(マイナス)である限り(ステップS112、NO)、-(マイナス)方向にモードジャンプするように、ミラー207の位置を制御する。
モードジャンプの前後間で反射光L3のレベルの変化が+(プラス)となった場合には(ステップS112、YES)、制御部10は、そのときのモードを、最適点を超えたモードとして認識し、直前のモード(Imax=i)を最適点として設定する。このとき、制御部10は、最適点に設定したモードにおける反射光L3のレベルを記憶しておく。
最適点を設定したら、制御部10は、当該最適点を基準として、あらかじめ決められたモード数nだけ-(マイナス)方向にモードジャンプするように、ミラー207の位置を制御する(ステップS115、NO)。
最適点を基準として、モード数nだけ-(マイナス)方向にモードジャンプするようにミラー207の位置を制御したら、制御部10は、モードジャンプ後における反射光L3の検出結果を光検出器41から取得する。そして、制御部10は、最適点に設定したモード(Imax=i)と、モードジャンプ後のモードとの間で反射光L3のレベルを比較する。
モードジャンプの前後間で反射光L3のレベルの変化が+(プラス)となった場合には(ステップS116、YES)、Imax=iに対応するモードにおいて、反射光L3のレベルが最小となったことを意味する。この場合には、制御部10は、モード数nだけ+(プラス)方向にモードジャンプするようにミラー207の位置を制御し、サーボの引き込みに係る一連の動作を終了する。これにより、ミラー207の位置が、Imax=iに対応するモードの位置に調整される。
なお、ステップS103において、モードジャンプの前後間における反射光L3のレベルの変化が-(マイナス)の場合(ステップS103、NO)についても、ミラー207の制御方向が異なる点を除けば、基本的な動作は、前述したステップS111~S117で示した動作と同様である。
以上のようにして、制御部10は、モードジャンプの前後間で反射光L3のレベルの変化が-(マイナス)である限り(ステップS122、NO)、+(プラス)方向にモードジャンプするように、ミラー207の位置を制御する。
モードジャンプの前後間で反射光L3のレベルの変化が+(プラス)となった場合には(ステップS122、YES)、制御部10は、そのときのモードを、最適点を超えたモードとして認識し、直前のモード(Imax=i)を最適点として設定する。このとき、制御部10は、最適点に設定したモードにおける反射光L3のレベルを記憶しておく。
最適点を設定したら、制御部10は、当該最適点を基準として、あらかじめ決められたモード数nだけ+(プラス)方向にモードジャンプするように、ミラー207の位置を制御する(ステップS125、NO)。
最適点を基準として、モード数nだけ+(プラス)方向にモードジャンプするようにミラー207の位置を制御したら、制御部10は、モードジャンプ後における反射光L3の検出結果を光検出器41から取得する。そして、制御部10は、最適点に設定したモード(Imax=i)と、モードジャンプ後のモードとの間で反射光L3のレベルを比較する。
モードジャンプの前後間で反射光L3のレベルの変化が+(プラス)となった場合には(ステップS126、YES)、Imax=iに対応するモードにおいて、反射光L3のレベルが最小となったことを意味する。そのため、制御部10は、モード数nだけ-(マイナス)方向にモードジャンプするようにミラー207の位置を制御し、サーボの引き込みに係る一連の動作を終了する。これにより、ミラー207の位置が、Imax=iに対応するモードの位置に調整される。
以上、本実施形態に係る制御部10の詳細について説明した。上記で説明したように、制御部10は、モードが逐次切り替わるように(即ち、モードジャンプするように)、ミラー207の位置を制御し、切り替わったモードそれぞれについて反射光L3のレベルを取得する。そして、制御部10は、モードジャンプの前後間で反射光L3のレベルの比較を行い、当該反射光L3のレベルが最低となるモードを特定する。このような構成より、本実施形態に係る制御部10は、より強度の高いOPOレーザー光L2を出力することが可能なモードで共振するように、共振器20内の光路長を制御することが可能となる。
[5.1.レーザー光発生装置の構成]
次に、前述した実施形態に係るレーザー光発生装置1の変形例について説明する。まず、図11を参照しながら、変形例に係るレーザー光発生装置1aの構成について説明する。図11は、変形例に係るレーザー光発生装置1aの構成を示した図である。
次に、図13を参照しながら、変形例に係る制御部10aによる、共振器20内における励起レーザーL1の光路長の制御に係る一連の動作について説明する。図13は、変形例に係る制御部10aの一連の動作の流れを示したフローチャートである。
レーザー光発生装置1が動作を開始すると、制御部10aは、モードを順次切り替えて、切り替えられたモードごとに、反射光L3のレベルの検出結果を取得し、当該反射光L3のレベルが最小となるモード(即ち、最適点)を特定する。そして、制御部10aは、励起レーザー光L1が特定したモードで共振するように、サーボの引き込みを行う。なお、サーボの引き込みに係る動作は、前述した実施形態に係る制御部10の場合(図9及び図10)と同様である。
サーボの引き込みが完了したら、制御部10aは、位置検出部221からミラー207の位置を示す位置情報を取得する。当該位置情報により、制御部10aは、反射光L3のレベルが最小となるモード(即ち、最適点)に対応するミラー207の位置を認識することが可能となる。制御部10aは、位置検出部221から取得した、最適点に対応するミラー207の位置情報を記録する。また、このとき、制御部10aは、位置検出部223からアウトプットカプラー211の位置情報を取得し、当該位置情報を記憶してもよい。
次いで、制御部10は、光検出器41から、共振器20からの反射光L3の検出結果を取得し、当該反射光L3のレベルに基づき、サーボ制御が正常に動作しているか否かを判定する。
サーボ制御が正常に動作していない場合には(ステップS20、NO)、制御部10は、あらかじめ記録した最適点に対応するミラー207の位置情報に基づき、当該最適点に対応する位置となるように、ミラー207の位置を制御する(ステップS52)。また、このとき、制御部10aは、あらかじめ記録したアウトプットカプラー211の位置情報に基づき、アウトプットカプラー211の位置を制御してもよい。あらかじめ記録した位置情報に基づきミラー207の位置を制御したら、制御部10は、改めてサーボの引き込み動作を実行する(ステップS10)。
なお、サーボ制御が正常に動作している場合には(ステップS20、YES)、制御部10aは、あらかじめ決められた期間だけ一時的に処理を停止し(ステップS30)、当該期間経過後に再度サーボ制御が正常に動作しているか否かを確認する。制御部10aは、以上のような動作を、例えば、レーザー光発生装置1の動作が停止するまで継続する(ステップS40、NO)。そして、レーザー光発生装置1の動作の停止が指示された場合には(ステップS40、YES)、制御部10aは、共振器20内における励起レーザーL1の光路長の制御に係る一連の処理を終了する。
以上説明したように、変形例に係る制御部10aは、最適点g27に対応するミラー207の位置を、位置検出部221の検出結果が示す位置情報に基づき認識することが可能である。そのため、制御部10aは、例えば、共振器20への衝撃等の外乱によりミラー207の位置が変化した場合においても、あらかじめ記憶した位置情報に基づき、最適点に対応する位置となるように、ミラー207の位置を調整することが可能となる。
次に、図14を参照して、本実施形態に係るレーザー光発生装置1のハードウェア構成の一例について説明する。図14は、本実施形態に係るレーザー光発生装置1のハードウェア構成の一例を示した図である。
以上、添付図面を参照しながら本開示の好適な実施形態について詳細に説明したが、本開示の技術的範囲はかかる例に限定されない。本開示の技術分野における通常の知識を有する者であれば、特許請求の範囲に記載された技術的思想の範疇内において、各種の変更例または修正例に想到し得ることは明らかであり、これらについても、当然に本開示の技術的範囲に属するものと了解される。
(1)
少なくとも一対の反射部と、非線形光学結晶とを含み、入射したレーザー光を共振させることで、当該レーザー光の波長を変換するものであり、かつ、入射したレーザー光の共振条件を満たすモードが複数存在する共振器における、前記一対の反射部のうち少なくとも一方の反射部を光軸方向に移動させる駆動部と、
前記共振器からの反射光の検出結果に基づき、前記共振器に入射したレーザー光が、前記複数のモードのうちの第1のモードで共振する状態から、当該第1のモードと異なる第2のモードで共振する状態に遷移するように、前記駆動部に前記少なくとも一方の反射部を移動させることで、前記共振器の光路長を制御する制御部と、
を備えた、制御装置。
(2)
前記制御部は、検出された前記反射光のレベルに応じて、前記複数のモードのうちの少なくとも一のモードで共振する状態に遷移するように、前記共振器の光路長を制御する、前記(1)に記載の制御装置。
(3)
前記制御部は、前記少なくとも一方の反射部を所定距離だけ移動させるためのキックパルスと、前記キックパルスに基づき移動した当該反射部を停止させるためのブレーキパルスとにより形成されたジャンプパルスを前記駆動部に供給することで、前記第1のモードで共振する状態から、第2のモードで共振する状態に遷移するように、前記共振器の光路長を制御する、前記(1)または(2)に記載の制御装置。
(4)
前記制御部は、
前記反射光の検出結果に基づき、前記共振器の光路長が前記複数のモードのうちの一のモードで共振する状態に遷移するように前記共振器の光路長を制御した場合に、前記反射部の位置を示す位置情報を記憶しておき、
記憶された前記位置情報に基づき、前記共振器の光路長を制御する、前記(1)~(3)のいずれか一項に記載の制御装置。
(5)
前記制御部は、前記共振器に入射したレーザー光が、前記複数のモードのうち、前記反射光のレベルが最小となるモードで共振するように、前記共振器の光路長を制御する、前記(1)~(4)のいずれか一項に記載の制御装置。
(6)
前記制御部は、前記モードが逐次切り替わるように前記共振器の光路長を制御して、切り替え後の各モードに対応する前記反射光のレベルを取得し、取得した当該各モードに対応する前記反射光のレベルに応じて、前記反射光のレベルが最小となるモードを特定する、前記(5)に記載の制御装置。
(7)
前記制御部は、
前記モードが、少なくとも隣接するモード間の距離よりも大きい第1の単位ごとに切り替わるように前記共振器の光路長を制御して、切り替えられた各モードに対応する前記反射光のレベルを取得し、取得した当該各モードに対応する前記反射光のレベルに応じて、当該各モードの中から前記反射光のレベルが最小となる第1のモードを特定した後、
前記第1のモードの近傍において、前記第1の単位よりも小さい第2の単位ごとに前記モードが切り替わるように前記共振器の光路長を制御して、切り替えられた各モードに対応する前記反射光のレベルを取得し、取得した当該各モードに対応する前記反射光のレベルに応じて、前記反射光のレベルが最小となるモードを特定する、前記(6)に記載の制御装置。
(8)
前記第2のモードは、前記第1のモードに隣接するモードである、前記(1)~(6)のいずれか一項に記載の制御装置。
(9)
前記制御部は、
前記共振器の光路長が設定されたモードに対応する共振条件を満たすように当該光路長をサーボ制御し、
前記共振器に入射したレーザー光が前記第1のモードで共振する状態から、前記第2のモードで共振する状態に遷移させる場合には、前記サーボ制御を停止し、当該状態の遷移後に、前記第2のモードを前記設定されたモードとして前記サーボ制御を再開する、前記(1)~(8)のいずれか一項に記載の制御装置。
(10)
前記制御部は、前記反射光の検出結果に基づき、前記共振器の光路長と、前記入射したレーザー光の共振条件を満たす光路長との間のずれを示す誤差信号を生成し、生成した当該誤差信号に基づき、前記共振器の光路長をサーボ制御する、前記(9)に記載の制御装置。
(11)
駆動部が、少なくとも一対の反射部と、非線形光学結晶とを含み、入射したレーザー光を共振させることで、当該レーザー光の波長を変換するものであり、かつ、入射したレーザー光の共振条件を満たすモードが複数存在する共振器における、前記一対の反射部のうち少なくとも一方の反射部を光軸方向に移動させることと、
プロセッサが、前記共振器からの反射光の検出結果に基づき、前記共振器に入射したレーザー光が、前記複数のモードのうちの第1のモードで共振する状態から、当該第1のモードと異なる第2のモードで共振する状態に遷移するように、前記駆動部に前記少なくとも一方の反射部を移動させることで、前記共振器の光路長を制御することと、
を含む、制御方法。
(12)
コンピュータに、
少なくとも一対の反射部と、非線形光学結晶とを含み、入射したレーザー光を共振させることで、当該レーザー光の波長を変換するものであり、かつ、入射したレーザー光の共振条件を満たすモードが複数存在する共振器の、前記一対の反射部のうち少なくとも一方の反射部を光軸方向に移動させるステップと、
前記共振器からの反射光の検出結果に基づき、前記共振器に入射したレーザー光が、前記複数のモードのうちの第1のモードで共振する状態から、当該第1のモードと異なる第2のモードで共振する状態に遷移するように、前記少なくとも一方の反射部を移動させることで、前記共振器の光路長を制御させるステップと、
を含む、プログラム。
10、10a 制御部
101 誤差信号生成部
103 レベル検出部
105 レベル検出部
107 サーボ制御部
109 スイッチ
111 位相補償部
113 VCMドライバ
121 サーボ制御部
123 ジャンプパルス生成部
125 スイッチ
125a 端子
125b 端子
125c 端子
11 発振器
20 共振器
201 インプットカプラー
203、205、207 ミラー
209 ダイクロイックミラー
211 アウトプットカプラー
213 非線形光学素子
221、223 位置検出部
30 駆動部
40 アイソレーター
41 光検出器
50 光源ユニット
51 レーザー光源
52 位相変調器
53 ドライバ
Claims (12)
- 少なくとも一対の反射部と、非線形光学結晶とを含み、入射したレーザー光を共振させることで、当該レーザー光の波長を変換するものであり、かつ、入射したレーザー光の共振条件を満たすモードが複数存在する共振器における、前記一対の反射部のうち少なくとも一方の反射部を光軸方向に移動させる駆動部と、
前記共振器からの反射光の検出結果に基づき、前記共振器に入射したレーザー光が、前記複数のモードのうちの第1のモードで共振する状態から、当該第1のモードと異なる第2のモードで共振する状態に遷移するように、前記駆動部に前記少なくとも一方の反射部を移動させることで、前記共振器の光路長を制御する制御部と、
を備えた、制御装置。 - 前記制御部は、検出された前記反射光のレベルに応じて、前記複数のモードのうちの少なくとも一のモードで共振する状態に遷移するように、前記共振器の光路長を制御する、請求項1に記載の制御装置。
- 前記制御部は、前記少なくとも一方の反射部を所定距離だけ移動させるためのキックパルスと、前記キックパルスに基づき移動した当該反射部を停止させるためのブレーキパルスとにより形成されたジャンプパルスを前記駆動部に供給することで、前記第1のモードで共振する状態から、第2のモードで共振する状態に遷移するように、前記共振器の光路長を制御する、請求項1に記載の制御装置。
- 前記制御部は、
前記反射光の検出結果に基づき、前記共振器の光路長が前記複数のモードのうちの一のモードで共振する状態に遷移するように前記共振器の光路長を制御した場合に、前記反射部の位置を示す位置情報を記憶しておき、
記憶された前記位置情報に基づき、前記共振器の光路長を制御する、請求項1に記載の制御装置。 - 前記制御部は、前記共振器に入射したレーザー光が、前記複数のモードのうち、前記反射光のレベルが最小となるモードで共振するように、前記共振器の光路長を制御する、請求項1に記載の制御装置。
- 前記制御部は、前記モードが逐次切り替わるように前記共振器の光路長を制御して、切り替え後の各モードに対応する前記反射光のレベルを取得し、取得した当該各モードに対応する前記反射光のレベルに応じて、前記反射光のレベルが最小となるモードを特定する、請求項5に記載の制御装置。
- 前記制御部は、
前記モードが、少なくとも隣接するモード間の距離よりも大きい第1の単位ごとに切り替わるように前記共振器の光路長を制御して、切り替えられた各モードに対応する前記反射光のレベルを取得し、取得した当該各モードに対応する前記反射光のレベルに応じて、当該各モードの中から前記反射光のレベルが最小となる第1のモードを特定した後、
前記第1のモードの近傍において、前記第1の単位よりも小さい第2の単位ごとに前記モードが切り替わるように前記共振器の光路長を制御して、切り替えられた各モードに対応する前記反射光のレベルを取得し、取得した当該各モードに対応する前記反射光のレベルに応じて、前記反射光のレベルが最小となるモードを特定する、請求項6に記載の制御装置。 - 前記第2のモードは、前記第1のモードに隣接するモードである、請求項1に記載の制御装置。
- 前記制御部は、
前記共振器の光路長が設定されたモードに対応する共振条件を満たすように当該光路長をサーボ制御し、
前記共振器に入射したレーザー光が前記第1のモードで共振する状態から、前記第2のモードで共振する状態に遷移させる場合には、前記サーボ制御を停止し、当該状態の遷移後に、前記第2のモードを前記設定されたモードとして前記サーボ制御を再開する、請求項1に記載の制御装置。 - 前記制御部は、前記反射光の検出結果に基づき、前記共振器の光路長と、前記入射したレーザー光の共振条件を満たす光路長との間のずれを示す誤差信号を生成し、生成した当該誤差信号に基づき、前記共振器の光路長をサーボ制御する、請求項9に記載の制御装置。
- 駆動部が、少なくとも一対の反射部と、非線形光学結晶とを含み、入射したレーザー光を共振させることで、当該レーザー光の波長を変換するものであり、かつ、入射したレーザー光の共振条件を満たすモードが複数存在する共振器における、前記一対の反射部のうち少なくとも一方の反射部を光軸方向に移動させることと、
プロセッサが、前記共振器からの反射光の検出結果に基づき、前記共振器に入射したレーザー光が、前記複数のモードのうちの第1のモードで共振する状態から、当該第1のモードと異なる第2のモードで共振する状態に遷移するように、前記駆動部に前記少なくとも一方の反射部を移動させることで、前記共振器の光路長を制御することと、
を含む、制御方法。 - コンピュータに、
少なくとも一対の反射部と、非線形光学結晶とを含み、入射したレーザー光を共振させることで、当該レーザー光の波長を変換するものであり、かつ、入射したレーザー光の共振条件を満たすモードが複数存在する共振器の、前記一対の反射部のうち少なくとも一方の反射部を光軸方向に移動させるステップと、
前記共振器からの反射光の検出結果に基づき、前記共振器に入射したレーザー光が、前記複数のモードのうちの第1のモードで共振する状態から、当該第1のモードと異なる第2のモードで共振する状態に遷移するように、前記少なくとも一方の反射部を移動させることで、前記共振器の光路長を制御させるステップと、
を含む、プログラム。
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