JP3976756B2 - Optical frequency comb generator controller - Google Patents

Description

  The present invention is an optical frequency comb generator that is applied to a field that requires a multi-wavelength, high-coherence standard light source such as optical communication, optical CT, or optical frequency standard machine, or a light source that can also use coherence between wavelengths. The present invention relates to a controller.

  Conventionally, for example, an optical frequency comb generator is used when measuring an optical frequency with high accuracy. That is, when heterodyne detection is performed on two laser beams and the difference frequency is measured, the band is limited by the band of the light receiving element and is generally about several tens of GHz. Therefore, a wideband heterodyne using an optical frequency comb generator is used. A detection system is constructed. The optical frequency comb generator generates several hundred sidebands of incident laser light at equal frequency intervals, and the frequency stability of the generated sideband is almost the same as that of the original laser light. Therefore, by performing heterodyne detection of the sideband wave and the laser beam to be measured, a wideband heterodyne detection system over several THz can be constructed.

  FIG. 14 shows the basic structure of the bulk optical frequency comb generator 400.

  This bulk type optical frequency comb generator 400 uses an optical resonator 410 composed of an optical phase modulator 411 and reflecting mirrors 412 and 413 installed so as to face each other through the optical phase modulator 411. Yes.

  In this optical resonator 410, the light Lin incident with a slight transmittance through the reflecting mirror 412 resonates between the reflecting mirrors 412 and 413, and a part of the light Lout is emitted through the reflecting mirror 413. The optical phase modulator 411 is made of an optical material for optical phase modulation whose refractive index changes when an electric field is applied, and is applied between the electrodes 416A and 416B with respect to the light passing through the optical resonator 410. Apply phase modulation according to the output of the AC power supply fm.

  The light Lin incident on the optical resonator 410 resonates between the reflecting mirrors 412 and 413, undergoes phase modulation by the optical phase modulator 411, and is emitted as the optical frequency comb output light Lout through the reflecting mirror 413. The

  Here, for example, as shown in FIG. 15, the bulk type optical frequency comb generator has an incident end and an emission end formed by high reflection films 512A and 512B on an electro-optic crystal 511 that transmits a light beam for optical modulation, respectively. By providing, a monolithic configuration in which the optical modulator and the optical resonator are integrated can be obtained. However, in the bulk-type optical frequency comb generator 500 having a monolithic configuration, the modulation frequency is determined by the crystal length of the electro-optic crystal 511, and thus cannot be adjusted, for example, when the wavelength of the light source is determined.

  On the other hand, a bulk-type optical modulator made of an electro-optic crystal having a high-reflection film on the incident end side, and a high-reflection film disposed on the output end side of the bulk-type optical modulator and moved by an electromechanical conversion element The modulation frequency can be arbitrarily set regardless of the crystal length of the electro-optic crystal.

  For example, as shown in FIG. 16, an optical frequency comb generator 600 having a semi-monolithic configuration includes a semi-monolithic light modulator 610 composed of an electro-optic crystal 611 that transmits a light beam for optical modulation, and the semi-monolithic optical modulator 610. And a movable mirror 630 disposed on the output end side.

The semi-monolithic light modulator 610 is composed of an electro-optic crystal 611 capable of phase-modulating light with a voltage, such as lithium niobate (LiNbO ₃ ), for example, and a highly reflective film 612A is formed on its incident end face by HR coating. An antireflective film 612B is formed on the emission end face by AR coating.

  The movable mirror 630 is formed with a high reflection film 631A, and the high reflection film 631A and the high reflection film 612A on the incident end face of the semimonolithic light modulator 610 constitute a resonator. The movable mirror 630 is moved by an electromechanical transducer 632 such as PZT.

  Thus, the semi-monolithic light modulator 610 composed of the electro-optic crystal 611 having the high reflection film 612A on the incident end side, and the electromechanical conversion element 632 such as PZT, which is disposed on the emission end side of the semi-monolithic light modulator 610. In an optical frequency comb generator 600 having a semi-monolithic configuration composed of a movable mirror 630 formed with a highly reflective film 631A moved by the above, coarse adjustment of the resonator length (FSR) is fixed to the electromechanical transducer 630. It is possible to finely adjust the resonator length (FSR) by moving the movable mirror 630 by driving the electromechanical transducer 632 and moving the movable mirror 630. .

  That is, in this optical frequency comb generator 600, a semi-monolithic light modulator 610 made of an electro-optic crystal 611 having a highly reflective film 612A on the incident end side, and an emission end side of the semi-monolithic light modulator 610, By adopting a semi-monolithic configuration composed of the movable mirror 630 formed with the highly reflective film 631A moved by the electromechanical transducer 632, the modulation frequency can be arbitrarily set regardless of the crystal length of the electro-optic crystal 611. Can be set.

  The optical frequency comb generator 600 having such a structure receives a light beam Lin as a fundamental wave via an incident side optical system 650 including a fiber input collimator light converter 651 and a condenser lens 652. In the semi-monolithic light modulator 610, by modulating the phase of the light beam Lin, the optical frequency comb Lout is taken out through the emission end made of a highly reflective film, and the condenser lens 661 and the fiber output collimator light converter are extracted. The optical frequency comb Lout is emitted through an emission side optical system 660 composed of 662.

  Here, a part of the optical frequency comb Lout emitted from the optical frequency comb generator 600 via the emission side optical system 660 is divided by the optical coupler 665 and supplied to the optical frequency comb generator controller 700. Is done.

  The optical frequency comb generator controller 700 includes a microwave oscillator 701 that generates a microwave signal to be given to the semi-monolithic optical modulator 610 as a phase control signal fm, and the microwave signal generated by the microwave oscillator 701 is Amplified by the microwave amplifier 702 and supplied to the semi-monolithic optical modulator 610 as the phase control signal fm, and also supplied to the double balanced modulator 707 via the phase shifter 703.

  Note that the semi-monolithic optical modulator 610 is controlled at a constant temperature by a Peltier element.

  The optical frequency comb generator controller 700 applies the microwave signal as a phase control signal fm to an electrode (not shown) of the semi-monolithic optical modulator 610. The semi-monolithic light modulator 610 modulates the phase of the light beam Lin as the fundamental wave incident through the incident-side optical system 650 in accordance with the phase control signal fm, so that the highly reflective film 631A is formed. The optical frequency comb Lout is output via the movable mirror 630.

  The optical frequency comb generator control device 700 includes a high-speed photodetector 706 into which the optical frequency comb Lout divided by the optical coupler 665 is incident via the optical chopper 705, and the output of the photodetector 706. Is supplied to the double balanced modulator 707. Then, the output of the double balanced modulator 707 is supplied to a lock-in amplifier 708, and the output of the lock-in amplifier 708 is supplied to the electromechanical conversion element 632 via an integrator 709, whereby the movable mirror 630. Is feedback controlled.

  That is, in the conventional optical frequency comb generator control device 700 having such a configuration, a control signal having a characteristic as shown in FIG. 17, for example, is obtained as an integration output by the integrator 709, and this control signal is used as the electric machine. The movable mirror 630 is feedback-controlled by supplying it to the conversion element 632. Here, FIG. 17 shows that the driving voltage (PZT voltage) of the electromechanical conversion element 632 is taken as the horizontal axis, and the light passes through the resonator when the light phase difference is swept 2π (distance by one wavelength). The control signal in the case where the phase modulation received during passing is π / 2 rad is shown.

Japanese Patent Laid-Open No. 15-043539

  By the way, in the conventional optical frequency comb generator control device 200 configured as described above, a part of the output is detected by a high-speed photodetector, and a component synchronized with the comparison comb drive frequency is detected as a double balanced modulator ( DBM: Double Balanced Mixer), but because the characteristics of DBM are not ideal, an unnecessary offset is added to the IF signal. The offset depends on the microwave power applied to the local oscillator and / or temperature. Therefore, it has been necessary to detect only a component depending on the optical signal in the IF signal with a lock-in amplifier using an expensive optical chopper. Moreover, high-speed photodetectors and high-frequency microwave components are expensive, and sensitivity at high frequencies is poor. Further, it is necessary to adjust the microwave phase, and it is necessary to use different parts for each modulation frequency. Further, there is a problem that the servo gain varies depending on the incident light intensity.

  Accordingly, an object of the present invention is to provide an optical frequency comb generator control device that can obtain a stable output without using an expensive high-speed photodetector in view of the conventional problems as described above. It is in.

  Other objects of the present invention and specific advantages obtained by the present invention will become more apparent from the description of embodiments described below.

The present invention relates to a control device for an optical frequency comb generator having an optical modulator made of an electro-optic crystal that transmits a light beam for optical modulation in an optical resonator, and provides the optical modulator as a phase control signal A microwave oscillator that generates a microwave signal, and an optical frequency comb emitted from the electro-optic crystal is incident , and light near the edge where the optical frequency comb away from the center frequency of the optical frequency comb abruptly attenuates An optical filter that extracts a frequency component; a photodetector that receives the optical frequency component extracted from the optical frequency comb by the optical filter to detect light intensity; and a detection signal of the photodetector based on the detection signal and an optical resonator length control section for feedback controlling the optical resonant length of the optical resonator, to detect the light intensity of the optical frequency components near the end of the optical frequency comb is rapidly attenuated in the optical resonator length controller Ri characterized by feedback controlling the optical resonant length of the optical resonator.

  An optical frequency comb generator control device according to the present invention includes a movable mirror disposed on an incident end or an emission end side of the optical modulator and formed with a highly reflective film that is moved by an electromechanical conversion element. The resonance length control unit may perform feedback control of the movable mirror to a predetermined position based on a detection signal of the photodetector.

  In the optical frequency comb generator control device according to the present invention, the optical modulator can be a semi-monolithic optical modulator made of an electro-optic crystal having a highly reflective film on the incident end face.

  In the optical frequency comb generator control device according to the present invention, the optical modulator is an optical waveguide type optical modulator, and a phase control signal and drive control are applied to the optical waveguide type optical modulator via a bias T. A signal may be supplied.

  ADVANTAGE OF THE INVENTION According to this invention, the optical frequency comb generator control apparatus which can obtain the stable output can be provided, without using an expensive optical chopper.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Needless to say, the present invention is not limited to the following examples, and can be arbitrarily changed without departing from the gist of the present invention.

  The present invention is applied to, for example, an optical frequency comb generator 100 having a structure as shown in FIG.

  The optical frequency comb generator 100 includes a semi-monolithic optical modulator 110 made of an electro-optic crystal 111 that transmits a light beam that performs optical modulation, a cavity microwave resonator 120 that contains the semi-monolithic optical modulator 110, and And a movable mirror 130 disposed on the output end side of the semi-monolithic light modulator 110.

The semi-monolithic light modulator 110 is made of an electro-optic crystal 111 capable of phase-modulating light with a voltage, such as lithium niobate (LiNbO ₃ ), for example, and a highly reflective film 112A is formed on its incident end face by HR coating, An antireflective film 112B is formed on the emission end face by AR coating.

  Note that the semi-monolithic optical modulator 110 is controlled at a constant temperature by a Peltier element.

  The movable mirror 130 has a high reflection film 131A formed by HR coating on the incident end face and a non-reflective film 131B formed by AR coating on the output end face. The high-reflection film 112A on the incident end face of the monolithic optical modulator 110 constitutes an optical resonator. The movable mirror 130 is moved by an electromechanical transducer 132 such as PZT.

  Thus, the semi-monolithic light modulator 110 made of the electro-optic crystal 111 having the high reflection film 112A on the incident end side, and the electromechanical conversion element 132 such as PZT, which is disposed on the emission end side of the semi-monolithic light modulator 110. In the optical frequency comb generator 100 having a semi-monolithic configuration composed of the movable mirror 130 formed with the highly reflective film 131 </ b> A moved by the above, the resonator length coarse adjustment is fixed to the electromechanical transducer 132. Fine adjustment of the resonator length can be performed by moving the movable mirror 130 by driving the electromechanical transducer 132 and adjusting the position of moving the entire movable mirror 130.

  That is, in the optical frequency comb generator 100, the semi-monolithic light modulator 110 made of the electro-optic crystal 111 having the high reflection film 112A on the incident end side, and the emission end side of the semi-monolithic light modulator 110 are arranged. By adopting a semi-monolithic configuration composed of the movable mirror 130 formed with the highly reflective film 131A moved by the electromechanical transducer 132, the modulation frequency can be arbitrarily set regardless of the crystal length of the electro-optic crystal 111. Can be set.

  The optical frequency comb generator 100 receives a light beam Lin as a fundamental wave via an incident side optical system 150 including a fiber input collimator light converter 151 and a condenser lens 152. In the semi-monolithic light modulator 110, by modulating the phase of the light beam Lin, the optical frequency comb Lout is extracted through the output end made of a highly reflective film, and the condenser lens 161 and the fiber output collimator light converter are extracted. The optical frequency comb Lout is emitted through an emission side optical system 160 composed of 162.

  Since the semi-monolithic optical modulator 110 is built in the cavity microwave resonator 120, the cavity microwave resonator 120 resonates with the microwave signal supplied thereto, so that it corresponds to the microwave signal. An electric field is applied, and the refractive index changes according to the microwave signal. As a result, the semi-monolithic optical modulator 110 is a bulk type optical phase modulator that performs optical phase modulation in accordance with the microwave signal with respect to the light beam Lin as a fundamental wave incident through the incident end reflection film. Function as.

  That is, in the optical frequency comb generator 100 having such a structure, the semi-monolithic optical modulator 110 responds to the microwave signal with respect to the light beam Lin as the fundamental wave incident through the incident side optical system 150. The phase of the light beam Lin is modulated, the optical frequency comb Lout is extracted via the exit end reflection film of the movable mirror 130, and the optical frequency comb is output via the exit side optical system 160. Lout is emitted.

  Here, the optical frequency comb Lout emitted from the optical frequency comb generator 100 via the emission-side optical system 160 is partly divided by the optical coupler 165 to have an optical frequency having a configuration as shown in FIG. This is supplied to the comb generator control device 200.

  The optical frequency comb generator control device 200 includes a microwave oscillator 201 that generates a microwave signal to be given as a phase control signal fm to the semimonolithic optical modulator 110, and the microwave signal generated by the microwave oscillator 201 is received. The semi-monolithic optical modulator 110 is driven by being amplified by the microwave amplifier 202 and applied to the semi-monolithic optical modulator 110 as the phase control signal fm.

  The optical frequency comb generator control apparatus 200 receives the optical frequency comb Lout divided by the optical coupler 165, and extracts an optical frequency component 203 near the end where the optical frequency comb abruptly attenuates. A photodetector 204 that receives and detects the optical frequency component extracted from the optical frequency comb by the optical filter 203, and an optical resonance length of the optical resonator based on a detection signal of the photodetector 204. Is provided with an optical resonance length control unit 210 for feedback control.

  As the optical filter 203, an interference filter, a wavelength selection filter using a dispersion element such as a diffraction grating or an etalon, or the like can be used.

  The optical resonance length control unit 210 includes an adder 205 that adds a bias voltage to the detection signal of the photodetector 204, an integrator 206 that integrates the output of the adder 205, and an output of the integrator 206. PZT driver 207 and the like. The adder 205 is supplied with an offset voltage determined manually.

  Here, an operation principle of the optical frequency comb generator control device 200 will be described.

  As shown in FIG. 3, the span of the optical frequency comb changes greatly by changing the control point, as shown in FIG. 3, in which the difference in the envelope when the output of the optical frequency comb generator 100 is measured with a spectrum analyzer when the control point is changed is shown. The spectrum of the optical frequency comb is maximized at the center, and decays exponentially with increasing distance from the center frequency on both the long wavelength side and the short wavelength side.

  This characteristic varies depending on the modulation frequency of the optical frequency comb, resonator length, temperature, wavelength dependency of the refractive index of the material, and the like, and can be controlled by adjusting them.

  Therefore, by measuring the light intensity near the end where the optical frequency comb abruptly attenuates, it is possible to obtain a control signal depending on the wavelength at which the optical frequency comb abruptly attenuates.

For example, the difference in the envelope when the output of the optical frequency comb generator when the control points (a, b,... G) of the normal control signal shown in FIG. the as shown in FIG. 3 (B), detects the rise of the optical frequency comb near 1510 nm, by detecting the end of the optical frequency comb is rapidly attenuated, normal control signal shown in (a) of FIG. 3 Stable feedback control having one lock point similar to the case of controlling to the control point d can be performed.

  In this optical frequency comb generator control device 200, an optical frequency component in the vicinity of the end where the optical frequency comb abruptly attenuates is extracted by an optical filter 203, and this optical frequency component is received and detected. Based on the signal, the optical resonance length of the optical resonator is feedback-controlled.

  FIG. 4 shows a light intensity signal of an optical frequency component extracted by the optical filter 203 when a band pass filter is used as the optical filter 203 and its center frequency is changed. In FIG. 4, A shows a light intensity signal when the optical filter 203 having a bandwidth of 3 nm and a center wavelength of 1500 nm is used, and B shows a case of using the optical filter 203 having a bandwidth of 3 nm and a center wavelength of 1510 nm. C represents the light intensity signal, C represents the light intensity signal when the optical filter 203 having a bandwidth of 3 nm and the center wavelength is 1520 nm, and D represents the optical filter 203 having a bandwidth of 3 nm and the center wavelength of 1530 nm. The light intensity signal when used is shown.

  FIG. 5 shows the light intensity signal obtained when the wavelength of the edge on the long wavelength side of the optical filter 203 is fixed and the bandwidth is changed. In FIG. 5, E indicates a light intensity signal when using the optical filter 203 having a long-wavelength edge wavelength of 1510 nm and a bandwidth of 3 nm, and F indicates a long-wavelength edge wavelength of 1510 nm and a bandwidth of The light intensity signal when the 10 nm optical filter 203 is used is shown.

  As described above, in the optical frequency comb generator control device 200, the optical frequency component near the end where the optical frequency comb abruptly attenuates is extracted by the optical filter 203, and the optical detection is performed by receiving and detecting the optical frequency component. By performing feedback control of the optical resonance length of the optical resonator based on the detection signal of the optical device 204, a stable optical frequency comb output can be obtained without using an expensive optical chopper. Further, in this optical frequency comb generator control device 200, an optical bandpass filter that is commercially available in large quantities for WDM (Wave length Division Multiplex) application in an optical communication system is used as the optical filter 203, thereby reducing the cost performance. A good control system can be constructed. Further, in this optical frequency comb generator control device 200, it is not necessary to adjust the microwave phase. In addition, the photodetector 203 in the optical frequency comb generator control device 200 may be a low-speed detector, so that it is inexpensive and highly sensitive. Furthermore, since the optical frequency comb generator control device 200 does not depend on the modulation frequency, the optical frequency comb generator 100 having different modulation frequencies can be controlled by the same device.

  Further, as described above, an optical frequency component near the end where the optical frequency comb abruptly attenuates is extracted by the optical filter 203, and based on the detection signal of the photodetector 204 that receives and detects this optical frequency component, In the optical frequency comb generator control device 200 in which the optical resonance length of the optical resonator is feedback-controlled, when the modulation amplitude is large, for example, the phase modulation received by the light while the light reciprocates in the resonator is π or more. The case can also be controlled.

  For example, when the phase difference of light is swept by 2π (one wavelength as a distance) by the electromechanical conversion element 132, and the phase modulation received by the light while the light reciprocates in the resonator is 4 rad (> In the case of π), in the conventional optical frequency comb generator control device, two control points are generated as shown in FIG. 6. In this optical frequency comb generator control device 200, an edge on the long wavelength side is generated. The light intensity signal obtained through the optical filter 204 having a wavelength of 1510 nm and a bandwidth of 10 nm has one control point as shown in FIG. 7, and can be controlled stably.

  Here, in the optical frequency comb generator control device 200, an offset voltage determined manually is applied to the adder 205. As shown in FIG. 8, the light incident on the optical frequency comb generator 100 is supplied. An optical coupler 265 that divides a part of the beam Lin is arranged in front of the incident optical system 150, and a part of the light beam Lin divided by the optical coupler 265 is detected by a photodetector, and is detected by the photodetector. If the light intensity signal of the light beam Lin is amplified by an amplifier and supplied to the adder, it is possible to prevent the control position from fluctuating due to the incident light intensity.

  Further, as shown in FIG. 9, a divider 211 is provided in the preceding stage of the adder 205, and the optical intensity of the optical frequency component near the end where the optical frequency comb obtained as the detection output by the optical detector 204 abruptly attenuates is obtained. When the signal A is divided by the light intensity signal B of the light beam Lin obtained as the detection output by the light detector 208 by the divider 211 and supplied to the adder 205, the incident light intensity is increased. It is possible to prevent the servo gain from fluctuating.

  Also, as shown in FIG. 10, by adding a lock-in amplifier 212 to the configuration shown in FIG. 9 and performing differentiation, the control variable range is enlarged as shown in FIG. 11, and the lock point is set to a high signal level. It can move to the center side. In FIG. 11, D indicates a light intensity signal when an optical filter having an edge wavelength on the long wavelength side of 1530 nm and a bandwidth of 3 nm is used, and G indicates a differential signal by the lock-in amplifier 212.

  Further, according to the present invention, as shown in FIG. 12, the output side optical system 160 is constituted by a spatial optical system, and a part of the optical frequency comb Lout is separated by a beam splitter 168 and is passed through an optical filter 203. It can also be made to enter into 204.

  Furthermore, in the above-described embodiment, the semimonolithic optical frequency comb generator 100 in which the semimonolithic optical modulator 110 made of the electro-optic crystal 111 that transmits the light beam that performs optical modulation is built in the cavity microwave resonator 120. However, the present invention is not limited to the above-described embodiment. For example, as shown in FIG. 13, the present invention is applied to an optical frequency comb generator 100A including a waveguide type optical modulator 110A. It can also be applied.

  The optical frequency comb generator 100A shown in FIG. 13 is configured to drive the waveguide type optical modulator 110A via the bias T220 by the optical frequency comb generator control device 200 having the configuration shown in FIG. Is.

  The waveguide-type optical modulator 110A in the optical frequency comb generator 100A has a phase control signal fm obtained by amplifying the microwave signal generated by the microwave oscillator 201 by the microwave amplifier 202 via the bias T220. The output of the adder 205 is integrated by being fed to the optical modulator 110A of the type, and the output of the integrator 206 is fed through the bias T220, so that the optical resonance length is feedback-controlled.

  The waveguide-type optical modulator 110A may be driven via the bias T220 by the optical frequency comb generator control device 200 having the configuration shown in FIGS.

  Here, the optical frequency comb generator 100A using the waveguide type optical modulator 110A can be formed in a small size, has a small heat capacity, and can perform temperature control quickly. Therefore, the optical resonance length controller 210 can also feedback control the optical resonance length of the optical resonator by applying feedback to the temperature control. Normally, the bias T has a large loss at high frequencies and is an expensive component, and the control system that feeds back temperature control to control the optical resonance length of the optical resonator requires an expensive high-frequency amplifier and bias T. Therefore, it is effective to construct a cheaper device.

It is typical sectional drawing which shows the structural example of the optical frequency comb generator to which this invention is applied. It is a block diagram which shows the structural example of the optical frequency comb generator control apparatus which controls the said optical frequency comb generator. It is a figure for demonstrating the principle of operation of the said optical frequency comb generator control apparatus. It is a figure which shows the optical intensity signal of the optical frequency component extracted by an optical filter, when a band pass filter is used as an optical filter in the said optical frequency comb generator control apparatus, and the center frequency is changed. It is a figure which shows the light intensity signal obtained when the wavelength of the edge of the long wavelength side of the said optical filter is fixed and a bandwidth is changed. It is a characteristic view which shows the state which two control points generate | occur | produce in an optical frequency comb generator control apparatus. It is a characteristic view which shows the control state by the light intensity signal obtained through the said optical filter. It is a block diagram which shows the other structural example of an optical frequency comb generator control apparatus. It is a block diagram which shows the other structural example of an optical frequency comb generator control apparatus. It is a block diagram which shows the other structural example of an optical frequency comb generator control apparatus. It is a characteristic view which shows the control state by the optical frequency comb generator control apparatus shown in FIG. It is a block diagram which shows the other structural example of an optical frequency comb generator control apparatus. It is a block diagram which shows the further another structural example of an optical frequency comb generator control apparatus. It is a figure which shows typically the structure of the conventional bulk type | mold optical frequency comb generator. It is a figure which shows typically the optical frequency comb generator of the conventional monolithic structure. It is a figure which shows typically the bulk type optical frequency comb generator of the conventional semimonolithic structure. It is a characteristic view which shows the operating characteristic of the conventional optical frequency comb generator control apparatus.

Explanation of symbols

100, 100A optical frequency comb generator, 110 semi-monolithic optical modulator, 110A waveguide-type optical phase modulator, 111 electro-optic crystal, 112A highly reflective film, 112B non-reflective film, 120 cavity microwave resonator, 130 movable Mirror, 131A High reflection film, 131B Non-reflection film, 132 Electromechanical conversion element, 165, 265 Optical coupler, 150 Incident side optical system, 151 Fiber input collimator light converter, 152 Condensing lens, 160 Output side optical system, 161 Condenser lens, 162 fiber output collimator light converter, 168 beam splitter, 200 optical frequency comb generator controller, 201 microwave oscillator, 202 microwave amplifier, 203 optical filter, 204, 208 photodetector, 205 adder 206 Integrator, 207 PZT driver, 209 increase Vessel, 210 optical resonator length control unit, 211 divider, 212 lock-in amplifier, 187 an integrator, 188 PZT driver, 189 a modulation signal generator, 190 a phase modulator, 220 bias T

Claims (5)

A control device for an optical frequency comb generator comprising an optical modulator made of an electro-optic crystal that transmits a beam of light to be modulated in an optical resonator,
A microwave oscillator for generating a microwave signal to be provided as a phase control signal to the optical modulator;
An optical filter for extracting an optical frequency component near an end where the optical frequency comb emitted from the electro-optic crystal is incident and the optical frequency comb separated from the center frequency of the optical frequency comb is rapidly attenuated ;
A photodetector for detecting the light intensity by receiving the optical frequency component extracted from the optical frequency comb by the optical filter;
Based on the detection signal of the photodetector, an optical resonance length control unit that feedback-controls the optical resonance length of the optical resonator ,
An optical frequency comb comprising: detecting an optical intensity of an optical frequency component near an end where the optical frequency comb abruptly attenuates; and feedback controlling the optical resonance length of the optical resonator by the optical resonance length control unit. Generator control device.   2. The optical frequency comb generator control device according to claim 1, wherein the optical resonance length control unit includes a lock-in amplifier for differentiating a detection signal of the photodetector. A movable mirror disposed on the incident end or emission end side of the optical modulator and formed with a highly reflective film that is moved by an electromechanical transducer;
2. The optical frequency comb generator control device according to claim 1, wherein the optical resonance length control unit feedback-controls the movable mirror to a predetermined position based on a detection signal of the photodetector. 4. The optical frequency comb generator control device according to claim 3 , wherein the optical modulator is a semi-monolithic optical modulator made of an electro-optic crystal having a highly reflective film on the incident end face.   2. The light according to claim 1, wherein the optical modulator is an optical waveguide type optical modulator, and a phase control signal and a drive control signal are supplied to the optical waveguide type optical modulator via a bias T. Frequency comb generator control device.

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