Integrated microcavity optical comb repetition frequency and optical frequency locking device and method

Abstract

The invention relates to an integrated microcavity optical comb repetition frequency and optical frequency locking device and method, and belongs to the technical field of integrated microcavity optical combs. The locking device comprises a pumping module, a power amplification module, a phase modulation module, an electro-optic driving module, an acousto-optic modulation module, an acousto-optic driving module, a band-pass filtering module, a micro-ring resonant cavity and a beam splitting module; the device comprises a soliton detection module, a control module, a repetition frequency detection module, a first feedback control module, an acetylene frequency stabilized laser, a beat frequency module, an optical frequency beat frequency detection module and a second feedback control module. The locking device can achieve full frequency locking of the microcavity optical comb, has the advantages of being high in frequency stability, wide in servo bandwidth, simple and compact in structure, tight in locking, low in noise, high in reliability and low in cost, and can provide a powerful tool for the field of precision measurement.

Description

Technical Field

[0001] The present invention relates to an integrated microcavity optical frequency comb repetition frequency and optical frequency locking device and method, belonging to the technical field of integrated microcavity optical frequency combs. Background Art

[0002] Since only an optical frequency measurement with a resolution of the order of MHz can be achieved by using a wavelength meter, it is still very difficult to obtain an optical frequency measurement with higher resolution and accuracy. The optical frequency comb technology has attracted wide attention due to its high-resolution and high-accuracy measurement ability of absolute optical frequencies, and its inventor was awarded the Nobel Prize in Physics in 2005. The optical frequency comb appears as a femtosecond laser pulse train in the time domain and as a series of equally spaced and discrete longitudinal mode comb teeth in the frequency domain. The interval between the longitudinal modes in the frequency domain is the repetition frequency f rep of the laser, and the initial frequency shift of the overall spectrum relative to the zero point is the carrier-envelope phase shift frequency f ceo . Since both the repetition frequency f rep and the carrier-envelope phase shift frequency f ceo are in the radio frequency and microwave fields, usually we can accurately detect and lock and control f rep and f ceo through specific methods, so as to obtain an optical frequency comb with stable frequency, and deduce that the frequency of any comb tooth is f n = nf rep + f ceo . Since the invention of the optical frequency comb, it has brought a disruptive revolution in precision measurement fields such as optical clock systems, high-precision time and frequency transfer, distance measurement, and spectral detection, and plays a crucial role especially in the generation of attosecond pulses.

[0003] As the optical frequency comb technology moves from the laboratory to applications and develops from scientific research applications to industrial, military and other practical applications, traditional fiber optical combs and solid optical combs are greatly restricted in large-scale deployment due to their large volume, complex structure, and cumbersome control, etc. The integrated microcavity optical frequency comb has quickly received extensive attention and research due to its characteristics such as miniaturization and integration. The generation principle of the integrated microcavity optical frequency comb is different from that of traditional optical combs. The pump laser generates equally spaced optical longitudinal modes through nonlinear effects such as four-wave mixing in a high-quality-factor on-chip microcavity, and forms optical solitons after balancing dispersion and nonlinear effects, gain and loss. Due to the extremely high quality factor of the microcavity and strong nonlinear effects, its pump threshold is several orders of magnitude lower than that of traditional optical combs, and the repetition frequency is usually above 20 GHz. Since the single-pulse energy of the output pulse of the microcavity optical frequency comb is extremely low, it is difficult to obtain a spectral broadening with an octave bandwidth, so it is very difficult to directly detect f ceo , so it is very difficult for the current microcavity optical frequency comb to achieve frequency resolution and precise locking through f n = nf rep + f ceo . Summary of the Invention

[0004] The object of the present invention is to overcome the above-mentioned defects of the prior art, and provide an integrated microcavity optical frequency comb repetition frequency and optical frequency locking device and method. The device has the characteristics of high frequency stability, wide servo bandwidth, simple and compact structure, and is tightly locked, with low noise, high reliability and low cost, and can provide a powerful tool for the field of precision measurement.

[0005] The above object of the present invention is mainly achieved by the following technical solutions:

[0006] An integrated microcavity optical frequency comb repetition frequency and optical frequency locking device, comprising:

[0007] A pump module, which provides a continuous pump laser output to a power amplification module; receives a control signal sent by a control module, and if solitons are generated, fixes the pump laser wavelength, otherwise continues to scan until solitons are generated;

[0008] A power amplification module, which amplifies the power of the pump laser received from the pump module and then outputs it to a phase modulation module;

[0009] A phase modulation module, which, under the drive of a radio frequency signal output by an electro-optic drive module, performs phase modulation on the pump laser received from the power amplification module, generates modulation sidebands on both sides of the pump laser wavelength, and outputs them to an acousto-optic modulation module;

[0010] An electro-optic drive module, which receives a first feedback control signal from a first feedback control module, generates a radio frequency signal for driving the phase modulation module, and outputs it to the phase modulation module;

[0011] An acousto-optic modulation module, which, under the drive of a radio frequency signal output by an acousto-optic drive module, generates an acousto-optic frequency shift effect on the pump laser received from the phase modulation module, outputs the first-order diffracted light of the pump laser to a band-pass filter module, and the first-order diffracted light has a frequency shift relative to the input pump laser;

[0012] An acousto-optic drive module, which receives a second feedback control signal from a second feedback control module, generates a radio frequency signal for driving the acousto-optic modulation module, and outputs it to the acousto-optic modulation module;

[0013] A band-pass filter module, which receives the pump laser from the acousto-optic modulation module, filters out the noise of the pump laser and then outputs it to a micro-ring resonator;

[0014] A micro-ring resonator, which receives the pump laser with noise filtered out from the band-pass filter module, the pump laser undergoes a non-linear effect, generates an optically frequency comb with equally spaced discrete frequencies in the frequency domain, and outputs it to a beam splitting module;

[0015] The beam splitting module splits the optical frequency comb received from the micro-ring resonator in terms of power into four beams, with three of them respectively output to the soliton detection module, the repetition frequency detection module, and the beat frequency module, and the other one output outward.

[0016] The soliton detection module monitors the output power change of the optical frequency comb output by the beam splitting module, observes the soliton step when scanning the pump wavelength, and outputs the voltage signal corresponding to the soliton step to the control module.

[0017] The control module determines whether solitons are generated according to the voltage signal received from the soliton detection module, and outputs the judgment result as a control signal to the pump module.

[0018] The repetition frequency detection module monitors the repetition frequency signal of the optical frequency comb output by the beam splitting module, and outputs the radio frequency signal of the repetition frequency to the first feedback control module.

[0019] The first feedback control module filters, amplifies, and down-converts the radio frequency signal of the repetition frequency received from the repetition frequency detection module, compares the repetition frequency signal with noise with the rubidium clock reference signal to obtain an error signal, and obtains a feedback control signal according to the error signal and outputs it to the electro-optic drive module.

[0020] The acetylene frequency-stabilized laser outputs a frequency-stable continuous laser to the beat frequency module as the frequency reference of the micro-cavity optical comb.

[0021] The beat frequency module combines the continuous laser output by the acetylene frequency-stabilized laser with one of the optical frequency combs output by the beam splitting module, and controls the power and polarization state of the two laser beams, thereby generating a beat frequency and outputting it to the optical frequency beat frequency detection module.

[0022] The optical frequency beat frequency detection module converts the beat frequency signal received from the beat frequency module from an optical signal to an electrical signal and outputs it to the second feedback control module.

[0023] The second feedback control module filters, amplifies, and down-converts the beat frequency electrical signal received from the optical frequency beat frequency detection module, compares the beat frequency signal with noise with the rubidium clock reference signal to obtain an error signal, obtains a feedback control signal according to the error signal, and outputs it to the acousto-optic drive module.

[0024] In the above-mentioned cavity optical comb repetition frequency and optical frequency locking device, the pump module is a continuous laser with a central wavelength of 1520 - 1580 nm and an output power of 1 - 100 mW.

[0025] In the above-mentioned cavity optical comb repetition frequency and optical frequency locking device, the power amplification module includes a fiber continuous laser power amplification device with an amplification bandwidth of 1545 - 1565 nm and an output power of 500 mW - 3 W.

[0026] In the above-mentioned cavity optical frequency comb repetition frequency and optical frequency locking device, the phase modulation module includes an electro-optic phase modulator with a bandwidth of 1 - 40 GHz; the electro-optic driving module includes a broadband high-power signal source with an external modulation port, and the bandwidth of the radio frequency signal generated to drive the phase modulation module covers 1 - 40 GHz, and the amplitude is greater than 12 dBm.

[0027] In the above-mentioned cavity optical frequency comb repetition frequency and optical frequency locking device, the acousto-optic modulation module includes an acousto-optic modulator. The light passing wavelength of the acousto-optic modulator is 1520 - 1580 nm, the diffraction efficiency is about 50% - 95%, and the insertion loss is 1 - 6 dB; the acousto-optic driving module includes a high-power voltage-controlled oscillator with an external modulation port. The frequency of the radio frequency signal generated to drive the acousto-optic modulator is equal to the frequency shift amount of the first-order diffracted light of the pump laser relative to the input light, the output frequency is 60 MHz - 200 MHz, and the output power is 31 - 35 dBm.

[0028] In the above-mentioned cavity optical frequency comb repetition frequency and optical frequency locking device, the band-pass filtering module includes a spectral band-pass filter with a center wavelength of 1520 - 1580 nm and a bandwidth of less than 1 nm; the microring resonator includes a silicon nitride microring resonator with a quality factor higher than 1E6 and a repetition frequency < 50 GHz.

[0029] In the above-mentioned cavity optical frequency comb repetition frequency and optical frequency locking device, the beam splitting module performs power splitting on the optical frequency comb received from the microring resonator into four beams. Except for the one beam output outward, the other three beams are respectively 5% - 10% of the optical frequency comb.

[0030] In the above-mentioned cavity optical frequency comb repetition frequency and optical frequency locking device, the soliton detection module includes a low-bandwidth photodetector with a bandwidth of 50 - 200 MHz, and the repetition frequency detection module includes a high-bandwidth photodetector with a bandwidth of 10 - 50 GHz; the first feedback control module includes a filter, an amplifier, a mixer, a phase detector, a signal source, and a PID module. The radio frequency signal of the repetition frequency received from the repetition frequency detection module is filtered and amplified through the filter and the amplifier, down-converted by the mixer, and then the phase detector is used to compare the repetition frequency signal carrying noise with the rubidium clock reference signal to obtain an error signal, and the error signal passes through the PID circuit to obtain the first feedback control signal.

[0031] In the above-mentioned cavity optical frequency comb repetition frequency and optical frequency locking device, the acetylene frequency-stabilized laser includes a laser and its acetylene frequency-stabilized module, and outputs continuous laser with an output frequency stability better than 2E-13@1s and a wavelength of 1542.38434720 nm ± 2.5 kHz; the beat frequency module includes an optical fiber combiner and a polarization controller; the optical frequency beat frequency detection module includes a photodetector with a bandwidth of 10 - 50 GHz.

[0032] In the above-mentioned cavity optical frequency comb repetition frequency and optical frequency locking device, the second feedback control module includes a filter, an amplifier, a mixer, a phase detector, a tunable signal source, and a PID module. The beat frequency electrical signal received from the optical frequency beat detection module is filtered and amplified by the filter and the amplifier, down-converted by the mixer, and the error signal is obtained by comparing the beat frequency signal carrying noise with the rubidium clock reference signal by the phase detector. The error signal passes through the PID circuit to obtain the second feedback control signal.

[0033] An integrated microcavity optical frequency comb repetition frequency and optical frequency locking method includes:

[0034] The pump module provides a continuous pump laser output to the power amplification module;

[0035] The power amplification module amplifies the pump laser received from the pump module and outputs it to the phase modulation module;

[0036] The electro-optic drive module receives the first feedback control signal from the first feedback control module, generates a radio frequency signal for driving the phase modulation module, and outputs it to the phase modulation module;

[0037] The phase modulation module, under the drive of the radio frequency signal output by the electro-optic drive module, performs phase modulation on the pump laser received from the power amplification module, generates modulation sidebands on both sides of the pump laser wavelength, and outputs it to the acousto-optic modulation module;

[0038] The acousto-optic drive module receives the second feedback control signal from the second feedback control module, generates a radio frequency signal for driving the acousto-optic modulation module, and outputs it to the acousto-optic modulation module;

[0039] The acousto-optic modulation module, under the drive of the radio frequency signal output by the acousto-optic drive module, produces an acousto-optic frequency shift effect on the pump laser received from the phase modulation module, outputs the first-order diffracted light of the pump laser to the band-pass filter module, and the first-order diffracted light has a frequency shift relative to the input pump laser;

[0040] The band-pass filter module receives the pump laser from the acousto-optic modulation module, filters out the noise of the pump laser and then outputs it to the micro-ring resonator;

[0041] The micro-ring resonator receives the pump laser with noise filtered out from the band-pass filter module, the pump laser undergoes a nonlinear effect, generates an equally spaced discrete optical frequency comb in the frequency domain, and outputs it to the beam splitting module;

[0042] The beam splitting module performs power splitting on the optical frequency comb received from the micro-ring resonator, divides it into four beams, three of which are respectively output to the soliton detection module, the repetition frequency detection module, and the beat frequency module, and the other beam is output outward;

[0043] The soliton detection module monitors the output power change of the optical frequency comb output by the beam splitting module, observes the soliton steps when scanning the pump wavelength, and outputs the voltage signal corresponding to the soliton steps to the control module;

[0044] The control module determines whether a soliton is generated according to the voltage signal received from the soliton detection module, and outputs the judgment result as a control signal to the pump module;

[0045] The pump module receives the control signal sent by the control module. If a soliton is generated, it fixes the pump laser wavelength; otherwise, it continues to scan until a soliton is generated;

[0046] The repetition rate detection module monitors the repetition rate signal of the optical frequency comb output by the beam splitting module, and outputs the radio frequency signal of the repetition rate to the first feedback control module;

[0047] The first feedback control module filters, amplifies, and down-converts the radio frequency signal of the repetition rate received from the repetition rate detection module, compares the repetition rate signal with noise with the rubidium clock reference signal to obtain an error signal, and obtains a feedback control signal according to the error signal and outputs it to the electro-optic drive module;

[0048] The acetylene frequency-stabilized laser outputs a continuous laser with stable frequency to the beat frequency module as the frequency reference of the microcavity optical frequency comb;

[0049] The beat frequency module combines the continuous laser output by the acetylene frequency-stabilized laser with a beam of optical frequency comb output by the beam splitting module, and controls the power and polarization states of the two laser beams, thereby generating a beat frequency and outputting it to the optical frequency beat frequency detection module;

[0050] The optical frequency beat frequency detection module converts the beat frequency signal received from the beat frequency module from an optical signal to an electrical signal and outputs it to the second feedback control module;

[0051] The second feedback control module filters, amplifies, and down-converts the beat frequency electrical signal received from the optical frequency beat frequency detection module, compares the beat frequency signal with noise with the rubidium clock reference signal to obtain an error signal, and obtains a feedback control signal according to the error signal and outputs it to the acousto-optic drive module.

[0052] The present invention has at least the following beneficial effects compared with the prior art:

[0053] (1) In the locking device provided by the embodiment of the present invention, the pump source emits pump laser, which is amplified in power by an optical fiber amplifier. The amplified laser generates modulation sidebands through an electro-optic phase modulator, and then is frequency-shifted through an acousto-optic modulator and injected into an integrated microcavity to excite nonlinear effects such as four-wave mixing, thereby outputting an optical comb spectrum. A low-bandwidth photodetector is used to detect soliton steps to form a soliton-state optical comb output. A high-bandwidth photodetector is used to detect the repetition frequency signal of the output spectrum of the microcavity optical comb. This signal passes through a feedback control module composed of filtering, mixing, and a PID locking circuit to obtain a control signal, which is fed back to the electro-optic drive module of the phase modulation module to lock the repetition frequency. A high-bandwidth photodetector is used to detect the beat frequency signal between the microcavity optical comb and an acetylene-stabilized laser with high frequency stability. This signal passes through a feedback control module composed of filtering, mixing, PID, etc. to obtain a control signal and is fed back to the acousto-optic drive module of the acousto-optic modulation module to lock the optical frequency of the microcavity optical comb. The present invention has the characteristics of wide servo bandwidth and simple and compact structure, and can provide a powerful tool for the field of precision measurement.

[0054] (2) The locking device provided by the embodiment of the present invention uses an acetylene-stabilized laser with high frequency stability and accuracy as a reference to lock the repetition frequency, so that the output frequency of the integrated microcavity optical comb is fully locked. The frequency of any comb tooth laser can be expressed as f m = mf rep + f CW + f beat , where f CW = 194369489384 kHz (1542.38434720 nm), and its frequency stability can reach 2E-13@1s. f rep and f beat can both be traced back to a rubidium clock, and the frequency stability can also reach the order of E-13;

[0055] (3) The locking device provided by the embodiment of the present invention has the characteristics of simple structure and low cost compared with a super-stable cavity and an optical fiber optical comb as a reference;

[0056] (4) The locking device provided by the embodiment of the present invention preferably uses an electro-optic phase modulator and an acousto-optic phase modulator to act on the pump power and frequency respectively to achieve full locking of the frequency of the microcavity optical comb. This mechanism has the characteristics of high servo bandwidth, tight locking, low noise, and high reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 is a schematic diagram of the composition of the integrated microcavity optical comb repetition frequency and optical frequency locking device proposed by the embodiment of the present invention;

[0058] Figure 2 is a schematic diagram of the output spectrum of the microcavity optical comb in the embodiment of the present invention;

[0059] Figure 3 Schematic diagram of the locking frequency change and Allan variance of the repetition frequency after locking in the embodiment of the present invention;

[0060] Figure 4 Schematic diagram of the frequency change and Allan variance of the locked optical comb teeth in the embodiment of the present invention. Detailed implementation manners

[0061] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:

[0062] As Figure 1 shown, the embodiment of the present invention provides an integrated microcavity optical comb repetition frequency and optical frequency locking device, including a pump module 1, a power amplification module 2, a phase modulation module 3, an electro-optic drive module 4, an acousto-optic modulation module 5, an acousto-optic drive module 6, a band-pass filtering module 7, a microring resonator 8, a beam splitting module 9, a soliton detection module 10, a control module 11, a repetition frequency detection module 12, a first feedback control module 13, an acetylene frequency-stabilized laser 14, a beat frequency module 15, an optical frequency beat frequency detection module 16 and a second feedback control module 17.

[0063] The pump module 1 provides a continuous pump laser output to the power amplification module; receives the control signal sent by the control module, and if solitons are generated, fixes the pump laser wavelength, otherwise continues to scan until solitons are generated.

[0064] In an optional embodiment, the pump module 1 is a fiber laser with a central wavelength of 1550 nm, its output power is about 40 mW, and it has current tuning ability. It is used to provide continuous laser as the pump seed laser of the microring resonator.

[0065] The power amplification module 2 amplifies the pump laser received from the pump module and then outputs it to the phase modulation module.

[0066] In an optional embodiment, the power amplification module 2 includes a fiber continuous laser power amplification device, its amplification bandwidth is 1545 - 1565 nm, and the output power is 2 W, outputting the pump laser of the microring resonator.

[0067] The phase modulation module 3, under the drive of the radio frequency signal output by the electro-optic drive module 4, generates phase modulation on the pump laser received from the power amplification module, generates modulation sidebands on both sides of the pump laser wavelength, and outputs them to the acousto-optic modulation module 5.

[0068] In an optional embodiment, the phase modulation module 3 includes an electro-optic phase modulator, its bandwidth reaches 40 GHz, and it is used to generate phase modulation on the pump laser and generate modulation sidebands on both sides of the pump laser wavelength.

[0069] The electro-optic drive module 4 receives a first feedback control signal from the first feedback control module, generates a radio frequency signal for driving the phase modulation module, and outputs it to the phase modulation module.

[0070] In an alternative embodiment, the electro-optic drive module 4 includes a broadband high-power signal source with an external modulation port for generating a radio frequency signal for driving the electro-optic phase modulator. The bandwidth of the radio frequency signal covers 1 - 40 GHz, and the amplitude is greater than 12 dBm.

[0071] The acousto-optic modulation module 5, driven by the radio frequency signal output by the acousto-optic drive module 6, generates an acousto-optic frequency shift effect on the pump laser received from the phase modulation module 3, and outputs the first-order diffracted light of the pump laser to the band-pass filtering module 7. The first-order diffracted light undergoes a frequency shift relative to the input pump laser.

[0072] In an alternative embodiment, the acousto-optic modulation module 5 includes an acousto-optic modulator for generating an acousto-optic frequency shift effect on the pump laser passing through it, and outputting the first-order diffracted light of the pump laser. The first-order diffracted light undergoes a frequency shift relative to the input pump laser. The power of the first-order diffracted light is related to the diffraction efficiency. The light passing wavelength of the acousto-optic modulator is 1.5 microns, the diffraction efficiency is approximately 85%, and the insertion loss is 3 dB.

[0073] The acousto-optic drive module 6 receives a second feedback control signal from the second feedback control module 17, generates a radio frequency signal for driving the acousto-optic modulation module 5, and outputs it to the acousto-optic modulation module 5.

[0074] In an alternative embodiment, the acousto-optic drive module 6 includes a high-power voltage-controlled oscillator with an external modulation port for generating a radio frequency signal for driving the acousto-optic modulator. The frequency of this signal is equal to the frequency shift amount of the first-order diffracted light of the pump laser relative to the input light, and the power of this signal determines the diffraction efficiency of the acousto-optic modulator. The output frequency of the acousto-optic drive module 6 is 100 MHz, and the output power is 33 dBm.

[0075] The band-pass filtering module 7 receives the pump laser from the acousto-optic modulation module 5, filters out the noise of the pump laser, and then outputs it to the micro-ring resonator 8.

[0076] In an alternative embodiment, the band-pass filtering module 7 includes a spectral band-pass filter for filtering out the ASE noise of the pump laser, with a center wavelength of 1550 nm and a bandwidth of 1 nm.

[0077] The micro-ring resonator 8 receives the pump laser with noise filtered out from the band-pass filtering module 7. This pump laser undergoes a nonlinear effect, generates equally spaced discrete optical frequency combs in the frequency domain, and outputs them to the beam splitting module 9.

[0078] In an alternative embodiment, the microring resonator 8 includes a silicon nitride microring resonator with a quality factor higher than 1E6. The pump laser generates nonlinear effects such as four-wave mixing in the microring resonator, producing equally spaced discrete optical frequency combs in the frequency domain, which appear as optical solitons in the time domain with a repetition frequency of 20 GHz.

[0079] The beam splitting module 9 splits the optical frequency comb received from the microring resonator 8 in terms of power into four beams, three of which are respectively output to the soliton detection module 10, the repetition frequency detection module 12, and the beat frequency module 15, and the other beam is output outward.

[0080] In an alternative embodiment, the beam splitting module 9 includes an optical fiber beam splitter for splitting the power of the soliton optical comb output from the microring resonator. Ten percent of the optical frequency comb is used to detect the output power, ten percent is used to detect the repetition frequency, ten percent is used to detect the optical frequency, and the remaining power is output as the output of the microcavity.

[0081] The soliton detection module 10 monitors the change in the output power of the optical frequency comb output by the beam splitting module 9, observes the soliton step when scanning the pump wavelength, and outputs the voltage signal corresponding to the soliton step to the control module 11.

[0082] In an alternative embodiment, the soliton detection module 10 includes a low-bandwidth (150 MHz) photodetector for monitoring the change in the output power of the microcavity, observing the soliton step when scanning the pump wavelength, and outputting the voltage signal corresponding to the soliton step to the control module 11.

[0083] The control module 11 determines whether solitons are generated based on the voltage signal received from the soliton detection module 10, and outputs the judgment result as a control signal to the pump module 1.

[0084] In an alternative embodiment, the control module 11 includes a signal source and a control circuit, determines whether solitons are generated based on the output voltage, and outputs the judgment result as a control signal to the pump module 1.

[0085] The repetition frequency detection module 12 monitors the repetition frequency signal of the optical frequency comb output by the beam splitting module 9, and outputs the radio frequency signal of the repetition frequency to the first feedback control module 13.

[0086] In an alternative embodiment, the repetition frequency detection module 12 includes a high-bandwidth (40 GHz) photodetector for monitoring the repetition frequency signal of the optical comb output from the microring resonator. A 20 GHz repetition frequency signal can be observed on the spectrum analyzer.

[0087] The first feedback control module 13 filters and amplifies the radio frequency signal of the repetition frequency received from the repetition frequency detection module 12. After down-converting the frequency, it compares the repetition frequency signal carrying noise with the rubidium clock reference signal to obtain an error signal, and obtains a feedback control signal according to the error signal, and outputs it to the electro-optic drive module 4.

[0088] In an optional embodiment, the first feedback control module 13 includes a filter, an amplifier, a mixer, a phase discriminator, a signal source, and a PID module. It filters and amplifies the 20 GHz repetition frequency signal detected by the photodetector, uses a mixer to down-convert the 20 GHz frequency to 100 MHz, and uses a phase discriminator to compare the 100 MHz repetition frequency signal carrying noise with the rubidium clock reference signal to obtain an error signal. The error signal passes through a PID circuit to obtain a feedback control signal, and this signal changes the modulation depth of the phase modulation module through the electro-optic drive module, thereby acting on the pump laser carrier power and sideband power.

[0089] The acetylene frequency-stabilized laser 14 outputs a continuous laser with stable frequency to the beat frequency module, serving as the frequency reference for the microcavity optical frequency comb.

[0090] In an optional embodiment, the acetylene frequency-stabilized laser 14 includes a 1542 nm laser and its acetylene frequency stabilization module, which is used to output a continuous laser with a frequency stability better than 2E-13@1s and a wavelength of 1542.38434720 nm, serving as the frequency reference for the microcavity optical frequency comb.

[0091] The beat frequency module 15 combines the continuous laser output by the acetylene frequency-stabilized laser 14 with an optical frequency comb output by the beam splitting module 9, and controls the power and polarization states of the two laser beams, thereby generating a beat frequency and outputting it to the optical frequency beat frequency detection module 16.

[0092] In an optional embodiment, the beat frequency module 15 includes an optical fiber combiner and a polarization controller, which are used to combine the output laser of the acetylene frequency-stabilized laser with the output laser of one path of the optical frequency comb of the beam splitter, and control the power and polarization states of the two laser beams through the polarization controller, thereby generating a beat frequency.

[0093] The optical frequency beat frequency detection module 16 converts the beat frequency signal received from the beat frequency module 15 from an optical signal to an electrical signal, and outputs it to the second feedback control module 17.

[0094] In an optional embodiment, the optical frequency beat frequency detection module 16 includes a broadband (20 GHz) photodetector, which is used to detect the beat frequency signal between the output optical frequency comb of the micro-ring resonator and the adjacent comb teeth of the acetylene frequency-stabilized laser and the acetylene frequency-stabilized laser, converts the optical signal to an electrical signal, and the beat frequency signal in the radio frequency domain can be observed on the spectrum analyzer.

[0095] The second feedback control module 17 filters and amplifies the beat frequency electrical signal received from the optical frequency beat detection module 16. After down-converting the frequency, it compares the beat frequency signal with noise with the rubidium clock reference signal to obtain an error signal, and obtains a feedback control signal according to the error signal, and outputs it to the acousto-optic drive module 6.

[0096] In an alternative embodiment, the second feedback control module 17 includes a filter, an amplifier, a mixer, a phase detector, a tunable signal source, and a PID module. It filters and amplifies the 6.5 GHz beat frequency signal detected by the photodetector, and uses a mixer to down-convert the 6.5 GHz frequency to 100 MHz. A phase detector is used to compare the 100 MHz beat frequency signal with noise with the rubidium clock reference signal to obtain an error signal. The error signal passes through a PID circuit to obtain a feedback control signal, and this signal changes the drive frequency of the acousto-optic modulator through the acousto-optic drive module, thereby acting on the central frequency of the pump laser. As Figure 2 shown is a schematic diagram of the output spectrum of the microcavity optical frequency comb in the embodiment of the present invention.

[0097] The present invention also provides an integrated method for locking the repetition frequency and optical frequency of a microcavity optical frequency comb, including the following steps:

[0098] 1) The pump module provides a continuous pump laser output to the power amplification module;

[0099] 2) The power amplification module amplifies the power of the pump laser received from the pump module and outputs it to the phase modulation module;

[0100] 3) The electro-optic drive module receives the first feedback control signal from the first feedback control module, generates a radio frequency signal for driving the phase modulation module, and outputs it to the phase modulation module;

[0101] 4) The phase modulation module, under the drive of the radio frequency signal output by the electro-optic drive module, generates a phase modulation on the pump laser received from the power amplification module, generates modulation sidebands on both sides of the pump laser wavelength, and outputs it to the acousto-optic modulation module;

[0102] 5) The acousto-optic drive module receives the second feedback control signal from the second feedback control module, generates a radio frequency signal for driving the acousto-optic modulation module, and outputs it to the acousto-optic modulation module;

[0103] 6) The acousto-optic modulation module, under the drive of the radio frequency signal output by the acousto-optic drive module, generates an acousto-optic frequency shift effect on the pump laser received from the phase modulation module, and outputs the first-order diffracted light of the pump laser to the band-pass filter module. The first-order diffracted light has a frequency shift relative to the input pump laser;

[0104] 7) The band-pass filter module receives the pump laser from the acousto-optic modulation module, filters out the noise of the pump laser and outputs it to the micro-ring resonator;

[0105] 8) The microring resonator receives the noise-filtered pump laser from the band-pass filtering module. The pump laser undergoes a nonlinear effect to generate equally spaced discrete optical frequency combs in the frequency domain and outputs them to the beam splitting module.

[0106] 9) The beam splitting module splits the optical frequency combs received from the microring resonator into four beams in terms of power. Three of the beams are respectively output to the soliton detection module, the repetition rate detection module, and the beat frequency module, and the other beam is output outward.

[0107] 10) The soliton detection module monitors the change in the output power of the optical frequency combs output by the beam splitting module, observes the soliton steps when scanning the pump wavelength, and outputs the voltage signal corresponding to the soliton steps to the control module.

[0108] 11) The control module determines whether solitons are generated based on the voltage signal received from the soliton detection module and outputs the determination result as a control signal to the pump module.

[0109] 12) The pump module receives the control signal sent by the control module. If solitons are generated, it fixes the pump laser wavelength; otherwise, it continues to scan until solitons are generated.

[0110] 13) The repetition rate detection module monitors the repetition rate signal of the optical frequency combs output by the beam splitting module and outputs the radio frequency signal of the repetition rate to the first feedback control module.

[0111] 14) The first feedback control module filters, amplifies, and down-converts the radio frequency signal of the repetition rate received from the repetition rate detection module. Then it compares the repetition rate signal with noise with the rubidium clock reference signal to obtain an error signal, and obtains a feedback control signal based on the error signal and outputs it to the electro-optic drive module.

[0112] 15) The acetylene frequency-stabilized laser outputs a frequency-stable continuous laser to the beat frequency module as the frequency reference of the microcavity optical frequency comb.

[0113] 16) The beat frequency module combines the continuous laser output by the acetylene frequency-stabilized laser with one of the optical frequency combs output by the beam splitting module, and controls the power and polarization states of the two laser beams, thereby generating a beat frequency and outputting it to the optical frequency beat frequency detection module.

[0114] 17) The optical frequency beat frequency detection module converts the beat frequency signal received from the beat frequency module from an optical signal to an electrical signal and outputs it to the second feedback control module.

[0115] 18) The second feedback control module filters, amplifies, and down-converts the beat frequency electrical signal received from the optical frequency beat frequency detection module. Then it compares the beat frequency signal with noise with the rubidium clock reference signal to obtain an error signal, and obtains a feedback control signal based on the error signal and outputs it to the acousto-optic drive module.

[0116] The present invention uses a frequency counter to count the changes in the repetition frequency and the optical beat frequency after locking and calculates the Allan variance. As Figure 3 shown, the repetition frequency after locking, as Figure 3 and Figure 4 shown, it can be seen that the change in the repetition frequency after locking over time is within ±40 mHz within 1000 seconds, and the Allan variance is the second stability of 6.7×10 -13 ; as Figure 4 shown, the change in the optical frequency after locking over time is within ±5 mHz within 1000 seconds, and the Allan variance is the second stability of 1.4×10 -17 The carrier frequency is taken as 194.55 THz (1542 nm). The above test results are sufficient to prove the stability and reliability of the frequency full-locking method and device of the integrated microcavity optical comb according to the present invention. A stable and reliable integrated microcavity optical frequency comb system has important applications in precision measurement.

[0117] The device and method provided by the embodiments of the present invention have the following advantages: ①Preferably, the embodiments of the present invention use an acetylene frequency-stabilized laser with high frequency stability and accuracy as a reference to lock the repetition frequency, so that the output frequency of the integrated microcavity optical comb is fully locked. Any comb tooth laser frequency can be expressed as f m = mf rep + f CW + f beat , where f CW = 194369489384 kHz (1542.38434720 nm), and its frequency stability can reach 2E-13@1s. f rep and f beat can both be traced back to the rubidium clock, and the frequency stability can also reach the order of E-13. ②Compared with the ultra-stable cavity and fiber optical comb as references, the present invention has the characteristics of simple structure and low cost. ③The present invention uses an electro-optic phase modulator and an acousto-optic phase modulator to act on the pump power and frequency respectively to achieve the full locking of the frequency of the microcavity optical comb. This mechanism has the characteristics of high servo bandwidth, tight locking, low noise, and high reliability.

[0118] The above is only the best specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered by the protection scope of the present invention.

[0119] The content not detailedly described in the specification of the present invention belongs to the well-known technology of those skilled in the art.

Claims

1. An integrated microcavity optical frequency comb repetition frequency and optical frequency locking device, characterized in that Including: A pump module that provides a continuous pump laser output to a power amplification module; receives a control signal sent by a control module, fixes the pump laser wavelength if solitons are generated, otherwise continues to scan until solitons are generated; A power amplification module that amplifies the pump laser received from the pump module and outputs it to a phase modulation module; A phase modulation module that, driven by a radio frequency signal output by an electro-optic drive module, performs phase modulation on the pump laser received from the power amplification module, generates modulation sidebands on both sides of the pump laser wavelength, and outputs it to an acousto-optic modulation module; An electro-optic drive module that receives a first feedback control signal from a first feedback control module, generates a radio frequency signal for driving the phase modulation module, and outputs it to the phase modulation module; An acousto-optic modulation module that, driven by a radio frequency signal output by an acousto-optic drive module, produces an acousto-optic frequency shift effect on the pump laser received from the phase modulation module, outputs the first-order diffracted light of the pump laser to a band-pass filter module, and the first-order diffracted light undergoes a frequency shift relative to the input pump laser; An acousto-optic drive module that receives a second feedback control signal from a second feedback control module, generates a radio frequency signal for driving the acousto-optic modulation module, and outputs it to the acousto-optic modulation module; A band-pass filter module that receives the pump laser from the acousto-optic modulation module, filters out the noise of the pump laser, and outputs it to a micro-ring resonator; A micro-ring resonator that receives the pump laser with noise filtered out from the band-pass filter module, the pump laser undergoes a non-linear effect, generates equally spaced discrete optical frequency combs in the frequency domain, and outputs them to a beam splitting module; A beam splitting module that power-splits the optical frequency combs received from the micro-ring resonator into four beams, three of which are respectively output to a soliton detection module, a repetition frequency detection module, and a beat frequency module, and the other beam is output outward; A soliton detection module that monitors the output power change of the optical frequency combs output by the beam splitting module, observes soliton steps when scanning the pump wavelength, and outputs the voltage signal corresponding to the soliton steps to the control module; A control module that determines whether solitons are generated based on the voltage signal received from the soliton detection module, and outputs the determination result as a control signal to the pump module; A repetition frequency detection module that monitors the repetition frequency signal of the optical frequency combs output by the beam splitting module, and outputs the radio frequency signal of the repetition frequency to the first feedback control module; A first feedback control module that filters, amplifies, and down-converts the radio frequency signal of the repetition frequency received from the repetition frequency detection module, compares the repetition frequency signal with noise with a rubidium clock reference signal to obtain an error signal, and obtains a feedback control signal based on the error signal and outputs it to the electro-optic drive module; An acetylene frequency-stabilized laser that outputs a frequency-stabilized continuous laser to the beat frequency module as the frequency reference of the micro-cavity optical comb; A beat frequency module that combines the continuous laser output by the acetylene frequency-stabilized laser with a beam of optical frequency combs output by the beam splitting module, and controls the power and polarization states of the two beams of laser, thereby generating a beat frequency and outputting it to an optical frequency beat frequency detection module; An optical frequency beat frequency detection module that converts the beat frequency signal received from the beat frequency module from an optical signal to an electrical signal and outputs it to the second feedback control module; The second feedback control module filters and amplifies the beat frequency electrical signal received from the optical frequency beat detection module, down-converts the frequency, compares the beat frequency signal with noise with the rubidium clock reference signal to obtain an error signal, and obtains a feedback control signal according to the error signal, and outputs it to the acousto-optic drive module.

2. The integrated microcavity optical frequency comb repetition frequency and optical frequency locking device according to claim 1, wherein The pump module is a continuous laser with a central wavelength of 1520 - 1580 nm and an output power of 1 - 100 mW.

3. The integrated microcavity optical frequency comb repetition frequency and optical frequency locking device according to claim 1, characterized in that The power amplification module includes a fiber continuous laser power amplification device with an amplification bandwidth of 1545 - 1565 nm and an output power of 500 mW - 3 W.

4. The integrated microcavity optical frequency comb repetition frequency and optical frequency locking device according to claim 1, characterized in that, The phase modulation module includes an electro-optic phase modulator with a bandwidth of 1 - 40 GHz; The electro-optic drive module includes a broadband high-power signal source with an external modulation port, generating a radio frequency signal for driving the phase modulation module with a bandwidth covering 1 - 40 GHz and an amplitude greater than 12 dBm.

5. The integrated microcavity optical frequency comb repetition frequency and optical frequency locking device according to claim 1, wherein The acousto-optic modulation module includes an acousto-optic modulator with a light passing wavelength of 1520 - 1580 nm, a diffraction efficiency of about 50% - 95%, and an insertion loss of 1 - 6 dB; The acousto-optic drive module includes a high-power voltage-controlled oscillator with an external modulation port, generating a radio frequency signal for driving the acousto-optic modulator with a frequency equal to the frequency shift of the first-order diffracted light of the pump laser relative to the input light, an output frequency of 60 MHz - 200 MHz, and an output power of 31 - 35 dBm.

6. The integrated microcavity optical frequency comb repetition frequency and optical frequency locking device according to claim 1, characterized in that, The band-pass filtering module includes a spectral band-pass filter with a central wavelength of 1520 - 1580 nm and a bandwidth of less than 1 nm; The micro-ring resonator includes a silicon nitride micro-ring resonator with a quality factor higher than 1E6 and a repetition frequency < 50 GHz.

7. The integrated microcavity optical frequency comb repetition frequency and optical frequency locking device according to claim 1, characterized in that, The beam splitting module power-splits the optical frequency comb received from the micro-ring resonator into four beams. Except for the one output outward, the other three beams are respectively 5% - 10% of the optical frequency comb.

8. The integrated microcavity optical frequency comb repetition frequency and optical frequency locking device according to claim 1, wherein, The soliton detection module includes a low-bandwidth photodetector with a bandwidth of 50 - 200 MHz, and the repetition frequency detection module includes a high-bandwidth photodetector with a bandwidth of 10 - 50 GHz; The first feedback control module includes a filter, an amplifier, a mixer, a phase detector, a signal source, and a PID module. It filters and amplifies the radio frequency signal of the repetition frequency received from the repetition frequency detection module through the filter and the amplifier, down-converts the frequency using the mixer, and then uses the phase detector to compare the repetition frequency signal with noise with the rubidium clock reference signal to obtain an error signal. The error signal passes through the PID circuit to obtain the first feedback control signal.

9. The integrated microcavity optical frequency comb repetition frequency and optical frequency locking device according to claim 1, characterized in that The acetylene frequency-stabilized laser includes a laser and its acetylene frequency-stabilized module, outputting continuous laser with an output frequency stability better than 2E-13@1s and a wavelength of 1542.38434720 nm ± 2.5 kHz; The beat frequency module includes an optical fiber combiner and a polarization controller; The optical frequency beat detection module includes a photodetector with a broadband of 10 - 50 GHz.

10. The integrated microcavity optical frequency comb repetition frequency and optical frequency locking device according to claim 1, wherein The second feedback control module includes a filter, an amplifier, a mixer, a phase detector, a tunable signal source, and a PID module. The beat frequency electrical signal received from the optical frequency beat detection module is filtered and amplified by the filter and the amplifier, down-converted by the mixer, and the error signal is obtained by comparing the beat frequency signal with noise with the rubidium clock reference signal by the phase detector. The error signal passes through the PID circuit to obtain the second feedback control signal.

11. An integrated microcavity optical frequency comb repetition frequency and optical frequency locking method, characterized in that, It includes: The pump module provides continuous pump laser output to the power amplification module; The power amplification module amplifies the pump laser received from the pump module and outputs it to the phase modulation module; The electro-optic drive module receives the first feedback control signal from the first feedback control module, generates a radio frequency signal for driving the phase modulation module, and outputs it to the phase modulation module; The phase modulation module, driven by the radio frequency signal output by the electro-optic drive module, performs phase modulation on the pump laser received from the power amplification module, generates modulation sidebands on both sides of the pump laser wavelength, and outputs it to the acousto-optic modulation module; The acousto-optic drive module receives the second feedback control signal from the second feedback control module, generates a radio frequency signal for driving the acousto-optic modulation module, and outputs it to the acousto-optic modulation module; The acousto-optic modulation module, driven by the radio frequency signal output by the acousto-optic drive module, generates an acousto-optic frequency shift effect on the pump laser received from the phase modulation module, and outputs the first-order diffracted light of the pump laser to the band-pass filter module. The first-order diffracted light has a frequency shift relative to the input pump laser; The band-pass filter module receives the pump laser from the acousto-optic modulation module, filters out the noise of the pump laser, and outputs it to the micro-ring resonator; The micro-ring resonator receives the pump laser with noise filtered out from the band-pass filter module. The pump laser undergoes a nonlinear effect, generates equally spaced discrete optical frequency combs in the frequency domain, and outputs them to the beam splitting module; The beam splitting module power-splits the optical frequency comb received from the micro-ring resonator into four beams. Three of them are respectively output to the soliton detection module, the repetition frequency detection module, and the beat frequency module, and the other beam is output outward; The soliton detection module monitors the output power change of the optical frequency comb output by the beam splitting module, observes the soliton step when scanning the pump wavelength, and outputs the voltage signal corresponding to the soliton step to the control module; The control module determines whether solitons are generated according to the voltage signal received from the soliton detection module, and outputs the judgment result as a control signal to the pump module; The pump module receives the control signal sent by the control module. If solitons are generated, the pump laser wavelength is fixed; otherwise, it continues to scan until solitons are generated; The repetition frequency detection module monitors the repetition frequency signal of the optical frequency comb output by the beam splitting module, and outputs the radio frequency signal of the repetition frequency to the first feedback control module; The first feedback control module filters and amplifies the radio frequency signal of the repetition frequency received from the repetition frequency detection module, down-converts it, compares the repetition frequency signal with noise with the rubidium clock reference signal to obtain an error signal, and obtains a feedback control signal according to the error signal and outputs it to the electro-optic drive module; The acetylene frequency-stabilized laser outputs a frequency-stable continuous laser to the beat frequency module as the frequency reference of the micro-cavity optical frequency comb; The beat frequency module combines the continuous laser output by the acetylene frequency-stabilized laser with an optical frequency comb output by the beam splitting module, and controls the power and polarization states of the two laser beams, thereby generating a beat frequency and outputting it to the optical frequency beat frequency detection module; The optical frequency beat frequency detection module converts the beat frequency signal received from the beat frequency module from an optical signal into an electrical signal and outputs it to the second feedback control module; The second feedback control module filters and amplifies the beat frequency electrical signal received from the optical frequency beat frequency detection module, down-converts it, compares the beat frequency signal carrying noise with the rubidium clock reference signal to obtain an error signal, obtains a feedback control signal based on the error signal, and outputs it to the acousto-optic drive module.

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