Generation device of microcavity frequency comb

Abstract

The invention provides a micro-cavity frequency comb generation device which can be applied to the technical field of optical frequency combs. The device comprises an optical generation module and an electro-optical modulation unit which are used for modulating output laser of a laser source unit and inputting the modulated laser to an optical amplifier unit; the optical amplifier unit is used for performing power amplification processing on the modulated laser to obtain amplified laser; the micro-cavity unit is used for converting the amplified laser into micro-comb signals, the micro-comb signals comprise a mixed micro-comb signal and a feedback micro-comb signal, the first port is used for outputting the mixed micro-comb signal, and the second port is used for outputting the feedback micro-comb signal; the detector unit is used for processing the feedback micro comb signal to obtain a repetition frequency microwave signal; the delay optical fiber module is used for providing target delay, so that the feedback micro comb signal is transmitted to the detector unit in a delayed manner; and the photoelectric oscillation feedback module is used for carrying out feedback gain adjustment on the repetition frequency microwave signal so as to obtain a driving signal for driving the electro-optical modulation unit.

Description

Technical Field

[0001] The present disclosure relates to the technical field of optical frequency combs, and more specifically, to a device for generating a microcavity frequency comb. Background Art

[0002] In recent years, the generation of microcavity laser frequency combs based on integrated microcavities has not only become a research hotspot but has also achieved certain development in practical application, effectively reducing the size, complexity and power consumption of laser frequency comb systems. It has broad application prospects in technical fields such as precision measurement, optical clocks, massively parallel coherent optical communications, fiber-optic wireless communications, microwave photonics, optical computing, astronomical spectroscopy and lidar.

[0003] In the process of realizing the concept of the present disclosure, the inventors discovered that the microcavity frequency comb (hereinafter referred to as "microcomb") generating device in the related art requires an external driving source, which leads to technical problems such as increased power consumption and larger volume, and it is difficult to obtain a target microcavity frequency comb with smaller phase noise. Summary of the invention

[0004] In view of this, the present disclosure provides a device for generating a microcavity frequency comb.

[0005] One aspect of the present disclosure provides a device for generating a microcavity frequency comb, comprising:

[0006] The optical generation module includes a laser source unit, an electro-optical modulation unit, an optical amplifier unit, a microcavity unit, and a detector unit; the electro-optical modulation unit is used to modulate the laser signal emitted by the laser source unit, and input the obtained modulated laser to the optical amplifier unit, wherein the frequency of the output laser of the laser source unit matches the resonance peak frequency of the microcavity unit; the optical amplifier unit is used to perform power amplification processing on the modulated laser to obtain an amplified laser, wherein the power of the amplified laser is greater than or equal to the threshold power required by the microcavity unit to generate a microcomb; the microcavity unit is used to convert the amplified laser into a microcomb signal, wherein the microcomb signal includes a mixed microcomb signal and a feedback A microcomb signal, a power proportion of the pump laser in the hybrid microcomb signal is greater than a power proportion of the pump laser in the feedback microcomb signal, a microcavity unit comprises a first port and a second port, the first port is used to output the hybrid microcomb signal, and the second port is used to output the feedback microcomb signal; a detector unit is used to process the feedback microcomb signal to obtain a repetition frequency microwave signal; a delay optical fiber module is connected between the second port and the detector unit, and is used to provide a target delay so that the feedback microcomb signal is delayed and transmitted to the detector unit; an optoelectronic oscillation feedback module is used to perform feedback gain adjustment on the repetition frequency microwave signal output by the detector unit to obtain a driving signal for driving the electro-optical modulation unit.

[0007] According to an embodiment of the present disclosure, the optoelectronic oscillation feedback module includes a radio frequency amplifier unit, an adjustable attenuator unit and a power divider unit; the feedback gain of the re-frequency microwave signal output by the detector unit is adjusted to obtain a driving signal for driving the electro-optical modulation unit, including: inputting the re-frequency microwave signal into the radio frequency amplifier unit for amplification to obtain an amplified re-frequency signal; inputting the amplified re-frequency signal into the adjustable attenuator unit to adjust the gain of the optoelectronic oscillation feedback module to obtain an attenuated re-frequency signal; inputting the attenuated re-frequency signal into the power divider unit to obtain a driving signal and a target microwave signal, respectively.

[0008] According to an embodiment of the present disclosure, an attenuated repetition frequency signal is input into a power divider unit to obtain a driving signal and a target microwave signal, respectively, including: allocating the attenuated repetition frequency signal according to a preset power of the power divider unit, wherein the preset power includes a first preset power and a second preset power; obtaining a driving signal from the attenuated repetition frequency signal according to the first preset power; and obtaining a target microwave signal from the attenuated repetition frequency signal according to the second preset power.

[0009] According to an embodiment of the present disclosure, the optoelectronic oscillation feedback module also includes a bias unit connected between the RF amplifier unit and the detector unit. The bias unit is used to provide a DC bias voltage for the detector unit and introduce the microwave signal of the detector unit into the RF amplifier unit for amplification.

[0010] According to an embodiment of the present disclosure, the bandwidth range of the bias unit includes the free spectral width of the microcavity unit.

[0011] According to an embodiment of the present disclosure, the time-delay optical fiber module includes a single-mode optical fiber of a predetermined length.

[0012] According to an embodiment of the present disclosure, the microcavity unit includes one of the following: a normal dispersion microcavity and an anomalous dispersion microcavity.

[0013] According to an embodiment of the present disclosure, the output end of the laser source unit includes a first laser isolator, and the output end of the optical amplifier unit includes a second laser isolator.

[0014] According to an embodiment of the present disclosure, the bandwidth of the detector unit is greater than the free spectrum width of the microcavity unit.

[0015] According to an embodiment of the present disclosure, the pump laser output by the laser source unit in the optical generation module is modulated by the electro-optical modulation unit, the modulated laser is power amplified by the optical amplifier unit, the amplified laser that meets the threshold power of the microcavity unit enters the microcavity unit to generate a micro-comb signal, the microcavity unit includes two ports, the first port outputs a mixed micro-comb signal, and the second port outputs a feedback micro-comb signal, the delay optical fiber module generates a delay corresponding to the feedback micro-comb signal, and the optoelectronic oscillation module is used to perform feedback gain adjustment on the repetition rate microwave signal output by the detector unit to obtain a driving signal whose signal strength meets the driving conditions, thereby driving the electro-optical modulation unit. Since the microcavity unit includes two ports, the feedback micro-comb signal output from the second port effectively reduces the power proportion of the pump laser, thereby avoiding the oversaturation of the detector unit caused by the excessively high power pump laser component. At the same time, the optical amplifier unit will introduce spontaneous radiation noise, and the microcavity unit can effectively filter out the spontaneous radiation noise, thereby outputting the feedback micro-comb signal through the second port, avoiding the use of additional filters. The delay fiber module can provide a target delay to reduce the phase noise of the repetition frequency microwave signal. The optoelectronic oscillation module can provide a driving signal for the electro-optical modulation unit, thereby realizing a self-excited and self-sustaining micro-comb generation device, avoiding the use of a high-cost and large-volume external microwave driving source, effectively reducing the power consumption and volume of the device, simplifying the device structure, and facilitating the integration and miniaturization of the device, so that the generated micro-comb can be suitable for more application scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The above and other objects, features and advantages of the present disclosure will become more apparent through the following description of the embodiments of the present disclosure with reference to the accompanying drawings, in which:

[0017] Figure 1 A schematic diagram of a conventional pump-modulated microcavity frequency comb generation device is shown schematically.

[0018] Figure 2 The structure block diagram of a device for generating a microcavity frequency comb according to an embodiment of the present disclosure is schematically shown.

[0019] Figure 3a The power diagram of laser emission under different driving currents of the laser source unit according to the embodiment of the present disclosure is schematically shown.

[0020] Figure 3b The schematic diagram shows the wavelength of the laser light emitted by the laser source unit under different driving currents according to the embodiment of the present disclosure.

[0021] Figure 4 The resonance peak fitting diagram of the microcavity unit according to the embodiment of the present disclosure is schematically shown.

[0022] Figure 5aThe spectrum diagram of the repetition frequency microwave signal of the delay-free optical fiber module according to the embodiment of the present disclosure is schematically shown.

[0023] Figure 5b The frequency spectrum of a repetitive frequency microwave signal when the predetermined length is 4.5 km according to an embodiment of the present disclosure is schematically shown.

[0024] Figure 6 A schematic diagram showing a comparison of phase noise of a repetitive frequency microwave signal in two cases with a delayed optical fiber module and without a delayed optical fiber module according to an embodiment of the present disclosure is schematically shown.

[0025] Figure 7 A schematic diagram of a device for generating a microcavity frequency comb according to an embodiment of the present disclosure is schematically shown.

[0026] Figure 8 The spectrum diagram of the hybrid microcomb signal generated by the normal dispersion microcavity according to the embodiment of the present disclosure is schematically shown. DETAILED DESCRIPTION

[0027] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the present disclosure. In the following detailed description, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of the embodiments of the present disclosure. However, it is apparent that one or more embodiments may also be implemented without these specific details. In addition, in the following description, descriptions of known structures and technologies are omitted to avoid unnecessary confusion of the concepts of the present disclosure.

[0028] The terms used herein are only for describing specific embodiments and are not intended to limit the present disclosure. The terms "comprise", "include", etc. used herein indicate the existence of the features, steps, operations and / or components, but do not exclude the existence or addition of one or more other features, steps, operations or components.

[0029] All terms (including technical and scientific terms) used herein have the meanings commonly understood by those skilled in the art unless otherwise defined. It should be noted that the terms used herein should be interpreted as having a meaning consistent with the context of this specification and should not be interpreted in an idealized or overly rigid manner.

[0030] When using expressions such as "at least one of A, B, and C, etc.", they should generally be interpreted according to the meaning of the expression commonly understood by those skilled in the art (for example, "a system having at least one of A, B, and C" should include but is not limited to a system having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, C, etc.).

[0031] In the embodiments of the present disclosure, the collection, updating, analysis, processing, use, transmission, provision, disclosure, storage, etc. of the data involved (for example, including but not limited to user personal information) are in compliance with the provisions of relevant laws and regulations, are used for legitimate purposes, and do not violate public order and good morals. In particular, necessary measures are taken for user personal information to prevent illegal access to user personal information data and maintain the security of user personal information, network security, and national security.

[0032] In the embodiments of the present disclosure, the user's authorization or consent is obtained before obtaining or collecting the user's personal information.

[0033] At present, the generation of microcombs based on microcavity self-injection locking is a common solution. Its advantage is that it does not require an additional low-noise microwave source for synchronization, so it can be miniaturized and integrated. Taking into account the different microcavity dispersions, the effects of generating microcombs are also different. One is to generate bright soliton pulses based on anomalous dispersion microcavity self-injection locking. The efficiency of converting the pump laser to the microcomb of this microcavity frequency comb is generally low. For a microcavity frequency comb with a free spectral width (FSR) close to 10GHz, its conversion efficiency is generally less than 1%, which leads to too low power of the microcomb teeth, affecting its application scenario promotion. Another way to generate microcombs is to generate dark pulses based on normal dispersion microcavity self-injection locking. Its advantage is that the conversion efficiency of the pump laser to the dark pulse microcomb is high, generally reaching more than 10%, but its microcomb spectral bandwidth is generally smaller than that of the soliton microcomb generated by the anomalous dispersion microcavity. In addition, although the microcavity frequency combs generated by the above two microcavity self-injection locking methods can be integrated at the chip level, the phase noise of the microcomb pulse repetition frequency (referred to as repetition frequency) signal is still relatively high. For some applications that require ultra-low phase noise in the repetition rate, such as coherent optical communications, lidar, quantum precision measurement, optical clocks, etc., the repetition rate phase noise of the frequency comb generated by microcavity self-injection locking is not good enough, which limits its application scenarios.

[0034] In addition to generating microcombs by self-injection locking, there is another way to generate microcombs by pump modulation. This method is to modulate the pump laser, and the modulation frequency is close to the free spectrum width (FSR) of the microcavity. The advantage of this method is that the laser modulator can be driven by an ultra-low noise microwave source, and the modulated laser can be synchronized in the microcavity, so that the phase noise of the generated microcomb repetition frequency can be purified. The disadvantage of this solution is that its device needs to add an expensive and high-volume microwave source as the driving source of the modulator. This is not conducive to the integration of the microcomb generation device, nor is it conducive to reducing the size and power consumption of the microcomb device. In addition, although the phase noise of the microcomb can be reduced without introducing a low-noise microwave source through the microcomb optical frequency division (OFD) method, this method requires the introduction of a complex frequency locking device and a laser power amplifier. At the same time, the laser phase noise of the pump source is also required to be very high, which is not conducive to the integration and miniaturization of the device.

[0035] In order to better reflect the components of the traditional micro-comb generating device, the following Figure 1 The conventional micro-comb generation device based on pump modulation is described.

[0036] Figure 1 A schematic diagram of a conventional pump-modulated microcavity frequency comb generation device is shown schematically.

[0037] like Figure 1 As shown, the device 100 includes a laser 110 , a microwave source 120 , a modulator 130 , an optical amplifier 140 , a filter 150 , a polarization controller 160 , an optical microcavity 170 , a detector 180 , a spectrometer 191 , and a spectrometer 192 .

[0038] The microwave source 120 brings higher power consumption and increases the cost, and the optical amplifier 140 and the filter 150 also make the size of the device too large.

[0039] In view of this, an embodiment of the present disclosure provides a device for generating a microcavity frequency comb, comprising: an optical generation module, including a laser source unit, an electro-optical modulation unit, an optical amplifier unit, a microcavity unit, and a detector unit; the electro-optical modulation unit is used to modulate the output laser of the laser source unit, and input the obtained modulated laser to the optical amplifier unit, wherein the frequency of the output laser of the laser source unit matches the resonance peak frequency of the microcavity unit; the optical amplifier unit is used to perform power amplification processing on the modulated laser to obtain an amplified laser, wherein the power of the amplified laser is greater than or equal to the threshold power required by the microcavity unit to generate a microcomb; the microcavity unit is used to convert the amplified laser into a microcomb signal, wherein the microcavity The comb signal includes a mixed micro-comb signal and a feedback micro-comb signal, the power proportion of the pump laser in the mixed micro-comb signal is greater than the power proportion of the pump laser in the feedback micro-comb signal, the micro-cavity unit includes a first port and a second port, the first port is used to output the mixed micro-comb signal, and the second port is used to output the feedback micro-comb signal; the detector unit is used to process the feedback micro-comb signal to obtain a repetition frequency microwave signal; the delay optical fiber module is connected between the second port and the detector unit, and is used to provide a target delay so that the feedback micro-comb signal is delayed and transmitted to the detector unit; the photoelectric oscillation feedback module is used to perform feedback gain adjustment on the repetition frequency microwave signal output by the detector unit to obtain a driving signal for driving the electro-optical modulation unit.

[0040] Figure 2 The structure block diagram of a device for generating a microcavity frequency comb according to an embodiment of the present disclosure is schematically shown.

[0041] like Figure 2 As shown, the device 200 includes an optical generation module 210, a time-delay fiber module 220 and an optoelectronic oscillation feedback module 230. The optical generation module 210 includes a laser source unit 211, an electro-optical modulation unit 212, an optical amplifier unit 213, a microcavity unit 214 and a detector unit 215.

[0042] According to an embodiment of the present disclosure, the electro-optical modulation unit 212 is used to modulate the laser signal emitted by the laser source unit 211, and input the obtained modulated laser to the optical amplifier unit 213; the optical amplifier unit 213 is used to perform power amplification processing on the modulated laser to obtain an amplified laser; the microcavity unit 214 converts the amplified laser into a micro-comb signal, the micro-comb signal includes a mixed micro-comb signal and a feedback micro-comb signal, the microcavity unit 214 includes a first port A and a second port B, the first port A is used to output the mixed micro-comb signal according to the modulated laser, and the second port B is used to output the feedback micro-comb signal according to the modulated laser; the delay optical fiber module 220 is connected between the second port B and the detector unit 215, and is used to delay the transmission of the feedback micro-comb optical pulse signal, and the detector unit 215 is used to obtain a repetition frequency microwave signal based on the delay processing feedback micro-comb signal; the photoelectric oscillation feedback module 230 is used to process the repetition frequency microwave signal output by the detector unit 215 to obtain a driving signal for driving the electro-optical modulation unit.

[0043] According to the embodiments of the present disclosure, the laser source unit 211, the electro-optical modulation unit 212, the optical amplifier unit 213, the microcavity unit 214, and the detector unit 215 can each be an integrated optical chip and then form an optical generation module 210 through hybrid integration, or they can be integrated into a single integrated optical chip as the optical generation module 210 through heterogeneous integration.

[0044] According to an embodiment of the present disclosure, the frequency of the laser signal output by the laser source unit needs to meet the resonance peak frequency matching condition of the microcavity unit. The frequency of the output laser signal can be adjusted by adjusting the pump current and temperature of the laser source unit so that the frequency of the laser signal matches the resonance peak frequency of the microcavity unit.

[0045] According to the embodiment of the present disclosure, the optical amplifier unit 213 is connected between the microcavity unit and the electro-optical modulation unit. The electro-optical modulation unit modulates the laser signal emitted by the laser source unit. However, the modulated laser power obtained at this time is relatively small, and it is difficult to reach the threshold power required by the microcavity unit to generate a micro-comb signal. Therefore, before the modulated laser enters the microcavity unit, the modulated laser can be amplified by the optical amplifier unit. The optical amplifier unit can be an integrated chip using a semiconductor laser power amplifier chip (SOA) or an integrated chip using an erbium-doped gain waveguide chip.

[0046] According to an embodiment of the present disclosure, the laser source unit 211 may use an electrically pumped distributed feedback (DFB) laser chip as a laser source chip.

[0047] Figure 3a The power diagram of laser emission under different driving currents of the laser source unit according to the embodiment of the present disclosure is schematically shown.

[0048] Figure 3b The schematic diagram shows the wavelength of the laser light emitted by the laser source unit under different driving currents according to the embodiment of the present disclosure.

[0049] like Figure 3a and Figure 3b As shown, when the threshold current of the laser source unit outputting the laser is 13mA and the pump current is 300mA, the output laser power is 83mW; when the pump current is 170nm, the central wavelength of the laser output by the laser source unit is 1558.3nm.

[0050] According to an embodiment of the present disclosure, the first port outputs a mixed microcomb signal according to the amplified laser, including a generated microcomb signal and a pump laser that is not converted into a microcomb signal, and the second port is used to output a feedback microcomb signal according to the modulated laser. The output feedback microcomb signal is transmitted to the delay fiber module through the second port. Compared with the microcavity unit with only one direct output port, the second port in the microcavity unit with two ports can effectively filter out the spontaneous radiation noise in the amplified laser, thereby avoiding the use of an additional laser filter structure between the optical amplifier unit and the microcavity unit.

[0051] According to the embodiments of the present disclosure, the second port mainly extracts the microcavity frequency comb, weakening the pump laser component that is not converted into the microcomb signal, thereby avoiding the situation where the detector unit is oversaturated due to excessive pump laser after entering the detector unit. At the same time, there is no need to filter out the excessive pump laser through an additional filter.

[0052] According to the embodiments of the present disclosure, the microcavity unit can use a silicon nitride annular microcavity, which has the lowest waveguide transmission loss value among all types of integrated microcavities at this stage. The higher the quality factor, the sharper the resonance peak of the microcavity unit, the narrower the half-width of the resonance peak, the lower the waveguide transmission loss, and the threshold laser power required to generate the microcomb will also be reduced.

[0053] Figure 4 The resonance peak fitting diagram of the microcavity unit according to the embodiment of the present disclosure is schematically shown.

[0054] like Figure 4 As shown, the horizontal axis is the frequency detuning amount, and the vertical axis is the transmittance. The oscilloscope collects transmission spectrum data according to a certain sampling rate, not continuous measurement, so it is mapped to many discrete data points on the transmission spectrum. These discrete data points are fitted to obtain the half-height width information of the resonance peak. The intrinsic quality factor is the ratio of the resonance frequency to the half-height width of the resonance peak. The intrinsic quality factor Q0=22×10 6, the corresponding waveguide loss is 1.68dB / m. The use of low-loss silicon nitride ring microcavity can reduce the threshold power required to generate a microcomb. Under the same pump laser power, the lower the loss of the microcavity unit, the wider the microcomb spectrum will be.

[0055] According to the embodiments of the present disclosure, the micro-comb generating device of embodiment 200 can not only meet the scientific research needs in the laboratory, but also has the potential for mass production and can be applied to a variety of application scenarios, including quantum precision measurement, optical clocks, large-scale parallel coherent optical communications, optical fiber wireless communications, microwave photonics, etc.

[0056] According to the embodiment of the present disclosure, the laser source unit in the optical generation module outputs a pump laser which is modulated by the electro-optical modulation unit, the modulated laser is power amplified by the optical amplifier unit, the amplified laser enters the micro-cavity unit to generate a micro-comb signal, the micro-cavity unit includes two ports, the first port outputs a mixed micro-comb signal, the second port outputs a feedback micro-comb signal, the delay fiber module generates a delay corresponding to the feedback micro-comb signal, and the photoelectric oscillation module is used to gain-adjust the repetition frequency microwave signal output by the detector unit to obtain a driving signal whose signal strength meets the driving conditions, thereby driving the electro-optical modulation unit. Since the micro-cavity unit includes two ports, the feedback micro-comb signal output by the second port effectively reduces the power proportion of the pump laser, thereby avoiding the oversaturation of the detector unit caused by the over-powered pump laser component, and the delay fiber module can provide a target delay to reduce the phase noise of the repetition frequency micro-comb signal. The photoelectric oscillation module can provide a driving signal for the electro-optical modulation unit to realize a self-excited and self-sustaining micro-comb generating device, thereby avoiding the use of a high-cost and large-volume external microwave driving source, effectively reducing the power consumption and volume of the device, simplifying the device structure, and facilitating the integration and miniaturization of the device, so that the generated micro-comb can be suitable for more application scenarios.

[0057] According to an embodiment of the present disclosure, the time-delay optical fiber module includes a single-mode optical fiber of a predetermined length.

[0058] According to the embodiments of the present disclosure, the predetermined length is in the kilometer range and can be determined according to actual needs and in combination with test optimization experiments. The increase in the predetermined length will reduce the phase noise near the carrier of the repetitive microwave signal, but at the same time, it will also reduce the mode spacing of the stray waves of the micro-comb repetitive microwave signal and reduce the side mode suppression ratio of the microwave signal.

[0059] Figure 5a The spectrum diagram of the repetition frequency microwave signal of the delay-free optical fiber module according to the embodiment of the present disclosure is schematically shown.

[0060] like Figure 5aAs shown, the horizontal axis is the frequency offset and the vertical axis is the power. In the case of no delay optical fiber module, the side mode suppression ratio of the repetitive frequency microwave signal is greater than 45dB, and the resolution bandwidth is 100kHz.

[0061] Figure 5b The frequency spectrum of a repetitive frequency microwave signal when the predetermined length is 4.5 km according to an embodiment of the present disclosure is schematically shown.

[0062] like Figure 5b As shown, the horizontal axis is the frequency offset and the vertical axis is the power. When a 4.5km single-mode optical fiber is selected, the side mode suppression ratio of the repetitive microwave signal is greater than 30dB and the resolution bandwidth is 1kHz.

[0063] contrast Figure 5a and Figure 5b The reduction of phase noise of repetition frequency microwave signal and the increase of side mode suppression ratio of repetition frequency microwave signal are conflicting with each other. Therefore, the phase noise of repetition frequency microwave signal should be optimized as much as possible by determining the predetermined length of delay optical fiber without significantly reducing mode spacing and side mode suppression ratio.

[0064] Figure 6 A schematic diagram showing a comparison of phase noise of a repetitive frequency microwave signal with and without a delay optical fiber module according to an embodiment of the present disclosure is shown.

[0065] like Figure 6 As shown, the horizontal axis is the frequency offset, and the vertical axis is the single-sideband phase noise. Adding a 4.5 km long single-mode delay optical fiber can effectively reduce the phase noise of the repetitive frequency microwave signal.

[0066] According to an embodiment of the present disclosure, the delay optical fiber module provides a target delay so that the feedback micro-comb signal is delayed in transmission to the detector unit to reduce the phase noise of the repetition-frequency microwave signal, and determines a suitable predetermined length through experiments to reduce noise while not excessively reducing the side mode suppression ratio.

[0067] According to an embodiment of the present disclosure, the bandwidth of the detector unit is greater than the free spectrum width of the microcavity unit.

[0068] According to the embodiments of the present disclosure, the detector unit can use a high-speed amplifier chip with a 3dB bandwidth of 110GHz and a photoelectric responsivity of 0.3A / W near 1560nm. The 3dB bandwidth of the detector unit needs to be greater than the free spectral width of the microcavity unit, and the free spectral width (FSR) of the microcavity is 10.699GHz.

[0069] According to the embodiments of the present disclosure, by limiting the size relationship between the bandwidth of the detector unit and the free spectral width of the microcavity unit, the detector unit receives a complete feedback micro-comb signal, while effectively ensuring the stability of the device and avoiding distortion of the micro-comb signal.

[0070] According to an embodiment of the present disclosure, the optoelectronic oscillation feedback module includes a radio frequency amplifier unit, an adjustable attenuator unit and a power divider unit; the re-frequency microwave signal output by the detector unit is processed to obtain a driving signal for driving the electro-optical modulation unit, including: inputting the re-frequency microwave signal into the radio frequency amplifier unit for amplification to obtain an amplified re-frequency signal; inputting the amplified re-frequency signal into the adjustable attenuator unit to adjust the gain of the optoelectronic oscillation feedback module to obtain an attenuated re-frequency signal; inputting the attenuated re-frequency signal into the power divider unit to obtain a driving signal and a target microwave signal, respectively.

[0071] According to an embodiment of the present disclosure, the radio frequency amplifier unit may be a high-gain, low-noise fixed-gain amplifier for amplifying the repetitive-frequency microwave signal output by the detector unit.

[0072] According to the embodiments of the present disclosure, the power of the re-frequency microwave signal directly output by the detector unit is usually very small, about -20dBm. Effectively driving the electro-optical modulation unit in the optical generation module usually requires a driving power of more than +17dBm. Due to line loss, adjustable attenuator unit loss, insertion loss of each device and power divider unit, a portion of the power will be divided as a low-noise target microwave signal. Therefore, the total gain of the RF amplifier unit generally needs to reach more than 45dB, and two RF amplifiers can also be cascaded to meet the gain threshold.

[0073] According to the embodiments of the present disclosure, when constructing the optoelectronic oscillation feedback loop of the optoelectronic oscillation feedback module, when the feedback gain of the entire loop is insufficient, the optoelectronic oscillation feedback loop cannot self-excite to generate and maintain the re-frequency microwave signal; conversely, when the feedback gain of the entire loop is too high, the phase noise of the generated re-frequency microwave signal will be high. Therefore, it is necessary to adjust the attenuation value of the adjustable attenuator unit according to the phase noise spectrum of the re-frequency microwave signal until the re-frequency microwave signal meets the condition of minimum phase noise.

[0074] According to an embodiment of the present disclosure, the target microwave signal can be used to provide a low-noise microcavity frequency comb and can also serve as a low-phase-noise microwave reference source.

[0075] According to the embodiments of the present disclosure, the re-frequency microwave signal output by the detector unit is processed by the optoelectronic oscillation feedback module to obtain a driving signal for driving the electro-optical modulation unit, and the amplified re-frequency signal is input into the adjustable attenuator unit to adjust the gain of the optoelectronic oscillation feedback module to obtain an attenuated re-frequency signal which is input into the power divider unit to obtain the driving signal and the target microwave signal respectively, so that the whole device can be self-sustaining, avoiding the use of expensive, bulky and high-power microwave sources, which is conducive to the integration and miniaturization of the micro-comb generating device.

[0076] According to an embodiment of the present disclosure, the optoelectronic oscillation feedback module further includes a bias unit connected between the radio frequency amplifier unit and the detector unit, and the bias unit is used to provide a DC bias voltage for the detector unit.

[0077] According to an embodiment of the present disclosure, when the detector unit is working, a DC bias voltage needs to be added through the DC port of the bias unit of the photoelectric oscillation feedback module. For example, the DC bias voltage value may be 2.0V.

[0078] Figure 7 A schematic diagram of a device for generating a microcavity frequency comb according to an embodiment of the present disclosure is schematically shown.

[0079] like Figure 7 As shown, the embodiment 700 includes an optical generation module 210, a delay fiber module 220 and an optoelectronic oscillation feedback module 230. The optical generation module 210 includes a laser source unit 211, an electro-optical modulation unit 212, an optical amplifier unit 213, a microcavity unit 214, and a detector unit 215, and the optoelectronic oscillation feedback module includes a bias unit 231, a radio frequency amplifier unit 232, an adjustable attenuator unit 233 and a power divider unit 234.

[0080] According to an embodiment of the present disclosure, the bias unit 231 has three ports: O, P, and Q. The O port is connected to an external DC voltage source through a photoelectric oscillation feedback module to provide a DC bias voltage for the detector unit and output the DC component of the photocurrent. The P port is connected to the detector unit, which provides a DC bias voltage to the detector unit on the one hand, and exports the high-speed repetition frequency microwave signal of the detector unit to the Q port of the bias unit on the other hand, and transmits it to the RF amplifier unit 232 for amplification.

[0081] According to an embodiment of the present disclosure, the bandwidth range of the bias unit includes the free spectral width of the microcavity unit.

[0082] According to an embodiment of the present disclosure, the bandwidth range of the bias unit is 40 kHz to 26.5 GHz, which includes the free spectrum width of the microcavity unit of 10.699 GHz, thereby meeting the matching requirements of the frequency range.

[0083] According to an embodiment of the present disclosure, an attenuated repetition frequency signal is input into a power divider unit to obtain a driving signal and a target microwave signal, respectively, including: allocating the attenuated repetition frequency signal according to a preset power of the power divider unit, wherein the preset power includes a first preset power and a second preset power; obtaining a driving signal from the attenuated repetition frequency signal according to the first preset power; and obtaining a target microwave signal from the attenuated repetition frequency signal according to the second preset power.

[0084] According to an embodiment of the present disclosure, the power divider unit can directly distribute power on demand from the attenuated repetition frequency signal. According to the second preset power, the low-noise target microwave signal is output through the RF output port of the optoelectronic oscillation feedback module. According to the first preset power, the driving signal is applied to the electro-optical modulator unit to modulate the pump laser output by the laser source unit.

[0085] According to an embodiment of the present disclosure, the attenuated repetition frequency signal is input into the power divider unit, and the driving signal and the target microwave signal are obtained according to the preset power distribution, that is, not only a low-noise micro-comb signal but also a low-noise microwave signal can be output, thereby improving the performance of the micro-comb generating device and enriching its functions.

[0086] According to an embodiment of the present disclosure, the microcavity unit includes one of the following: a normal dispersion microcavity and an anomalous dispersion microcavity.

[0087] According to the embodiments of the present disclosure, the dispersion of the microcavity unit will affect the form of the generated pulse. The silicon nitride ring microcavity with normal dispersion can generate dark pulses, so that the conversion efficiency between the emitted laser of the laser source unit and the microcomb signal is relatively high, which can reach more than 10%.

[0088] According to the embodiments of the present disclosure, the anomalous dispersion silicon nitride microcavity can generate bright pulses, and the spectrum of the microcomb signal is wider, which has the advantage of expanding the communication channel for communication experiments. However, for a single-ring microcavity unit, the conversion efficiency between the pump laser of the bright pulse laser source unit and the microcomb signal is low, generally less than 1%.

[0089] Figure 8 The diagram schematically shows a spectrum diagram of a hybrid microcomb signal generated using a normal dispersion microcavity according to an embodiment of the present disclosure.

[0090] like Figure 8 As shown, the horizontal axis is wavelength, the vertical axis is power, the central wavelength is 1558.3 ​​nm, and the free spectral width of the microcavity is 10.699 GHz.

[0091] According to an embodiment of the present disclosure, the output end of the laser source unit includes a first laser isolator, and the output end of the optical amplifier unit includes a second laser isolator.

[0092] According to the embodiment of the present disclosure, for the laser source unit and the optical amplifier unit, the reflected light in the optical path transmission will affect the frequency and power stability of the output laser, thereby affecting the stable generation of the micro-comb signal, and even damaging the laser gain chip in the laser source unit and the optical amplifier unit. Therefore, a first laser isolator is set at the output end of the laser source unit, and a second laser isolator is set at the output end of the optical amplifier unit to isolate the influence of the reflected light on the stable operation of the device.

[0093] The experimental diagrams and block diagrams in the accompanying drawings illustrate the possible architecture, functions and operations of the devices according to various embodiments of the present disclosure. It should also be noted that in some alternative implementations, the functions marked in the boxes may also occur in an order different from that marked in the accompanying drawings. For example, two boxes represented in succession can actually be executed substantially in parallel, and they can sometimes be executed in the opposite order, depending on the functions involved. It should also be noted that each box in the block diagram or flow chart, and the combination of boxes in the block diagram or flow chart, can be implemented with a dedicated hardware-based system that performs a specified function or operation, or can be implemented with a combination of dedicated hardware and computer instructions. It can be understood by those skilled in the art that the features recorded in the various embodiments of the present disclosure can be combined and / or combined in various ways, even if such combinations or combinations are not explicitly recorded in the present disclosure. In particular, without departing from the spirit and teachings of the present disclosure, the features recorded in the various embodiments of the present disclosure can be combined and / or combined in various ways. All these combinations and / or combinations fall within the scope of the present disclosure.

[0094] The embodiments of the present disclosure are described above. However, these embodiments are only for illustrative purposes and are not intended to limit the scope of the present disclosure. Although the embodiments are described above, this does not mean that the measures in the various embodiments cannot be used in combination to advantage. Without departing from the scope of the present disclosure, those skilled in the art may make a variety of substitutions and modifications, which should all fall within the scope of the present disclosure.

Claims

1. A device for generating a microcavity frequency comb, characterized in that: include: An optical generation module, including a laser source unit, an electro-optical modulation unit, an optical amplifier unit, a microcavity unit, and a detector unit; The electro-optical modulation unit is used to modulate the output laser of the laser source unit and input the obtained modulated laser to the optical amplifier unit, wherein the frequency of the output laser of the laser source unit matches the resonance peak frequency of the microcavity unit; The optical amplifier unit is used to perform power amplification processing on the modulated laser to obtain an amplified laser, wherein the power of the amplified laser is greater than or equal to the threshold power required by the microcavity unit to generate a microcomb; The microcavity unit is used to convert the amplified laser into a microcomb signal, wherein the microcomb signal includes a mixed microcomb signal and a feedback microcomb signal, the power proportion of the pump laser in the mixed microcomb signal is greater than the power proportion of the pump laser in the feedback microcomb signal, and the microcavity unit includes a first port and a second port, the first port is used to output the mixed microcomb signal, and the second port is used to output the feedback microcomb signal; The detector unit is used to process the feedback micro-comb signal to obtain a repetitive frequency microwave signal; A delay optical fiber module, connected between the second port and the detector unit, for providing a target delay so that the feedback micro-comb signal is transmitted to the detector unit with a delay; The photoelectric oscillation feedback module is used to perform feedback gain adjustment on the repetitive frequency microwave signal output by the detector unit to obtain a driving signal for driving the electro-optical modulation unit.

2. The device according to claim 1, characterized in that The optoelectronic oscillation feedback module includes a radio frequency amplifier unit, an adjustable attenuator unit and a power divider unit; the feedback gain adjustment of the repetitive frequency microwave signal output by the detector unit to obtain a driving signal for driving the electro-optical modulation unit includes: Inputting the repetitive frequency microwave signal into a radio frequency amplifier unit for amplification to obtain an amplified repetitive frequency microwave signal; Inputting the amplified repetition frequency microwave signal into an adjustable attenuator unit to adjust the gain of the optoelectronic oscillation feedback module to obtain an attenuated repetition frequency signal; The attenuated repetition frequency signal is input into a power divider unit to obtain the driving signal and the target microwave signal respectively.

3. The device according to claim 2, characterized in that The step of inputting the attenuated repetition frequency signal into a power divider unit to obtain the driving signal and the target microwave signal respectively comprises: Distributing the attenuated repetition frequency signal according to a preset power of the power divider unit, wherein the preset power includes a first preset power and a second preset power; Obtaining the driving signal from the attenuated repetition rate signal according to the first preset power; The target microwave signal is obtained from the attenuated repetition frequency signal according to the second preset power.

4. The device according to claim 2, characterized in that The photoelectric oscillation feedback module further includes a bias unit connected between the radio frequency amplifier unit and the detector unit, and the bias unit is used to provide a DC bias voltage for the detector unit.

5. The device according to claim 4, characterized in that The bandwidth range of the bias unit includes the free spectral width of the microcavity unit.

6. The device according to claim 1, characterized in that The delay optical fiber module includes a single-mode optical fiber of a predetermined length.

7. The device according to claim 1, characterized in that The microcavity unit includes one of the following: a normal dispersion microcavity and an anomalous dispersion microcavity.

8. The device according to claim 1, characterized in that The output end of the laser source unit includes a first laser isolator, and the output end of the optical amplifier unit includes a second laser isolator.

9. The device according to claim 1, characterized in that The bandwidth of the detector unit is greater than the free spectrum width of the microcavity unit.

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