Microcavity frequency comb generation device

Abstract

The present disclosure provides a device for generating a microcavity frequency comb, which can be applied to the field of optical frequency comb technology. The device includes: an optical generation module, an electro-optical modulation unit, which is used to modulate the output laser of a laser source unit and input the modulated laser into an optical amplifier unit; the optical amplifier unit, which is used to perform power amplification processing on the modulated laser to obtain an amplified laser; a microcavity unit, which 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, wherein the first port is used to output the mixed microcomb signal and the second port is used to output the feedback microcomb signal; a detector unit, which is used to process the feedback microcomb signal to obtain a repetition frequency microwave signal; a delay optical fiber module, which is used to provide a target delay so that the feedback microcomb signal is delayed and transmitted to the detector unit; and an optoelectronic oscillation feedback module, which is used to perform feedback gain adjustment on the repetition frequency microwave signal 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 particularly, 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 applications, 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") generation 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 lower 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 into the optical amplifier unit, wherein the frequency of the output laser of the laser source unit matches the resonant 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, wherein the power proportion of the pump laser in the hybrid microcomb signal is greater than the power proportion of the pump laser in the feedback microcomb signal, the microcavity unit includes 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 in transmission to the detector unit; and 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 splitter unit to obtain a driving signal and a target microwave signal, respectively, including: distributing the attenuated repetition frequency signal according to a preset power of the power splitter 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 spectral 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, and the amplified laser that meets the threshold power of the microcavity unit enters the microcavity unit to generate a microcomb signal. The microcavity unit includes two ports, the first port outputs a mixed microcomb signal, and the second port outputs a feedback microcomb signal. The delay fiber module generates a delay corresponding to the feedback microcomb signal. The optoelectronic oscillation module is used to perform feedback gain adjustment on the repetitive 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 microcomb 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 microcomb signal through the second port, avoiding the use of additional filters. The delay fiber module can provide the target delay to reduce the phase noise of the repetitive 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 microcomb 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 microcomb 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.

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

[0019] Figure 3a The figure schematically shows the power of laser light emitted by a laser source unit under different driving currents according to an embodiment of the present disclosure.

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

[0021] Figure 4 The figure schematically shows a resonance peak fitting diagram of a microcavity unit according to an embodiment of the present disclosure.

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

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

[0024] 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.

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

[0026] Figure 8 The diagram schematically shows a spectrum of a hybrid microcomb signal generated by a normal dispersion microcavity according to an embodiment of the present disclosure. 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 merely exemplary and are not intended to limit the scope of the present disclosure. In the detailed description below, 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 well-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 presence of the features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0029] All terms used herein (including technical and scientific terms) 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 expressions such as "at least one of A, B, and C, etc." are used, they should generally be interpreted in accordance with the meaning 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 this disclosure, the collection, updating, analysis, processing, use, transmission, provision, disclosure, and storage of all data involved (including, but not limited to, user personal information) comply with relevant laws and regulations, are used for legitimate purposes, and do not violate public order and good morals. In particular, necessary measures have been taken to prevent unauthorized access to user personal information data and to safeguard 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] Currently, microcomb generation based on microcavity self-injection locking is a commonly used approach. Its advantage is that it does not require an additional low-noise microwave source for synchronization, thus enabling miniaturized integration. However, the effectiveness of microcomb generation varies depending on the dispersion of the microcavity. One approach is to generate bright soliton pulses using anomalous dispersion microcavity self-injection locking. The conversion efficiency of pump lasers to the microcomb for this type of microcavity frequency comb is generally low. For microcavity frequency combs with a free spectral width (FSR) approaching 10 GHz, the conversion efficiency is typically less than 1%. This results in excessively low microcomb tooth power, hindering its widespread application. Another approach to microcomb generation is to generate dark pulses using normal dispersion microcavity self-injection locking. This approach offers a high conversion efficiency from pump lasers to dark pulse microcombs, typically exceeding 10%. However, the resulting microcomb spectral bandwidth is generally smaller than that of soliton microcombs generated using anomalous dispersion microcavities. Furthermore, while microcavity frequency combs generated using these two microcavity self-injection locking methods can be integrated on a chip, the phase noise of the microcomb pulse repetition frequency (PRF) signal remains relatively high. For some applications that require ultra-low phase noise in repetition frequency, such as coherent optical communications, lidar, quantum precision measurement, optical clocks, etc., the repetition frequency 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 through self-injection locking, another approach is pump modulation. This involves modulating the pump laser at a frequency close to the free spectral width (FSR) of the microcavity. The advantage of this approach is that an ultra-low-noise microwave source can be used to drive the laser modulator. The modulated laser synchronizes within the microcavity, thereby purifying the phase noise of the generated microcomb repetition rate. However, this approach requires an expensive, bulky, and power-hungry microwave source to drive the modulator. This hinders the integration of the microcomb generation device and hinders its size and power consumption. Furthermore, while optical frequency division (OFD) of the microcomb can currently be used to reduce microcomb phase noise without requiring a low-noise microwave source, this approach requires complex frequency locking and laser power amplification. Furthermore, it places high demands on the pump source's laser phase noise, hindering device integration and miniaturization.

[0035] In order to better reflect the components of the traditional micro-comb generating device, the following Figure 1 The traditional 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.

[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 about higher power consumption and increases the cost, and the optical amplifier 140 and the filter 150 also make 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 into the optical amplifier unit, wherein the frequency of the output laser of the laser source unit matches the resonant peak frequency of the microcavity unit; the optical amplifier unit is used to power-amplify 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 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 microcomb 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 microcomb 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 figure schematically shows a structural block diagram of a device for generating a microcavity frequency comb according to an embodiment of the present disclosure.

[0041] like Figure 2 As shown, the device 200 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.

[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 into 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 microcomb signal, which includes a mixed microcomb signal and a feedback microcomb 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 microcomb signal according to the modulated laser, and the second port B is used to output the feedback microcomb 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 microcomb optical pulse signal. The detector unit 215 is used to obtain a repetition frequency microwave signal based on the delayed processing of the feedback microcomb signal; the optoelectronic 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 an embodiment 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 the 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 resonant 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 resonant peak frequency of the microcavity unit.

[0045] According to an 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 low, making it difficult to reach the threshold power required by the microcavity unit to generate a microcomb signal. Therefore, before the modulated laser enters the microcavity unit, an optical amplifier unit can be used to amplify the modulated laser. 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 the laser source chip.

[0047] Figure 3a The figure schematically shows the power of laser light emitted by a laser source unit under different driving currents according to an embodiment of the present disclosure.

[0048] Figure 3b The figure schematically shows the wavelength of the laser light emitted by the laser source unit under different driving currents according to an 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 center wavelength of the laser output by the laser source unit is 1558.3nm.

[0050] According to an embodiment of the present disclosure, the hybrid microcomb signal outputted by the first port based on the amplified laser light includes the generated microcomb signal and the pump laser light that has not been converted into a microcomb signal. The second port is used to output a feedback microcomb signal based on the modulated laser light. The output feedback microcomb signal is transmitted to the delay fiber module through the second port. Compared with a microcavity unit with only one direct output port, the second port in the microcavity unit with two ports can effectively filter out the spontaneous emission noise in the amplified laser light, thus 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 utilize a silicon nitride ring microcavity, which exhibits the lowest waveguide transmission loss among currently available integrated microcavities. A higher quality factor indicates a sharper resonance peak, a narrower full width at half maximum (FWHM) of the microcavity unit, and lower waveguide transmission loss. This also reduces the threshold laser power required to generate the microcomb.

[0053] Figure 4 The figure schematically shows a resonance peak fitting diagram of a microcavity unit according to an embodiment of the present disclosure.

[0054] like Figure 4 As shown in the figure, 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, which is not a continuous measurement. Therefore, it is mapped into many discrete data points on the transmission spectrum. These discrete data points are fitted to obtain the half-height width 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 microcomb. Under the same pump laser power, the lower the loss of the microcavity unit, the wider the microcomb spectrum.

[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, fiber-optic wireless communications, microwave photonics, etc.

[0056] According to an embodiment of the present disclosure, the laser source unit in the optical generation module outputs a pump laser that is modulated by the electro-optical modulation unit. The modulated laser is power-amplified by the optical amplifier unit. The amplified laser enters the microcavity unit to generate a microcomb signal. The microcavity unit includes two ports, the first port outputs a mixed microcomb signal, and the second port outputs a feedback microcomb signal. The delay fiber module generates a delay corresponding to the feedback microcomb signal. The optoelectronic oscillator module is used to gain-adjust the repetition rate microwave signal output by the detector unit to obtain a drive signal whose signal strength meets the driving conditions, thereby driving the electro-optical modulation unit. Because the microcavity unit includes two ports, the feedback microcomb signal output by the second port effectively reduces the power proportion of the pump laser, thereby avoiding oversaturation of the detector unit caused by the excessively high power pump laser component. The delay fiber module can provide a target delay to reduce the phase noise of the repetition rate microcomb signal. The optoelectronic oscillation module can provide a driving signal for the electro-optical modulation unit to realize a self-excited and self-sustaining micro-comb generation device, thereby avoiding the use of a high-cost and large 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 on the order of kilometers and can be determined based on actual needs and in conjunction with test optimization experiments. Increasing the predetermined length reduces phase noise near the carrier of the repetitive microwave signal, but at the same time, it also reduces the mode spacing of spurious waves in the micro-comb repetitive microwave signal and reduces the side-mode suppression ratio of the microwave signal.

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

[0060] like Figure 5aAs shown in the figure, the horizontal axis is the frequency offset and the vertical axis is the power. Without the delay fiber module, the side mode suppression ratio of the repetitive microwave signal is greater than 45dB, and the resolution bandwidth is 100kHz.

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

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

[0063] contrast Figure 5a and Figure 5b The reduction of the phase noise of the repetition frequency microwave signal and the increase of the side mode suppression ratio of the repetition frequency microwave signal are in conflict with each other. Therefore, the phase noise of the repetition frequency microwave signal should be optimized as much as possible by determining the predetermined length of the delay fiber without significantly reducing the mode spacing and the 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 in the figure, the horizontal axis is the frequency offset and the vertical axis is the single-sideband phase noise. Adding a 4.5 km single-mode delay 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 repetitive microwave signal, and determines the appropriate predetermined length through experiments to reduce noise without 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 spectral width of the microcavity unit.

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

[0069] According to an embodiment 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, used to amplify 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 typically very low, approximately -20dBm. However, effectively driving the electro-optical modulation unit in the optical generation module typically requires a drive power of +17dBm or more. Due to line losses, losses in the adjustable attenuator unit, insertion losses in various components, and the power splitter unit, a portion of the power is diverted as a low-noise target microwave signal. Therefore, the total gain of the RF amplifier unit generally needs to be above 45dB. Alternatively, two RF amplifiers can be cascaded to meet the gain threshold.

[0073] According to an embodiment of the present disclosure, when constructing the optoelectronic oscillation feedback loop of the optoelectronic oscillation feedback module, if 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, if the feedback gain of the entire loop is too high, the phase noise of the generated re-frequency microwave signal will be too 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 repetition 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 repetition frequency signal is input into the adjustable attenuator unit to adjust the gain of the optoelectronic oscillation feedback module to obtain an attenuated repetition frequency signal which is input into the power divider unit to obtain the driving signal and the target microwave signal respectively, so that the entire device can self-sustain and avoid 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 The figure schematically shows a schematic diagram of a device for generating a microcavity frequency comb according to an embodiment of the present disclosure.

[0079] like Figure 7 As shown, this 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. 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 via a photoelectric oscillation feedback module to provide a DC bias for the detector unit and output the DC component of the photocurrent. The P port is connected to the detector unit, providing a DC bias and directing the high-speed repetition rate microwave signal from the detector unit to the Q port of the bias unit for transmission 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 tee 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 splitter unit to obtain a driving signal and a target microwave signal, respectively, including: distributing the attenuated repetition frequency signal according to a preset power of the power splitter 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 the embodiments of the present disclosure, the power splitter unit can directly allocate power on demand from the attenuated repetition frequency signal. Based on the second preset power, the low-noise target microwave signal is output through the RF output port of the optoelectronic oscillation feedback module. Based on the first preset power, the drive signal is applied to the electro-optical modulator unit, which modulates 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 can be output, 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 affects 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, anomalous dispersion silicon nitride microcavities can generate bright pulses, broadening the spectrum of microcomb signals. This has the advantage of expanding communication channels for communication experiments. However, for single-ring microcavity units, the conversion efficiency between the pump laser and the microcomb signal in the bright pulse laser source unit is low, typically less than 1%.

[0089] Figure 8 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 disclosed embodiments, for the laser source unit and optical amplifier unit, reflected light during optical transmission can affect the frequency and power stability of the output laser, thereby affecting the stable generation of micro-comb signals and even damaging the laser gain chips in the laser source unit and the optical amplifier unit. Therefore, a first laser isolator is installed at the output end of the laser source unit, and a second laser isolator is installed at the output end of the optical amplifier unit to isolate the reflected light from affecting the stable operation of the device.

[0093] The experimental diagrams and block diagrams in the accompanying drawings illustrate the possible architectures, 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 blocks may occur in an order different from that marked in the drawings. For example, two blocks shown in succession may actually be executed substantially in parallel, or they may sometimes be executed in the opposite order, depending on the functions involved. It should also be noted that each block in a block diagram or flowchart, as well as the combination of blocks in a block diagram or flowchart, may be implemented using a dedicated hardware-based system that performs the specified function or operation, or may be implemented using a combination of dedicated hardware and computer instructions. It will be understood by those skilled in the art that the features described in the various embodiments of the present disclosure may be combined and / or combined in various ways, even if such combinations or combinations are not explicitly described in the present disclosure. In particular, the features described in the various embodiments of the present disclosure may be combined and / or combined in various ways without departing from the spirit and teachings of the present disclosure. All such combinations and / or combinations fall within the scope of the present disclosure.

[0094] The above describes the embodiments of the present disclosure. However, these embodiments are for illustrative purposes only and are not intended to limit the scope of the present disclosure. Although each embodiment has been described separately above, this does not mean that the measures in each embodiment cannot be advantageously used in combination. Without departing from the scope of the present disclosure, those skilled in the art may make various 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 into 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 configured 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 configured to convert the amplified laser light into a microcomb signal, wherein the microcomb signal includes a mixed microcomb signal and a feedback microcomb signal, the power ratio of the pump laser in the mixed microcomb signal is greater than the power ratio 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 configured to output the mixed microcomb signal, and the second port is configured 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 delayed transmission time; 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 repetitive 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 repetitive frequency signal into a power splitter 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 frequency 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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