Frequency tuning system and frequency stabilization method based on microcavity soliton optical frequency comb

Abstract

The application provides a repetition frequency tuning system and a frequency stabilization method based on a microcavity soliton optical frequency comb, which comprises: a pump laser generation module, which is suitable for providing continuous pump laser; a pump laser feedback module, which is suitable for monitoring the pump laser in real time, so that after the microcavity soliton optical frequency comb is generated, a first error signal is transmitted to the pump laser generation module to lock the frequency of the pump laser; a whispering gallery mode microcavity, which is suitable for providing a reaction space for generating the microcavity soliton optical frequency comb based on the pump laser generated by the pump laser generation module; an auxiliary laser generation module, which is suitable for providing auxiliary laser for inhibiting the thermal effect in the whispering gallery mode microcavity and transmitting the auxiliary laser to the whispering gallery mode microcavity, so that the generation of the auxiliary microcavity soliton optical frequency comb and the adjustment of the local dispersion in the whispering gallery mode microcavity are realized; and an auxiliary laser feedback module, which is suitable for monitoring the repetition frequency in real time and transmitting a second error signal to the auxiliary laser generation module, so that the tuning and locking of the repetition frequency are realized.

Description

Technical Field

[0001] This invention relates to the field of microcavity optical frequency combs and frequency stabilization technology, specifically to a frequency repetition tuning system and frequency stabilization method based on a microcavity soliton optical frequency comb. Background Technology

[0002] An optical frequency comb is composed of a coherent comb structure with many single-frequency modes in the frequency domain, and appears as a series of equally spaced femtosecond pulses in the time domain. Optical frequency combs can achieve direct locking of all wavelengths within their frequency coverage range and can be traced back to a microwave frequency reference. Therefore, establishing a direct link between optical and microwave frequencies plays a crucial role in establishing global time standards, precise spectral measurements, coherent communication, and frequency synthesis.

[0003] However, traditional optical frequency combs, such as mode-locked laser frequency combs and electro-optic frequency combs, are often quite large in size and consume considerable power, thus severely limiting their application in many laboratory settings. In recent years, microcavity soliton frequency combs based on cascaded nonlinear interactions within microcavities have emerged as a new solution for reducing the size and power consumption of optical frequency comb systems. This technology platform can meet the miniaturization requirements of future technologies.

[0004] For the numerous applications of microcavity soliton optical frequency combs, a key scientific problem is how to achieve precise adjustment of the repetition rate. Currently, this is typically achieved through the thermo-optic effect, i.e., by changing the temperature applied to the microcavity, which in turn alters the refractive index and size, thereby changing the free spectral range of the microcavity to adjust the repetition rate. However, changes in temperature along with the repetition rate also cause changes in the frequency of the microcavity optical modes, necessitating adjustment of the pump laser frequency to maintain the state of the microcavity soliton optical frequency comb. This limitation prevents independent and precise adjustment of the repetition rate of the microcavity soliton optical frequency comb, hindering its further applications. Summary of the Invention

[0005] To address the above problems, this application provides a frequency repetition rate tuning system based on a microcavity soliton optical frequency comb, comprising:

[0006] Pump laser generation module, suitable for providing continuous pump laser;

[0007] The pump laser feedback module is suitable for real-time monitoring of the pump laser, so as to transmit a first error signal to the pump laser generation module after the microcavity soliton optical frequency comb is generated to lock the frequency of the pump laser.

[0008] The whispering-gallery mode microcavity has third-order nonlinearity, anomalous dispersion and generation cascaded four-wave mixing function, and is suitable for providing a reaction space for generating the above-mentioned microcavity soliton optical frequency comb based on the pump laser generated by the pump laser generation module.

[0009] An auxiliary laser generation module is suitable for providing an auxiliary laser to suppress the thermal effects generated in the aforementioned whispering-gallery mode microcavity and transmitting it to the whispering-gallery mode microcavity to assist in the generation of the aforementioned microcavity soliton optical frequency comb and to adjust the local dispersion of the aforementioned whispering-gallery mode microcavity.

[0010] An auxiliary laser feedback module is used to monitor the repetition frequency in real time and transmit a second error signal to the auxiliary laser generation module to achieve tuning and locking of the repetition frequency. The repetition frequency represents the frequency interval between two adjacent comb teeth of the microcavity soliton microcavity optical frequency comb generated based on the pump laser in the whispering-gallery mode microcavity.

[0011] According to an embodiment of the present invention, the pump laser generation module includes: a pump laser adapted to generate continuous pump laser; an optical fiber beam splitter, the input end of which is connected to the output end of the pump laser, adapted to split the pump laser into beams; and a pump laser feedback module including: an optical reference cavity, the input end of which is connected to the first output port of the optical fiber beam splitter, adapted to provide a stable optical frequency reference; a first photodetector adapted to convert the optical signal passing through the optical reference cavity into an electrical signal; and a first feedback loop, the input end of which is connected to the output end of the first photodetector, and the output end of which is connected to the input end of the pump laser; adapted to generate the first error signal and load the first error signal onto the modulation port of the pump laser to lock the frequency of the pump laser; wherein the second output port of the optical fiber beam splitter is connected to the first port of the whispering-gallery mode microcavity.

[0012] According to an embodiment of the present invention, the auxiliary laser generation module includes: an auxiliary laser adapted to provide an auxiliary laser that suppresses thermal effects generated in the whispering-gallery mode microcavity; a fiber optic circulator adapted to ensure unidirectional transmission of the auxiliary laser among three ports, wherein the first port of the fiber optic circulator is connected to the output of the auxiliary laser; the auxiliary laser feedback module includes: a second photodetector, the third port of the fiber optic circulator being connected to the input of the second photodetector, adapted to convert the optical signal passing through the fiber optic circulator into an electrical signal; a second feedback loop, the input of the second feedback loop being connected to the output of the second photodetector, and the output of the second feedback loop being connected to the input of the auxiliary laser, adapted to generate the second error signal and load the second error signal onto the modulation port of the auxiliary laser to achieve tuning and locking of the repetition frequency; wherein the second port of the fiber optic circulator is connected to the second port of the whispering-gallery mode microcavity.

[0013] According to an embodiment of the present invention, the pump laser is a tunable laser, comprising: a tunable laser and an on-chip semiconductor light source; the auxiliary laser is a tunable laser, comprising: a tunable laser and an on-chip semiconductor light source; the optical reference cavity comprises: a Fabry-Perot optical reference cavity and an on-chip optical reference cavity.

[0014] According to embodiments of the present invention, the whispering-gallery mode microcavity described above is applicable to two different mode families based on the pump laser described above and the auxiliary laser excitation described above.

[0015] According to an embodiment of the present invention, the first photodetector and the second photodetector have the same structure; the first feedback loop and the second feedback loop have the same structure.

[0016] Another aspect of the present invention provides a frequency stabilization method for a microcavity soliton optical frequency comb, applied to the frequency repetition tuning system of the microcavity soliton optical frequency comb described in any one of the above claims, the method comprising:

[0017] A pump laser generation module is used to provide a continuous pump laser and transmit it to a whispering-gallery mode microcavity to generate a soliton optical frequency comb within the whispering-gallery mode microcavity.

[0018] The pump laser is monitored in real time using a pump laser feedback module so that after the microcavity soliton optical frequency comb is generated, the first error signal is transmitted to the pump laser generation module to lock the frequency of the pump laser.

[0019] An auxiliary laser generation module is used to provide an auxiliary laser to suppress the thermal effects in the aforementioned whispering-gallery mode microcavity, and the laser is transmitted to the whispering-gallery mode microcavity to assist in the generation of the aforementioned microcavity soliton optical frequency comb and to adjust the local dispersion within the aforementioned whispering-gallery mode microcavity.

[0020] The repetition frequency is monitored in real time using an auxiliary laser feedback module, and the second error signal is transmitted to the auxiliary laser generation module to achieve tuning and locking of the repetition frequency.

[0021] According to an embodiment of the present invention, after the pump laser reaches the whispering-gallery mode microcavity, a first mode family is excited; after the auxiliary laser reaches the whispering-gallery mode microcavity, a second mode family is excited; wherein the first mode family is different from the second mode family.

[0022] According to an embodiment of the present invention, the first mode family has multiple modes with different frequencies, each mode corresponding to a tooth of the microcavity soliton optical frequency comb, and the frequency interval between two adjacent teeth of the microcavity soliton optical frequency comb is called the repetition frequency.

[0023] According to an embodiment of the present invention, in pump mode, the pump laser frequency is locked, and the repetition frequency is determined by the auxiliary laser frequency.

[0024] According to an embodiment of the present invention, by introducing an auxiliary laser generation module and an auxiliary laser feedback module, the local dispersion within the whispering-gallery mode microcavity is adjusted using the auxiliary laser, thereby decoupling the repetition frequency and the pump laser, and thus achieving independent and precise adjustment of the repetition frequency.

[0025] According to embodiments of the present invention, by introducing an auxiliary laser generation module and an auxiliary laser feedback module, and by precisely tuning the repetition frequency using the auxiliary laser, the repetition frequency and pump laser frequency of the microcavity soliton optical frequency comb can be locked respectively, further locking the comb tooth frequency of the microcavity soliton optical frequency comb, thereby achieving a stable comb tooth frequency. This locking method is simple to operate and can be applied to all microcavity soliton optical frequency comb platforms. Attached Figure Description

[0026] The above-described features, other objects, and advantages of the present invention will become clearer from the following description of embodiments of the invention with reference to the accompanying drawings, in which:

[0027] Figure 1 The schematic diagram illustrates the structure of a frequency repetition rate tuning system based on a microcavity soliton optical frequency comb according to an embodiment of the present invention;

[0028] Figure 2 A schematic diagram illustrating the power variation within a whispering-gallery mode microcavity according to an embodiment of the present invention is shown.

[0029] Figure 3 A flowchart illustrating a frequency repetition rate tuning and frequency stabilization method based on a microcavity soliton optical frequency comb according to an embodiment of the present invention is shown.

[0030] Figure 4 This diagram schematically illustrates a comparison of different modes and corresponding thermal field distributions within a whispering-gallery mode microcavity according to an embodiment of the present invention.

[0031] Figure 5 This schematic diagram illustrates the decoupling and locking of the pump laser frequency and repetition frequency according to an embodiment of the present invention.

[0032] Figure 6 The diagram illustrates the relationship between the auxiliary laser frequency and the comb tooth frequency of the soliton optical frequency comb according to an embodiment of the present invention.

[0033] Figure 7 The schematic diagram illustrates the structure of a frequency repetition rate tuning system based on a microcavity soliton optical frequency comb according to a second embodiment of the present invention;

[0034] Figure 8The schematic diagram illustrates the structure of a frequency repetition tuning system based on a microcavity soliton optical frequency comb according to a third embodiment of the present invention.

[0035] In the above figures, the corresponding reference numerals are explained as follows:

[0036] 1: Pumped laser generation module;

[0037] 11: Pump laser;

[0038] 12: Fiber optic beam splitter;

[0039] 13: First fiber polarization controller;

[0040] 14: First fiber optic power amplifier;

[0041] 2: Pumped laser feedback module;

[0042] 21: Optical reference cavity;

[0043] 22: First photodetector;

[0044] 23: First feedback loop;

[0045] 3: Whispering-gallery mode microcavity;

[0046] 4: Auxiliary laser generation module;

[0047] 41: Auxiliary laser;

[0048] 42: Fiber optic circulator;

[0049] 43: Second fiber polarization controller;

[0050] 44: Second fiber optic power amplifier;

[0051] 5: Auxiliary laser feedback module;

[0052] 51: Second photodetector;

[0053] 52: Second feedback loop. Detailed Implementation

[0054] The embodiments of the present disclosure will now 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 disclosure. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the embodiments of the present disclosure for ease of explanation. However, it will be apparent that one or more embodiments may be practiced without these specific details. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concepts of the present disclosure.

[0055] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this disclosure. The terms “comprising,” “including,” etc., as used herein indicate the presence of the stated features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0056] 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 are to be interpreted in a manner consistent with the context of this specification, and not in an idealized or overly rigid way.

[0057] When using expressions such as "at least one of A, B, and C", they should generally be interpreted in accordance with the meaning that is commonly understood by a person skilled in the art (e.g., "a system having at least one of A, B, and C" should include, but is not limited to, a system having A alone, a system having B alone, a system having C alone, a system having A and B, a system having A and C, a system having B and C, and / or a system having A, B, and C, etc.).

[0058] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0059] Figure 1 The schematic diagram illustrates the structure of a frequency repetition tuning system based on a microcavity soliton optical frequency comb according to an embodiment of the present invention.

[0060] like Figure 1As shown, an embodiment of the present invention provides a frequency repetition tuning system based on a microcavity soliton optical frequency comb, including: a pump laser generation module 1, a pump laser feedback module 2, a whispering-gallery mode microcavity 3, an auxiliary laser generation module 4, and an auxiliary laser feedback module 5. Pump laser generation module 1 is suitable for providing continuous pump laser; pump laser feedback module 2 is suitable for real-time monitoring of pump laser to achieve the transmission of a first error signal to pump laser generation module 1 to lock the frequency of pump laser after generating microcavity soliton optical frequency comb; whispering-gallery mode microcavity 3 has third-order nonlinearity, anomalous dispersion and generation cascaded four-wave mixing functions, suitable for providing the reaction space for generating microcavity soliton optical frequency comb based on pump laser generated by pump laser generation module 1; auxiliary laser generation module 4 is suitable for providing auxiliary laser to suppress thermal effects generated in whispering-gallery mode microcavity 3 and transmitting it to whispering-gallery mode microcavity 3 to achieve auxiliary microcavity soliton optical frequency comb generation and adjust local dispersion of whispering-gallery mode microcavity 3; auxiliary laser feedback module 5 is suitable for real-time monitoring of auxiliary laser and transmitting a second error signal to auxiliary laser generation module 4 to achieve tuning and locking repetition frequency, wherein the repetition frequency characterizes the frequency interval between two adjacent modes generated based on pump laser in whispering-gallery mode microcavity 3.

[0061] According to an embodiment of the present invention, by introducing an auxiliary laser generation module 4 and an auxiliary laser feedback module 5, the local dispersion within the whispering-gallery mode microcavity 3 is adjusted using the auxiliary laser, thereby achieving decoupling of the repetition frequency and the pump laser, and thus realizing independent and precise adjustment of the repetition frequency.

[0062] According to an embodiment of the present invention, by introducing an auxiliary laser generation module 4 and an auxiliary laser feedback module 5, and by precisely tuning the repetition frequency using the auxiliary laser, the repetition frequency and pump laser frequency of the microcavity soliton optical frequency comb can be locked respectively, further locking the comb tooth frequency of the microcavity soliton optical frequency comb, thereby achieving a stable comb tooth frequency of the microcavity soliton optical frequency comb. This locking method is simple to operate and can be applied to all microcavity soliton optical frequency comb platforms.

[0063] According to an embodiment of the present invention, the pump laser generation module 1 includes a pump laser 11 and an optical fiber beam splitter 12. The pump laser 11 is suitable for generating continuous pump laser; the optical fiber beam splitter 12 has its input end connected to the output end of the pump laser 11 and is suitable for splitting the pump laser beam.

[0064] The pump laser feedback module 2 includes: an optical reference cavity 21, a first photodetector 22, and a first feedback loop 23. The optical reference cavity 21 has its input end connected to the first output port of the fiber optic beam splitter 12, and is suitable for providing a stable optical frequency reference. The first photodetector 22 has its output end connected to its input end, and is suitable for converting the optical signal passing through the optical reference cavity 21 into an electrical signal. The first feedback loop 23 has its input end connected to the output end of the first photodetector 22, and its output end connected to the input end of the pump laser 11. It is suitable for generating a first error signal and loading the first error signal onto the modulation port of the pump laser 11 to lock the pump laser frequency. The second output port of the fiber optic beam splitter 12 is connected to the first port of the whispering-gallery mode microcavity 3.

[0065] According to an embodiment of the present invention, a portion of the pump laser emitted from the output end of the pump laser 11 passes sequentially through the second output port of the fiber beam splitter 12 and the first port of the whispering-gallery mode microcavity 3 to reach the whispering-gallery mode microcavity 3, thereby generating a microcavity soliton optical frequency comb. The portion of the pump laser emitted from the output end of the pump laser 11 enters the optical reference cavity 21 through the first output port of the fiber beam splitter 12, where the optical mode of the reference cavity is detected. The measured optical mode passes through the first feedback loop 23 to generate a first error signal, which enters the current modulation input port of the pump laser 11, locking the frequency of the pump laser to the optical mode of the optical reference cavity 21.

[0066] Figure 2 The diagram illustrates the power variation within a whispering-gallery mode microcavity according to an embodiment of the present invention.

[0067] It should be noted that an oscilloscope can also be connected to the output of the pump laser 11. First, by adjusting the frequency of the pump laser, the oscilloscope displays the frequency stabilized at a certain point. Figure 2 On the solitary step shown ( Figure 2 The arrows indicate the frequency range within which a microcavity soliton optical frequency comb can be generated, thus generating a microcavity soliton optical frequency comb in the whispering-gallery mode microcavity 3. In this stage, the microcavity soliton optical frequency comb is generated by simultaneously controlling the pump laser and the auxiliary laser. The auxiliary laser suppresses thermal effects within the whispering-gallery mode microcavity 3, allowing the pump laser frequency to be stably maintained within the soliton step range. Thereafter, the pump laser frequency is no longer changed and is locked to the optical reference cavity 21 via the first feedback loop 23.

[0068] According to an embodiment of the present invention, the auxiliary laser generation module 4 includes an auxiliary laser 41 and an optical fiber circulator 42. The auxiliary laser 41 is adapted to provide an auxiliary laser that suppresses thermal effects generated in the whispering-gallery mode microcavity 3; the optical fiber circulator 42 is adapted to ensure unidirectional transmission of the auxiliary laser among three ports, wherein the first port of the optical fiber circulator 42 is connected to the output of the auxiliary laser 41.

[0069] The auxiliary laser feedback module 5 includes a second photodetector 51 and a second feedback loop 52. The third port of the fiber optic circulator 42 is connected to the input of the second photodetector 51, and it is used to convert the optical signal passing through the fiber optic circulator 42 into an electrical signal. The input of the second feedback loop 52 is connected to the output of the second photodetector 51, and the output of the second feedback loop 52 is connected to the input of the auxiliary laser 41. It is used to generate a second error signal and load the second error signal onto the modulation port of the auxiliary laser 41 to achieve tuning and locking of the repetition frequency. The second port of the fiber optic circulator 42 is connected to the second port of the whispering-gallery mode microcavity 3.

[0070] According to an embodiment of the present invention, the auxiliary laser emitted from the output end of the auxiliary laser 41 passes sequentially through the first port of the fiber optic circulator 42 and the second port of the whispering-gallery mode microcavity 3 to reach the whispering-gallery mode microcavity 3, thereby assisting in the generation of the microcavity soliton optical frequency comb and adjusting the local dispersion within the whispering-gallery mode microcavity 3, thereby suppressing the thermal effect in the whispering-gallery mode microcavity 3.

[0071] Next, the microcavity soliton optical frequency comb generated in the whispering-gallery mode microcavity 3 is output from the second port of the whispering-gallery mode microcavity 3 and enters the second port of the fiber optic circulator 42. It is then output from the third port of the fiber optic circulator 42 and finally its repetition frequency is measured by the second photodetector 51. The measured repetition frequency generates a second error signal through the second feedback loop 52, which enters the current modulation input of the auxiliary laser 41. Since the auxiliary laser has the function of adjusting the local dispersion within the microcavity, the repetition frequency can be independently adjusted without changing the pump mode frequency, thus enabling adjustment and locking of the repetition frequency. After locking the pump laser frequency and the repetition frequency, the spectrum of the microcavity soliton optical frequency comb is stabilized.

[0072] According to an embodiment of the present invention, the pump laser 11 is a tunable laser, including: a tunable laser and an on-chip semiconductor light source; the auxiliary laser 41 is a tunable laser, including: a tunable laser and an on-chip semiconductor light source; the optical reference cavity 21 includes: a Fabry-Perot optical reference cavity 21 and an on-chip optical reference cavity 21.

[0073] According to an embodiment of the present invention, the first photodetector 22 and the second photodetector 51 have the same structure; the first feedback loop 23 and the second feedback loop 52 have the same structure.

[0074] Figure 3 A flowchart illustrating a frequency repetition rate tuning and frequency stabilization method based on a microcavity soliton optical frequency comb according to an embodiment of the present invention is shown.

[0075] like Figure 3 As shown, the frequency repetition rate tuning and frequency stabilization method based on microcavity soliton optical frequency comb may include steps S301 to S304.

[0076] In operation S301, the pump laser generation module 1 provides a continuous pump laser and transmits it to the whispering-gallery mode microcavity 3 to generate a microcavity soliton optical frequency comb in the whispering-gallery mode microcavity 3.

[0077] In operation S302, the pump laser feedback module 2 is used to monitor the pump laser in real time so that after the microcavity soliton optical frequency comb is generated, the first error signal is transmitted to the pump laser generation module 1 to lock the frequency of the pump laser.

[0078] In operation S303, the auxiliary laser generation module 4 is used to provide an auxiliary laser to suppress the thermal effect generated in the whispering-gallery mode microcavity 3, and transmits it to the whispering-gallery mode microcavity 3 to realize the generation of the auxiliary microcavity soliton optical frequency comb and adjust the local dispersion in the whispering-gallery mode microcavity 3.

[0079] In operation S304, the auxiliary laser feedback module 5 is used to monitor the repetition frequency of the microcavity soliton optical frequency comb in real time and transmits a second error signal to the auxiliary laser generation module 4 to achieve tuning and locking of the repetition frequency.

[0080] According to an embodiment of the present invention, after the pump laser reaches the whispering-gallery mode microcavity 3, a first mode family is excited; after the auxiliary laser reaches the whispering-gallery mode microcavity 3, a second mode family is excited; wherein, the first mode family and the second mode family are different, and the first mode family and the second mode family can be in the same polarization direction or in different polarization directions.

[0081] According to an embodiment of the present invention, the first mode family has multiple modes with different frequencies, each mode corresponding to a comb tooth of a microcavity soliton optical frequency comb, and the frequency interval between the comb teeth of two adjacent microcavity soliton optical frequency combs is called the repetition frequency.

[0082] According to an embodiment of the present invention, in pump mode, the pump laser frequency is locked, and the repetition frequency is determined by the auxiliary laser frequency.

[0083] Figure 4 The diagram illustrates a comparison of different modes and corresponding thermal field distributions within a whispering-gallery mode microcavity according to an embodiment of the present invention.

[0084] Due to the thermo-optical effect, the laser field within the whispering-gallery mode microcavity 3 heats the microcavity, causing a change in its refractive index and consequently altering the frequency of the modes within it. For example... Figure 4 As shown, E represents the laser-excited mode, and T represents the thermal field corresponding to the mode; Figure 4 Figure (a) shows the pump laser excitation mode and the corresponding thermal field. Figure 4 Figure (b) shows the assisted laser excitation modes and their corresponding thermal field distributions. It can be observed that the optical field distributions of the two mode families are different, and the corresponding thermal field distributions are also different, so the effect on the refractive index of the whispering-gallery mode microcavity 3 will also be different.

[0085] According to an embodiment of the present invention, by controlling the frequency and power of the auxiliary laser, the entire system exists within a specific bias range. Within this range, η1dn1 + η2dn2 remains constant, where η1 and η2 are the proportions of the influence of the thermal fields of the pump laser and the auxiliary laser on the microcavity modes excited by the pump laser, respectively, which are related to the magnitude of the temperature changes caused by the two thermal fields; dn1 and dn2 are the influences of the thermal fields of the pump laser and the auxiliary laser on the refractive index of the microcavity modes excited by the pump laser, respectively, which are related to the mode field distribution of the mode family. Therefore, within this specific bias range, changing the frequency of the auxiliary laser does not change the refractive index of the microcavity modes excited by the pump laser, and thus the frequency of the pump mode remains constant. The pump laser frequency does not need to be changed, thereby achieving pump laser frequency locking.

[0086] Figure 5 The diagram illustrates the decoupling and locking of the pump laser frequency and repetition frequency according to an embodiment of the present invention.

[0087] In contrast. Figure 5 Figure (a) in the figure shows the tuning relationship between the pump laser frequency and the repetition frequency when the bias is not within this special range; Figure 5 Figure (b) in the figure shows a schematic diagram of the decoupling and locking of the pump laser frequency and the repetition frequency within this specific bias range; Figure 5 The arrows in the text indicate the direction of frequency spectrum shift.

[0088] like Figure 5 As shown in Figure (a), when the entire system is not within a specific bias range, changing the frequency of the auxiliary laser will cause the pump mode family (including the pump mode itself) to shift due to thermal effects. In this case, to maintain the soliton state, the pump laser frequency needs to move along with the pump mode. Figure 5As shown in Figure (b), when the power and frequency of the auxiliary laser are within the bias range, changing the frequency of the auxiliary laser will not change the pump mode, but the frequency of other modes in the same mode family will change due to the change in refractive index, and the frequency of the responding comb will also change accordingly. This achieves the change of repetition frequency while keeping the pump laser frequency constant.

[0089] Therefore, it can be seen that, in addition to the pump mode, other modes in the pump laser-excited mode family are also affected by thermal effects. Furthermore, due to material dispersion and geometrical dispersion, cavity modes of different frequencies within the same mode family respond differently to the same thermal field. However, within a specific bias range, even if the frequency of the auxiliary laser is changed, the frequency of the pump mode does not change with the frequency of the auxiliary laser, while the frequencies of other modes within the pump mode are affected by changes in the auxiliary laser frequency, with the impact being greater the further away from the pump mode.

[0090] According to an embodiment of the present invention, within this specific bias range, the pump laser frequency can be locked, and the repetition frequency changes with the auxiliary laser frequency. Furthermore, by changing the auxiliary laser frequency, the repetition frequency can be modulated; and by feeding the repetition frequency back to the auxiliary laser frequency in real time, the repetition frequency can be stabilized; and by locking the pump laser frequency onto the optical reference cavity 21, the stability of the entire microcavity soliton optical frequency comb is ultimately achieved.

[0091] Since the comb teeth of the microcavity soliton optical frequency comb can only exist stably within a mode, as the mode frequency changes, the pump laser frequency remains unchanged, and the frequency corresponding to adjacent comb teeth changes due to the change in mode frequency, and the comb tooth frequency of the microcavity soliton optical frequency comb will also change accordingly.

[0092] The comb tooth frequency of the microcavity soliton optical frequency comb is expressed by formula (1):

[0093] f = f pump +μf rep (1);

[0094] In formula (1), f pump f represents the pump laser frequency. rep Let μ represent the repetition frequency, and μ represent the interval between the comb teeth and the pump frequency. Here, the repetition frequency is expressed as the frequency interval between two adjacent comb teeth, and this frequency interval is strictly equal across all comb teeth. Therefore, it can be concluded that once the pump laser frequency and repetition frequency are stable, the frequency corresponding to each comb tooth on the microcavity soliton optical frequency comb can be stabilized.

[0095] Figure 6 The diagram illustrates the relationship between the auxiliary laser frequency and the comb tooth frequency of the microcavity soliton optical frequency comb according to an embodiment of the present invention.

[0096] Figure 6 Figure (a) in the figure shows the relationship between the auxiliary laser frequency and the repetition frequency. Figure 6 Figure (b) shows the relationship between the auxiliary laser frequency and the comb frequency; μ in the figure represents the interval between the comb and the pump frequency.

[0097] like Figure 6 As shown in Figure (a), the repetition frequency and the auxiliary laser frequency exhibit a positive linear relationship; specifically, a 20 MHz change in the auxiliary laser frequency results in an almost linear change in the repetition frequency of 200 kHz. Figure 6 As shown in Figure (b), each line in the figure represents a comb tooth at a different interval from the pump frequency. When the auxiliary laser frequency changes, the change in the comb tooth frequency relative to the initial state is roughly positive or negative linear. The greater the change in the comb tooth frequency corresponding to the mode that is further away from the pump mode, the greater the change in the comb tooth frequency.

[0098] Figure 7 The schematic diagram illustrates the structure of a frequency repetition tuning system based on a microcavity soliton optical frequency comb according to a second embodiment of the present invention.

[0099] like Figure 7 As shown, in this embodiment, the pump laser generation module 1 includes: a pump laser 11, an optical fiber beam splitter 12, and a first optical fiber polarization controller 13. The pump laser 11 is suitable for generating continuous pump laser light; the optical fiber beam splitter 12 has its input end connected to the output end of the pump laser 11, and is suitable for splitting the pump laser beam; the first optical fiber polarization controller 13 has its input end connected to the second output port of the optical fiber beam splitter 12, and its output end connected to the whispering-gallery mode microcavity 3, and is suitable for polarization control of a portion of the pump laser transmitted by the optical fiber beam splitter 12, ensuring that as much of the pump laser light as possible enters the whispering-gallery mode microcavity 3, thereby improving its utilization rate.

[0100] The auxiliary laser generation module 4 includes an auxiliary laser 41, a second fiber polarization controller 43, and a fiber circulator 42. The auxiliary laser 41 is used to provide auxiliary laser light to suppress thermal effects in the whispering-gallery mode microcavity 3. The second fiber polarization controller 43, with its input connected to the auxiliary laser 41, is used to control the polarization of the auxiliary laser emitted by the auxiliary laser 41, ensuring that as much of the auxiliary laser light as possible enters the whispering-gallery mode microcavity 3, thus improving its utilization. The fiber circulator 42 is used to ensure unidirectional transmission of the auxiliary laser light between its three ports; the first port of the fiber circulator 42 is connected to the output of the second fiber polarization controller 43. All other optical components and their positional relationships are identical to those in the first embodiment.

[0101] According to an embodiment of the present invention, a portion of the pump laser emitted from the output end of the pump laser 11 sequentially passes through the second output port of the fiber beam splitter 12, the first fiber polarization controller 13, and the first port of the whispering-gallery mode microcavity 3 to reach the whispering-gallery mode microcavity 3, thereby generating a microcavity soliton optical frequency comb. A portion of the pump laser emitted from the output end of the pump laser 11 enters the optical reference cavity 21 through the first output port of the fiber beam splitter 12, where the optical mode of the reference cavity is detected. The measured optical mode passes through the first feedback loop 23 to generate a first error signal, which enters the current modulation input port of the pump laser 11, locking the frequency of the pump laser to the optical mode of the optical reference cavity 21.

[0102] Figure 8 The schematic diagram illustrates the structure of a frequency repetition tuning system based on a microcavity soliton optical frequency comb according to a third embodiment of the present invention.

[0103] like Figure 8 As shown, in this embodiment, the pump laser generation module 1 includes: a pump laser 11, an optical fiber beam splitter 12, a first optical fiber power amplifier 14, and a first optical fiber polarization controller 13. The pump laser 11 is suitable for generating continuous pump laser light; the optical fiber beam splitter 12 has its input end connected to the output end of the pump laser 11, and is suitable for splitting the pump laser beam; the first optical fiber power amplifier 14 has its input end connected to the second output port of the optical fiber beam splitter 12, and is suitable for amplifying the power of a portion of the pump laser transmitted by the optical fiber beam splitter 12; the first optical fiber polarization controller 13 has its input end connected to the output end of the first optical fiber power amplifier 14, and its output end connected to the whispering-gallery mode microcavity 3, and is suitable for polarization control of the pump laser transmitted by the first optical fiber power amplifier 14, ensuring that as much of the pump laser light as possible enters the whispering-gallery mode microcavity 3, thereby improving its utilization rate.

[0104] The auxiliary laser generation module 4 includes: an auxiliary laser 41, a second fiber power amplifier 44, a second fiber polarization controller 43, and a fiber circulator 42. The auxiliary laser 41 is used to provide auxiliary laser light to suppress thermal effects in the whispering-gallery mode microcavity 3. The second fiber power amplifier 44 has its input connected to the auxiliary laser 41 and amplifies the power of the auxiliary laser emitted by the auxiliary laser 41. The second fiber polarization controller 43 has its input connected to the output of the second fiber power amplifier 44 and is used to control the polarization of the auxiliary laser transmitted by the second fiber power amplifier 44, ensuring that the auxiliary laser enters the whispering-gallery mode microcavity 3 as much as possible, thus improving its utilization. The fiber circulator 42 is used to ensure unidirectional transmission of the auxiliary laser among its three ports; wherein, the first port of the fiber circulator 42 is connected to the output of the second fiber polarization controller 43. The other optical components and their positional relationships are exactly the same as in the first embodiment.

[0105] According to an embodiment of the present invention, a portion of the pump laser emitted from the output end of the pump laser 11 passes sequentially through the second output port of the fiber beam splitter 12, the first fiber power amplifier 14, the first fiber polarization controller 13, and the first port of the whispering-gallery mode microcavity 3 to reach the whispering-gallery mode microcavity 3, thereby generating a microcavity soliton optical frequency comb. A portion of the pump laser emitted from the output end of the pump laser 11 enters the optical reference cavity 21 through the first output port of the fiber beam splitter 12, where the optical mode of the reference cavity is detected. The measured optical mode is then processed by the first feedback loop 23 to generate a first error signal, which enters the current modulation input port of the pump laser 11, locking the frequency of the pump laser to the optical mode of the optical reference cavity 21.

[0106] According to an embodiment of the present invention, by introducing an auxiliary laser generation module 4 and an auxiliary laser feedback module 5, the local dispersion within the whispering-gallery mode microcavity 3 is adjusted using the auxiliary laser, thereby achieving decoupling of the repetition frequency and the pump laser, and thus realizing independent and precise adjustment of the repetition frequency.

[0107] According to an embodiment of the present invention, by introducing an auxiliary laser generation module 4 and an auxiliary laser feedback module 5, and by precisely tuning the repetition frequency using the auxiliary laser, the repetition frequency and pump laser frequency of the microcavity soliton optical frequency comb can be locked respectively, further locking the comb tooth frequency of the microcavity soliton optical frequency comb, thereby achieving a stable comb tooth frequency. This locking method is simple to operate and has broad application prospects in the field of precision metrology. Specifically, it can be applied to all microcavity soliton optical frequency comb platforms, and has significant value and importance for promoting the practical application of microcavity soliton optical frequency combs.

[0108] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A frequency repetition rate tuning system based on a microcavity soliton optical frequency comb, comprising: Pump laser generation module (1), suitable for providing continuous pump laser; The pump laser feedback module (2) is suitable for real-time monitoring of the pump laser, so as to transmit a first error signal to the pump laser generation module (1) after generating the microcavity soliton optical frequency comb to lock the frequency of the pump laser; The whispering-gallery mode microcavity (3) has third-order nonlinearity, anomalous dispersion and generation cascaded four-wave mixing function, and is suitable for providing a reaction space for generating the soliton optical frequency comb of the microcavity based on the pump laser generated by the pump laser generation module (1); The auxiliary laser generation module (4) is adapted to provide an auxiliary laser that suppresses the thermal effect generated in the whispering-gallery mode microcavity (3) and transmits it to the whispering-gallery mode microcavity (3) to assist in the generation of the microcavity soliton optical frequency comb and adjust the local dispersion in the whispering-gallery mode microcavity (3) so as to independently adjust the repetition frequency without changing the frequency of the pump laser, thereby locking the repetition frequency. The auxiliary laser feedback module (5) is suitable for real-time monitoring of the repetition frequency and transmitting a second error signal to the auxiliary laser generation module (4) to achieve tuning and locking of the repetition frequency, wherein the repetition frequency characterizes the frequency interval between two adjacent modes of the microcavity soliton optical frequency comb generated based on the pump laser in the whispering-gallery mode microcavity (3); Within the target bias range, η1dn1+η2dn2 of the repetition rate tuning system remains unchanged, where η1 and η2 are the proportions of the influence of the thermal fields of the pump laser and the auxiliary laser on the microcavity mode excited by the pump laser, respectively; dn1 and dn2 are the influences of the thermal fields of the pump laser and the auxiliary laser on the refractive index of the microcavity mode excited by the pump laser, respectively; within the target bias range, when the frequency of the auxiliary laser is changed, the refractive index of the microcavity mode excited by the pump laser remains unchanged, and the frequency of the pump mode remains unchanged, thereby achieving frequency locking of the pump laser.

2. The system according to claim 1, wherein, The pump laser generation module (1) includes: A pump laser (11) is adapted to generate the continuous pump laser; Fiber beam splitter (12), the input end of which is connected to the output end of the pump laser (11), is suitable for splitting the pump laser beam; The pumped laser feedback module (2) includes: An optical reference cavity (21) is provided, the input end of which is connected to the first output port of the fiber optic beam splitter (12), and is suitable for providing a stable optical frequency reference. The first photodetector (22) is suitable for converting optical signals passing through the optical reference cavity (21) into electrical signals; The first feedback loop (23) has its input end connected to the output end of the first photodetector (22) and its output end connected to the input end of the pump laser (11). It is suitable for generating the first error signal and loading the first error signal onto the modulation port of the pump laser (11) to lock the frequency of the pump laser. The second output port of the fiber beam splitter (12) is connected to the first port of the whispering-gallery mode microcavity (3).

3. The system according to claim 2, wherein, The auxiliary laser generation module (4) includes: An auxiliary laser (41) is adapted to provide an auxiliary laser that suppresses thermal effects generated in the whispering-gallery mode microcavity; A fiber optic circulator (42) is used to ensure unidirectional transmission of the auxiliary laser among three ports, wherein the first port of the fiber optic circulator (42) is connected to the output of the auxiliary laser (41); The auxiliary laser feedback module (5) includes: The second photodetector (51) has its third port connected to the input end of the fiber optic circulator (42), which is suitable for converting the optical signal passing through the fiber optic circulator (42) into an electrical signal. The second feedback loop (52) has its input end connected to the output end of the second photodetector (51) and its output end connected to the input end of the auxiliary laser (41). It is suitable for generating the second error signal and loading the second error signal onto the modulation port of the auxiliary laser (41) to achieve the tuning and locking of the repetition frequency. The second port of the fiber optic circulator (42) is connected to the second port of the whispering-gallery mode microcavity (3).

4. The system according to claim 3, wherein, The pump laser (11) is a tunable laser, including: a tunable laser and an on-chip semiconductor light source; The auxiliary laser (41) is a tunable laser, including: a tunable laser and an on-chip semiconductor light source; The optical reference cavity (21) includes either a Fabry-Perot optical reference cavity or an on-chip optical reference cavity.

5. The system according to claim 4, wherein, The whispering-gallery mode microcavity (3) is applicable to two different mode families based on the pump laser and the auxiliary laser excitation.

6. The system according to claim 2 or 3, wherein, The first photodetector (22) has the same structure as the second photodetector (51); The first feedback loop (23) has the same structure as the second feedback loop (52).

7. A frequency stabilization method based on a microcavity soliton optical frequency comb, applied to a frequency repetition rate tuning system based on a microcavity soliton optical frequency comb as described in any one of claims 1 to 6, the method comprising: A pump laser generation module (1) is used to provide a continuous pump laser and transmit it to a whispering-gallery mode microcavity (3) to generate a microcavity soliton optical frequency comb in the whispering-gallery mode microcavity. The pump laser is monitored in real time using the pump laser feedback module (2) so that after the microcavity soliton optical frequency comb is generated, the first error signal is transmitted to the pump laser generation module (1) to lock the frequency of the pump laser. The auxiliary laser generation module (4) is used to provide an auxiliary laser to suppress the thermal effect generated in the whispering-gallery mode microcavity and transmit it to the whispering-gallery mode microcavity (3) to assist in the generation of the microcavity soliton optical frequency comb and adjust the local dispersion in the whispering-gallery mode microcavity (3); The repetition frequency of the microcavity soliton optical frequency comb is monitored in real time by the auxiliary laser feedback module (5), and the second error signal is transmitted to the auxiliary laser generation module (4) to achieve tuning and locking of the repetition frequency.

8. The method according to claim 7, wherein, After the pump laser reaches the whispering-gallery mode microcavity (3), it excites the first mode family; After the auxiliary laser reaches the whispering-gallery mode microcavity (3), it excites the second mode family; The first mode family is different from the second mode family.

9. The method according to claim 8, wherein, The first mode family has multiple modes with different frequencies. Each mode corresponds to a tooth of the microcavity soliton optical frequency comb. The frequency interval between two adjacent teeth of the microcavity soliton optical frequency comb is called the repetition frequency.

10. The method according to claim 9, wherein, In pump mode, the pump laser frequency is locked, and the repetition frequency is determined by the auxiliary laser frequency.

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