Apparatus and method suitable for generating a frequency stabilized microcavity optical frequency comb

Abstract

The present disclosure provides a device suitable for generating a frequency-stable microcavity optical frequency comb, comprising: a light source part configured to emit a light beam; a beam splitting device configured to split the light beam emitted by the light source part into a plurality of first light beams; a light source frequency determination unit connected with a first output port of the beam splitting device, the adjustment frequency being determined based on the absorption of the first light beams by atoms in the light source frequency determination unit, and the light source part adjusting the frequency of the emitted second light beams based on the adjustment frequency; a resonant microcavity connected with the light source frequency determination unit, the second light beams generating a first microcavity optical frequency comb in the resonant microcavity; and a modulation unit arranged between a second output port of the beam splitting device and the resonant microcavity, configured to modulate the second light beams into third light beams with repetition frequency information based on the repetition frequency of the first microcavity optical frequency comb, and the third light beams generating a second microcavity optical frequency comb in the resonant microcavity.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the technical field of microcavity optical frequency comb, and particularly to a device and method for generating frequency-stable microcavity optical frequency comb. BACKGROUND

[0002] Optical frequency comb is a series of equally spaced frequency comb teeth in the frequency domain, which can cover all wavelengths in its frequency range and can be traced back to the microwave frequency standard. There are several types of optical frequency combs, including mode-locked laser optical frequency comb, electro-optical optical frequency comb, quantum cascade laser optical frequency comb and microcavity optical frequency comb. Among them, the microcavity optical frequency comb has the characteristics of integration, low power consumption, high repetition frequency and wide waveband, and has important application value in coherent optical communication, precision spectroscopy and optical ranging.

[0003] How to accurately regulate and stabilize the frequency spectrum of the optical frequency comb is crucial for the application of the microcavity optical frequency comb. The frequency spectrum of the microcavity optical frequency comb is usually determined by the repetition frequency and the offset frequency, but the offset frequency is difficult to obtain and requires a high frequency spectrum expansion. On the other hand, the existing scheme for regulating and stabilizing the frequency spectrum of the optical frequency comb requires a large reference system, which is not conducive to miniaturization. SUMMARY

[0004] To at least partially overcome the technical defects of at least one of the above-mentioned or other inventions, at least one embodiment of the present disclosure provides a device and method for generating frequency-stable microcavity optical frequency comb. By setting the light source frequency determination unit and the modulation unit, the frequency-stable microcavity optical frequency comb can be outputted, and the frequency of the optical comb teeth can be directly determined by the atomic transition line.

[0005] According to an aspect of the present disclosure, a device for generating frequency-stable microcavity optical frequency comb is provided, comprising: a light source part configured to emit a light beam; a beam splitting device configured to split the light beam emitted by the light source part into a plurality of first light beams; a light source frequency determination unit connected to a first output port of the beam splitting device, which determines an adjustment frequency based on the absorption of the first light beam by atoms in the light source frequency determination unit, and the light source part adjusts the frequency of the second light beam based on the adjustment frequency; a resonant microcavity connected to the light source frequency determination unit, the second light beam generates a first microcavity optical frequency comb in the resonant microcavity; and a modulation unit arranged between a second output port of the beam splitting device and the resonant microcavity, which is configured to modulate the second light beam into a third light beam with repetition frequency information based on the repetition frequency of the first microcavity optical frequency comb, and the third light beam generates a second microcavity optical frequency comb in the resonant microcavity.

[0006] In some embodiments, the light source frequency determination unit comprises: a frequency doubling crystal connected with the first output port of the beam splitting device, configured to perform frequency conversion on the first light beam so that the wavelength of the converted first light beam matches the transition energy level of the atom; an atomic cell connected with the frequency doubling crystal, through which the frequency-converted first light beam is emitted after being absorbed by the atom; a photodetector configured to convert the optical signal of the first light beam absorbed by the atom in the atomic cell into an electrical signal; and a feedback system connected with the photodetector, configured to calculate an error signal based on the electrical signal and determine the adjustment frequency based on the error signal.

[0007] In some embodiments, the modulation unit comprises: an electro-optical modulator arranged between the second output port of the beam splitting device and the resonant microcavity, configured to modulate the second light beam; and a microwave source connected with the electro-optical modulator, configured to modulate the electro-optical modulator, wherein the modulation signal frequency of the microwave source is set based on the repetition frequency of the first microcavity optical frequency comb, so that the third light beam obtained after modulation by the electro-optical modulator carries the repetition frequency information of the first microcavity optical frequency comb.

[0008] In some embodiments, further comprising: a plurality of transmission units through which the third light beam is unidirectionally injected into the resonant microcavity; and an auxiliary unit connected with the resonant microcavity, configured to emit an auxiliary light beam to balance the thermal effect in the case that a microcavity optical frequency comb is generated in the resonant microcavity.

[0009] In some embodiments, the auxiliary light beam is unidirectionally injected into the resonant microcavity through the transmission unit.

[0010] In some embodiments, the plurality of transmission units comprises: a fiber polarization controller arranged between the light source part and / or the auxiliary unit and the resonant microcavity, configured to control the polarization of the third light beam and / or the auxiliary light beam; and a fiber isolator connected with the fiber polarization controller, configured to unidirectionally inject the third light beam and / or the auxiliary light beam into the resonant microcavity.

[0011] In some embodiments, the plurality of transmission units further comprises: a fiber amplifier, one end of which is connected with the light source part and / or the auxiliary unit, and the other end of which is connected with the fiber polarization controller, the fiber amplifier being configured to amplify the power of the third light beam and / or the auxiliary light beam.

[0012] In some embodiments, the feedback system comprises: an oscilloscope configured to obtain a saturated absorption spectrum of the atom based on the electrical signal; a modulator configured to obtain the error signal based on an absorption peak in the saturated absorption spectrum; and a proportional-integral-derivative feedback device configured to determine the adjustment frequency based on the error signal.

[0013] In some embodiments, the atomic cell is a rubidium atomic cell.

[0014] According to another aspect of the present application, there is provided a method for generating a frequency-stable microcavity optical frequency comb using the above device, comprising: after the first light beam is injected into the light source frequency determination unit, determining the adjustment frequency based on the absorption of the first light beam by the atom, so that the frequency of the second light beam is kept within a preset range; modulating the second light beam into a third light beam with repetition frequency information based on the repetition frequency of the first microcavity optical frequency comb generated by the second light beam in the resonant microcavity; and injecting the third light beam into the resonant microcavity and locking the repetition frequency through an injection locking process to generate a second microcavity optical frequency comb in the resonant microcavity.

[0015] According to the device and method for generating a frequency-stable microcavity optical frequency comb according to the embodiments of the present disclosure, the light beam emitted by the laser can be stably locked to the transition energy level of the atom by setting the light source frequency determination unit, and the second light beam locked to the transition energy level of the atom can generate a first microcavity optical frequency comb with a stable center frequency in the resonant microcavity. The repetition frequency of the first microcavity optical frequency comb can be modulated onto the second light beam to form a third light beam by setting the modulation unit, and since the third light beam obtained after modulation has similar frequency components to the first microcavity optical frequency comb, the purpose of stabilizing the repetition frequency of the first microcavity optical frequency comb can be achieved through an injection locking process after the third light beam is injected into the first microcavity optical frequency comb. Therefore, a second microcavity optical frequency comb with frequency-stable teeth can be formed in the resonant microcavity after the third light beam is injected into the first microcavity optical frequency comb. In addition, the frequency domain of each tooth of the second microcavity optical frequency comb can be directly determined by the transition frequency of the atom, thereby avoiding the need to set multiple feedback systems and multiple additional reference light sources, simplifying the complexity of the system, and avoiding the need to detect the offset frequency, reducing the requirement for spectral broadening of the optical frequency comb system, and enabling the system to be extended to more microcavity optical frequency comb systems. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 A schematic diagram of the device for generating a frequency-stable microcavity optical frequency comb according to the embodiments of the present disclosure is shown schematically;

[0017] Figure 2Fig. 6 schematically shows a cross-sectional view of a resonant microcavity after encapsulation of the resonant microcavity suitable for generating a frequency-stable microcavity optical frequency comb according to an embodiment of the present disclosure;

[0018] Figure 3 Fig. 7 schematically shows a flow chart of a method of generating a frequency-stable microcavity optical frequency comb using the above-described apparatus according to an embodiment of the present disclosure; and

[0019] Figure 4 Fig. 8 schematically shows a frequency-stable microcavity optical frequency comb generated using the above-described method according to an embodiment of the present disclosure.

[0020] BRIEF DESCRIPTION OF DRAWINGS

[0021] 1: light source unit;

[0022] 2: beam splitting apparatus;

[0023] 3: light source frequency determination unit;

[0024] 31: frequency-doubling crystal;

[0025] 32: atomic gas cell;

[0026] 33: photodetector;

[0027] 34: feedback system;

[0028] 4: resonant microcavity;

[0029] 5: modulation unit;

[0030] 51: electro-optic modulator;

[0031] 52: microwave source;

[0032] 6: plurality of transmission units;

[0033] 61: fiber amplifier;

[0034] 62: fiber polarization controller;

[0035] 63: fiber isolator;

[0036] 7: auxiliary unit;

[0037] 8: optical fiber;

[0038] 9: optical fiber array;

[0039] 10: waveguide. DETAILED DESCRIPTION

[0040] In order to make the objects, technical solutions and advantages of the present disclosure clearer, the following will further describe the present disclosure in detail with reference to specific embodiments and drawings. However, the present application can be implemented in different forms and should not be interpreted as limited to the embodiments presented here. On the contrary, the embodiments are provided to make the disclosure thorough and complete and to fully convey the scope of the present application to those skilled in the art. In the drawings, the sizes and relative sizes of layers and regions can be exaggerated for clarity, and the same reference numerals represent the same elements throughout.

[0041] In the following, embodiments of the present application will be described with reference to the drawings. It should be understood, however, that these descriptions are merely exemplary and are not intended to limit the scope of the present application. In the following detailed description of the embodiments, numerous specific details are set forth in order to provide a thorough understanding of the embodiments of the present application. However, it will be apparent to one of ordinary skill in the art that the embodiments can be practiced without these specific details. In addition, in the following description, descriptions of well-known structures and techniques have been omitted to avoid unnecessarily obscuring the concept of the present application.

[0042] The terminology used herein is for the purpose of describing specific embodiments only and is not intended to limit the present application. The terms "comprising," "including," and the like as used herein specify the presence of stated features, steps, operations, and / or components, but do not preclude the presence or addition of one or more other features, steps, operations, or components.

[0043] All terms used herein, including technical and scientific terms, have the meanings commonly understood by one of ordinary skill in the art, unless otherwise defined. It should be noted that the terms used herein should be interpreted as having meanings consistent with the context of the specification, and should not be interpreted in an idealized or overly formal manner.

[0044] In order for those skilled in the art to understand the technical solutions of the present application, the following technical terms are explained.

[0045] In the case of using expressions similar to "at least one of A, B, and C, etc.", it should be generally interpreted as having the meaning of including at least one of the items listed after the conjunction, without excluding others not listed (e.g., "a system having at least one of A, B, and C" should include, but not be limited to, a system having A alone, a system having B alone, a system having C alone, a system having both A and B, a system having both A and C, a system having both B and C, and / or a system having A, B, and C, etc.). In the case of using expressions similar to "at least one of A, B, or C, etc.", it should be generally interpreted as having the meaning of including at least one of the items listed after the conjunction, without excluding others not listed (e.g., "a system having at least one of A, B, or C" should include, but not be limited to, a system having A alone, a system having B alone, a system having C alone, a system having both A and B, a system having both A and C, a system having both B and C, and / or a system having A, B, and C, etc.).

[0046] Figure 1 A schematic diagram of an apparatus for generating a frequency-stable microcavity optical frequency comb is shown.

[0047] As shown in Figure 1 The apparatus for generating a frequency-stable microcavity optical frequency comb provided by the present disclosure includes a light source part 1, a beam splitting device 2, a light source frequency determination unit 3, a resonant microcavity 4, and a modulation unit 5.

[0048] Specifically, the light source part 1 is configured to emit a light beam. The beam splitting device 2 is configured to split the light beam emitted by the light source part 1 into multiple first light beams. The light source frequency determination unit 3 is connected to the first output port of the beam splitting device 2, and the adjustment frequency is determined based on the absorption of the first light beam by the atoms in the light source frequency determination unit 3. The light source part 1 adjusts the frequency of the emitted second light beam based on the adjustment frequency. The resonant microcavity 4 is connected to the light source frequency determination unit 3, and the second light beam generates a first microcavity optical frequency comb in the resonant microcavity 4. The modulation unit 5 is arranged between the second output port of the beam splitting device 2 and the resonant microcavity 4, and is configured to modulate the second light beam into a third light beam with repetition frequency information based on the repetition frequency of the first microcavity optical frequency comb. The third light beam generates a second microcavity optical frequency comb in the resonant microcavity 4.

[0049] The apparatus for generating a frequency-stable microcavity optical frequency comb according to the above-mentioned embodiments of the present disclosure, by splitting the light beam emitted by the light source part 1 into multiple first light beams through the beam splitting device 2, and by the absorption of the first light beam by the atoms in the light source frequency determination unit 3, the adjustment frequency that needs to be adjusted by the light source part 1 can be determined. Specifically, the absorption of the first light beam by the atoms in the light source frequency determination unit 3 can be determined by the atomic absorption spectrum. For example, the frequency of the light beam emitted by the light source part 1 can be adjusted to be on the atomic absorption peak to achieve the frequency locking of the light beam to the transition energy level of the atom. For example, by observing the change of the atomic absorption peak in real time, the frequency of the light beam emitted by the light source part 1 can be adjusted to achieve the stability of the light beam emitted by the light source part 1 on the same atomic absorption peak. The light source part 1 can use a pump laser, and the beam splitting device 2 can use a fiber beam splitter. It should be noted that the first light beam and the second light beam can be continuously changed, for example, the second light beam emitted after adjustment can become a new first light beam after splitting by the beam splitting device 2 and enter the light source frequency determination unit 3.

[0050] Further, the first microcavity optical frequency comb can be generated by injecting a second light beam modulated and locked to the transition energy level of the atom into the resonant microcavity 4, modulating the repetition frequency of the first microcavity optical frequency comb on the second light beam, and then injecting a modulated third light beam into the resonant microcavity 4 to determine the frequency-stable microcavity optical frequency comb. For example, the repetition frequency of the first microcavity optical frequency comb can be modulated on the second light beam by a modulation unit 5, which can be any device capable of frequency modulation.

[0051] According to the device for generating a frequency-stable microcavity optical frequency comb, the frequency of the light beam emitted by the laser can be stably locked to the transition energy level of the atom by the light source frequency determination unit 3, and the second light beam locked to the transition energy level of the atom can generate a first microcavity optical frequency comb with a stable center frequency in the resonant microcavity 4. The repetition frequency of the first microcavity optical frequency comb can be modulated on the second light beam by the modulation unit 5 to form a third light beam. Since the third light beam obtained after modulation has similar frequency components to the first microcavity optical frequency comb, the purpose of stabilizing the repetition frequency of the first microcavity optical frequency comb can be achieved after the third light beam is injected into the first microcavity optical frequency comb. Therefore, a second microcavity optical frequency comb with stable comb tooth frequencies can be formed in the resonant microcavity 4 after the third light beam is injected into the first microcavity optical frequency comb, and the frequency domain of each comb tooth of the second microcavity optical frequency comb can be directly determined by the transition frequency of the atom. In this way, the complexity of the system can be simplified by avoiding the need to set up multiple feedback systems and multiple additional reference light sources, and the requirement for spectral broadening of the optical frequency comb system can be reduced by avoiding the need to detect the offset frequency, which can be extended to more microcavity optical frequency comb systems.

[0052] In some embodiments, the light source frequency determination unit 3 includes a frequency-doubling crystal 31, an atomic cell 32, a photodetector 33, and a feedback system 34.

[0053] Specifically, the frequency-doubling crystal 31 is connected to the first output port of the beam splitting device 2 and is configured to perform frequency conversion on the first light beam so that the wavelength of the converted first light beam matches the transition energy level of the atom. The frequency-doubling crystal 31 can be a lithium niobate frequency-doubling crystal. The atomic cell 32 is connected to the frequency-doubling crystal 31, and the frequency-converted first light beam is emitted after being absorbed by the atoms in the atomic cell 32. The atomic cell 32 can be a rubidium atomic cell. The photodetector 33 is configured to convert the optical signal of the first light beam absorbed by the atoms in the atomic cell 32 into an electrical signal. The feedback system 34 is connected to the photodetector 33 and is configured to calculate an error signal based on the electrical signal and determine an adjustment frequency based on the error signal.

[0054] Further, after the first light beam enters the frequency doubling crystal 31, the frequency doubling crystal 31 can cause frequency conversion of the first light beam. For example, the wavelength of the light beam before entering the frequency doubling crystal 31 is 1560.48 nm, and after passing through the frequency doubling crystal 31, the wavelength is converted to 780.24 nm, so that the wavelength of the light beam after frequency doubling can match the transition energy level of the atoms in the atomic cell 32, so that the atoms in the atomic cell 32 can be caused to transition after the light beam enters the atomic cell 32, and in the case of scanning the absorbed light beam, the saturated absorption spectrum of the atoms can be observed. The photodetector 33 converts the optical signal of the atomic saturated absorption spectrum into an electrical signal. The feedback system 34 can determine the adjustment frequency of the light source unit 1 by converting the electrical signal obtained by the photodetector 33 into an error signal, and by the error signal. Through the above process, the frequency of the light beam emitted by the light source unit 1 can be detected and adjusted in real time, so that the light source unit 1 emits a stable light beam, and the emitted light beam is locked to the transition energy level of the atoms.

[0055] In some embodiments, the feedback system 34 can include an oscilloscope, a proportional-integral-derivative feedback device, and a modem.

[0056] Specifically, the oscilloscope can be used to observe the saturated absorption spectrum of the atoms based on the electrical signal converted by the photodetector 33. The modem can calculate an error signal based on the absorption peak in the saturated absorption spectrum. The proportional-integral-derivative feedback device can determine the adjustment frequency of the light source unit 1 based on the error signal, so that the light source unit 1 emits a stable light beam and the emitted light beam can be locked to the transition energy level of the atoms.

[0057] In some embodiments, the modulation unit 5 includes an electro-optical modulator 51 and a microwave source 52.

[0058] Specifically, the electro-optical modulator 51 is arranged between the second output port of the beam splitting device 2 and the resonant microcavity 4, and is configured to modulate the second light beam. The microwave source 52 is connected to the electro-optical modulator 51 and is configured to modulate the electro-optical modulator 51. The modulation signal frequency of the microwave source 52 is set based on the repetition frequency of the first microcavity optical frequency comb, so that the third light beam obtained after the electro-optical modulator 51 is modulated carries the repetition frequency information of the first microcavity optical frequency comb.

[0059] Further, the electro-optical modulator 51 can be modulated by the microwave source 52, and the second light beam can be modulated by the modulated electro-optical modulator 51. For example, the repetition frequency of the first microcavity optical frequency comb can be modulated on the microwave source 52. The electro-optical modulator 51 can be modulated by the microwave source 52, and the modulated electro-optical modulator 51 can modulate the second light beam into a third light beam. The frequency information of the third light beam can include at least one of the frequency of the second light beam, the frequency of the second light beam plus the repetition frequency of the first microcavity optical frequency comb, and the frequency of the second light beam minus the repetition frequency of the first microcavity optical frequency comb. In other words, the third light beam can be modulated by the microwave source 52 and the electro-optical modulator 51 to have the repetition frequency information of the first microcavity optical frequency comb. After the third light beam enters the resonant microcavity 4, the repetition frequency is locked to the microwave source 52 based on the repetition frequency setting of the first microcavity optical frequency comb through the injection locking process, and a frequency-stable microcavity optical frequency comb is generated in the resonant microcavity 4 without the need to obtain the offset frequency again.

[0060] In some embodiments, the device suitable for generating a frequency-stable microcavity optical frequency comb further comprises a plurality of transmission units 6 and an auxiliary unit 7.

[0061] Specifically, the third light beam can be unidirectionally injected into the resonant microcavity 4 through the plurality of transmission units 6. The auxiliary light beam can also be unidirectionally injected into the resonant microcavity 4 through the plurality of transmission units 6.

[0062] The transmission unit 6 can include a fiber amplifier 61, a fiber polarization controller 62, and a fiber isolator 63. The fiber polarization controller 62 is arranged between the light source part 1 and / or the auxiliary unit 7 and the resonant microcavity 4, and can be used to control the polarization of at least one of the third light beam and the auxiliary light beam. The fiber isolator 63 is connected to the fiber polarization controller 62, and can be used to unidirectionally inject at least one of the third light beam and the auxiliary light beam into the resonant microcavity 4, preventing the reflected light beam from damaging the fiber amplifier 61. The fiber amplifier 61 is connected to the light source part 1 and / or the auxiliary unit 7 at one end, and connected to the fiber polarization controller 62 at the other end, and can be used to amplify the power of at least one of the third light beam and the auxiliary light beam. The fiber isolator 63 can be replaced by a fiber circulator, which also achieves similar effects. The auxiliary unit 7 is connected to the resonant microcavity 4, and can be used to emit the auxiliary light beam to balance the thermal effect in the process of generating the microcavity optical frequency comb in the resonant microcavity 4. Specifically, the resonant microcavity 4 has a strong thermal effect, and the auxiliary unit 7 emits the auxiliary light beam in the opposite direction of the third light beam to balance the thermal effect in the resonant microcavity 4, thereby assisting in generating the second microcavity optical frequency comb.

[0063] Figure 2Fig. 3 schematically shows a cross-sectional view of the packaged resonant microcavity according to an embodiment of the present disclosure.

[0064] As shown in Fig. 3, the packaged resonant microcavity includes a resonant microcavity 4, an optical fiber 8, an optical fiber array 9, and a waveguide 10. Specifically, the light beam enters the optical fiber array 9 through the optical fiber 8, forms an array to couple with the waveguide 10, and generates a microcavity optical frequency comb inside the resonant microcavity 4 through the waveguide 10. After the optical fiber array 9 is aligned with the waveguide 10, the two are fixed by using a low refractive index glue to ensure the relative stability of the package. Figure 2

[0065] Fig. 4 schematically shows a flowchart of a method for generating a frequency-stable microcavity optical frequency comb according to an embodiment of the present disclosure. Figure 3 As shown in Fig. 4, the method can include operations S301-S303.

[0066] Figure 3 At operation S301, after a first light beam is injected into a light source frequency determination unit, the frequency of a second light beam is adjusted based on the absorption of the first light beam by atoms, so that the frequency of the second light beam is kept within a preset range.

[0067] At operation S301, after a first light beam is injected into a light source frequency determination unit, the frequency of a second light beam is adjusted based on the absorption of the first light beam by atoms, so that the frequency of the second light beam is kept within a preset range.

[0068] At operation S302, the second light beam is modulated into a third light beam with repetition frequency information based on the repetition frequency of a first microcavity optical frequency comb generated by the second light beam in the resonant microcavity.

[0069] At operation S303, the third light beam is injected into the resonant microcavity and the repetition frequency is locked through an injection locking process, and a second microcavity optical frequency comb is generated in the resonant microcavity.

[0070] ​According to the embodiment of the present disclosure, the light source frequency determination unit 3 can adjust the first light beam to the second light beam which is kept in the preset range, that is, the light emitting unit can emit a stable light beam, and in the process, considering the absorption of the atom to the light beam, the light beam emitted by the light source part 1 can be locked to the atomic transition energy level. Further, after the stable second light beam is injected into the resonant microcavity 4, the first microcavity optical frequency comb can be generated. After the repetition frequency of the first microcavity optical frequency comb is modulated to the second light beam, the third light beam with repetition frequency information can be obtained. After the third light beam is injected into the resonant microcavity 4, the third light beam is injected into the first microcavity optical frequency comb, and through the injection locking process, the second microcavity optical frequency comb with frequency stable comb tooth frequency can be generated. The frequency domain of each comb tooth of the generated second microcavity optical frequency comb can be directly determined by the transition frequency of the atom, which can avoid setting multiple feedback systems and multiple additional reference light sources, simplify the complexity of the system, and at the same time avoid the detection of the offset frequency, thereby reducing the requirement for the spectral broadening of the optical frequency comb system and expanding to more optical frequency comb systems.

[0071] Embodiment:

[0072] Taking the light source part 1 as the pump laser 1, the beam splitting device 2 as the fiber beam splitter 2, the frequency doubling crystal 31 as the lithium niobate frequency doubling crystal 31, and the auxiliary light beam as the auxiliary laser as an example, the resonant microcavity 4 is a micro-ring resonant microcavity 4.

[0073] After the pump laser 1 is split by the fiber beam splitter 2, part of the laser is frequency converted by the lithium niobate frequency doubling crystal 31. After the pump laser 1 after frequency doubling passes through the rubidium atom cell 32, the photodetector 33 can convert the detected optical signal into an electrical signal and send it to the feedback system 34. The feedback system 34 can detect the saturated absorption spectrum of the rubidium atom through the oscilloscope, and obtain the error signal through the detection of the change of the absorption peak of the saturated absorption spectrum of the rubidium atom and the modulator. Through the error signal and the proportional-integral-derivative feedback device, the adjustment frequency of the light beam emitted by the pump laser 1 can be determined, so that the pump laser 1 emits a stable light beam and the frequency is locked to the saturated absorption spectrum of the rubidium atom.

[0074] After the adjusted laser is injected into the micro-ring resonant microcavity 4, the first microcavity optical frequency comb with a stable center frequency can be generated. After the repetition frequency of the first microcavity optical frequency comb is injected into the microwave source 52, the laser with repetition frequency information can be generated by modulating the laser by the electro-optical modulator 51, so as to generate the second microcavity optical frequency comb with stable repetition frequency.

[0075] Figure 4A schematic diagram of a frequency stabilized microcavity optical frequency comb generated by the above method is shown.

[0076] As shown in the embodiments of the present disclosure, a second microcavity optical frequency comb can be generated after the thermal effect in the auxiliary laser balanced cavity. Figure 4

[0077] The microcavity optical frequency comb with stable center frequency and repetition frequency can be generated by the above method.

[0078] In the embodiments of the present disclosure, the above devices, such as a rubidium atom cell, an electro-optical modulator, a lithium niobate crystal, and a micro-ring resonant microcavity, can be integrated, and thus the device for generating a microcavity optical frequency comb can be miniaturized and integrated, and can be applied in multiple practical scenarios.

[0079] According to the above description, those skilled in the art should have a clear understanding of the device and method for generating a frequency stabilized microcavity optical frequency comb according to the present disclosure.

[0080] It should be further noted that the directional phrases mentioned in the embodiments, such as "up", "down", "front", "back", "left", "right", etc., are only the directions of the drawings and are not intended to limit the protection scope of the present disclosure. Throughout the drawings, the same elements are represented by the same or similar reference numerals. When the conventional structures or configurations may cause confusion to the understanding of the present disclosure, they will be omitted, and the shapes and sizes of the components in the drawings do not reflect the actual sizes and proportions, but only illustrate the contents of the embodiments of the present disclosure.

[0081] Unless otherwise known as the opposite meaning, the numerical parameters in the specification and the appended claims are approximate values, which can be changed according to the desired characteristics obtained by the content of the present disclosure. Specifically, all the numbers used in the specification and claims to express the content of the composition, reaction conditions, etc. should be understood as being modified by the term "about" in all cases. Generally, it is expressed to mean that it includes a change of ±10% in some embodiments, a change of ±5% in some embodiments, a change of ±1% in some embodiments, a change of ±0.5% in some embodiments.

[0082] The ordinal numbers used in the specification and claims, such as "first", "second", "third", etc., are used to modify the corresponding elements, which do not mean that the elements have any ordinal number, nor represent the order of one element and another element, or the order of the manufacturing method. The use of these ordinal numbers is only used to make the element with a certain name clearly distinguishable from another element with the same name.

[0083] ​Moreover, the order of execution or performance of the above-described operations is not limited to the above-described order unless otherwise specified and can be changed or re-arranged according to the desired design or implementation. Also, the above-described embodiments can be used in combination with each other or in combination with other embodiments, based on design and reliability considerations, i.e., technical features in different embodiments can be freely combined to form further embodiments.

[0084] The above detailed description has been described for the purposes of clarity and understanding. It is not intended to limit the present disclosure to the precise steps described or to the precise embodiments described above. Many modifications, equivalents, and variations are possible within the spirit and scope of the present disclosure. Thus, the present disclosure is not intended to be limited to the embodiments described above but is to be accorded the widest scope consistent with the claims.

Claims

1. An apparatus suitable for generating a frequency-stable microcavity optical frequency comb, comprising: a light source unit configured to emit a light beam; a beam splitting device configured to split the light beam emitted by the light source unit into a plurality of first light beams; a light source frequency determination unit connected to a first output port of the beam splitting device, a modulation frequency being determined based on absorption of the first light beams by atoms in the light source frequency determination unit, the light source unit adjusting a frequency of a second light beam emitted based on the modulation frequency; a resonant microcavity, the second light beam generating a first microcavity optical frequency comb in the resonant microcavity; and a modulation unit disposed between a second output port of the beam splitting device and the resonant microcavity, configured to modulate the second light beam into a third light beam with information of a repetition frequency of the first microcavity optical frequency comb based on the repetition frequency, the third light beam generating a second microcavity optical frequency comb in the resonant microcavity; the modulation unit comprising: an electro-optical modulator disposed between the second output port of the beam splitting device and the resonant microcavity, configured to modulate the second light beam; and a microwave source connected to the electro-optical modulator, configured to modulate the electro-optical modulator, wherein a modulation signal frequency of the microwave source is set based on the repetition frequency of the first microcavity optical frequency comb, so that the third light beam obtained after modulation by the electro-optical modulator has information of the repetition frequency of the first microcavity optical frequency comb. the light source frequency determination unit comprising:

2. The apparatus of claim 1, wherein, a frequency doubling crystal connected to the first output port of the beam splitting device, configured to perform frequency conversion on the first light beams so that a wavelength of the converted first light beams matches a transition energy level of the atoms; an atomic cell connected to the frequency doubling crystal, the converted first light beams being emitted after being absorbed by the atoms in the atomic cell; a photodetector configured to convert an optical signal of the first light beams absorbed by the atoms in the atomic cell into an electrical signal; and a feedback system connected to the photodetector, configured to calculate an error signal based on the electrical signal and determine the modulation frequency based on the error signal. further comprising:

3. The apparatus of claim 1, wherein, first and second transmission units, the third light beam being unidirectionally injected into the resonant microcavity through the first transmission unit; and an auxiliary unit connected to the resonant microcavity, configured to emit an auxiliary light beam to balance thermal effects in the case of generating a microcavity optical frequency comb in the resonant microcavity. the auxiliary light beam being unidirectionally injected into the resonant microcavity through the second transmission unit. the first transmission unit comprising:

4. The apparatus of claim 3, wherein, a fiber polarization controller disposed between the light source unit and the resonant microcavity, configured to control polarization of the third light beam; and 5. The apparatus of claim 4, wherein, a fiber isolator connected to the fiber polarization controller, configured to unidirectionally inject the third light beam into the resonant microcavity. the first transmission unit further comprising: a fiber amplifier having one end connected to the light source unit and the other end connected to the fiber polarization controller, the fiber amplifier being configured to amplify power of the third light beam.

6. The apparatus of claim 5, wherein, the feedback system comprising: ​ 7. The apparatus of claim 2, wherein, ​ an oscilloscope configured to obtain a saturated absorption spectrum of the atom based on the electrical signal; a modulator configured to calculate the error signal based on an absorption peak in the saturated absorption spectrum; and a proportional-integral-derivative feedback device configured to determine the adjustment frequency based on the error signal.

8. The apparatus of claim 2, wherein, The atom cell is a rubidium atom cell.

9. A method for generating a frequency-stable microcavity optical frequency comb using the apparatus of any one of claims 1-8, comprising: determining the adjustment frequency based on absorption of the first light beam by the atom after the first light beam is injected into the frequency-determining unit of the light source, so that the frequency of the second light beam is kept within a preset range; modulating the second light beam into a third light beam with information of a repetition frequency of a first microcavity optical frequency comb generated by the second light beam in the resonant microcavity based on the repetition frequency; and injecting the third light beam into the resonant microcavity and locking the repetition frequency through an injection locking process to generate a second microcavity optical frequency comb in the resonant microcavity. ​

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