Normal dispersion microcavity optical frequency comb generation device and method based on bidirectional pumping

Abstract

The invention provides a normal dispersion micro-cavity optical frequency comb generation device and method based on bidirectional pumping, the device comprises a pumping unit and a micro-ring resonance unit, the micro-ring resonance unit comprises a micro-ring resonant cavity and a coupling waveguide, the coupling waveguide couples incident pumping light into the micro-ring resonant cavity from two opposite directions, and the pumping light is coupled into the micro-ring resonant cavity through the coupling waveguide. High-robustness and high-repeatability generation and output of the optical frequency comb are realized by utilizing a feedback effect and a cross phase modulation effect of residual pump light reversely injected into the micro-ring resonant cavity on a clockwise light field of the micro-ring resonant cavity and by scanning the output frequency of the pump light or the resonant frequency of the micro-ring resonant cavity. By changing the output frequency of the pumping laser or the resonant frequency of the micro-ring resonant cavity, the optical frequency comb can be generated at any harmonic peak of the normal dispersion micro-cavity, and the flexibility of the optical frequency comb generation device and method is improved.

Description

Technical Field

[0001] The present application relates to the technical field of optical frequency combs, and in particular to a device and method for generating a normal dispersion microcavity optical frequency comb based on bidirectional pumping. Background Art

[0002] Optical frequency combs, also known as optical frequency combs, are composed of a series of equally spaced frequency components in the frequency domain. They have important applications in the fields of precision ranging, precision spectral measurement, microwave photon signal processing, and high-capacity optical communications. Compared with traditional optical frequency comb generation schemes, optical frequency combs based on micro-resonators have the advantages of high integration and high repetition frequency, and have become a research hotspot in recent years.

[0003] The optical frequency comb based on normal group velocity dispersion microcavity has the advantages of high energy conversion efficiency and high comb tooth flatness. However, due to the lack of modulation instability in the upper branch of the bistable working curve of the normal dispersion microcavity, the normal dispersion optical frequency comb is difficult to generate spontaneously through conventional frequency sweeping. To solve this problem, one solution is to pump the microcavity with modulated pump light, but such a solution will bring complexity to the pump light system and increase the demand for modulators and microwave sources. Another solution is to use the mode coupling effect between different mode families to cause the resonance peak shift and construct local anomalous dispersion. Mode coupling requires the control of the strict alignment of the resonance peaks of the two mode families, which increases the difficulty of control. In addition, the pump laser and microcavity self-injection locking scheme can also make the microcavity work at an unstable point with modulation instability, thereby realizing the generation of optical combs, but this structure is very sensitive to the phase between the microcavity and the laser chip, and also requires the addition of additional control parameters.

[0004] Therefore, the existing normal dispersion microcavity optical frequency comb generation devices and methods require complex parameter control, which limits their application in practical scenarios. How to obtain a highly robust normal dispersion optical frequency comb is still a problem that people in this field urgently need to solve. Summary of the invention

[0005] The present application aims to solve one of the technical problems in the related art at least to some extent.

[0006] To this end, the first objective of the present application is to propose a normal dispersion microcavity optical frequency comb generation device and method based on bidirectional pumping, which can obtain a normal dispersion optical frequency comb with high robustness.

[0007] To achieve the above-mentioned purpose, the first embodiment of the present application proposes a normal dispersion microcavity optical frequency comb generation device based on bidirectional pumping, comprising:

[0008] A pump unit, used for providing pump light;

[0009] The microring resonance unit comprises a microring resonance cavity and a coupling waveguide, wherein the input end of the coupling waveguide is connected to the pump unit for receiving the pump light, and the output end of the coupling waveguide is used for outputting an optical frequency comb; wherein,

[0010] The coupling waveguide is arranged on the peripheral side of the microring resonant cavity, and is coupled to the microring resonant cavity to form a plurality of coupling points. The plurality of coupling points couple the pump light to the microring resonant cavity from two opposite directions, respectively, so as to form a clockwise light field and a counterclockwise light field in the microring resonant cavity, and excite the generation of a normal dispersion optical frequency comb in the process of sweeping and adjusting the output frequency of the pump light or the resonant frequency of the microring resonant cavity.

[0011] Optionally, the output frequency of the pump light is tuned and swept from the blue detuned position of the resonance frequency of the microring resonator toward a decreasing frequency direction until the microring resonator operates at an operating point with modulation instability under the combined action of self-phase modulation effect and cross-phase modulation effect, thereby exciting the generation of a normal dispersion optical frequency comb.

[0012] Optionally, the microring resonance unit further includes a voltage source, and the resonance frequency of the microring resonance cavity is swept from the red detuned position of the output frequency of the pump light in the direction of increasing frequency under the voltage drive of the voltage source, until the clockwise light field operates at an operating point with modulation instability under the combined action of the self-phase modulation effect and the cross-phase modulation effect, thereby exciting the generation of a normal dispersion optical frequency comb.

[0013] Optionally, the coupling waveguide and the microring resonant cavity include a first coupling point and a second coupling point; the coupling waveguide couples the pump light from the first coupling point into the microring resonant cavity to form the clockwise light field, and the residual pump light after coupling at the first coupling point is reversely coupled from the second coupling point into the microring resonant cavity to form the counterclockwise light field.

[0014] Optionally, a third coupling point is included between the coupling waveguide and the microring resonant cavity, and an integrated grating is provided on the coupling waveguide between the third coupling point and the output end of the coupling waveguide. The coupling waveguide directly couples the pump light from the third coupling point into the microring resonant cavity to form the clockwise light field, and the residual pump light after coupling at the third coupling point is emitted by the integrated grating and then reversely coupled from the third coupling point into the microring resonant cavity to form the counterclockwise light field.

[0015] Optionally, the central wavelength of the integrated grating is consistent with the wavelength range of the pump light, and the bandwidth of the integrated grating is consistent with the free spectrum range of the microring resonant cavity.

[0016] Optionally, the pump unit at least includes a laser, a polarization controller, an optical amplifier, an optical filter and an optical circulator connected in sequence by optical fibers; the laser is used to output pump light; the polarization controller is arranged at the output end of the laser, and is used to adjust the polarization direction of the laser; the optical amplifier is arranged at the output end of the polarization controller, and is used to adjust the output power of the laser; the optical filter is arranged at the output end of the optical amplifier, and is used to filter out the amplified laser spontaneous radiation noise; the optical circulator is arranged between the optical filter and the microring resonance unit, and is used to isolate the optical signal reversely output by the microring resonance unit.

[0017] Optionally, the laser includes at least one of a fixed frequency laser and a tunable laser.

[0018] To achieve the above-mentioned purpose, the second embodiment of the present application proposes a method for generating a normal dispersion microcavity optical frequency comb based on bidirectional pumping, which is characterized by comprising:

[0019] The output end of the pump unit is coupled to the input end of the micro-ring resonance unit, so that the pump light output by the pump unit is incident into the coupling waveguide of the micro-ring resonance unit; the coupling waveguide couples the incident pump light into the micro-ring resonance cavity of the micro-ring resonance unit from two opposite directions respectively;

[0020] A resonance peak of the microring resonant cavity is selected as a reference resonance peak, and the pump light output frequency of the pump unit or the resonance frequency of the microring resonant cavity is adjusted, so that the frequency difference between the pump light output frequency of the pump unit and the resonance frequency of the microring resonant cavity is tuned from a direction greater than 0 to a direction less than 0, until the microring resonant cavity is excited to generate a normal dispersion optical frequency comb under the combined action of the self-phase modulation effect and the cross-phase modulation effect.

[0021] Optionally, the step of adjusting the pump light output frequency of the pump unit or the resonant frequency of the microring resonant cavity so that the frequency difference between the pump light output frequency of the pump unit and the resonant frequency of the microring resonant cavity is tuned from a direction greater than 0 to a direction less than 0 specifically includes:

[0022] When the laser in the pump unit is a tunable laser, the output frequency of the tunable laser is adjusted so that the output frequency of the tunable laser is continuously tuned and swept from the blue detuning position to the red detuning position relative to the resonance frequency of the microring resonant cavity; or,

[0023] When the laser in the pump unit is a fixed frequency laser, the resonant frequency of the microring resonant cavity is continuously tuned and swept from a red detuned position to a blue detuned position relative to the output frequency of the fixed frequency laser by adjusting the input voltage of the microring resonant cavity.

[0024] The normal dispersion microcavity optical frequency comb generation device and method based on bidirectional pumping provided in the present application include at least the following beneficial effects:

[0025] The present application provides a normal dispersion microcavity optical frequency comb generation device and method based on bidirectional pumping, the device includes a pump unit and a microring resonance unit, the microring resonance unit includes a microring resonant cavity and a coupling waveguide, the coupling waveguide couples the incident pump light into the microring resonant cavity from two opposite directions respectively, utilizes the feedback effect and cross-phase modulation effect of the residual pump light injected into the microring resonant cavity on the clockwise light field of the microring resonant cavity, and scans the output frequency of the pump light or the resonant frequency of the microring resonant cavity, thereby achieving high robustness and high repeatability generation and output of the optical frequency comb. Compared with the existing normal dispersion microcavity optical frequency comb generation scheme, the present application does not need to rely on mode coupling or pump light self-injection locking, and the phase of the pump light reverse injection path in the present application does not affect the optical frequency comb generation effect, reducing the additional control parameters of the optical frequency comb generation device and method.

[0026] At the same time, the present application can realize the generation of an optical frequency comb at any resonance peak of a normal dispersion microcavity by simply changing the pump laser output frequency or the resonance frequency of the microring resonant cavity, thereby improving the flexibility of the optical frequency comb generation device and method.

[0027] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0029] Figure 1 It is a schematic structural diagram of a normal dispersion microcavity optical frequency comb generation device based on bidirectional pumping according to an embodiment of the present application.

[0030] Figure 2 The figure is a schematic diagram of the structure of a micro-ring resonance unit according to an embodiment of the present application.

[0031] Figure 3 It is a schematic diagram of the structure of another micro-ring resonance unit according to an embodiment of the present application.

[0032] Figure 4It is a schematic structural diagram of another normal dispersion microcavity optical frequency comb generation device based on bidirectional pumping according to an embodiment of the present application.

[0033] Figure 5 The figure is a transmission power curve of the micro-ring resonant cavity output shown by the spectrometer during the frequency sweep process according to the present application.

[0034] Figure 6 This is a diagram of the optical frequency comb spectrum output by the oscilloscope during the frequency sweeping process of the present application.

[0035] Figure 7 The present invention is a flow chart of a method for generating a normal dispersion microcavity optical frequency comb based on bidirectional pumping according to an embodiment of the present application.

[0036] 1 laser; 2 polarization controller; 3 optical amplifier; 4 optical filter; 5 optical circulator; 6 coupled waveguide; 7 microring resonator; 8 voltage source; 9 optical coupler; 10 spectrometer; 11 photodetector; 12 oscilloscope. DETAILED DESCRIPTION

[0037] Embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present application, and should not be construed as limiting the present application.

[0038] Since the upper branch of the bistable working curve of the normal dispersion microcavity lacks modulation instability, it is difficult to spontaneously generate a normal dispersion optical frequency comb through conventional frequency sweeping. To solve this problem, the existing technology usually uses a modulated pump light to pump the microcavity. The modulation frequency of the pump light is synchronized with the free spectrum range of the microcavity. The normal dispersion optical comb can be obtained by broadening the modulated pump light through a non-degenerate four-wave mixing process. Therefore, the optical comb generation process will not require modulation instability. However, such a pump light modulation scheme will bring complexity to the pump light system and increase the demand for modulators and microwave sources.

[0039] In order to realize normal dispersion optical frequency comb using continuous wave pump light and induce modulation instability in normal dispersion, a common solution is to use the mode coupling effect between different mode families to cause resonance peak shift and construct local anomalous dispersion. The specific implementation methods include coupling between the fundamental mode and the high-order mode in a single microcavity and dual-cavity coupling structure. However, mode coupling often requires strict alignment of the resonance peaks of the two mode families, which further increases the difficulty of control. Photonic crystal microcavity utilizes the coupling between the two propagation direction modes, but it is still necessary to adjust the center frequency of the grating in the microring to align it with the pump frequency, and its preparation requires high-resolution lithography technology, which increases the process difficulty. In addition to the mode coupling scheme, the pump laser and microcavity self-injection locking scheme can make the microcavity work at an unstable point with modulation instability, thereby realizing the generation of optical comb, but this structure is very sensitive to the phase between the microcavity and the laser chip, and also requires additional control parameters.

[0040] Based on the above problems, the embodiments of the present application provide a device and method for generating a normal dispersion microcavity optical frequency comb based on bidirectional pumping. The device and method feature a design between a microring resonator and a coupled waveguide so that the pump light can be coupled to the clockwise light field and the counterclockwise light field of the microring resonator from two opposite directions, respectively, so that a conventional frequency sweeping scheme, that is, tuning the output frequency of the pump light from a direction greater than the resonant frequency of the microring resonator to a direction less than the resonant frequency of the microring resonator, can stably achieve the generation of a normal dispersion optical frequency comb, and no additional control is required for parameters other than the pump laser and the microcavity used to generate the optical frequency comb, thereby simplifying the generation and control scheme of the normal dispersion optical frequency comb, and the optical frequency comb generation process has extremely high repeatability and robustness, laying a foundation for the practical application of the normal dispersion microcavity optical frequency comb.

[0041] According to one aspect of the embodiments of the present application, a normal dispersion microcavity optical frequency comb generation device based on bidirectional pumping is provided, such as Figure 1 to Figure 4 As shown, the device includes a pump unit and a microcavity resonance unit. The pump unit is used to provide pump light to the microcavity resonance unit, and the microring resonance unit is used to convert the received pump light into a normal dispersion optical frequency comb output.

[0042] The microring resonance unit specifically includes a microring resonance cavity 7 and a coupling waveguide 6. The input end of the coupling waveguide 6 is connected to the pump unit to receive the pump light input by the pump unit. The output end of the coupling waveguide 6 is used to output the normal dispersion light frequency comb generated by the excitation in the microring resonance cavity 7 to the outside.

[0043] The coupling waveguide 6 is arranged on the peripheral side of the micro-ring resonant cavity 7, and is coupled to the micro-ring resonant cavity 7 to form a plurality of coupling points. The plurality of coupling points couple the pump light to the micro-ring resonant cavity 7 from two opposite directions, respectively, so as to form a clockwise light field and a counterclockwise light field in the micro-ring resonant cavity 7, and in the process of sweeping and adjusting the output frequency of the pump light or the resonant frequency of the ring resonant cavity, the frequency difference between the pump light output frequency of the pump unit and the resonant frequency of the micro-ring resonant cavity 7 is tuned from a direction greater than 0 to a direction less than 0, so as to excite and generate a normal dispersion optical frequency comb in the micro-ring resonant cavity 7.

[0044] It is understandable that in the process of generating an optical frequency comb by conventional frequency sweep tuning, the frequency of the pump light will sweep from the blue detuned position of the resonance peak of the microring resonator 7 (the difference between the resonance frequency of the microring resonator 7 and the output frequency of the pump light is negative) to the direction of decreasing frequency.

[0045] At the beginning of the frequency sweep of a conventional normal dispersion microcavity, the power in the microcavity will gradually increase, and the self-phase modulation effect will be correspondingly enhanced, causing the center frequency of the microcavity resonance peak to redshift (move toward the low frequency direction). When the pump light frequency is tuned to be basically consistent with the center frequency of the resonance peak after the redshift, the power in the microcavity begins to decrease, and the self-phase modulation effect is correspondingly weakened, causing the center frequency of the microcavity resonance peak to begin to blueshift (toward the high frequency direction), thereby further reducing the power in the microcavity. The positive feedback process formed by this will cause the microcavity operating point to jump directly from the bistable upper branch to the lower branch, and it cannot work in a state with modulation instability, making it difficult to achieve the generation of an optical frequency comb.

[0046] For the normal dispersion microcavity optical frequency comb generation device based on bidirectional pumping provided in the present application, by coupling the pump light to the microring resonant cavity 7 from two opposite directions respectively, a clockwise light field and a counterclockwise light field are formed in the microring resonant cavity 7, so that at the beginning of the frequency sweep process, the pump light power felt by the clockwise light field will gradually increase. Due to the consumption of the pump light by the clockwise light field, the residual pump light power felt by the counterclockwise light field will gradually decrease, and the power of the counterclockwise light field will decrease accordingly. At the same time, due to the cross-phase modulation effect of the clockwise light field on the counterclockwise light field, the center frequency of the resonance peak of the counterclockwise light field will move toward the low frequency direction, and the power of the counterclockwise light field will be further reduced. When the pump light frequency is tuned to be basically consistent with the center frequency of the resonance peak of the clockwise light field, the pump light power felt by the clockwise light field gradually begins to decrease, and the pump light power felt by the counterclockwise light field gradually increases. At the same time, due to the weakening of the cross-phase modulation effect of the clockwise light field on the counterclockwise light field, the resonance peak center frequency of the counterclockwise light field gradually moves toward the pump light frequency, causing the power of the counterclockwise light field to gradually increase. In other words, the increase in the cross-phase modulation effect provided by the counterclockwise light field to the clockwise light field compensates for the weakening of the self-phase modulation effect of the clockwise light field, allowing the clockwise light field to stably work at a modulation instability operating point where a conventional microcavity structure cannot stably work, thereby realizing the spontaneous generation of a normal dispersion light comb.

[0047] It should be noted that the above-mentioned normal sweep tuning process is through tuning the output frequency of the pump light, that is, when the output frequency of the pump light is tunable, the sweep process is through pre-tuning the output frequency of the pump light to the blue detuning position relative to the resonant frequency of the microring resonant cavity 7, and then continuously sweeping the output frequency of the pump light from the blue detuning position to the red detuning position.

[0048] The actual frequency sweeping process can also be achieved by tuning the resonant frequency of the microring resonant cavity 7. That is to say, when the output frequency of the pump light is a fixed frequency, the frequency sweeping process is achieved by pre-tuning the resonant frequency of the microring resonant cavity 7 to a red detuned position relative to the output frequency of the pump light, and then continuously sweeping the resonant frequency of the microring resonant cavity 7 from the red detuned position to the blue detuned position.

[0049] As an example, the microring resonance unit further includes a voltage source 8, and the output end of the voltage source 8 loads a voltage signal to a hot electrode integrated on the microring resonance cavity 7 through a probe, and controls the resonance frequency of the microring resonance cavity by thermal tuning. That is, by increasing the output voltage of the voltage source 8, the heating power of the microring resonance cavity 7 can be increased, so that the resonance frequency of the microring resonance cavity 7 can be tuned to a red detuned position relative to the output frequency of the pump light, and then reducing the output voltage of the voltage source 8 reduces the heating power of the microring resonance cavity 7, thereby driving the resonance frequency of the microring resonance cavity 7 to continuously sweep from the red detuned position to the blue detuned position.

[0050] In some embodiments, Figure 2 As shown, the coupling waveguide 6 and the microring resonant cavity 7 may include a first coupling point and a second coupling point. The coupling waveguide 6 couples the pump light into the microring resonant cavity 7 through the first coupling point to form a clockwise light field, and the residual pump light generated after coupling through the first coupling point is reversely coupled into the microring resonant cavity 7 through the second coupling point to form the counterclockwise light field, thereby enabling the pump light to be coupled into the microring resonant cavity 7 from two opposite directions, respectively, to achieve bidirectional pumping.

[0051] In other embodiments, Figure 3 As shown, a third coupling point may be included between the coupling waveguide 6 and the micro-ring resonant cavity 7, and an integrated grating is also arranged between the third coupling point of the coupling waveguide 6 and its output end, so as to realize on-chip integration of the integrated gate. Thus, the coupling waveguide 6 can directly couple the pump light into the micro-ring resonant cavity 7 through the third coupling point to form the clockwise light field, and the residual pump light generated after coupling through the third coupling point is incident on the integrated grating through the coupling waveguide 6, and after being reflected by the integrated grating, it is reversely coupled to the micro-ring resonant cavity 7 through the third coupling point to form the counterclockwise light field, thereby enabling the pump light to be coupled into the micro-ring resonant cavity 7 from two opposite directions, respectively, to realize bidirectional pumping. Among them, the central wavelength of the integrated grating needs to be consistent with the wavelength range of the pump light, and the bandwidth of the integrated grating needs to be consistent with the free spectrum range of the micro-ring resonant cavity 7.

[0052] It should be noted that the above-mentioned coupling waveguide 6 and micro-ring resonator 7 (and integrated grating) can be a chip structure integrated on the same substrate.

[0053] In some embodiments, Figure 4As shown, the pump unit at least includes a laser 1, a polarization controller 2, an optical amplifier 3, an optical filter 4 and an optical circulator 5 connected in sequence by optical fibers. Among them, the laser 1 is used to output laser light, including but not limited to one of a fixed frequency laser and a tunable laser. The polarization controller 2 is arranged at the output end of the laser 1, and is used to adjust the polarization direction of the laser light output by the laser 1. The optical amplifier 3 is arranged at the output end of the polarization controller 2, and is used to adjust the output power of the laser light. The optical filter 4 is arranged at the output end of the optical amplifier 3, and is used to filter out the spontaneous radiation noise of the amplified laser light. The optical circulator 5 is arranged between the optical filter 4 and the microring resonance unit, and is used to isolate the optical signal outputted in reverse by the microring resonance unit.

[0054] The laser 1, the polarization controller 2, the optical amplifier 3, the optical filter 4 and the optical circulator 5 are coupled and connected in sequence through single-mode optical fibers, and the optical circulator 5 is coupled and connected to the microring resonator unit through a tapered optical fiber.

[0055] Furthermore, the device may also include a detection unit, which may include an optical coupler 9, a spectrometer 10, a photodetector 11 and an oscilloscope 12. The optical coupler 9 is coupled to the output end of the micro-ring resonance unit through a single-mode optical fiber, and divides the optical signal output by the micro-ring resonance unit into two paths. That is to say, the optical coupler 9 includes a first output end and a second output end, the first output end is coupled to the spectrometer 10 through a single-mode optical fiber, so that the spectrometer 10 can collect and display the spectrum of the optical signal output by the micro-ring resonance unit, and the second output end is coupled to the photodetector 11 through a single-mode optical fiber, so that the photodetector 11 can convert the optical signal output by the micro-ring resonance unit into an electrical signal that can be identified by the oscilloscope 12, thereby realizing the collection and display of the change in the transmission power of the optical signal output by the micro-ring resonance unit.

[0056] like Figure 5 As shown, in the initial stage of frequency sweeping, the transmission power of the microring resonant cavity 7 will gradually decrease, and only the pump light frequency component can be recorded on the spectrometer 10. When the transmission power reaches the lowest point, a step will occur and remain at a step until it is further tuned and jumps out of the resonance peak, and the transmission power returns to the maximum value.

[0057] Therefore, when the transmission power curve on the spectrometer 10 reaches the step position, the frequency sweep is stopped, and the normal dispersion microcavity optical frequency comb can be observed on the spectrometer 10. Figure 6 As shown, the normal dispersion microcavity optical frequency comb spectrum recorded on the spectrometer 10. This embodiment realizes the generation of normal dispersion optical frequency comb by pump light at various resonance peak positions in the range of 1542.17nm to 1557.72nm. Figure 4The optical frequency comb spectrum results with pump light wavelengths of 1543.62nm, 1548.27nm, 1552.93nm and 1557.72nm are shown respectively.

[0058] According to a second aspect of an embodiment of the present application, a method for generating a normal dispersion microcavity optical frequency comb based on bidirectional pumping is provided, such as Figure 4 and Figure 7 As shown, the method adopts the device described in any of the above embodiments, and includes the following steps:

[0059] S1, couple the output end of the pump unit with the input end of the microring resonance unit, so that the pump light output by the pump unit is incident on the coupling waveguide 6 of the microring resonance unit, and the incident pump light is coupled from two opposite directions to the microring resonance cavity 7 of the microring resonance unit through the coupling waveguide 6.

[0060] S2, select a resonance peak of the microring resonant cavity 7 as a reference resonance peak, adjust the pump light output frequency of the pump unit or the resonance frequency of the microring resonant cavity 7, so that the frequency difference between the pump light output frequency of the pump unit and the resonance frequency of the microring resonant cavity 7 is tuned from a direction greater than 0 to a direction less than 0, until the microring resonant cavity 7 is excited to produce a normal dispersion optical frequency comb under the combined action of the self-phase modulation effect and the cross-phase modulation effect.

[0061] In one embodiment, the step of adjusting the pump light output frequency of the pump unit is that when the laser 1 in the pump unit is a tunable laser, by adjusting the output frequency of the tunable laser, the output frequency of the tunable laser is continuously tuned and swept from the blue detuning position to the red detuning position relative to the resonant frequency of the microring resonant cavity 7, and at the same time, the transmission power curve recorded by the oscilloscope 12 and the spectrum recorded by the spectrometer 10 are observed.

[0062] In another embodiment, the step of adjusting the resonant frequency of the microring resonant cavity 7 is that when the laser 1 in the pump unit is a fixed-frequency laser, by adjusting the input voltage of the microring resonant cavity 7, the resonant frequency of the microring resonant cavity 7 is continuously tuned and swept from the red detuning position to the blue detuning position relative to the output frequency of the pump light (fixed-frequency laser).

[0063] Specifically, in the initial stage of frequency sweeping, the transmission power of the micro-ring resonator 7 will gradually decrease, and only the pump light frequency component can be recorded on the spectrometer 10. When the transmission power reaches the lowest point, a step will occur and remain at a step until it is further tuned and jumps out of the resonance peak, and the transmission power recovers to the maximum value. Therefore, when the transmission power curve reaches the step position, the frequency sweep is stopped, and the normal dispersion micro-cavity optical frequency comb can be observed on the spectrometer 10.

[0064] In summary, the present application provides a normal dispersion microcavity optical frequency comb generation device and method based on bidirectional pumping, which achieves high robustness and high repeatability generation of optical frequency comb by coupling pump light into the microring resonator 7 from two opposite directions and utilizing the feedback effect of reverse injection of residual pump light and cross-phase modulation. Compared with the existing normal dispersion microcavity optical frequency comb generation scheme, the present application does not need to rely on mode coupling or pump light self-injection locking, and the reverse injection path phase of the pump light in the present application does not affect the optical frequency comb generation effect, reducing the system's additional control parameters.

[0065] At the same time, the present application can realize the generation of optical frequency comb at any resonance peak of the normal dispersion microcavity by only changing the pump laser output frequency or the resonance frequency of the microring resonator 7, thereby improving the flexibility of the optical frequency comb generation device and method.

[0066] In the description of the aforementioned embodiments, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0067] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of this application, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

Claims

1. A normal dispersion microcavity optical frequency comb generation device based on bidirectional pumping, characterized in that: include: A pump unit, used for providing pump light; The microring resonance unit comprises a microring resonance cavity and a coupling waveguide, wherein the input end of the coupling waveguide is connected to the pump unit for receiving the pump light, and the output end of the coupling waveguide is used for outputting an optical frequency comb; wherein, The coupling waveguide is arranged on the peripheral side of the microring resonant cavity, and is coupled to the microring resonant cavity to form a plurality of coupling points. The plurality of coupling points couple the pump light to the microring resonant cavity from two opposite directions, respectively, so as to form a clockwise light field and a counterclockwise light field in the microring resonant cavity, and excite the generation of a normal dispersion optical frequency comb in the process of sweeping and adjusting the output frequency of the pump light or the resonant frequency of the microring resonant cavity.

2. The device according to claim 1, characterized in that The output frequency of the pump light is tuned and swept from the blue detuned position of the resonance frequency of the microring resonant cavity toward the direction of decreasing frequency until the microring resonant cavity operates at an operating point with modulation instability under the combined action of the self-phase modulation effect and the cross-phase modulation effect, thereby exciting the generation of a normal dispersion optical frequency comb.

3. The device according to claim 1, characterized in that The microring resonance unit also includes a voltage source. Driven by the voltage of the voltage source, the resonance frequency of the microring resonance cavity is swept from the red detuned position of the output frequency of the pump light in the direction of increasing frequency until the clockwise light field operates at an operating point with modulation instability under the combined action of the self-phase modulation effect and the cross-phase modulation effect, thereby exciting the generation of a normal dispersion optical frequency comb.

4. The device according to any one of claims 1 to 3, characterized in that: The coupling waveguide and the microring resonant cavity include a first coupling point and a second coupling point; the coupling waveguide couples the pump light from the first coupling point into the microring resonant cavity to form the clockwise light field, and the residual pump light after coupling at the first coupling point is reversely coupled from the second coupling point into the microring resonant cavity to form the counterclockwise light field.

5. The device according to any one of claims 1 to 3, characterized in that: A third coupling point is included between the coupling waveguide and the microring resonant cavity. An integrated grating is provided on the coupling waveguide between the third coupling point and the output end of the coupling waveguide. The coupling waveguide directly couples the pump light from the third coupling point into the microring resonant cavity to form the clockwise light field. The residual pump light after coupling at the third coupling point is emitted by the integrated grating and then reversely coupled from the third coupling point into the microring resonant cavity to form the counterclockwise light field.

6. The device according to claim 5, characterized in that The central wavelength of the integrated grating is consistent with the wavelength range of the pump light, and the bandwidth of the integrated grating is consistent with the free spectrum range of the micro-ring resonant cavity.

7. The device according to claim 1, characterized in that The pump unit at least comprises a laser, a polarization controller, an optical amplifier, an optical filter and an optical circulator connected in sequence by optical fibers; the laser is used to output laser light; the polarization controller is arranged at the output end of the laser, and is used to adjust the polarization direction of the laser light; the optical amplifier is arranged at the output end of the polarization controller, and is used to adjust the output power of the laser light; the optical filter is arranged at the output end of the optical amplifier, and is used to filter out the spontaneous radiation noise of the amplified laser light; The optical circulator is arranged between the optical filter and the micro-ring resonance unit, and is used for isolating the optical signal reversely outputted by the micro-ring resonance unit.

8. The device according to claim 7, characterized in that The laser includes at least one of a fixed frequency laser and a tunable laser.

9. A method for generating a normal dispersion microcavity optical frequency comb based on bidirectional pumping, characterized in that: include: The output end of the pump unit is coupled to the input end of the micro-ring resonance unit, so that the pump light output by the pump unit is incident into the coupling waveguide of the micro-ring resonance unit; The coupling waveguide couples the incident pump light into the microring resonant cavity of the microring resonant unit from two opposite directions respectively; A resonance peak of the microring resonant cavity is selected as a reference resonance peak, and the pump light output frequency of the pump unit or the resonance frequency of the microring resonant cavity is adjusted, so that the frequency difference between the pump light output frequency of the pump unit and the resonance frequency of the microring resonant cavity is tuned from a direction greater than 0 to a direction less than 0, until the microring resonant cavity is excited to generate a normal dispersion optical frequency comb under the combined action of the self-phase modulation effect and the cross-phase modulation effect.

10. The method according to claim 9, characterized in that The step of adjusting the pump light output frequency of the pump unit or the resonant frequency of the microring resonant cavity so that the frequency difference between the pump light output frequency of the pump unit and the resonant frequency of the microring resonant cavity is tuned from a direction greater than 0 to a direction less than 0 specifically includes: When the laser in the pump unit is a tunable laser, the output frequency of the tunable laser is adjusted so that the output frequency of the tunable laser is continuously tuned and swept from the blue detuning position to the red detuning position relative to the resonance frequency of the microring resonant cavity; or, When the laser in the pump unit is a fixed frequency laser, the input voltage of the microring resonant cavity is adjusted so that the resonant frequency of the microring resonant cavity is continuously tuned and swept from the red detuning position to the blue detuning position relative to the output frequency of the fixed frequency laser.

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