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

Abstract

The application provides a normal dispersion microcavity optical frequency comb generation device and method based on bidirectional pumping, the device comprising a pumping unit and a micro-ring resonant unit, the micro-ring resonant unit comprising a micro-ring resonant cavity and a coupling waveguide, the coupling waveguide coupling incident pumping light into the micro-ring resonant cavity from two opposite directions respectively, utilizing the feedback effect and cross-phase modulation effect of the residual pumping light injected into the micro-ring resonant cavity in the clockwise direction on the micro-ring resonant cavity, and through scanning the output frequency of the pumping light or the resonant frequency of the micro-ring resonant cavity, high robustness and high repeatability of the optical frequency comb are realized. By changing the output frequency of the pumping laser or the resonant frequency of the micro-ring resonant cavity, the generation of the optical frequency comb can be realized at any resonant peak of the normal dispersion microcavity, and the flexibility of the optical frequency comb generation device and method is improved.

Description

Technical Field

[0001] This application relates to the field of optical frequency comb technology, and in particular to a normal dispersive microcavity optical frequency comb generation device and method based on bidirectional pumping. Background Technology

[0002] Optical frequency combs, also known as optical frequency combs, consist of a series of equally spaced frequency components in the frequency domain and have important applications in precision ranging, precision spectral measurement, microwave photonic signal processing, and high-capacity optical communication. Compared with traditional optical frequency comb generation schemes, microcavity-based optical frequency combs have advantages such as high integration and high repetition rate, making them a research hotspot in recent years.

[0003] Optical frequency combs based on normal group velocity dispersive microcavities (NCDs) offer advantages such as high energy conversion efficiency and high comb flatness. However, due to the lack of modulation instability in the upper branch of the bistable operating curve of a NCD, spontaneous generation of NCD optical frequency combs is difficult through conventional frequency sweeping methods. To address this issue, one approach is to pump the microcavity with modulated pump light, but this introduces complexity to the pump light system and increases the requirements for modulators and microwave sources. Another approach utilizes the mode coupling effect between different mode families to cause resonant peak shifts, constructing localized anomalous dispersion. Mode coupling requires strict alignment of the resonant peaks of the two mode families, increasing control difficulty. Furthermore, a pump laser and microcavity self-injection locking scheme can also enable the microcavity to operate at an unstable point with modulation instability, thereby achieving optical comb generation. However, this structure is highly sensitive to the phase between the microcavity and the laser chip, also requiring additional control parameters.

[0004] Therefore, existing normal dispersion microcavity optical frequency comb generation devices and methods all require complex parameter control, which limits their application in practical scenarios. How to obtain a highly robust normal dispersion optical frequency comb remains a problem that urgently needs to be solved by those in the field. Summary of the Invention

[0005] This application aims to at least partially address one of the technical problems in the related art.

[0006] Therefore, the first objective of this application is to propose a bidirectional pump-based normal dispersive microcavity optical frequency comb generation device and method, which can robustly obtain normal dispersive optical frequency combs.

[0007] To achieve the above objectives, a first aspect of this application provides a normal dispersive microcavity optical frequency comb generation device based on bidirectional pumping, comprising:

[0008] Pump unit, used to provide pump light;

[0009] A microring resonant unit includes a microring resonant cavity and a coupling waveguide. 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 to output an optical frequency comb.

[0010] The coupling waveguide is disposed on the periphery of the microring resonator and is coupled to the microring resonator to form a plurality of coupling points. The plurality of coupling points couple the pump light to the microring resonator from two opposite directions to form a clockwise and a counterclockwise optical field in the microring resonator. During the frequency sweep adjustment of the output frequency of the pump light or the resonant frequency of the microring resonator, a normal dispersive optical frequency comb is excited.

[0011] Optionally, the output frequency of the pump light is tuned and swept from the blue detuning position of the resonant frequency of the microring resonator towards a decreasing frequency direction until the microring resonator operates at a modulation instability point under the combined effect of self-phase modulation and cross-phase modulation, thereby exciting the generation of a normal dispersive optical frequency comb.

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

[0013] Optionally, the coupling waveguide and the micro-ring resonator include a first coupling point and a second coupling point; the coupling waveguide couples the pump light from the first coupling point into the micro-ring resonator to form the clockwise light field, and the pump light remaining after coupling at the first coupling point is coupled in the opposite direction from the second coupling point into the micro-ring resonator to form the counterclockwise light field.

[0014] Optionally, the coupling waveguide and the micro-ring resonator include a third coupling point. 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 micro-ring resonator to form the clockwise light field. The pump light remaining after coupling at the third coupling point is emitted by the integrated grating and then coupled in the opposite direction from the third coupling point into the micro-ring resonator to form the counterclockwise light field.

[0015] Optionally, the center 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 spectral range of the micro-ring resonator.

[0016] Optionally, the pumping unit includes at least 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 disposed at the output end of the laser and is used to adjust the polarization direction of the laser; the optical amplifier is disposed at the output end of the polarization controller and is used to adjust the output power of the laser; the optical filter is disposed at the output end of the optical amplifier and is used to filter out the spontaneous emission noise of the amplified laser; the optical circulator is disposed between the optical filter and the micro-ring resonator unit and is used to isolate the optical signal output in reverse by the micro-ring resonator unit.

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

[0018] To achieve the above objectives, a second aspect of this application proposes a method for generating a normal dispersive microcavity optical frequency comb based on bidirectional pumping, characterized by comprising:

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

[0020] Select a resonant peak of the microring resonator as a reference resonant peak, and adjust the pump light output frequency of the pump unit or the resonant frequency of the microring resonator so that the frequency difference between the pump light output frequency of the pump unit and the resonant frequency of the microring resonator is tuned from a direction greater than 0 to a direction less than 0, until the microring resonator is excited to generate a normal dispersive optical frequency comb under the combined effect of self-phase modulation effect and 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 micro-ring resonator, so that the frequency difference between the pump light output frequency of the pump unit and the resonant frequency of the micro-ring resonator changes 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 continuously tuned and swept from the blue detuning position to the red detuning position relative to the resonant frequency of the microring resonator by adjusting the output frequency of the tunable laser; or...

[0023] When the laser in the pump unit is a fixed-frequency laser, the resonant frequency of the micro-ring resonator 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 by adjusting the input voltage of the micro-ring resonator.

[0024] The bidirectional pump-based normal dispersive microcavity optical frequency comb generation device and method provided in this application have at least the following beneficial effects:

[0025] This application provides a bidirectional pump-based normal dispersive microcavity optical frequency comb generation device and method. The device includes a pump unit and a microring resonator unit. The microring resonator unit includes a microring resonator cavity and a coupling waveguide. The coupling waveguide couples incident pump light into the microring resonator cavity from two opposite directions. Utilizing the feedback effect and cross-phase modulation effect of the residual pump light injected into the microring resonator cavity on the clockwise optical field of the cavity, and by scanning the output frequency of the pump light or the resonant frequency of the microring resonator cavity, the optical frequency comb is generated and output with high robustness and high repeatability. Compared with existing normal dispersive microcavity optical frequency comb generation schemes, this application does not require mode coupling or pump light self-injection locking, and the phase of the pump light reverse injection path does not affect the optical frequency comb generation effect, reducing the additional control parameters of the optical frequency comb generation device and method.

[0026] Meanwhile, this application can generate an optical frequency comb at any resonance peak of a normal dispersive microcavity simply by changing the pump laser output frequency or the microring resonant cavity resonant frequency, thus improving the flexibility of the optical frequency comb generation device and method.

[0027] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

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

[0029] Figure 1 This is a schematic diagram of a normal dispersive microcavity optical frequency comb generation device based on bidirectional pumping, according to an embodiment of this application.

[0030] Figure 2 This is a schematic diagram of the structure of a microring resonant unit according to an embodiment of this application.

[0031] Figure 3 This is a schematic diagram of another microring resonant unit structure according to an embodiment of this application.

[0032] Figure 4This is a schematic diagram of another bidirectional pumped normal dispersive microcavity optical frequency comb generation device according to an embodiment of this application.

[0033] Figure 5 The image shows the transmission power curve of the microring resonator output as displayed by the spectrometer during the frequency sweep process according to this application.

[0034] Figure 6 The optical frequency comb spectrum output by the oscilloscope during the frequency sweep process according to this application is shown.

[0035] Figure 7 This is a schematic flowchart illustrating a method for generating a normal dispersive microcavity optical frequency comb based on bidirectional pumping, according to an embodiment of this application.

[0036] 1 Laser; 2 Polarization controller; 3 Optical amplifier; 4 Optical filter; 5 Optical circulator; 6 Coupled waveguide; 7 Micro-ring resonator; 8 Voltage source; 9 Optical coupler; 10 Spectrometer; 11 Photodetector; 12 Oscilloscope. Detailed Implementation

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

[0038] Because the upper branch of the bistable operating curve of a normal dispersive microcavity lacks modulation instability, a normal dispersive optical frequency comb is difficult to generate spontaneously through conventional frequency sweeping methods. To address this issue, existing technologies typically employ modulated pump light to pump the microcavity. The modulation frequency of the pump light is synchronized with the free spectral range of the microcavity. The normal dispersive optical comb can be broadened from the modulated pump light through a non-degenerate four-wave mixing process, thus eliminating the need for modulation instability in the comb generation process. However, such pump light modulation schemes introduce complexity into the pump light system, increasing the requirements for modulators and microwave sources.

[0039] To achieve a normal dispersion optical frequency comb using continuous-wave pump light and induce modulation instability in normal dispersion, a common approach is to utilize the mode coupling effect between different mode families to cause a resonant peak shift, constructing localized anomalous dispersion. Specific implementations include coupling between the fundamental mode and higher-order modes within a single microcavity and dual-cavity coupling structures. However, mode coupling often requires strict alignment of the resonant peaks of the two mode families, further increasing the control complexity. Photonic crystal microcavities utilize coupling between modes in two propagation directions, but still require adjusting the center frequency of the grating within the microring to align it with the pump frequency, and their fabrication requires high-resolution photolithography, increasing the processing difficulty. Besides mode coupling, a pump laser and microcavity self-injection locking scheme can allow the microcavity to operate at an unstable point with modulation instability, thereby generating an optical comb. However, this structure is highly sensitive to the phase between the microcavity and the laser chip, also requiring additional control parameters.

[0040] To address the aforementioned issues, this application provides a bidirectional pumped normal dispersive microcavity optical frequency comb generation device and method. This device and method, through a unique design between the microring resonator and the coupling waveguide, enables the pump light to couple to the clockwise and counterclockwise optical fields of the microring resonator from two opposite directions. This allows for stable normal dispersive optical frequency comb generation by resolving the 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. Furthermore, it eliminates the need for additional control over parameters other than the pump laser and the microcavity used to generate the optical frequency comb, simplifying the generation and control scheme of the normal dispersive optical frequency comb. Moreover, the optical frequency comb generation process exhibits extremely high repeatability and robustness, laying the foundation for the practical application of normal dispersive microcavity optical frequency combs.

[0041] According to one aspect of the embodiments of this application, a normal dispersive microcavity optical frequency comb generation device based on bidirectional pumping is provided, such as... Figures 1-4 As shown, the device includes a pump unit and a microcavity resonator unit. The pump unit provides pump light to the microcavity resonator unit, while the microring resonator unit converts the received pump light into a normal dispersive light frequency comb output.

[0042] The microring resonant unit specifically includes a microring resonant 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 from the pump unit, and the output end of the coupling waveguide 6 is used to output the normal dispersive light frequency comb generated in the microring resonant cavity 7 to the outside.

[0043] The coupling waveguide 6 is arranged on the periphery of the micro-ring resonator 7 and is coupled to the micro-ring resonator 7 to form several coupling points. The coupling points couple the pump light to the micro-ring resonator 7 from two opposite directions to form clockwise and counterclockwise light fields in the micro-ring resonator 7. During the frequency sweep adjustment of the output frequency of the pump light or the resonant frequency of the ring resonator, the frequency difference between the output frequency of the pump light of the pump unit and the resonant frequency of the micro-ring resonator 7 is tuned from the direction greater than 0 to the direction less than 0, so as to excite the generation of a normal dispersive optical frequency comb in the micro-ring resonator 7.

[0044] It is understandable that during the generation of the optical frequency comb using conventional frequency sweeping tuning, the frequency of the pump light will sweep from the blue detuning position of the resonant peak of the micro-ring resonator 7 (the difference between the resonant frequency of the micro-ring resonator 7 and the output frequency of the pump light is negative) towards the direction of decreasing frequency.

[0045] In a conventional normal dispersive microcavity, the power within the microcavity gradually increases at the start of a frequency sweep, and the self-phase modulation effect is correspondingly enhanced, causing a redshift (moving towards lower frequencies) of the center frequency of the microcavity resonant peak. When the pump light frequency is tuned to be basically consistent with the center frequency of the redshifted resonant peak, the power within the microcavity begins to decrease, and the self-phase modulation effect weakens accordingly, causing a blueshift (towards higher frequencies) of the center frequency of the microcavity resonant peak. This further reduces the power within the microcavity. The resulting positive feedback process causes the microcavity operating point to jump directly from the upper branch of the bistable state to the lower branch, making it unable to operate in a state with modulation instability and making it difficult to generate an optical frequency comb.

[0046] The bidirectional pump-based normal dispersive microcavity optical frequency comb generation device provided in this application couples pump light into the microring resonator 7 from two opposite directions to form clockwise and counterclockwise optical fields within the microring resonator 7. This causes the pump light power experienced in the clockwise optical field to gradually increase during the initial stage of the frequency sweep process. Due to the consumption of pump light by the clockwise optical field, the residual pump light power experienced in the counterclockwise optical field gradually decreases, and the power of the counterclockwise optical field decreases accordingly. Simultaneously, due to the cross-phase modulation effect of the clockwise optical field on the counterclockwise optical field, the center frequency of the resonant peak of the counterclockwise optical field shifts to a lower frequency, further reducing the power of the counterclockwise optical field. Once the pump light frequency is tuned to approximately match the center frequency of the resonant peak of the clockwise optical field, the pump light power experienced in the clockwise optical field gradually decreases, while the pump light power experienced in the counterclockwise optical field gradually increases. Simultaneously, due to the weakening of the cross-phase modulation effect of the clockwise optical field on the counterclockwise optical field, the center frequency of the resonant peak of the counterclockwise optical field gradually shifts towards the pump light frequency, resulting in a gradual increase in the power of the counterclockwise optical field. In other words, the increased cross-phase modulation effect provided by the counterclockwise optical field on the clockwise optical field compensates for the weakening of the self-phase modulation effect of the clockwise optical field, enabling the clockwise optical field to operate stably at a modulation instability point where conventional microcavity structures cannot operate stably, thus achieving the spontaneous generation of a normal dispersion comb.

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

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

[0049] As an example, the microring resonant unit also includes a voltage source 8. The output of the voltage source 8 applies a voltage signal to the thermoelectrode integrated on the microring resonant cavity 7 via a probe, and controls the resonant frequency of the microring cavity through thermal tuning. That is, by increasing the output voltage of the voltage source 8, the heating power of the microring resonant cavity 7 can be increased, so that the resonant frequency of the microring resonant cavity 7 can be tuned to the red detuning position relative to the pump light output frequency. Subsequently, decreasing the output voltage of the voltage source 8 reduces the heating power of the microring resonant cavity 7, thereby driving the resonant frequency of the microring resonant cavity 7 to continuously sweep from the red detuning position to the blue detuning position.

[0050] In some embodiments, such as Figure 2 As shown, the coupling waveguide 6 and the microring resonator 7 may include a first coupling point and a second coupling point. The coupling waveguide 6 couples the pump light into the microring resonator 7 through the first coupling point to form a clockwise optical field, while the residual pump light generated after coupling through the first coupling point couples back into the microring resonator 7 through the second coupling point to form the counterclockwise optical field. This allows the pump light to couple into the microring resonator 7 from two opposite directions, achieving bidirectional pumping.

[0051] In other embodiments, such as Figure 3 As shown, a third coupling point may be included between the coupling waveguide 6 and the microring resonator 7. An integrated grating is also provided between the third coupling point and the output end of the coupling waveguide 6, achieving on-chip integration of the integrated grating. Thus, the coupling waveguide 6 can directly couple the pump light into the microring resonator 7 through the third coupling point to form the clockwise light field. The residual pump light generated after coupling through the third coupling point is incident on the integrated grating through the coupling waveguide 6, reflected by the integrated grating, and then coupled back into the microring resonator 7 through the third coupling point to form the counterclockwise light field. This allows the pump light to be coupled into the microring resonator 7 from two opposite directions, achieving bidirectional pumping. The center wavelength of the integrated grating must match the wavelength range of the pump light, and the bandwidth of the integrated grating must match the free spectral range of the microring resonator 7.

[0052] It should be noted that the aforementioned coupled waveguide 6 and micro-ring resonator 7 (and integrated grating) can be chip structures integrated on the same substrate.

[0053] In some embodiments, such as Figure 4As shown, the pumping unit includes at least 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. The laser 1 is used to output laser light, including but not limited to a fixed-frequency laser and a tunable laser. The polarization controller 2 is located at the output end of the laser 1 and is used to adjust the polarization direction of the laser light output from the laser 1. The optical amplifier 3 is located 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 located at the output end of the optical amplifier 3 and is used to filter out the spontaneous emission noise of the amplified laser light. The optical circulator 5 is located between the optical filter 4 and the micro-ring resonator unit and is used to isolate the optical signal output in reverse from the micro-ring resonator unit.

[0054] Laser 1, polarization controller 2, optical amplifier 3, optical filter 4 and optical circulator 5 are sequentially coupled through single-mode optical fiber, and optical circulator 5 is coupled to micro-ring resonator unit through 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 of the micro-ring resonator via a single-mode optical fiber, splitting the optical signal output by the micro-ring resonator into two paths. That is, the optical coupler 9 includes a first output and a second output. The first output is coupled to the spectrometer 10 via a single-mode optical fiber, enabling the spectrometer 10 to acquire and display the spectrum of the optical signal output by the micro-ring resonator. The second output is coupled to the photodetector 11 via a single-mode optical fiber, allowing the photodetector 11 to convert the optical signal output by the micro-ring resonator into an electrical signal recognizable by the oscilloscope 12, thereby enabling the acquisition and display of changes in the transmission power of the optical signal output by the micro-ring resonator.

[0056] like Figure 5 As shown, in the initial stage of frequency sweep, the transmission power of the micro-ring resonator 7 gradually decreases, 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 it will remain on a step until it is further tuned and jumps out of the resonance peak, and the transmission power recovers 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 dispersive microcavity optical frequency comb can be observed on the spectrometer 10. Figure 6 The image shows the spectrum of a normal dispersive microcavity optical frequency comb recorded on spectrometer 10. This embodiment achieves the generation of a normal dispersive optical frequency comb by pump light at various resonant peak positions within the range of 1542.17 nm to 1557.72 nm. Figure 4The results show the optical frequency comb spectra at pump wavelengths of 1543.62 nm, 1548.27 nm, 1552.93 nm and 1557.72 nm, respectively.

[0058] According to a second aspect of the embodiments of this application, a method for generating a normal dispersive microcavity optical frequency comb based on bidirectional pumping is provided, such as... Figure 4 and Figure 7 As shown, the method employs the apparatus described in any of the above embodiments and includes the following steps:

[0059] S1, the output end of the pump unit is coupled to the input end of the micro-ring resonator, so that the pump light output by the pump unit is incident into the coupling waveguide 6 of the micro-ring resonator, and the incident pump light is coupled into the micro-ring resonator cavity 7 of the micro-ring resonator from two opposite directions through the coupling waveguide 6.

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

[0061] In one embodiment, the step of adjusting the pump light output frequency of the pump unit is as follows: when the laser 1 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 resonant frequency of the micro-ring resonator 7. 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 resonator 7 is to adjust the input voltage of the microring resonator 7 so that the resonant frequency of the microring resonator 7 is continuously tuned and swept relative to the output frequency of the pump light (fixed frequency laser) from the red detuning position to the blue detuning position when the laser 1 in the pump unit is a fixed frequency laser.

[0063] Specifically, in the initial stage of the frequency sweep, the transmission power of the microring resonator 7 gradually decreases, and only the pump light frequency component can be recorded on the spectrometer 10. When the transmission power reaches its lowest point, a step occurs and it remains at a certain level until further tuning and jumping out of the resonance peak, at which point the transmission power recovers to its maximum value. Therefore, when the transmission power curve reaches the step position, the frequency sweep is stopped, and the normal dispersive microcavity optical frequency comb can be observed on the spectrometer 10.

[0064] In summary, this application provides a bidirectional pump-based normal dispersive microcavity optical frequency comb generation device and method. By coupling pump light into the microring resonator 7 from two opposite directions, and utilizing the feedback effect of the reverse injection of residual pump light and the cross-phase modulation effect, the optical frequency comb is generated with high robustness and high repeatability. Compared with existing normal dispersive microcavity optical frequency comb generation schemes, this application does not require mode coupling or pump light self-injection locking, and the phase of the reverse injection path of the pump light in this application does not affect the optical frequency comb generation effect, reducing additional control parameters of the system.

[0065] Meanwhile, this application can generate an optical frequency comb at any resonance peak of a normal dispersive microcavity simply by changing the pump laser output frequency or the resonant frequency of the microring resonator 7, thus improving the flexibility of the optical frequency comb generation device and method.

[0066] In the foregoing descriptions of the embodiments, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0067] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

Claims

1. A normal dispersion microcavity optical frequency comb generation device based on bidirectional pumping, characterized in that, Comprising: a pumping unit for providing pumping light; a micro-ring resonant unit including a micro-ring resonant cavity and a coupling waveguide, an input end of the coupling waveguide being connected with the pumping unit for receiving the pumping light, and an output end of the coupling waveguide being used for outputting an optical frequency comb; wherein the coupling waveguide is configured on a side of the micro-ring resonant cavity and is coupled with the micro-ring resonant cavity to form a plurality of coupling points, the plurality of coupling points coupling the pumping light to the micro-ring resonant cavity from two opposite directions respectively to form clockwise optical field and counterclockwise optical field in the micro-ring resonant cavity, and to excite generation of normal dispersion optical frequency comb in a process of sweeping frequency to adjust an output frequency of the pumping light or a resonant frequency of the micro-ring resonant cavity.

2. The apparatus of claim 1, wherein, The output frequency of the pumping light is tuned and swept from a blue detuning position of the resonant frequency of the micro-ring resonant cavity to a direction of decreasing frequency until the micro-ring resonant cavity works at a working point with modulation instability under joint action of self-phase modulation effect and cross-phase modulation effect to excite generation of normal dispersion optical frequency comb.

3. The apparatus of claim 1, wherein, The micro-ring resonant unit further includes a voltage source, and the resonant frequency of the micro-ring resonant cavity is swept from a red detuning position of the output frequency of the pumping light to a direction of increasing frequency under voltage driving of the voltage source until the clockwise optical field works at a working point with modulation instability under joint action of self-phase modulation effect and cross-phase modulation effect to excite generation of 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 micro-ring resonant cavity include a first coupling point and a second coupling point; the coupling waveguide couples the pumping light from the first coupling point to the micro-ring resonant cavity to form the clockwise optical field, and the residual pumping light after the first coupling is coupled reversely from the second coupling point to the micro-ring resonant cavity to form the counterclockwise optical field.

5. The device according to any one of claims 1 to 3, characterized in that The coupling waveguide and the micro-ring resonant cavity include a third coupling point, an integrated grating is arranged on the coupling waveguide between the third coupling point and the output end of the coupling waveguide, the coupling waveguide directly couples the pumping light from the third coupling point to the micro-ring resonant cavity to form the clockwise optical field, and the residual pumping light after the third coupling is emitted by the integrated grating and then reversely coupled from the third coupling point to the micro-ring resonant cavity to form the counterclockwise optical field.

6. The apparatus of claim 5, wherein, The center wavelength of the integrated grating is consistent with the wavelength range of the pumping light, and the bandwidth of the integrated grating is consistent with the free spectral range of the micro-ring resonant cavity.

7. The apparatus of claim 1, wherein, The pumping unit at least includes a fiber-optic sequentially connected laser, a polarization controller, an optical amplifier, an optical filter and an optical circulator; the laser is used for outputting laser; the polarization controller is arranged at an output end of the laser and is used for adjusting a polarization direction of the laser; the optical amplifier is arranged at an output end of the polarization controller and is used for adjusting an output power of the laser; the optical filter is arranged at an output end of the optical amplifier and is used for filtering spontaneous emission noise of the amplified laser; The optical circulator is arranged between the optical filter and the micro-ring resonant unit, and is used for isolating the optical signal output reversely by the micro-ring resonant unit.

8. The apparatus of claim 7, wherein, The laser at least includes 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, The method comprises the following steps: The output end of the pump unit is coupled to the input end of the micro-ring resonant unit, so that the pump light output by the pump unit is incident into the coupling waveguide of the micro-ring resonant unit; The coupling waveguide couples the incident pump light into the micro-ring resonant cavity of the micro-ring resonant unit from two opposite directions, respectively; A resonant peak of the micro-ring resonant cavity is selected as a reference resonant peak, and the output frequency of the pump light of the pump unit or the resonant frequency of the micro-ring resonant cavity is adjusted, so that the frequency difference between the output frequency of the pump light of the pump unit and the resonant frequency of the micro-ring resonant cavity is tuned from a direction greater than 0 to a direction less than 0 until the micro-ring 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 of claim 9, wherein, The step of adjusting the output frequency of the pump light of the pump unit or the resonant frequency of the micro-ring resonant cavity, so that the frequency difference between the output frequency of the pump light of the pump unit and the resonant frequency of the micro-ring resonant cavity is tuned from a direction greater than 0 to a direction less than 0, specifically comprises: 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 a blue detuning position to a red detuning position relative to the resonant frequency of the micro-ring resonant cavity; or When the laser in the pump unit is a fixed frequency laser, the input voltage of the micro-ring resonant cavity is adjusted so that the resonant frequency of the micro-ring resonant cavity is continuously tuned and swept from a red detuning position to a blue detuning position relative to the output frequency of the fixed frequency laser.

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