Octave light frequency comb generation system

Abstract

The application provides an octave light frequency comb generation system, which can be applied to the fields of light frequency precision measurement and optical clock, etc. The octave light frequency comb generation system comprises a double-pumped Brillouin loop subsystem and a nonlinear optical fiber spectrum expansion subsystem. The application utilizes dispersion compensation and pulse narrowing technology to expand the light frequency comb generated by the double-pumped Brillouin loop subsystem to an octave light frequency comb. Fiber gratings are used to suppress two pump lights in the Brillouin light frequency comb, which is simpler and more practical than space light modulator filtering. Dispersion compensation optical fiber is used for pulse shaping, and fiber amplifier is used to improve the pulse peak power entering the second high nonlinear optical fiber, and the second high nonlinear optical fiber utilizes self-phase modulation and four-wave mixing effect for spectrum expansion. Thus, the embodiment of the application solves the problem of low pulse energy of the double-pumped Brillouin light frequency comb, and realizes high-repetition-rate octave light frequency comb.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor optoelectronics, microwave photonics and nonlinear optics, and in particular to a octave optical frequency comb generation system. BACKGROUND

[0002] Optical frequency comb (referred to as optical frequency comb for short) is a mode-locked laser with equal frequency interval comb teeth in the frequency domain, and is a pulse light with fixed repetition frequency in the time domain. A stable optical frequency comb effectively links the optical wave and the microwave, and can directly measure the laser frequency, which plays an important role in the fields of optical frequency precision measurement, optical clock, spectroscopy, molecular identification and high-precision precision measurement. In terms of communication, the optical frequency comb can be used as a multi-wavelength light source in wavelength division multiplexing, and each comb tooth can be used as a data channel. In the field of microwave photonics, the beat frequency between the comb lines can generate microwaves, and radio frequency processing technology such as microwave photonics filter can be realized. The optical frequency comb is derived from the mode-locked laser, and the repetition frequency is in the order of megahertz. When it is expanded to gigahertz, the cavity length must be shortened, which is relatively difficult to achieve. The optical frequency comb with high repetition frequency (10-100GHz) has the advantages of high energy of a single comb tooth and easy to distinguish. At present, both the electro-optic modulation method and the microcavity Kerr optical frequency comb have realized octave optical frequency comb with a repetition frequency of more than 10GHz. However, the electro-optic modulation scheme needs cascaded lithium niobate modulators, the system insertion loss is high, the system is more complex, and the repetition frequency is limited by the frequency of the radio frequency source, which is difficult to reach hundreds of GHz. The microcavity Kerr optical frequency comb can achieve a repetition frequency of hundreds of GHz, but the tunability is poor, and only a small range of adjustment can be achieved by using the effect of refractive index change caused by material absorption heat light, and the process requirement is high. When the double-pumped light propagates in the high nonlinear optical fiber, the four-wave mixing effect can be used to realize the optical frequency comb with large and adjustable repetition frequency.

[0003] The realization of the optical frequency comb usually needs two commercial tunable lasers as pump light, which makes the system expensive and complex. CN104765218A proposes an optical frequency comb based on a single integrated microcavity laser, which no longer needs two commercial tunable lasers, making the system simpler. However, when the pump power increases to the Brillouin threshold in the optical fiber, most of the power is converted into counter-stokes light, which limits the bandwidth of the generated optical frequency comb. CN107465108A uses a nonlinear optical fiber loop to solve the influence of the Brillouin effect in the system, and enhances the four-wave mixing effect in the loop. However, it is difficult to further expand the Brillouin optical frequency comb to octave optical frequency comb, which limits its application in the field of high-precision precision measurement.

[0004] In order to realize the wide application of the optical frequency comb, it is necessary to propose a simple octave optical frequency comb system to better apply to the fields of optical frequency precision measurement, optical clock, etc. SUMMARY

[0005] The octave light frequency comb generation system provided by the present application can solve the problems of the prior art.

[0006] The octave light frequency comb generation system provided by the present application comprises a double-pumped Brillouin loop subsystem and a nonlinear fiber spectrum expansion subsystem.

[0007] The double-pumped Brillouin loop subsystem comprises a microcavity laser 101, a fiber circulator 102, a first high-nonlinear fiber 103 and an optical beam splitter 104.

[0008] The nonlinear fiber spectrum expansion subsystem comprises a fiber grating 105, a dispersion compensation fiber 106, a first fiber amplifier 107 and a second high-nonlinear fiber 108.

[0009] Optionally, the fiber circulator 102 is a three-port circulator, and the first port, the second port and the third port are sequentially arranged in a clockwise direction.

[0010] Optionally, the optical beam splitter 104 is further configured to split the input light beam into the first light beam and the second light beam according to a preset splitting ratio.

[0011] Optionally, the octave light frequency comb generation system further comprises a second fiber amplifier arranged between the microcavity laser 101 and the fiber circulator 102.

[0012] Optionally, the octave light frequency comb generation system further comprises a polarization controller arranged between the first high nonlinearity fiber 103 and the optical beam splitter 104, and the polarization controller is used to adjust the polarization state of the pump wave and the Stokes wave in the Brillouin loop.

[0013] Optionally, the fiber grating 105 is two cascaded fiber gratings, and the transmission light of the fiber grating 105 is input to the dispersion compensation fiber 106.

[0014] Optionally, the microcavity laser 101 comprises an electrically injected semiconductor microcavity laser, and the double-mode lasing with adjustable interval is realized by applying different injection currents; the cavity shape of the microcavity laser 101 comprises a square, an arc four-edged shape or a hexagon.

[0015] Optionally, the microcavity laser 101 comprises a coupled-cavity dual-wavelength laser, and the coupled-cavity dual-wavelength laser comprises a double-circular coupled-cavity laser or a double-square coupled-cavity laser.

[0016] Optionally, the double-mode laser beam emitted by the microcavity laser 101 is coupled out to the fiber optical circulator 102 through a tapered single-mode fiber.

[0017] Optionally, the octave light frequency comb generation system further comprises an optical spectrum analyzer connected to the output end of the second high nonlinearity fiber 108, and the optical spectrum analyzer is used for monitoring the spectrum of the generated light frequency comb by a user.

[0018] The octave light frequency comb generation system provided by the application has at least the following beneficial effects:

[0019] (1) The continuous wave generated by the double-pumped Brillouin loop is compressed into a time-domain narrow pulse by using the fiber grating, so that subsequent dispersion compensation and nonlinear spectrum expansion can be performed, and the problem that the Brillouin light frequency comb cannot be further expanded is solved. Compared with using a spatial light modulator, the application can realize spectrum shaping in a simpler and more practical way without complex programming control;

[0020] (2) By reasonably optimizing the length of the dispersion compensation fiber, the problem of input narrow pulse waveform distortion caused by the fiber amplifier is solved, which is beneficial to further expansion to an octave light frequency comb;

[0021] (3) The microcavity laser has the characteristics of small mode volume, high quality factor and low power consumption, and as the seed light of the octave light frequency comb, a direct current is applied on the cavity to realize double-mode lasing, so that two commercial tunable lasers are no longer needed, and a small-sized, low-power and tunable octave light frequency comb generation system is realized;

[0022] (4) By using the principle of compression pulse and dispersion compensation, only one order of spectrum expansion is needed after the Brillouin optical frequency comb to obtain the octave optical frequency comb with the spectral width of 1100nm-2200nm, the experimental system is simple and the repetition frequency is adjustable, and can be used for optical frequency precision measurement, optical clock and high-precision precision measurement field. BRIEF DESCRIPTION OF DRAWINGS

[0023] The above and other objects, features and advantages of the present application will become more apparent from the following description of embodiments of the present application, taken in conjunction with the accompanying drawings, in which:

[0024] Figure 1 The structure diagram of the octave optical frequency comb generation system of the embodiment of the present application is schematically shown;

[0025] Figure 2 The lasing spectrum of the microcavity laser of the embodiment of the present application when the injection current is 24mA is schematically shown;

[0026] Figure 3 The spectrum of the output of the beam splitter of the embodiment of the present application, i.e. the Brillouin loop, is schematically shown;

[0027] Figure 4 The transmission characteristics of one fiber grating and two cascaded fiber gratings of the embodiment of the present application are schematically shown;

[0028] Figure 5 The transmission spectrum of the Brillouin optical frequency comb of the embodiment of the present application through two cascaded fiber gratings is schematically shown;

[0029] Figure 6 The time-domain pulse contrast diagram of the Brillouin loop output and the fiber grating of the embodiment of the present application is schematically shown;

[0030] Figure 7 The time-domain pulse contrast diagram before and after the dispersion compensation of the embodiment of the present application is schematically shown;

[0031] Figure 8 The octave optical frequency comb spectrum diagram obtained by the high nonlinearity fiber spectrum expansion of the embodiment of the present application is schematically shown.

[0032]

BRIEF DESCRIPTION OF DRAWINGS

[0033] 101-microcavity laser; 102-fiber ring; 103-first high nonlinearity fiber; 104-optical beam splitter; 105-fiber grating; 106-dispersion compensation fiber; 107-first fiber amplifier; 108-second high nonlinearity fiber. DETAILED DESCRIPTION

[0034] In order to make the objects, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to specific embodiments and drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0035] The terms used herein are only used to describe specific embodiments, and are not intended to limit the present application. The terms "comprise", "contain", and the like used herein indicate the existence of the described features, steps, operations and / or components, but do not exclude the existence or addition of one or more other features, steps, operations or components.

[0036] In addition, in the following description, the description of well-known structures and techniques is omitted to avoid unnecessary confusion of the concept of the present application. All terms used herein (including technical and scientific terms) have meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein should be interpreted to have meanings consistent with the context of the present specification, and should not be interpreted in an idealized or overly formal manner.

[0037] Figure 1 The structure diagram of the octave light frequency comb generation system according to an embodiment of the present application is schematically shown.

[0038] As shown in Figure 1 The octave light frequency comb generation system according to an embodiment of the present application includes two subsystems, i.e. a dual-pumped Brillouin loop subsystem and a nonlinear fiber spectrum expansion subsystem.

[0039] The dual-pumped Brillouin loop subsystem includes a microcavity laser 101, a fiber circulator 102, a first high nonlinear fiber 103 and an optical beam splitter 104. The microcavity laser 101 is used to emit a dual-mode laser beam as seed light for light frequency comb generation; the fiber circulator 102 is used to transmit a Brillouin optical frequency comb generated by the first high nonlinear fiber 103 clockwise; the fiber circulator 102 transmits the dual-mode laser beam and the Brillouin optical frequency comb to the first high nonlinear fiber 103 and the optical beam splitter 104, respectively; the first high nonlinear fiber 103 is used to provide Brillouin gain and parametric gain for the input light beam to generate the Brillouin optical frequency comb; the optical beam splitter 104 is used to divide the input light beam into a first beam and a second beam, the first beam output from the first high nonlinear fiber 103 forms a Brillouin loop, and the second beam is transmitted to the nonlinear fiber spectrum expansion subsystem.

[0040] The nonlinear fiber spectrum expansion subsystem comprises a fiber grating 105, a dispersion compensation fiber 106, a first fiber amplifier 107 and a second high nonlinear fiber 108. The fiber grating 105 is used to output the input Brillouin optical frequency comb as narrow pulses; the dispersion compensation fiber 106 is used to pre-chirp the input narrow pulses; the first fiber amplifier 107 is used to amplify the optical power after the dispersion compensation fiber 106 to achieve the required pulse peak power of the second high nonlinear fiber 108; and the second high nonlinear fiber 108 is used to nonlinearly spectrally broaden the input light beam to generate an octave optical frequency comb.

[0041] According to the embodiment of the present application, the dual-pumped Brillouin ring subsystem can generate a Brillouin optical frequency comb, and the nonlinear fiber spectrum expansion subsystem uses a fiber grating and a dispersion compensation fiber to narrow the pulse, and obtain a narrow pulse of the order of hundreds of femtoseconds. The fiber grating is used to suppress two pump lights in the Brillouin optical frequency comb, which is more simple and practical than spatial light modulator filtering. The dispersion compensation fiber is used for pulse shaping, and the fiber amplifier increases the pulse peak power into the second high nonlinear fiber. The second high nonlinear fiber uses self-phase modulation and four-wave mixing effect for spectrum expansion. The present application solves the problem of low pulse energy of the dual-pumped Brillouin optical frequency comb by using dispersion compensation and pulse narrowing technology, and can realize a high repetition rate (20GHz-50GHz) octave optical frequency comb.

[0042] Specifically, the center wavelength of the fiber grating 105 is located at the pump light, which suppresses two pump lights of the Brillouin optical frequency comb and narrows the time-domain pulse to achieve narrow pulse output, which is beneficial to subsequent dispersion compensation and nonlinear spectral broadening. The dispersion compensation fiber 106 performs dispersion compensation and pulse shaping by optimizing its length, so that the waveform of the narrow pulse does not distort in the first fiber amplifier 107, effectively solving the problem of waveform distortion of the narrow pulse into the first fiber amplifier 107. The first fiber amplifier 107 can increase the pulse peak power into the second high nonlinear fiber 108, meeting the requirement of spectrum expansion to an octave optical frequency comb in the second high nonlinear fiber 108. The second high nonlinear fiber 108 as a nonlinear medium has a high nonlinear coefficient and a low group velocity dispersion coefficient, and can use four-wave mixing effect and self-phase modulation effect for nonlinear spectral broadening, thereby realizing an octave optical frequency comb.

[0043] In the embodiment of the present application, the fiber circulator 102 can be a three-port circulator, and the first port, the second port and the third port are sequentially arranged in a clockwise direction. The first port inputs a dual-mode laser beam, the second port is connected with the first high nonlinear fiber 103, and the third port is connected with the optical beam splitter 104.

[0044] Specifically, the optical beam splitter 104 is also configured to split the input light beam into a first beam and a second beam according to a preset splitting ratio. The preset splitting ratio can be, for example, 9:1, that is, the optical beam splitter 104 can split the light output from the third port of the fiber ring 102 into two parts according to a ratio of 9:1, in which 90% of the light is terminated to the first high nonlinear fiber 103 to form a Brillouin loop, and 10% of the light is terminated to the nonlinear fiber spectrum expansion subsystem.

[0045] In the embodiment of the present application, the octave light frequency comb generation system can further include a second fiber amplifier arranged between the microcavity laser 101 and the fiber ring 102, and the second fiber amplifier is configured to amplify the double-mode laser beam to achieve the required power for the Brillouin light frequency comb generation in the first high nonlinear fiber 103.

[0046] In the embodiment of the present application, the octave light frequency comb generation system can further include a polarization controller arranged between the first high nonlinear fiber 103 and the optical beam splitter 104, and the polarization controller is configured to adjust the polarization state of the pump wave and the Stokes wave in the Brillouin loop to obtain the maximum Brillouin gain.

[0047] In the embodiment of the present application, the fiber grating 105 is two cascaded fiber gratings, and the transmitted light of the fiber grating 105 is input to the dispersion compensation fiber 106. Thus, the octave light frequency comb generation system according to the embodiment can effectively suppress the pump light by using two cascaded fiber gratings according to the intensity difference between the pump light and the four-wave mixing frequency component in the Brillouin light frequency comb, to achieve time-domain pulse shaping. Compared with using a spatial light modulator, the embodiment of the present application does not need complex programming control, and can achieve spectral shaping in a simpler and more practical way.

[0048] In the embodiment of the present application, the microcavity laser 101 can include an electrically injected semiconductor microcavity laser, and the double-mode lasing interval can be adjusted by applying different injection currents. Thus, it can be seen that the technical solution can change the double-mode interval of the laser lasing by changing the injection current of the microcavity laser 101, so as to realize the octave light frequency comb with tunable repetition frequency.

[0049] Specifically, the cavity shape of the microcavity laser 101 can include a square, an arc-edged quadrilateral, or a hexagon. It should be noted that in other embodiments, the microcavity laser 101 can also use other microcavity shapes to achieve a larger range of tunable repetition frequency.

[0050] In the embodiment of the present application, the microcavity laser 101 can also include a coupled-cavity dual-wavelength laser, which includes a double-circular coupled-cavity laser or a double-square coupled-cavity laser. Thus, the microcavity laser 101 can adjust the interval of the dual-wavelength by changing the injection current of the two coupled cavities, to realize the tunable repetition frequency.

[0051] In the embodiment of the present application, the bimodal laser beam emitted by the microcavity laser 101 is coupled out to the fiber ring 102 through a tapered single-mode fiber.

[0052] In addition, the octave light frequency comb generation system can also use other optical devices to receive or monitor the characteristics of the generated octave light frequency comb. For example, in some embodiments, the octave light frequency comb generation system can also include a spectrometer connected to the output end of the second high nonlinearity fiber 108, and the spectrometer is used for the user to monitor the spectrum of the generated light frequency comb.

[0053] Based on the above disclosed technical solutions, the working principle of the nonlinear optical fiber spectrum expansion subsystem in the embodiment of the present application is as follows:

[0054] The function of the fiber grating 105 is to narrow the time-domain pulse generated by the double-pumped Brillouin loop. Because the pump light in the Brillouin light frequency comb is relatively strong, there is a large power difference with the newly generated frequency component, resulting in a continuous wave form of the time-domain pulse. The fiber grating 105 reflects the light at the pump wavelength, suppresses the pump light to achieve pulse narrowing, which is beneficial to subsequent dispersion compensation and nonlinear spectrum expansion. In order to amplify the power of the pulse, the dispersion compensation fiber 106 is used to pre-chirp the input pulse. Since the narrow pulse will cause nonlinear effects when entering the first fiber amplifier 107, and the single-mode fiber in the first fiber amplifier 107 has abnormal dispersion, which further causes distortion of the input pulse waveform, it is necessary to reasonably optimize the length of the dispersion compensation fiber 106 for dispersion compensation and pulse shaping. Then, the input pulse is amplified by the first fiber amplifier 107 to increase the pulse peak power to meet the requirements of realizing the octave light frequency comb.

[0055] The following will be based on the structure of Figure 1 , and the element structure of the octave light frequency comb generation system will be described in detail through Figures 2-8 a specific embodiment.

[0056] In an embodiment of the present application, the microcavity laser 101 is a square laser with a side length of 30 μm and a waveguide width of 2.5 μm.

[0057] In an embodiment of the present application, the fiber grating 105 is two cascaded fiber gratings, the center wavelength of the fiber grating 105 is located at 1550 nm, the filter bandwidth is > 2 nm, and the reflectivity is > 99%. According to the difference in the strength of the teeth in the Brillouin light frequency comb, the fiber grating 105 in an embodiment of the present application uses two cascaded fiber gratings to effectively suppress the pump light.

[0058] In one embodiment of the present invention, the dispersion compensation fiber 106 exhibits normal dispersion in the range of 1525nm-1575nm, with a dispersion coefficient larger than that of standard single-mode fiber. The dispersion coefficient at 1550nm is -140ps / nm / km, and only a length of 5m is required to meet the dispersion compensation of the pulse.

[0059] In one embodiment of the present invention, a second fiber amplifier is connected after the microcavity laser 101 to amplify the optical signal and achieve the power required for the Brillouin optical frequency comb to be generated in the highly nonlinear fiber 103.

[0060] In one embodiment of the present invention, a spectrometer and an optical pulse analyzer are connected after the second highly nonlinear optical fiber 108, wherein the spectrometer is used to monitor the results in the frequency domain and the optical pulse analyzer is used to acquire pulse information in the time domain.

[0061] The above is merely an illustrative example, and the embodiments of the present invention are not limited thereto. For example, the microcavity laser 101, the fiber circulator 102, the first highly nonlinear fiber 103, the optical beam splitter 104, the fiber grating 105, the dispersion compensation fiber 106, the first fiber amplifier 107, and the second highly nonlinear fiber 108 are all interconnected via standard single-mode optical fibers.

[0062] Figure 2 The diagram illustrates the lasing spectrum of a microcavity laser with an injection current of 24 mA according to an embodiment of the present invention.

[0063] like Figure 2 As shown, in some embodiments, the lasing spectrum of the microcavity laser 101 with an injection current of 24 mA achieves dual-mode lasing, with lasing wavelengths of 1550.0 nm and 1550.3 nm, respectively, a dual-mode interval of 0.3 nm, and a corresponding frequency interval of 38 GHz. Therefore, it can be seen that the microcavity laser 101 in this embodiment can achieve dual-mode lasing through injection current.

[0064] Figure 3 The diagram illustrates the spectrum output from one end of the beam splitter, i.e., the Brillouin loop, according to an embodiment of the present invention.

[0065] like Figure 3 As shown, a Brillouin frequency comb spectrum with a width of 50 nm is generated when a dual-pump light with a power of 640 mW enters a 120 m Brillouin loop. However, due to the 22 dB intensity difference between the dual-pump light of the Brillouin frequency comb and the newly generated frequency, the optical pulse width is relatively wide, which is not conducive to generating an octave band frequency comb in subsequent spectral spreading.

[0066] Figure 4 The illustration schematically shows the transmission characteristics of a fiber Bragg grating and two cascaded fiber Bragg gratings according to an embodiment of the present invention.

[0067] likeFigure 4 The figure shows the transmission characteristics of a single fiber Bragg grating and two cascaded fiber Bragg gratings. A broadband light source was used to test the transmission characteristics within fiber Bragg grating 105. The dashed line represents the broadband light source spectrum without passing through the fiber Bragg grating, while the dotted line represents the transmission spectrum after passing through a single fiber Bragg grating, attenuating the light at 1550 nm by 20 dB with a filtering bandwidth of 2 nm. The straight line represents the transmission spectrum after passing through two cascaded fiber Bragg gratings, where the light source attenuation increased to 30 dB. Since the intensity difference between the pump light and the four-wave mixing frequency components in the Brillouin optical frequency comb is approximately 22 dB, this embodiment uses two cascaded fiber Bragg gratings to suppress the pump light.

[0068] Figure 5 The illustration shows the transmission spectrum of a Brillouin optical frequency comb through two cascaded fiber gratings according to an embodiment of the present invention.

[0069] like Figure 5 As shown, the transmission spectrum of the Brillouin optical frequency comb after passing through the fiber grating 105 is illustrated. Connecting a fiber grating 105 with a center wavelength of 1550 nm after the Brillouin loop utilizes the reflectivity of the fiber grating 105 to suppress the pump light, reducing the intensity difference between the comb teeth and solving the problem of subsequent spectral expansion of the Brillouin optical frequency comb.

[0070] Figure 6 The diagram illustrates a comparison of the time-domain pulses after the Brillouin loop output and the fiber grating in an embodiment of the present invention.

[0071] like Figure 6 The image shows a comparison of the time-domain pulse results of the Brillouin loop output and the fiber Bragg grating 105 output. The Brillouin loop output is continuous light with a large base; however, after passing through the fiber Bragg grating, the pulse is significantly narrowed, and the base is reduced, which is beneficial for subsequent dispersion compensation and nonlinear spectral spreading.

[0072] Figure 7 The diagram illustrates a comparison of time-domain pulses before and after dispersion compensation according to an embodiment of the present invention.

[0073] like Figure 7 The image shows a comparison before and after pulse shaping using dispersion-compensating fiber. The dispersion-compensating fiber 106 is pre-chirped, and the average power of the pulse is amplified to 316mW by the first fiber amplifier 107, generating a narrow pulse with a pulse width of 494fs, and the base is further reduced.

[0074] Figure 8 The diagram illustrates an octave band optical comb spectrum obtained by spreading a highly nonlinear optical fiber according to an embodiment of the present invention.

[0075] like Figure 8As shown, the narrow pulse with the pulse width of 494fs pumps the high nonlinear fiber of 20m to expand the spectrum and obtain the optical frequency comb spectrum. It can be seen that the spectrum range is 1100nm-2200nm, and a octave optical frequency comb is realized. The optical frequency comb with a wider spectrum can be realized by continuously increasing the amplification power of the first fiber amplifier 107 or lengthening the second high nonlinear fiber 108.

[0076] In summary, the embodiment of the present application provides a octave optical frequency comb generation system, which uses dispersion compensation and pulse narrowing technology to expand the optical frequency comb generated by the double-pumped Brillouin loop subsystem to a octave optical frequency comb. The fiber grating is used to suppress the two pump lights in the Brillouin optical frequency comb, which is more simple and practical than the spatial light modulator filtering. The dispersion compensation fiber is used for pulse shaping, the fiber amplifier increases the pulse peak power into the second high nonlinear fiber, and the second high nonlinear fiber uses self-phase modulation and four-wave mixing effect for spectrum expansion. Thus, the embodiment of the present application solves the problem of low pulse energy of the double-pumped Brillouin optical frequency comb by using dispersion compensation and pulse narrowing technology, and can realize a high repetition rate (20GHz-50GHz) octave optical frequency comb.

[0077] It should be noted that throughout the drawings, identical elements are represented by the same or similar reference numerals. When it may cause confusion in understanding the present application, conventional structures or configurations will be omitted. And the shape, size, positional relationship of the components in the drawings do not reflect the true size, proportion and actual positional relationship. In addition, in the claims, any reference symbols located between parentheses should not be construed as a limitation on the claims.

[0078] In addition, the terms "first", "second" are only used for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "a plurality of" is at least two, such as two, three, etc., unless otherwise explicitly specified.

[0079] The above-described specific embodiments further illustrate the purpose, technical solutions and beneficial effects of the present application. It should be understood that the above-described specific embodiments are only specific embodiments of the present application and are not used to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. An octave band optical frequency comb generation system, characterized in that, include: The dual-pump Brillouin loop subsystem includes a microcavity laser (101), an optical fiber circulator (102), a first highly nonlinear optical fiber (103), and an optical beam splitter (104), wherein: A microcavity laser (101) is used to emit a dual-mode laser beam as a seed light for the generation of an optical frequency comb; an optical fiber circulator (102) is used to transmit the Brillouin optical frequency comb generated by a first highly nonlinear fiber (103) clockwise, wherein the optical fiber circulator (102) transmits the dual-mode laser beam and the Brillouin optical frequency comb to the first highly nonlinear fiber (103) and the optical beam splitter (104) respectively; the first highly nonlinear fiber (103) is used to provide Brillouin gain and parametric gain to the input beam to generate the Brillouin optical frequency comb; the optical beam splitter (104) is used to split the input beam into a first beam and a second beam, wherein the first beam is transmitted to the first highly nonlinear fiber (103) to form a Brillouin loop, and the second beam is transmitted to the nonlinear fiber spread spectrum subsystem; The nonlinear fiber spectral spreading subsystem includes a fiber grating (105), a dispersion-compensating fiber (106), a first fiber amplifier (107), and a second highly nonlinear fiber (108), wherein: A fiber grating (105) is used to output the input Brillouin optical frequency comb as a narrow pulse; a dispersion-compensating fiber (106) is used to pre-chirp the input narrow pulse; a first fiber amplifier (107) is used to amplify the optical power after passing through the dispersion-compensating fiber (106) to achieve the pulse peak power required by the second high nonlinear fiber (108); and the second high nonlinear fiber (108) is used to nonlinearly broaden the input beam to generate an octave optical frequency comb.

2. The octave band optical frequency comb generation system according to claim 1, wherein, The fiber optic circulator (102) is a three-port circulator, with a first port, a second port and a third port arranged in a clockwise direction; The first port receives the dual-mode laser beam, the second port is connected to a first highly nonlinear optical fiber (103), and the third port is connected to an optical beam splitter (104).

3. The octave band optical frequency comb generation system according to claim 1, wherein, The optical beam splitter (104) is also used to split the input beam into a first beam and a second beam according to a preset beam splitting ratio.

4. The octave band optical frequency comb generation system according to claim 1, wherein, The octave band optical frequency comb generation system also includes: A second fiber amplifier is disposed between the microcavity laser (101) and the fiber circulator (102). The second fiber amplifier is used to amplify the dual-mode laser beam to achieve the power required for the Brillouin optical frequency comb in the first highly nonlinear fiber (103) to generate.

5. The octave band optical frequency comb generation system according to claim 1, wherein, The octave band optical frequency comb generation system also includes: A polarization controller is disposed between a first highly nonlinear fiber (103) and an optical beam splitter (104), the polarization controller being used to adjust the polarization state of the pump wave and the Stokes wave in the Brillouin loop.

6. The octave band optical frequency comb generation system according to claim 1, wherein, The fiber grating (105) consists of two cascaded fiber gratings, and the transmitted light of the fiber grating (105) is input to the dispersion compensation fiber (106).

7. The octave band optical frequency comb generation system according to claim 1, wherein, The microcavity laser (101) includes an electrically injected semiconductor microcavity laser, which achieves tunable dual-mode lasing by applying different injection currents; The cavity shape of the microcavity laser (101) includes a square, a curved quadrilateral, or a hexagon.

8. The octave band optical frequency comb generation system according to claim 1, wherein, The microcavity laser (101) includes a coupled-cavity dual-wavelength laser, which includes a dual-circular coupled-cavity laser or a dual-square coupled-cavity laser.

9. The octave band optical frequency comb generation system according to claim 1, wherein, The dual-mode laser beam emitted by the microcavity laser (101) is coupled to the fiber optic circulator (102) through a tapered single-mode fiber.

10. The octave band optical frequency comb generation system according to claim 1, wherein, The octave band optical frequency comb generation system also includes: A spectrometer, connected to the output of a second highly nonlinear optical fiber (108), is used by a user to monitor the spectrum of the generated optical frequency comb.

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