Optical frequency comb generating device, application system and method

Abstract

The present invention discloses an optical frequency comb generation device, application system and method. The present invention generates an optical frequency comb array through spatial multiplexing locking of an integrated gain waveguide structure, and the pulse repetition frequency can reach the GHz level, which can solve the technical problems of the existing optical frequency comb structure being complex and having limited application scenarios, and realize the integration and functionality of the optical frequency comb system.

Description

Technical Field

[0001] The present invention relates to the field of optics, and in particular to an optical frequency comb generating device, an application system and a method. Background Art

[0002] As a bridge between radio frequency and light waves, optical frequency comb is a revolutionary technology in the field of precision measurement, playing an important role in ultra-fine spectroscopy, global satellite positioning, time-frequency transfer and high-precision ranging. Existing optical frequency combs are mainly based on mode-locked lasers and electro-optic modulators. Although the optical frequency comb generated by electro-optical modulation can produce repetition rates above GHz, there are problems with time domain pulse jitter and excessive modulation depth in the frequency domain. Additional circuit units are required to reduce noise, making the system very complicated to implement. Mode-locked lasers are currently the mainstream way to achieve high-energy, high-stability optical combs. However, the frequency of commercial optical frequency combs is at the hundreds of MHz level, and the usage scenarios are limited. Expansion to other bands requires nonlinear frequency conversion, which will increase the complexity of the system. Summary of the invention

[0003] In view of this, an object of the present invention is to provide an optical frequency comb generating device, an application system and a method.

[0004] To achieve this object, the present invention adopts the following technical solutions:

[0005] According to one aspect of the present application, there is provided an optical frequency comb generating device, comprising:

[0006] A gain waveguide module, used for generating a mode-locked laser output through a gain waveguide;

[0007] A pumping and wavelength division multiplexing module, used for pumping each gain waveguide in the gain waveguide module, and coupling and outputting a frequency comb signal of each gain waveguide in the gain waveguide module;

[0008] A pulse modulation and PZT driving module, used for pulse modulation of the mode-locked laser output, and receiving a control signal to control the mode-locked pulse repetition frequency of the gain waveguide;

[0009] A pulse repetition frequency and carrier envelope test module, used to detect and output the pulse repetition frequency information and carrier envelope beat frequency information of the frequency comb signal;

[0010] A radio frequency signal generating module, used for generating a radio frequency reference signal;

[0011] A phase-locked circuit module is used to generate a control signal for the pulse modulation and PZT driving module according to the RF reference signal and the pulse repetition frequency information; generate a control signal for the pump and wavelength division multiplexing module according to the carrier-envelope beat frequency information and the RF reference signal, and synchronously control the carrier-envelope phase of the gain waveguide module.

[0012] Optionally, the gain waveguide module includes 1 to n gain waveguides to form a gain waveguide array, where n≥1;

[0013] The active ions of the gain waveguide include rare earth ions that can cover wavelengths from 1 μm to 3 μm, and the rare earth ions include Tm, Er, Yb and other transition metal ions, including Cr, Ti, Fe and Co;

[0014] The activation ions and waveguide materials are determined according to the output wavelength, and the corresponding pump source wavelength is determined according to the absorption spectrum of the activated ions in the waveguide material.

[0015] Optionally, the first end face of each gain waveguide in the gain waveguide module is provided with a film layer that enhances the transmittance of the pump light and partially reflects the gain medium laser, and the second end face is provided with a film layer that enhances the transmittance of the gain medium laser. The gain medium laser oscillates in a resonant cavity composed of the first end face film layer and the pulse modulation and PZT drive module to generate a mode-locked laser output array.

[0016] Furthermore, the pulse repetition frequency and carrier envelope test module may include:

[0017] A beam splitting submodule, used for splitting the mode-locked laser outputted from one of the gain waveguides again to obtain at least two split beam signals;

[0018] A detection submodule, used for detecting one of the split beam signals, obtaining a pulse repetition frequency signal, and sending the signal to the phase-locked circuit module;

[0019] The laser amplification and carrier envelope detection submodule is used to perform laser amplification and carrier envelope phase shift frequency detection according to another split beam signal, obtain a beat frequency signal, and send it to the phase-locked circuit module.

[0020] Furthermore, the pulse modulation and PZT driving module may include:

[0021] A mode-locked pulse modulation submodule, which, together with the gain waveguide end face of the gain waveguide module, forms a laser resonant cavity of each gain waveguide;

[0022] The PZT driving submodule is used to receive the control signal of the phase-locked circuit module, adjust the relative position of the mode-locked pulse modulation submodule and the gain waveguide module, and control the cavity length of each gain waveguide and the corresponding pulse repetition frequency.

[0023] According to another aspect of the present application, an optical frequency comb application system is provided, comprising the generating device described above, which is applied to ranging systems, gas detection systems, spectroscopy measurement systems, and quantum manipulation systems, etc.

[0024] According to another aspect of the present application, a method for generating an optical frequency comb is provided, comprising the following steps:

[0025] Producing a gain waveguide array structure based on a solid laser gain medium;

[0026] According to the resonant cavity formed by the end face of the gain waveguide and the pulse modulation and PZT driving module, a mode-locked pulse laser frequency comb array is generated;

[0027] According to the splitting signal after the splitting of one of the gain waveguides and the radio frequency reference signal, a control signal for modulating the mode-locked pulse is obtained to control the repetition frequency of the mode-locked pulse of each gain waveguide;

[0028] A carrier-envelope beat frequency signal is generated according to another split signal after one of the gain waveguides is split, and a control signal of the carrier-envelope phase of each gain waveguide is generated according to the carrier-envelope beat frequency signal and a radio frequency reference signal.

[0029] Furthermore, the step of obtaining a modulated mode-locked pulse control signal according to a splitting signal after the splitting of one of the gain waveguides and a radio frequency reference signal, and controlling the mode-locked pulse repetition frequency of each gain waveguide may specifically include:

[0030] One of the split beam signals after the gain waveguide splitting is detected to obtain a radio frequency pulse signal;

[0031] Mixing the radio frequency pulse signal and the radio frequency reference signal to obtain an error signal;

[0032] generating a mode-locked pulse repetition frequency control signal according to the error signal;

[0033] The relative position of the corresponding gain waveguide and the pulse modulation and PZT driving module is controlled according to the pulse repetition frequency control signal, and the repetition frequency of the mode-locking pulse of each corresponding gain waveguide is locked.

[0034] Optionally, generating a carrier-envelope beat frequency signal according to another split signal after one of the gain waveguides is split, and generating a control signal of the carrier-envelope phase of each gain waveguide according to the carrier-envelope beat frequency signal and a radio frequency reference signal may specifically include:

[0035] Performing laser amplification and carrier envelope offset frequency detection on another split signal after one of the gain waveguide splits, to obtain a 2f-f beat frequency signal;

[0036] Mixing the carrier envelope 2f-f beat frequency signal and the radio frequency reference signal to obtain an error signal;

[0037] A current driving control signal of a pump driving power supply in a pump and wavelength division multiplexing module is generated according to the error signal, and the carrier envelope phase offset frequency of each gain waveguide is synchronously controlled.

[0038] The optical frequency comb generating device, application system and method proposed in this solution have one or more of the following beneficial effects:

[0039] 1. The spatial multiplexing mode-locking of the integrated gain waveguide structure is used to generate an optical frequency comb array. The technical solution proposed in the present invention can simultaneously generate multiple mode-locked optical frequency combs from a compact waveguide structure, and the pulse repetition frequency can reach the GHz level, which expands the pulse repetition frequency of existing optical frequency combs.

[0040] 2. Depending on the type of gain medium selected by the gain waveguide array, the laser wavelength can cover the mid-infrared 2μm band.

[0041] 3. The existing optical frequency comb has only one light source, and it is difficult to realize the synchronous spatial multiplexing output of multiple frequency comb light sources in an integrated device. The present invention can realize multiple light sources through waveguide arrays, realize multiple optical frequency combs, and further realize the integration and functionality of the optical frequency comb system.

[0042] In the prior art, early optical frequency combs were mainly based on all-solid-state lasers, especially titanium sapphire lasers operating in the 800nm ​​band. However, the cavity length of the all-solid-state mode-locked laser is in the meter level, and multiple cavity mirrors are required for reflection, as well as dispersion management in the cavity, making the system structure very large and complex. With the development of fiber laser technology, especially polarization-maintaining fiber technology, most of the optical elements of the mode-locked laser resonant cavity can be composed of all-fiber devices fused to each other, but limited by the coiling radius of the optical fiber, the size of the overall structure can only be controlled within a space of more than ten to tens of centimeters. The stacked coiling of the mode-locked fiber laser can effectively shorten the cavity length of the fiber laser, which enables the pulse repetition rate of the mode-locked laser to be controlled below several hundred MHz. Ordinary technicians in this field can only think of using conventional optical fibers, crystals and other laser gain components to generate optical frequency combs, and would not think of using integrated gain waveguide arrays. First, the existing reported crystal gain waveguides use traditional cutting and polishing processes, and the waveguide size is large, at a size of hundreds of microns, and it is difficult to process gain waveguide arrays on a single crystal; second, the substrate of the waveguide requires a transparent dielectric material with a lower refractive index, which involves low-loss bonding of the material to the gain waveguide, making the complexity of the entire process beyond the scope of existing solid-state laser technology.

[0043] The inventors of this applicant have long-term research experience in solid-state laser technology and lithium niobate integrated waveguide technology. They found that increasing the active ion doping concentration of laser crystals can significantly shorten the required laser crystal length, controlling the crystal length from dozens of millimeters to a few millimeters (1-2 mm), which is very suitable for processing into a gain waveguide array integrated on a single crystal. Therefore, in this application, the light-proof characteristics of the gain waveguide can significantly improve the laser efficiency, and cooperate with the waveguide and pulse modulation module ( Figure 1 The special coating process of the two end faces of the middle module 3 (as shown in Figure 3) can control the resonant cavity length to a few mm, and produce a multi-channel spatial multiplexing mode-locked laser frequency comb. In terms of coupling the fiber laser into the optical waveguide, it can be achieved by coupling the multi-channel fiber output beam into multiple waveguides. This application couples the multi-channel fiber output beam into multiple waveguides, and through the wavelength division multiplexing array, while realizing the pump light entering the waveguide, the mode-locked optical frequency comb signal of each waveguide is extracted, which solves the difficulties of the prior art, realizes multi-channel light sources through the waveguide array, realizes multi-channel optical frequency comb, and further realizes the integration and functionality of the optical frequency comb system.

[0044] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the written description, claims, and drawings.

[0045] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0047] Figure 1 It is a structural schematic diagram of Embodiment 1 of the optical frequency comb generating device and method proposed by the present invention;

[0048] Figure 2 It is a structural schematic diagram of Embodiment 2 of the optical frequency comb generating device and method proposed by the present invention;

[0049] Figure 3a Schematic diagram of an embodiment of a gain waveguide module in an optical frequency comb generating device proposed by the present invention;

[0050] Figure 3b is a schematic diagram of another embodiment of a gain waveguide module in the optical frequency comb generating device proposed by the present invention;

[0051] Figure 4 It is a schematic diagram of the structure of an embodiment of a pump and wavelength division multiplexing module in an optical frequency comb generating device proposed in the present invention;

[0052] Figure 5 This is a schematic diagram of an embodiment of a pulse modulation and PZT driving module in an optical frequency comb generating device proposed by the present invention;

[0053] Figure 6 This is a schematic diagram of an embodiment of the laser amplification and carrier envelope detection submodule in the optical frequency comb generation device proposed in the present invention.

[0054] Description of reference numerals:

[0055] 1——gain waveguide module; 101, 102, ..., 10n——the first, second, ..., nth gain waveguide; 110——waveguide substrate; 121, 122——the first and second coating layers;

[0056] 2——Pump and wavelength division multiplexing module; 21, 22, 23, 24——1st, 2nd, 3rd, 4th wavelength division multiplexer; 25——Pump laser module; 261, 262, 263——Beam splitter; 27——Pump laser driving power supply; 211, 221, 231, 241——Pump port; 213, 223, 233, 243——Multiplexing port; 212, 222, 232, 242——Output port;

[0057] 3——Pulse modulation and PZT driving module; 31——Pulse modulator; 32——PZT crystal; 33——PZT driving submodule;

[0058] 4——beam splitter; 401, 402, 403——ports 401-403 of beam splitter 4;

[0059] 5, 7 - photodetectors; 6 - laser amplification and carrier envelope detection submodule; 61 - laser amplification submodule; 62 - supercontinuum and double frequency cascade waveguide submodule; 63 - group velocity matching submodule;

[0060] 8——RF signal generator; 801, 802——RF reference signal;

[0061] 9, 10——phase-locked circuit module; 901, 902, 903——ports of phase-locked circuit 9; 1001, 1002, 1003——ports of phase-locked circuit 10;

[0062] 11——Pulse repetition frequency and carrier envelope test module. DETAILED DESCRIPTION

[0063] The preferred embodiments of the present invention are described below in conjunction with the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0064] Figure 1 FIG. 1 is a schematic diagram of the structure of an optical frequency comb generating device and method according to an aspect of the present invention; Figure 1 As shown, the device of this embodiment includes:

[0065] A gain waveguide module 1 having a micro-nano structure, a pump and wavelength division multiplexing module 2, a pulse modulation and PZT driving module 3, a pulse repetition frequency and carrier envelope detection module 11, a radio frequency signal generation module 8, and phase-locked circuit modules 9 and 10.

[0066] like Figure 1 As shown, including:

[0067] A gain waveguide module 1, used for generating a mode-locked laser output through a gain waveguide;

[0068] A pumping and wavelength division multiplexing module 2, used for pumping each gain waveguide outputted by the mode-locked laser, and coupling and outputting a frequency comb signal of each gain waveguide in the gain waveguide module;

[0069] A pulse modulation and PZT driving module 3, used for pulse modulation of the mode-locked laser output, and receiving a control signal to control the mode-locked pulse repetition frequency of the gain waveguide;

[0070] The pulse repetition frequency and carrier envelope test module 11 is used to detect and output the pulse repetition frequency information and carrier envelope beat frequency information of the frequency comb signal;

[0071] A radio frequency signal generating module 8, used for generating a radio frequency reference signal;

[0072] The phase-locked circuit modules 9 and 10 are used to generate control signals of the pulse modulation and PZT drive modules according to the RF reference information and the pulse repetition frequency signal, and control the mode-locked pulse repetition frequency of the gain waveguide module 1; and to generate control signals of the wavelength division multiplexing module according to the carrier envelope beat frequency signal and the RF reference signal, such as generating a pump drive power supply 27 (such as Figure 4 The control signal (as shown) is used to synchronously control the carrier envelope phase of the gain waveguide module.

[0073] like Figure 1 As shown, the method of this embodiment includes:

[0074] Producing a gain waveguide array structure based on a solid laser gain medium;

[0075] According to the resonant cavity formed by the end face of the gain waveguide 1 and the pulse modulation and PZT driving module 3, a mode-locked pulse laser frequency comb array is generated;

[0076] According to the splitting signal after the splitting of one of the gain waveguides and the radio frequency reference signal, a control signal for modulating the mode-locked pulse is obtained to control the repetition frequency of the mode-locked pulse of each gain waveguide;

[0077] A carrier envelope beat frequency signal is generated according to another split signal after one of the gain waveguides is split, and a control signal of the carrier envelope phase of each gain waveguide is generated according to the carrier envelope beat frequency signal and the RF reference signal. Figure 1 is implemented in the device shown.

[0078] Figure 2 FIG. 1 is a schematic diagram of a second embodiment of an optical frequency comb generating device and method according to one aspect of the present invention. Figure 2 As shown, in the device of this embodiment, the pulse repetition frequency and carrier envelope test module 11 includes:

[0079] Beam splitting submodule 4, such as Figure 2 The middle part may be an online beam splitter 4, which is used to split the mode-locked laser 401 output after coupling from one of the gain waveguides again to obtain at least two split signals 402 and 403. This embodiment only takes two split signals as an example. If divided into three beams, two of the split signals are used to test the repetition rate and carrier envelope, and the remaining split signal can also be used for detection like other waveguides.

[0080] The first detection submodule 5, such as Figure 2 The photodetector 5 may be used to detect one of the split beam signals 402, obtain a pulse repetition frequency signal, and send it to the phase-locked circuit module 10;

[0081] The laser amplification and carrier envelope detection module 6 is used to perform laser amplification and carrier envelope phase shift frequency detection according to another split beam signal 403 to obtain a beat frequency signal;

[0082] The second detection submodule 7, such as Figure 2 The photoelectric detector 7 can be used to detect the beat frequency signal and send the phase-locked circuit module 9. The module 6 and the module 7 can also be integrated to realize the corresponding functions of laser amplification and carrier envelope detection.

[0083] like Figure 1-2 As shown, in the optical frequency comb generation method,

[0084] The modulation mode-locked pulse control signal is obtained according to the splitting signal after the splitting of one of the gain waveguides and the radio frequency reference signal, and the mode-locked pulse repetition frequency of each gain waveguide is controlled, which may specifically include:

[0085] One of the split beam signals after the gain waveguide splitting is detected to obtain a radio frequency pulse signal;

[0086] Mixing the radio frequency pulse signal and the radio frequency reference signal to obtain an error signal;

[0087] generating a mode-locked pulse repetition frequency control signal according to the error signal;

[0088] The relative position of the corresponding gain waveguide is controlled according to the pulse repetition frequency control signal, and the mode-locking pulse repetition frequency of each corresponding gain waveguide is locked.

[0089] Generating a carrier envelope beat frequency signal according to another split signal after one of the gain waveguides is split, and generating a control signal of the carrier envelope phase of each gain waveguide according to the carrier envelope beat frequency signal and the radio frequency reference signal may specifically include:

[0090] The other split signal after one of the gain waveguide splits is subjected to laser amplification and carrier envelope offset frequency detection to obtain a 2f-f beat frequency signal;

[0091] Mixing the carrier envelope 2f-f beat frequency signal and the radio frequency reference signal to obtain an error signal;

[0092] A control signal is generated according to the error signal to synchronously control the carrier envelope phase offset frequency of each gain waveguide.

[0093] like Figure 1-Figure 2 As shown, the device and method of the present invention can be understood, but not limited to Figure 1-Figure 2The embodiment structure can also be modified accordingly based on the essence of the present invention. For example, the solid laser gain medium can be processed into an array waveguide structure (such as Figure 3a and Figure 3b As shown), each waveguide end face is connected to the pulse modulation and the pulse modulation submodule in the PZT driving module 3 (eg Figure 5 The centimeter-level small resonant cavity formed by the mode-locked pulse modulator 31 in the middle can generate a GHz-level mode-locked pulse laser array. The first split beam signal 402 after the first waveguide split is further detected by a photodetector such as a detection submodule 5, and the detected RF pulse signal is connected to the mixing ports 1001 and 1002 of the phase-locked circuit module 10 together with the RF reference signal 801 generated by the RF signal generation module 8, for example, calibrated by a rubidium atomic clock, to obtain an error signal and output a high-voltage control signal 1003, and the PZT drive module equipped with the pulse modulation device is controlled, such as by controlling the drive submodule 33. Figure 5 The relative position of the mode-locked pulse modulator 31 and the waveguide module 1 can thereby simultaneously lock the mode-locked pulse repetition frequency of each stage of the waveguide.

[0094] The second split signal 403 after the first waveguide is split is connected to the laser amplification and carrier envelope detection submodule 6, that is, the laser signal is amplified and coupled into the cascade waveguide composed of the high nonlinear waveguide and the frequency doubling waveguide to generate a supercontinuum signal greater than one octave, and the frequency doubling signal generated by the laser in the frequency doubling waveguide is subjected to f-2f beat frequency with the laser wavelength of the same frequency doubling signal in the supercontinuum spectrum, and the obtained beat frequency signal and the radio frequency reference signal 802 are connected to the mixing ports 901 and 902 of the phase-locked circuit module 9 together, and the error signal is obtained and the high-voltage control signal 903 is output to control the driving current of the pump and wavelength division multiplexing module 2 so that the error signal is controlled within the minimum allowable limit, and then the carrier envelope phase offset frequency of each gain waveguide can be synchronously controlled. Under the condition that the carrier envelope offset frequency and pulse repetition frequency of each waveguide can be accurately controlled, an optical frequency comb array that meets the requirements is obtained.

[0095] Those skilled in the art should understand that the above method embodiments include specific signals and process directions, and are not limited to the above method embodiments as long as the corresponding process is implemented. Figure 1-Figure 2 Specific implementation structure and corresponding execution entities and modules.

[0096] The above-mentioned device and method embodiments of the present invention can produce a mode-locked optical frequency comb array operating in the mid-infrared 2μm band, and simultaneously generate multiple mode-locked optical frequency combs from a compact waveguide structure, with a pulse repetition frequency of the order of GHz, which expands the pulse repetition frequency and functionality of existing optical frequency combs, and the laser wavelength can cover the mid-infrared 2μm band. Existing optical frequency combs have only one light source, and it is difficult to achieve synchronous spatial multiplexing output of multiple frequency comb light sources in an integrated device. The present invention can further achieve the integration and functionality of the optical frequency comb system.

[0097] Figure 3a 1 is a schematic diagram of an embodiment of a gain waveguide module in an optical frequency comb generating device according to one aspect of the present invention; Figure 3b It is a schematic diagram of another embodiment of a gain waveguide module in an optical frequency comb generating device proposed in one aspect of the present invention.

[0098] As shown in FIG3 , the gain waveguide module 1 can be a thulium (Tm)-doped gain medium, such as a crystal such as Tm:YAG, Tm:LuAG, Tm:YLF, Tm:LuLiF, Tm:YAP, Tm:YAB, Tm:KGW, Tm:GdVO 4 and Tm:YVO 4 Etc., ceramics such as Tm:YAG, Tm:Y 2 O 3 and Tm:Sc 2 O 3 Etc., glass such as Tm-doped silicate, phosphate or germanate glass. Tm:YAG crystal is used here. Through a thermal diffusion bonding process, a transparent medium material with a lower refractive index, such as SiC, sapphire or fused quartz crystal, is used as the waveguide substrate layer 110, and a discrete ridge Tm:YAG waveguide array with a cross-sectional size of 10μm×10μm and a length of 10mm is prepared through a micromachining process. The arrays are numbered 101, 102, 103, ... 10n, and an array composed of 4 gain waveguides is taken as an example here. The gain medium in this application is the gain waveguide.

[0099] In the prior art, early optical frequency combs were mainly based on all-solid-state lasers, especially titanium sapphire lasers operating in the 800nm ​​band. However, the cavity length of the all-solid-state mode-locked laser is in the meter level, and multiple cavity mirrors are required for reflection, as well as dispersion management in the cavity, making the system structure very large and complex. With the development of fiber laser technology, especially polarization-maintaining fiber technology, most of the optical elements of the mode-locked laser resonant cavity can be composed of all-fiber devices fused to each other, but limited by the coiling radius of the optical fiber, the size of the overall structure can only be controlled within a space of more than ten to tens of centimeters. The stacked coiling of the mode-locked fiber laser can effectively shorten the cavity length of the fiber laser, which enables the pulse repetition rate of the mode-locked laser to be controlled below several hundred MHz. Ordinary technicians in this field can only think of using conventional optical fibers, crystals and other laser gain components to generate optical frequency combs, and would not think of using integrated gain waveguide arrays. First, the existing reported crystal gain waveguides use traditional cutting and polishing processes, and the waveguide size is large, at a size of hundreds of microns, and it is difficult to process gain waveguide arrays on a single crystal; second, the substrate of the waveguide requires a transparent dielectric material with a lower refractive index, which involves low-loss bonding of the material to the gain waveguide, making the complexity of the entire process beyond the scope of existing solid-state laser technology.

[0100] The applicant has found that increasing the active ion doping concentration of the laser crystal can significantly shorten the required laser crystal length, controlling the crystal length from dozens of millimeters to a few millimeters (1-2 mm), which is very suitable for processing into a gain waveguide array integrated on a single crystal. Therefore, in this application, the light-proof characteristics of the gain waveguide can significantly improve the laser efficiency, and in combination with the waveguide and pulse modulation module (such as Figure 1 3) The special coating process of the two end faces can control the resonant cavity length to a few mm, generating a multi-channel spatially multiplexed mode-locked laser frequency comb. In terms of coupling the fiber laser into the optical waveguide, it can be achieved by coupling the multi-channel fiber output beam into multiple waveguides. The embodiments of the present application couple the multi-channel fiber output beam into multiple waveguides, and through the wavelength division multiplexing array, while realizing the pump light entering the waveguide, the mode-locked optical frequency comb signal of each waveguide is extracted, which solves the difficulties of the prior art.

[0101] Focused ion beam etching, femtosecond laser direct writing, photolithography plus plasma etching and other methods can be used to prepare gain waveguide array modules. Figure 3a As shown, one end face of each waveguide is coated with a film layer 121 that increases the transmittance of pump light and partially reflects Tm laser light, and the other end face is coated with a film layer 122 that increases the transmittance of Tm laser light, thereby enabling Tm laser light to be transmitted between the film layer 121 and the pulse modulation and PZT drive module (e.g. Figure 5 The laser array oscillates in a resonant cavity composed of a pulse modulator 31 to generate a laser array output.

[0102] Figure 4FIG. 1 is a schematic diagram of an embodiment of a pump and wavelength division multiplexing module in an optical frequency comb generating device according to an aspect of the present invention. Figure 4 As shown, the pump light passes through a multi-stage beam splitter (261, 262, 263), such as a 50:50 beam splitter. The use of a 50:50 beam splitter can ensure that the power of the pump light entering each path is equal as much as possible, that is, the final mode-locked laser power of each waveguide is consistent. According to the difference in internal losses of different waveguides, it is not necessary to strictly 50:50, such as Figure 4 The pump power is evenly distributed to the corresponding wavelength division multiplexers (21, 22, 23 and 24), and the wavelength division multiplexers connect the pump laser from the pump port (211, 221, 231, 241), couple it into the multiplexing port (213, 223, 233, 243), and pump each gain waveguide. The generated laser array enters the multiplexing port and is output from the output port (212, 222, 232, 242).

[0103] Figure 5 FIG. 1 is a schematic diagram of an embodiment of a pulse modulation and PZT driving module in an optical frequency comb generating device according to an aspect of the present invention. Figure 5 , the pulse modulation submodule 31 in the pulse modulation and piezoelectric ceramic actuator (PZT) driving module 3 can be an acousto-optic or electro-optic modulator driven by a high-frequency signal to generate an active mode-locked laser output, or it can be a saturable absorber material, such as a semiconductor saturable absorber SESAM. In this embodiment, SESAM can be used as a pulse modulator, and together with the coated end face 121 of the array waveguide, it forms a laser resonant cavity of each gain waveguide. The pulse modulator 31 can be fixed with the PZT crystal 32, and can be retracted and moved with a small amplitude relative to the array waveguide 1 under the control of the PZT driving submodule 33. According to the absorption spectrum of the Tm:YAG gain medium, the pump laser can be a conventional 785nm semiconductor laser or an Er-doped laser in the 1.6μm band. In order to improve the laser efficiency of the Tm:YAG gain waveguide and reduce the thermal effect, this embodiment uses an Er-doped fiber laser with a wavelength of 1.6μm as the pump source 25 of the array waveguide. In a specific embodiment, the rare earth activation ions and waveguide materials of the gain medium can be determined according to the output wavelength, and the corresponding pump source wavelength can be determined according to the absorption spectrum of the activated ions in the waveguide material. The specific pump laser wavelength can be changed accordingly.

[0104] like Figure 1-Figure 5, the mode-locked laser of the first waveguide enters the beam splitter 4, and the photodetector 5 connects the mode-locked pulse signal measured from the splitting port 402 and the RF reference signal 801 generated from the RF signal generator 8 to the 1002 and 1001 ports of the phase-locked circuit 10 respectively for mixing to obtain an error signal. The high-voltage drive signal generated by the error signal is output from the 1003 port to control the pulse modulation and PZT drive module 3, drive the PZT crystal 32, and then control the phase position of the pulse modulation submodule 31 and the array waveguide 1, and control the cavity length of each array waveguide and the corresponding pulse repetition frequency; the mode-locked laser separated from the 403 port enters the laser amplification and carrier envelope detection submodule 6, for example Figure 6 The laser amplification system 61 amplifies the pulse energy to a level sufficient to generate a supercontinuum laser output greater than one octave in the high nonlinear waveguide 621, and then enters the frequency doubling waveguide 622 to frequency-double the residual laser signal to generate a 2f signal. The 2f signal will beat with the f signal of the same wavelength in the supercontinuum spectrum to generate a beat signal.

[0105] Figure 6 It is a schematic diagram of an embodiment of a laser amplification and carrier envelope detection submodule in an optical frequency comb generation device proposed in one aspect of the present invention.

[0106] Figure 6 In the embodiment, the high nonlinear waveguide 621 can be a microstructured optical fiber or a photonic crystal optical fiber, or a waveguide made of lithium niobate material, and the double frequency waveguide 622 can be a double frequency crystal with a second-order nonlinear effect, such as KTP, LBO and PPLN. Here, in order to ensure the compactness and miniaturization of the cascade waveguide structure, the high nonlinear waveguide and the double frequency waveguide can be prepared on the same lithium niobate LN crystal, and the double frequency waveguide is formed by periodic polarization in the LN crystal waveguide. In order to improve the signal-to-noise ratio of the beat frequency signal, the 2f signal is synchronized with the f signal through the group velocity compensation module 63 formed by fusion of polarization-maintaining optical fibers.

[0107] like Figure 1-6 As shown, the 2f-f beat signal detected by the detector 7 and the RF reference signal 802 generated by the RF signal generator 8 are respectively connected to the 902 and 901 ports of the phase-locked circuit 9 for mixing, and the error signal is obtained. The high-voltage driving signal generated by the error signal is output from the 903 port to control the driving power supply 27 of the pump and wavelength division multiplexing module 2, thereby modulating the output power of the pump laser module 25, and synchronously locking the carrier envelope offset frequency of each waveguide, so as to realize the optical frequency comb array working in the 2μm band.

[0108] In another implementation of the present invention, the Tm ions in the Tm:YAG waveguide array can be replaced with Er ions, and a pump laser module with an output wavelength located at the Er laser waveguide pump absorption peak is selected. According to the above control process, a laser frequency comb array operating in the 1.5 micron band can be generated.

[0109] In another implementation of the present invention, the Tm ions in the Tm:YAG waveguide array can be replaced with Yb ions, and a pump laser module with an output wavelength located at the Yb laser waveguide pump absorption peak is selected. According to the above control process, a laser frequency comb array operating in the 1 micron band can be generated.

[0110] The present invention also encompasses an optical frequency comb application system, including the above-mentioned generating device, and is applied to ranging systems, gas detection systems, spectroscopy measurement systems, and quantum manipulation systems for specific applications.

[0111] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage and optical storage, etc.) containing computer-usable program code. These computer program instructions may be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the instructions in the process. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0112] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0113] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process in the computer or other programmable device. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0114] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. An optical frequency comb generating device, characterized in that: include: A gain waveguide module, used for generating a mode-locked laser output through a gain waveguide; A pumping and wavelength division multiplexing module, used for pumping each gain waveguide in the gain waveguide module, and coupling and outputting a frequency comb signal of each gain waveguide in the gain waveguide module; A pulse modulation and PZT driving module, used for pulse modulation of the mode-locked laser output, and receiving a control signal to control the mode-locked pulse repetition frequency of the gain waveguide; A pulse repetition frequency and carrier envelope test module, used to detect and output the pulse repetition frequency information and carrier envelope beat frequency information of the frequency comb signal; A radio frequency signal generating module, used for generating a radio frequency reference signal; A phase-locked circuit module, used for generating a control signal of the pulse modulation and PZT driving module according to the radio frequency reference signal and the pulse repetition frequency information; Generate a control signal for the pump and wavelength division multiplexing module according to the carrier-envelope beat frequency information and the radio frequency reference signal, and synchronously control the carrier-envelope phase of the gain waveguide module; The gain waveguide module includes 1 to n gain waveguides to form a gain waveguide array, where n≥1; The active ions of the gain waveguide include rare earth ions that can cover wavelengths from 1 micron to 3 microns, and the rare earth ions include Tm, Er ions, Yb ions and other transition metal ions, including Cr, Ti, Fe, and Co; The gain waveguide array is a ridge waveguide array; The activation ions and waveguide materials are determined according to the output wavelength, and the corresponding pump source wavelength is determined according to the absorption spectrum of the activated ions in the waveguide material.

2. The device according to claim 1, characterized in that The first end face of each gain waveguide in the gain waveguide module is provided with a film layer that enhances the transmittance of pump light and partially reflects the gain medium laser, and the second end face is provided with a film layer that enhances the transmittance of the gain medium laser. The gain medium laser oscillates in a resonant cavity composed of the first end face film layer and the pulse modulation and PZT drive module to generate a mode-locked laser output array.

3. The device according to claim 1, characterized in that The pulse repetition frequency and carrier envelope test module includes: A beam splitting submodule, used for splitting the mode-locked laser outputted from one of the gain waveguides again to obtain at least two split beam signals; A detection submodule, used for detecting one of the split beam signals, obtaining a pulse repetition frequency signal, and sending the signal to the phase-locked circuit module; The laser amplification and carrier envelope detection submodule is used to perform laser amplification and carrier envelope phase shift frequency detection according to another split beam signal, obtain a beat frequency signal, and send it to the phase-locked circuit module.

4. The device according to any one of claims 1 to 3, characterized in that: The pulse modulation and PZT driving module includes: A mode-locked pulse modulation submodule, which, together with the gain waveguide end face of the gain waveguide module, forms a laser resonant cavity of each gain waveguide; The PZT driving submodule is used to receive the control signal of the phase-locked circuit module, adjust the relative position of the mode-locked pulse modulation submodule and the gain waveguide module, and control the cavity length of each gain waveguide and the corresponding pulse repetition frequency.

5. An optical frequency comb application system, characterized in that: The invention comprises a generating device as described in any one of claims 1 to 4, which is applied to a ranging system, a gas detection system, a spectroscopy measurement system, and a quantum manipulation system.

6. A method for generating an optical frequency comb, characterized in that: The generating device applied to any one of claims 1 to 4 comprises: generating a gain waveguide array structure according to a solid laser gain medium; According to the resonant cavity formed by the end face of the gain waveguide and the pulse modulation and PZT driving module, a mode-locked pulse laser frequency comb array is generated; According to the splitting signal after the splitting of one of the gain waveguides and the radio frequency reference signal, a control signal for modulating the mode-locked pulse is obtained to control the repetition frequency of the mode-locked pulse of each gain waveguide; A carrier-envelope beat frequency signal is generated according to another split signal after one of the gain waveguides is split, and a control signal of the carrier-envelope phase of each gain waveguide is generated according to the carrier-envelope beat frequency signal and a radio frequency reference signal.

7. The method according to claim 6, characterized in that The step of obtaining a modulated mode-locked pulse control signal according to a splitting signal after the splitting of one of the gain waveguides and a radio frequency reference signal, and controlling the mode-locked pulse repetition frequency of each gain waveguide specifically includes: One of the split beam signals after the gain waveguide splitting is detected to obtain a radio frequency pulse signal; Mixing the radio frequency pulse signal and the radio frequency reference signal to obtain an error signal; generating a mode-locked pulse repetition frequency control signal according to the error signal; The relative position of the corresponding gain waveguide is controlled according to the pulse repetition frequency control signal, and the mode-locking pulse repetition frequency of each corresponding gain waveguide is locked.

8. The method according to claim 6, characterized in that The step of generating a carrier envelope beat frequency signal according to another split signal after one of the gain waveguides is split, and generating a control signal of the carrier envelope phase of each gain waveguide according to the carrier envelope beat frequency signal and a radio frequency reference signal specifically includes: Performing laser amplification and carrier envelope offset frequency detection on another split signal after one of the gain waveguide splits, to obtain a 2f-f beat frequency signal; Mixing the carrier envelope 2f-f beat frequency signal and the radio frequency reference signal to obtain an error signal; A control signal is generated according to the error signal to synchronously control the carrier envelope phase offset frequency of each gain waveguide.

9. The method according to any one of claims 6 to 8, characterized in that: The method of generating a mode-locked pulse laser frequency comb array according to the resonant cavity formed by the end face of the gain waveguide and the pulse modulation and PZT driving module comprises: A film layer that increases the transmittance of pump light and partially reflects the gain medium laser is provided on the first end face of each gain waveguide, and a film layer that increases the transmittance of the gain medium laser is provided on the second end face. The gain medium laser oscillates in a resonant cavity composed of the first end face film layer and the pulse modulation and PZT drive module to generate laser and output a frequency comb array.

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