A terahertz optical comb spectroscopy digital adaptive control method and system

Abstract

The present invention relates to the field of terahertz control technology, and specifically relates to a terahertz optical comb spectrum digital adaptive control method and system. The system includes a THz optical comb spectrum generation and heterodyne detection optical module, a time jitter extraction and all-digital processing module, a THz frequency feedback control module, and a high-speed data acquisition module. Among them, the time jitter extraction and all-digital processing module is used to generate continuous laser light through a continuous light source, perform beat frequency processing with corresponding first and second THz optical comb spectra to generate corresponding beat frequency signals, convert the beat frequency signals to obtain converted signals, then filter out the beat frequency signals through an IIR digital bandpass filter based on FPGA, perform digital mixing on the filtered beat frequency signals, and process the mixed signals to obtain corresponding clock signals. This solution can achieve fast and accurate extraction of the time jitter of the THz optical comb spectrum, greatly reducing the possibility of the THz optical comb spectrum being affected by external factors.

Description

Technical Field

[0001] The present invention relates to the field of terahertz control technology, and in particular to a method and system for digital adaptive control of a terahertz optical comb spectrum. Background Art

[0002] Terahertz (THz) radiation, defined as electromagnetic waves with frequencies between 0.1 and 10 THz and wavelengths between 0.03 and 3 mm, is of great significance in spectral analysis and imaging, as many molecules exhibit strong vibrational and rotational resonance absorption within this frequency range. Exploring new THz spectroscopy detection technologies to address the constraints between detection bandwidth, spectral resolution, and acquisition time has been a pressing challenge in the field.

[0003] Fourier transform infrared spectroscopy and terahertz time-domain spectroscopy (THz-TDS) are inherently capable of broadband spectral detection, but typically require a mechanical delay arm to achieve time-domain signal scanning, thus limiting spectral resolution and acquisition time.

[0004] Dual-comb spectroscopy allows real-time detection of high-resolution spectra over a wide bandwidth, but its coherent integration requires extremely high accuracy of the carrier-envelope phase and repetition frequency. The phase and time errors of the comb teeth can be minimized by precisely controlling their stability or eliminated through correction to reduce their impact on coherence.

[0005] Existing precision control and correction elimination methods require the use of a large number of electrical components such as electrical filtering, mixing, amplification, and phase shifting to extract and process the radio frequency electrical signals containing error signals. These electronic components are limited by bandwidth and working environment, resulting in complex system structure and stringent environmental requirements, which limits the applicability of the technology. Summary of the Invention

[0006] The purpose of the present invention is to provide a method and system for digital adaptive control of THz optical comb spectra, which can achieve rapid and accurate extraction of THz optical comb spectrum time jitter, so that the system can be in a stable operation state for a long time, thereby improving the robustness of the system.

[0007] To achieve the above objectives, the technical solution of the present invention provides a terahertz optical comb spectrum digital adaptive control system, including a THz optical comb spectrum generation and heterodyne detection optical module, a time jitter extraction and full digital processing module, a THz frequency feedback control module, and a high-speed data acquisition module;

[0008] The THz optical comb spectrum generation and heterodyne detection optical module is used to generate respective corresponding laser spectra through two femtosecond optical combs with a certain inherent offset in their repetition frequencies, and process these two laser spectra. Specifically, one of the laser spectra is converted to generate the corresponding first THz optical comb spectrum, and the other laser spectrum is subjected to heterodyne detection to generate the corresponding second THz optical comb spectrum;

[0009] The time jitter extraction and all-digital processing module is used to generate continuous laser through a continuous light source, perform beat frequency processing with the corresponding first THz optical comb spectrum and second THz optical comb spectrum to generate the corresponding beat frequency signal, convert the beat frequency signal to obtain a converted signal, then filter out the beat frequency signal through an IIR digital bandpass filter based on FPGA, perform digital mixing on the filtered beat frequency signal, and process the mixed signal to obtain the corresponding clock signal;

[0010] The THz frequency feedback control module is used to use the mixed signal as the corresponding feedback control signal 1 and feedback control signal 2, and control the respective femtosecond optical combs;

[0011] The high-speed data acquisition module is used to input the corresponding clock signal and the second THz optical comb spectrum into the corresponding ports of the DAP respectively.

[0012] The technical principle of this solution: In this solution, corresponding laser pulses, i.e., laser spectra, are output through two femtosecond optical combs with a certain inherent offset, and then these two laser spectra are processed. One of them is subjected to spectral conversion to realize the generation of the first THz optical comb spectrum, and the other laser spectrum is obtained through heterodyne detection to get the second THz optical comb spectrum, thus realizing the generation and detection of the THz optical comb spectrum;

[0013] Use a continuous light source to generate the corresponding continuous laser, then perform beat frequency processing on the three spectra of the continuous laser, the first THz optical comb spectrum, and the second THz optical comb spectrum to generate the corresponding beat frequency signal, then convert the corresponding beat frequency signal to obtain the corresponding converted signal, then use an IIR digital bandpass filter based on FPGA to filter out the corresponding beat frequency signal, and perform digital mixing after the beat frequency signal is filtered, and process the mixed signal, thus obtaining the corresponding clock signal. This clock signal is a signal only related to the repetition frequency jitter, which can completely compensate for the terahertz signal drift caused by the repetition frequency jitter of the two lasers.

[0014] Of course, the mixed signal is also used as the respective feedback control signal to control the respective femtosecond optical combs, so that the system can be in a stable operation state for a long time, improving the robustness of the system. Then the clock signal and the second THz optical comb spectrum are input into the input ports of the DAP.

[0015] Beneficial effects of this solution compared with the prior art:

[0016] 1. Through the time jitter extraction and all-digital processing module, digital electrical signal processing is realized to replace analog signal processing, without the need to add hardware devices, and signals with very low frequencies can be filtered. It has high reliability and good stability, greatly improving the reliability and robustness of the instrument and equipment; and the extraction of the repetition frequency in the femtosecond optical frequency comb is realized, greatly improving the rapidity and accuracy of time jitter extraction;

[0017] 2. The THz frequency feedback control module cancels the THz spectrum drift caused by external environmental factors, ensures that the electrical signal operates within the allowable frequency range, and improves the long-term stability of the system;

[0018] 3. The long-term stable operation of the system ensures the narrow linewidth detection of the THz spectrum. By adaptively compensating for the jitter of the femtosecond optical frequency comb frequency scale in different frequency bands, high measurement accuracy can be achieved in a relatively wide spectrum range.

[0019] Furthermore, the time jitter extraction and all-digital processing module includes:

[0020] The beat frequency processing module is used to obtain the corresponding continuous laser according to the type of the continuous light source, and perform beat frequency processing on the corresponding continuous light source with the first THz optical comb spectrum and the second THz optical comb spectrum respectively; the types of the continuous light source include a continuous light source with a single frequency and two continuous lasers operating in the laser spectral band;

[0021] The beat frequency signal detection module is used to directly detect the corresponding beat frequency signal through the THz detector to obtain the corresponding beat frequency signal;

[0022] The conversion strategy module is used to pre-store the conversion strategies corresponding one-to-one to the types of the continuous light source;

[0023] The signal conversion module is used to retrieve the corresponding conversion strategy according to the type of the continuous light source, and perform corresponding conversions on the corresponding beat frequency signals according to the conversion strategy to generate corresponding conversion signals;

[0024] The processing module is used to filter the corresponding conversion signals according to the IIR digital band-pass filter based on FPGA, filter out the corresponding beat frequency signals respectively, and perform digital mixing on the signals after filtering the beat frequency signals to generate the corresponding clock signals.

[0025] Beneficial effects: In this solution, by performing beat frequency processing on the continuous laser of the continuous light source, the first THz optical comb spectrum, and the second THz optical comb spectrum respectively, and then using a THz detector, the corresponding beat frequency signal can be directly detected. Then, the conversion strategy is used to convert the beat frequency signal, and the converted signal can be filtered by an IIR digital bandpass filter, thus realizing the filtering of the beat frequency signal and achieving real-time correction of the THz spectrum.

[0026] In this solution, different types of continuous light sources are converted in different ways to achieve corresponding real-time correction, which can extract time jitters in multiple situations, resulting in a higher correct rate of real-time correction of the spectrum, better accuracy, and stronger adaptability.

[0027] Furthermore, the conversion strategy module includes a first conversion module and a second conversion module;

[0028] The first conversion module is used to convert the beat frequency signal into a corresponding digital signal through an A / D analog-to-digital converter when the type of the continuous light source is a continuous light source with a single frequency;

[0029] The second conversion module is used to convert the beat frequency signal into an analog electrical signal through a photodiode and then into a corresponding digital signal through an A / D analog-to-digital converter when the type of the continuous light source is two continuous lasers operating in the laser spectral band.

[0030] Beneficial effects: When converting the beat frequency signal, different conversion strategies are applied for different types of continuous light sources, greatly improving the feasibility and effectiveness of the conversion.

[0031] Furthermore, the THz frequency feedback control module includes:

[0032] A temperature detection module is used to detect the current ambient temperature and judge the change of the corresponding current ambient temperature;

[0033] A feedback adjustment module is used to control the repeated signal of the mixed signal according to the change of the corresponding current ambient temperature and feedback it to the corresponding femtosecond optical comb.

[0034] Beneficial effects: In this solution, by detecting the current ambient temperature, feedback on the repeated signal of the mixed signal is realized, so that the repeated signal corresponding to the mixed signal can be accurately adjusted, greatly offsetting the THz spectrum drift problem caused by external environmental factors.

[0035] The present invention also provides a terahertz optical comb spectrum digital adaptive control method, including the following steps:

[0036] S1. Generate respective corresponding laser spectra using two femtosecond optical combs with a certain inherent offset in repetition frequencies, and process these two laser spectra. Specifically, convert one of the laser spectra to generate the corresponding first THz optical comb spectrum, and perform heterodyne detection on the other laser spectrum to generate the corresponding second THz optical comb spectrum;

[0037] S2. Generate continuous laser light from a continuous light source, perform beat frequency processing with the corresponding first THz optical comb spectrum and second THz optical comb spectrum to generate corresponding beat frequency signals, convert the beat frequency signals to obtain converted signals, then filter out the beat frequency signals through an IIR digital bandpass filter based on FPGA, perform digital mixing on the filtered beat frequency signals, and process the mixed signals to obtain the corresponding clock signals;

[0038] S3. Use the mixed signals as the corresponding feedback control signal 1 and feedback control signal 2, and control the respective femtosecond optical combs;

[0039] S4. Input the corresponding clock signals and second THz optical comb spectra into the corresponding ports of the DAP.

[0040] The technical principle and effect of this solution: In this solution, two femtosecond optical combs with a certain inherent offset in repetition frequencies are used to generate laser spectra, and then these two laser spectra are processed to correspondingly generate the first THz optical comb spectrum and the second THz optical comb spectrum, thereby achieving the acquisition of terahertz spectra.

[0041] After that, the continuous laser light from the continuous light source is subjected to beat frequency processing with the corresponding two terahertz optical comb spectra, so that the generation of beat frequency signals can be realized. Then, the beat frequency signals are converted so that the converted signals can filter out the beat frequency signals through an IIR digital bandpass filter. After that, digital mixing is performed on the refined filtered beat frequency signals. In this way, the processed mixed signals can achieve the extraction of time jitter and realize the real-time correction of the THz optical comb spectrum.

[0042] Of course, the mixed signals are also used as respective feedback control signals to control the respective femtosecond optical combs, so that the system can operate stably for a long time and improve the robustness of the system. Then, the clock signals and the second THz optical comb spectra are input into the input ports of the DAP.

[0043] In this solution, compared with the prior art of processing the time jitter of terahertz optical comb spectra through digital electrical signal processing, digital signal processing is used in this application, so that there is no need to add too many hardware devices, and signals with very low frequencies can be filtered. This not only greatly improves the reliability and stability of the corresponding system, but also greatly enhances the reliability and robustness of the instrument equipment.

[0044] Meanwhile, the femtosecond optical frequency comb is inversely controlled by the mixed signal, and through this inverse control, the drift of the THz optical frequency comb spectrum caused by other external factors is cancelled, so as to ensure that the electrical signal operates within the allowed frequency range and improve the long-term stability of the system. The long-term stable operation of the system ensures the narrow linewidth detection of the THz spectrum. By adaptively compensating for the jitter of the femtosecond optical frequency comb frequency scale in different frequency bands, high measurement accuracy can be achieved in a relatively wide spectrum range.

[0045] Further, S2 includes the following steps:

[0046] S20. According to the type of the continuous light source, obtain the corresponding continuous laser, and perform beat frequency processing on the corresponding continuous light source with the first THz optical frequency comb spectrum and the second THz optical frequency comb spectrum respectively; the types of the continuous light source include a continuous light source with a single frequency and two continuous lasers operating in the laser spectral band;

[0047] S21. Directly detect the corresponding beat frequency signal through a THz detector to obtain the corresponding beat frequency signal;

[0048] S22. According to the type of the continuous light source, retrieve the conversion strategy stored in advance that corresponds one-to-one to the type of the continuous light source, and according to the conversion strategy, perform corresponding conversions on the corresponding beat frequency signals respectively to generate corresponding conversion signals; the conversion strategy includes that when the type of the continuous light source is a continuous light source with a single frequency, converting the beat frequency signal into a corresponding digital signal through an A / D analog-to-digital converter, and when the type of the continuous light source is two continuous lasers operating in the laser spectral band, converting the beat frequency signal into an analog electrical signal through a photodiode and then converting it into a corresponding digital signal through an A / D analog-to-digital converter;

[0049] S23. According to the IIR digital band-pass filter based on FPGA, filter the corresponding conversion signals respectively to filter out the corresponding beat frequency signals, and perform digital mixing on the signals after filtering the beat frequency signals to generate corresponding clock signals.

[0050] Beneficial effects: In this solution, different types of continuous light sources are identified. After identifying the corresponding type, the corresponding conversion strategy is retrieved for corresponding conversion, so as to realize the extraction of the jitter of the repetition frequency on the femtosecond optical frequency comb. Compared with the existing adaptive control scheme, the clock signal in this application can come from the same continuous light source or two continuous light sources, greatly improving the accuracy of extracting the time jitter on the femtosecond optical frequency comb, making the possibility of extracting the time jitter stronger and more targeted.

[0051] Further, S3 includes the following steps:

[0052] S30. Detect the current ambient temperature and determine the change of the corresponding current ambient temperature;

[0053] S31. Control the repeated signal of the mixed signal according to the change of the corresponding current ambient temperature and feedback it to the corresponding femtosecond optical frequency comb.

[0054] Beneficial effects: In this solution, by detecting the current ambient temperature, the feedback of the repeated signal of the mixed signal is realized, so that the repeated signal corresponding to the mixed signal can be accurately adjusted, greatly offsetting the THz spectrum drift problem caused by external environmental factors, ensuring that the system works within a suitable working bandwidth range, and improving the long-term stability of the system. Description of the Drawings

[0055] Figure 1 It is the logic block diagram of the terahertz optical frequency comb spectrum digital adaptive control system in Embodiment 1 of the present invention.

[0056] Figure 2 It is the flowchart of the terahertz optical frequency comb spectrum digital adaptive control method in Embodiment 1 of the present invention.

[0057] Figure 3 It is the schematic diagram of extracting time jitter by using laser spectrum and continuous optical beat frequency in Embodiment 1 of the present invention.

[0058] Figure 4 It is the schematic diagram of the terahertz optical frequency comb spectrum digital adaptive control system in Embodiment 1 of the present invention. Detailed Embodiments

[0059] The following is further detailed through specific embodiments: [[ID=3`1]]

[0060] Embodiment 1:

[0061] Embodiment 1 is basically as shown in Figure 1 、 Figure 2 and Figure 4 : A terahertz optical frequency comb spectrum digital adaptive control system includes a THz optical frequency comb spectrum generation and heterodyne detection optical module, a time jitter extraction and all-digital processing module, a THz frequency feedback control module, and a high-speed data acquisition module;

[0062] The THz optical comb spectrum generation and heterodyne detection optical module is used to generate respective corresponding laser spectra through two femtosecond optical combs with a certain inherent offset in repetition frequencies, and process these two laser spectra. Specifically, one of the laser spectra is converted to generate the corresponding first THz optical comb spectrum, and the other laser spectrum is subjected to heterodyne detection to generate the corresponding second THz optical comb spectrum. In this embodiment, the THz optical comb spectrum generation and heterodyne detection optical module includes two femtosecond laser light sources, a THz pulse generation device, a THz wave focusing module, and a THz pulse detection device. The femtosecond laser light sources are two femtosecond lasers with slightly different repetition frequencies, which are used as THz pump sources and are respectively called Laser A (repetition frequency is f rA ) and Laser B (repetition frequency is f rB ). There is a certain inherent offset Df r between the repetition frequencies of the two laser light sources. The laser pulses output by Laser A pump the THz pulse generation device (which can be a THz photoconductive antenna, lithium niobate crystal, organic crystal, etc. here), and the laser pulses output by Laser B are used as the pump source for THz heterodyne detection (the detection here can be methods such as THz photoconductive antenna or electro-optic sampling detection, etc.).

[0063] The THz wave focusing system (which can be THz focusing elements such as a parabolic mirror pair or a TPX lens, etc.) focuses the THz pulses generated by Laser A pumping to the detection system pumped by Laser B. Through heterodyne detection on the THz detection element, the THz frequency band is down-converted to the radio frequency band. The time magnification is frB / Dfr, the heterodyne signal repetition frequency is Dfr, and the single-signal appearance time period is 1 / Dfr.

[0064] The time jitter extraction and all-digital processing module is used to generate continuous laser by a continuous light source, perform beat frequency processing with the corresponding first THz optical comb spectrum and second THz optical comb spectrum to generate corresponding beat frequency signals, convert the beat frequency signals to obtain converted signals, then filter out the beat frequency signals through an IIR digital band-pass filter based on FPGA, perform digital mixing on the filtered beat frequency signals, and process the mixed signals to obtain corresponding clock signals;

[0065] The time jitter extraction and all-digital processing module includes:

[0066] The beat frequency processing module is used to obtain continuous laser of the corresponding type according to the type of the continuous light source, and perform beat frequency processing with the first THz optical comb spectrum and the second THz optical comb spectrum respectively through the corresponding continuous light source. The types of the continuous light sources include continuous light sources with a single frequency and two continuous lasers operating in the laser spectral band;

[0067] Beat frequency signal detection module, which is used to directly detect the corresponding beat frequency signal through a THz detector to obtain the corresponding beat frequency signal;

[0068] Conversion strategy module, which is used to pre-store conversion strategies corresponding one by one to the types of continuous light sources;

[0069] The conversion strategy module includes a first conversion module and a second conversion module;

[0070] The first conversion module is used to convert the beat frequency signal into a corresponding digital signal through an A / D analog-to-digital converter when the type of the continuous light source is a continuous light source with a single frequency;

[0071] The second conversion module is used to convert the beat frequency signal into an analog electrical signal through a photodiode and then into a corresponding digital signal through an A / D analog-to-digital converter when the type of the continuous light source is two continuous lasers operating in the laser spectral band.

[0072] Signal conversion module, which is used to retrieve the corresponding conversion strategy according to the type of the continuous light source, and perform corresponding conversions on the corresponding beat frequency signals according to the conversion strategy to generate corresponding conversion signals;

[0073] Processing module, which is used to filter the corresponding conversion signal according to an IIR digital band-pass filter based on FPGA, filter out the corresponding beat frequency signals respectively, and perform digital mixing on the signals after filtering the beat frequency signals to generate corresponding clock signals.

[0074] In this embodiment, the entire time jitter extraction is implemented in two ways.

[0075] Among them, the first one is to use a continuous light source with a frequency of f cw to beat frequency with two heterodyne-detected THz spectra (THz A and THz B) respectively, and directly detect the beat frequency signal by a THz detector. The processing process of the beat frequency signal is as shown in the appendix Figure 3 . At this time, the beat frequency signals detected by detector 1 (PD1) and detector 2 (PD2) are f cw -kf rA and kf rB -f cw respectively. The above two analog signals are converted into digital signals through an A / D analog-to-digital converter, which are respectively called data1 and data2. These two digital signals are respectively filtered through an IIR digital band-pass filter based on FPGA to filter out the beat frequency signals to isolate other beat frequency signals and low-frequency noise; the beat frequency signals are digitally mixed after filtering. The mixed signal is kf rB -kf rA . The influence of the continuous light has been eliminated, and its jitter only includes the repetition frequency jitter kf rA and kfrB . Taking this signal as an adaptive clock signal can achieve real-time correction of the THz spectrum. The implementation methods of the above-mentioned filtering and mixing are not limited to FPGA, and can also be various methods such as C++ and matlab.

[0076] Another method is: using two continuous lasers (f cw1 and f cw2 ) operating in the laser spectral band to beat with the laser spectra output by LaserA and LaserB respectively, and obtaining beat signals (mf rA +f cepA )-f cw1 , (m’f rB +f cepB )-f cw1 ; f cw2 -(nf rA +f cepA ) and f cw2 -(n’f rB +f cepB ). The beat signals are converted into analog electrical signals through a photodiode, and the above four analog signals are converted into digital signals through an A / D analog-to-digital converter, which are respectively called data1, data2, data3, and data4. The four digital signals are respectively filtered by an IIR digital band-pass filter based on FPGA to filter out the beat signals to isolate other beat signals and low-frequency noise; after filtering, digital mixing is performed, that is, (mf rA +f cepA )-f cw1 is mixed with (m’f rB +f cepB )-f cw1 , and f cw1 -(nf rA +f cepA ) is mixed with f cw2 -(n’f rB +f cepB ); the difference frequency signals after mixing are extracted by a digital band-pass filter to obtain difference frequency signals (m1-n1)(f rA -f rB )+(f cepA -f cepB ) and (m2-n2)(f rA -f rB )+(f cepA -f cepB ) that are independent of the continuous light frequency drift and only related to the repetition frequencies of the two lasers and the carrier envelope phase jitter; the two difference frequency signals are mixed again to obtain a signal k(f rA -f rC), use this signal as the clock signal. The implementation methods of the above-mentioned filtering and mixing are not limited to FPGA, and can also be various methods such as C++ and matlab; adjust the optical path of the clock signal to be consistent with the THz optical path to ensure that only the jitters of the repetition frequencies of the two lasers are synchronized with the jitter of the clock signal AS, so that the drift of the terahertz signal caused by the jitters of the repetition frequencies of the two lasers can be completely compensated.

[0077] The THz frequency feedback control module is used to use the mixed signal as the corresponding feedback control signal 1 and feedback control signal 2, and control the corresponding femtosecond optical combs respectively.

[0078] The THz frequency feedback control module includes:

[0079] The temperature detection module is used to detect the current ambient temperature and judge the change of the corresponding current ambient temperature.

[0080] The feedback adjustment module is used to control the repetition signal of the mixed signal according to the change of the corresponding current ambient temperature and feedback it to the corresponding femtosecond optical comb. For example, when the ambient temperature decreases, the cavity length of the laser resonator becomes longer, the pulse laser repetition frequency becomes smaller, and at this time the beat frequency signal becomes larger until the beat frequency signal exceeds the set range. When the beat frequency signal exceeds the filter range, by changing the driving voltage of the piezoelectric ceramic in the cavity, the cavity length of the laser is shortened, the repetition frequency is increased, and the original resonator cavity length is returned.

[0081] The high-speed data acquisition module is used to input the corresponding clock signal and the second THz optical comb spectrum into the corresponding ports of the DAP respectively.

[0082] This embodiment also provides a terahertz optical comb spectrum digital adaptive control method, including the following steps:

[0083] S1. Generate the respective corresponding laser spectra through two femtosecond optical combs with a certain inherent bias in the repetition frequencies, and process these two laser spectra, that is, convert one of the laser spectra to generate the corresponding first THz optical comb spectrum, and generate the corresponding second THz optical comb spectrum by heterodyne detection of the other laser spectrum;

[0084] S2. Generate the continuous laser generated by the continuous light source, perform beat frequency processing with the corresponding first THz optical comb spectrum and second THz optical comb spectrum to generate the corresponding beat frequency signal, convert the beat frequency signal to obtain the converted signal, then filter out the beat frequency signal through the IIR digital band-pass filter based on FPGA, perform digital mixing on the filtered beat frequency signal, and process the mixed signal to obtain the corresponding clock signal;

[0085] The S2 includes the following steps:

[0086] S20. Obtain continuous lasers of corresponding types according to the type of the continuous light source, and perform beat frequency processing on the first THz comb spectrum and the second THz comb spectrum respectively through the corresponding continuous light sources; the types of the continuous light sources include continuous light sources with a single frequency and two continuous lasers operating in the laser spectral band.

[0087] S21. Directly detect the corresponding beat frequency signal through a THz detector to obtain the corresponding beat frequency signal.

[0088] S22. According to the type of the continuous light source, retrieve the transformation strategies stored in advance that correspond one-to-one to the type of the continuous light source, and according to the transformation strategies, perform corresponding transformations on the corresponding beat frequency signals respectively to generate corresponding transformed signals; the transformation strategies include, when the type of the continuous light source is a continuous light source with a single frequency, converting the beat frequency signal into a corresponding digital signal through an A / D analog-to-digital converter, and when the type of the continuous light source is two continuous lasers operating in the laser spectral band, converting the beat frequency signal into an analog electrical signal through a photodiode and then converting it into a corresponding digital signal through an A / D analog-to-digital converter.

[0089] S23. According to the IIR digital band-pass filter based on FPGA, filter the corresponding transformed signals, filter out the corresponding beat frequency signals respectively, and perform digital mixing on the signals after filtering the beat frequency signals to generate corresponding clock signals.

[0090] S3. Use the mixed signal as the corresponding feedback control signal 1 and feedback control signal 2, and control the respective femtosecond optical combs.

[0091] S3 includes the following steps:

[0092] S30. Detect the current ambient temperature and judge the change situation of the corresponding current ambient temperature.

[0093] S31. According to the change situation of the corresponding current ambient temperature, control the repetition signal of the mixed signal and feedback it to the corresponding femtosecond optical comb.

[0094] S4. Input the corresponding clock signal and the second THz comb spectrum into the corresponding ports of the DAP respectively.

[0095] The above are only embodiments of the present invention. The invention is not limited to the fields involved in this embodiment. Common knowledge such as specific structures and characteristics known in the art are not described in detail herein. Those of ordinary skill in the art know all the common general technical knowledge in the technical field to which the invention pertains before the filing date or the priority date, can learn about all the prior art in this field, and have the ability to apply conventional experimental means before this date. Those of ordinary skill in the art can, under the inspiration given in this application, combine their own abilities to improve and implement this solution. Some typical well-known structures or well-known methods should not become obstacles for those of ordinary skill in the art to implement this application. It should be noted that for those skilled in the art, without departing from the structure of the present invention, several deformations and improvements can still be made, and these should also be regarded as the protection scope of the present invention, and these will not affect the implementation effect of the present invention and the practicality of the patent. The protection scope required by this application should be based on the content of its claims, and the specific implementation manners described in the specification can be used to interpret the content of the claims.

Claims

1. A terahertz optical comb spectroscopy digital adaptive control system, characterized in that: It includes a THz optical comb spectrum generation and heterodyne detection optical module, a time jitter extraction and full-digital processing module, a THz frequency feedback control module, and a high-speed data acquisition module; The THz optical comb spectrum generation and heterodyne detection optical module is used to generate respective corresponding laser spectra through two femtosecond optical combs with a certain inherent offset in repetition frequencies, and process these two laser spectra, that is, convert one of the laser spectra to generate a corresponding first THz optical comb spectrum, and generate a corresponding second THz optical comb spectrum by heterodyne detection of the other laser spectrum; The time jitter extraction and full-digital processing module is used to generate continuous laser by a continuous light source, perform beat frequency processing with the corresponding first THz optical comb spectrum and second THz optical comb spectrum to generate corresponding beat frequency signals, convert the beat frequency signals to obtain converted signals, then filter out the beat frequency signals through an IIR digital band-pass filter based on FPGA, perform digital mixing on the filtered beat frequency signals, and process the mixed signals to obtain corresponding clock signals; The THz frequency feedback control module is used to use the mixed signals as corresponding feedback control signal 1 and feedback control signal 2, and control the respective corresponding femtosecond optical combs; The high-speed data acquisition module is used to input the corresponding clock signal and the second THz optical comb spectrum into the corresponding ports of the DAP respectively; The time jitter extraction and full-digital processing module includes: The beat frequency processing module is used to obtain continuous laser of the corresponding type according to the type of the continuous light source, and perform beat frequency processing with the first THz optical comb spectrum and the second THz optical comb spectrum respectively through the corresponding continuous light source; the types of the continuous light source include a continuous light source with a single frequency and two continuous lasers operating in the laser spectrum band; The beat frequency signal detection module is used to directly detect the corresponding beat frequency signal through a THz detector to obtain the corresponding beat frequency signal; The conversion strategy module is used to pre-store conversion strategies corresponding one-to-one to the types of the continuous light source; The signal conversion module is used to retrieve the corresponding conversion strategy according to the type of the continuous light source, and perform corresponding conversions on the corresponding beat frequency signals according to the conversion strategy to generate corresponding converted signals; The processing module is used to filter the corresponding converted signals according to the IIR digital band-pass filter based on FPGA, filter out the corresponding beat frequency signals respectively, and perform digital mixing on the filtered beat frequency signals to generate corresponding clock signals.

2. The terahertz optical comb spectroscopy digital adaptive control system according to claim 1, characterized in that: The conversion strategy module includes a first conversion module and a second conversion module; The first conversion module is used to convert the beat frequency signal into a corresponding digital signal through an A / D analog-to-digital converter when the type of the continuous light source is a continuous light source with a single frequency; The second conversion module is used to convert the beat frequency signal into an analog electrical signal through a photodiode and then into a corresponding digital signal through an A / D analog-to-digital converter when the type of the continuous light source is two continuous lasers operating in the laser spectrum band.

3. A terahertz optical comb spectroscopy digital adaptive control system according to claim 2, characterized in that: The THz frequency feedback control module includes: A temperature detection module is used to detect the current ambient temperature and judge the change of the corresponding current ambient temperature; A feedback adjustment module is used to control the repeated signal of the mixed signal according to the change of the corresponding current ambient temperature and feedback it to the corresponding femtosecond optical frequency comb.

4. A terahertz optical comb spectroscopy digital adaptive control method, characterized in that: It includes the following steps: S1. Generate respective corresponding laser spectra by two femtosecond optical frequency combs with a certain inherent offset in the repetition frequencies, and process these two laser spectra. Specifically, convert one of the laser spectra to generate the corresponding first THz optical frequency comb spectrum, and generate the corresponding second THz optical frequency comb spectrum by heterodyne detection of the other laser spectrum; S2. Generate a continuous laser from a continuous light source, perform beat frequency processing with the corresponding first THz optical frequency comb spectrum and second THz optical frequency comb spectrum to generate the corresponding beat frequency signal, convert the beat frequency signal to obtain a converted signal, then filter out the beat frequency signal through an IIR digital bandpass filter based on FPGA, perform digital mixing on the filtered beat frequency signal, and process the mixed signal to obtain the corresponding clock signal; S3. Use the mixed signal as the corresponding feedback control signal 1 and feedback control signal 2, and control the corresponding femtosecond optical frequency comb; S4. Input the corresponding clock signal and the second THz optical frequency comb spectrum into the corresponding ports of the DAP; The S2 includes the following steps: S20. Obtain the continuous laser of the corresponding type according to the type of the continuous light source, and perform beat frequency processing with the first THz optical frequency comb spectrum and the second THz optical frequency comb spectrum respectively by the corresponding continuous light source; the types of the continuous light source include a continuous light source with a single frequency and two continuous lasers operating in the laser spectrum band; S21. Directly detect the corresponding beat frequency signal through a THz detector to obtain the corresponding beat frequency signal; S22. According to the type of the continuous light source, retrieve the conversion strategy stored in advance that corresponds one-to-one with the type of the continuous light source, and perform corresponding conversions on the corresponding beat frequency signals according to the conversion strategy to generate the corresponding conversion signals; the conversion strategy includes converting the beat frequency signal into the corresponding digital signal through an A / D analog-to-digital converter when the type of the continuous light source is a continuous light source with a single frequency, and converting the beat frequency signal into an analog electrical signal through a photodiode and then into the corresponding digital signal through an A / D analog-to-digital converter when the type of the continuous light source is two continuous lasers operating in the laser spectrum band; S23. Filter the corresponding conversion signal according to the IIR digital bandpass filter based on FPGA, filter out the corresponding beat frequency signals respectively, and perform digital mixing on the filtered beat frequency signal to generate the corresponding clock signal.

5. A terahertz optical comb spectroscopy digital adaptive control method according to claim 4, characterized in that: The S3 includes the following steps: S30. Detect the current ambient temperature and judge the change of the corresponding current ambient temperature; S31. Control the repeated signal of the mixed signal according to the change of the corresponding current ambient temperature and feedback it to the corresponding femtosecond optical frequency comb.

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