A method and system for generating a high precision reference light for a fourier infrared spectrometer

Abstract

This invention relates to the field of infrared spectroscopy measurement technology, and particularly to a method and system for generating high-precision reference light for a Fourier transform infrared (FTIR) spectrometer. The high-precision reference light generation system for a Fourier transform infrared spectrometer includes a DFB laser module, a frequency stabilization feedback control module, a current drive module, a temperature control module, and a reference signal generation module. This invention also provides a high-precision reference light generation system for a Fourier transform infrared spectrometer, which, based on the instrument's linear function frequency doubling technique, generates a high-precision reference signal with an arbitrarily variable reference frequency. This invention uses a DFB laser as the light source, possessing significant advantages such as no need for high-voltage drive, small size, compact structure for easy integration, full utilization of DFB semiconductor laser development, and low price. Furthermore, it effectively overcomes the problems of low frequency stability and low reference frequency of DFB lasers, and has good application value.

Description

Technical Field

[0001] This invention relates to the field of infrared spectroscopy measurement technology, and in particular to a method and system for generating high-precision reference light for a Fourier transform infrared spectrometer. Background Technology

[0002] Fourier transform spectroscopy offers advantages such as high spectral resolution, high optical flux, multi-channel operation, and wide spectral coverage, making it a widely used high-resolution spectral analysis technique. In particular, wide-band infrared spectral parameter measurement is currently widely applied in various fields including space remote sensing, target characteristic research, atmospheric detection, material analysis, security and chemical defense, metrology, laboratories, environment, medicine, and criminal investigation.

[0003] Fourier transform infrared (FTIR) spectrometers typically include a laser interferometer, which, combined with a built-in high-precision reference light source, generates a reference standard used for sampling triggering references for interferometric data acquisition, interferometer mirror motion control, and wavelength calibration of inverted spectral data. The accuracy of the reference light source directly affects the measurement accuracy and spectral data quality of the Fourier transform infrared spectrometer. While commonly used HeNe lasers offer high accuracy, they also suffer from significant drawbacks such as large size and the need for thousands of volts of driving voltage. Semiconductor DFB lasers represent a promising light source with significant advantages, including no need for high-voltage driving, small size, compact structure for easy integration, full utilization of semiconductor laser development, and low cost. However, their applications are limited by issues such as low frequency stability, low reference frequency, and a relatively large central 1550nm wavelength that restricts the operating wavelength range of the Fourier transform infrared spectrometer.

[0004] Therefore, how to achieve easy-to-use, low-cost, arbitrary reference frequency, and high-precision reference light generation is also an important problem that needs to be solved in the development of Fourier transform infrared spectrometers. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a method and system for generating high-precision reference light for a Fourier transform infrared spectrometer, achieving easy-to-use, low-cost, freely variable reference frequency, and high-precision reference standard generation.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a high-precision reference light generation system for a Fourier transform infrared spectrometer, comprising a DFB laser module, a frequency stabilization feedback control module, a current drive module, a temperature control module, and a reference signal generation module; The DFB laser module is used to generate a high-frequency stable single-wavelength laser signal; The frequency stabilization feedback control module is connected to the DFB laser module and is used to receive part of the laser signal output by the DFB laser module, thereby generating a feedback control signal for frequency stabilization of the DFB laser. The current drive module is connected to the DFB laser module and the frequency stabilization feedback control module. It is used to receive the frequency stabilization feedback control signal output by the frequency stabilization feedback control module, thereby providing the required drive current for the operation of the DFB laser module. The temperature control module is connected to the DFB laser module and is used to control the operating temperature of the DFB laser at the optimal temperature. The reference signal generation module is connected to the DFB laser module and is used to detect and receive the high-frequency stable single-wavelength laser output by the DFB laser module to generate a high-precision reference reference of arbitrary frequency required for the operation of the Fourier transform infrared spectrometer.

[0007] In the above scheme, the DFB laser module includes a DFB laser, a TEC cooler, and a splitter; The DFB laser is used to generate a single-wavelength laser signal; The TEC cooler and the DFB laser are integrated into one unit to control the operating temperature of the DFB laser at the optimal temperature. The splitter is connected to the DFB laser and is used to guide the output light of the DFB laser into the frequency stabilization feedback control module and the reference signal generation module, respectively.

[0008] In the above scheme, the frequency stabilization feedback control module includes an RF local oscillator circuit, a gas chamber, a photodetector, a mixer circuit, and a frequency stabilization control unit; The radio frequency local oscillator circuit connects the mixer circuit and the DFB laser, and is used to provide the radio frequency local oscillator signal required for the operation of the mixer circuit, as well as to modulate the frequency of the DFB laser to generate modulated laser output. The gas cell connection splitter is used to provide the standard reference frequency required for locking the laser beam frequency and to absorb part of the modulated laser output from the DFB laser, thereby introducing characteristic spectral lines. The photodetector is connected to the gas chamber and is used to convert the modulated laser absorbed by the gas chamber into an electrical signal; The mixing circuit connects the radio frequency local oscillator circuit and the photodetector, and is used to mix the local oscillator signal output by the radio frequency local oscillator circuit with the electrical signal output by the photodetector to generate a laser frequency stabilization error signal. The frequency stabilization control unit is connected to the mixer circuit and is used to receive the laser frequency stabilization error signal and provide the drive current regulation signal.

[0009] In the above scheme, the current drive module includes a current control unit and a constant current source circuit; The current control unit is connected to the frequency stabilization control unit and is used for real-time adjustment of the operating parameters of the constant current source circuit; The constant current source circuit is connected to the current control unit and is used to provide the high-precision drive current required for the DFB laser to output high-frequency stable laser.

[0010] In the above scheme, the temperature control module includes a temperature sensor, a temperature regulation unit, and a TEC drive circuit; The temperature sensor is connected to the DFB laser and is used to monitor the operating temperature of the DFB laser in real time. The temperature control unit is connected to a temperature sensor to provide temperature control information; The TEC drive circuit is connected to the temperature control unit and is used for real-time adjustment of TEC operating parameters; The TEC is connected to the TEC drive circuit and is used for cooling or heating to keep the operating temperature of the DFB laser constant.

[0011] In the above scheme, the reference signal generation module includes a laser interferometer, a photoelectric detection and data acquisition unit, and an FPGA; The laser interferometer is connected to a splitter to perform interference modulation on the laser output from the DFB laser, generating high-precision interference light; The photoelectric detection and data acquisition unit is connected to the laser interferometer and is used for photoelectric conversion of the interference light output by the laser interferometer, analog electrical signal conditioning and shaping, data acquisition, etc., and outputs a high-precision cosine signal of a specific frequency. The FPGA is connected to the photoelectric detection and data acquisition unit, which is used to generate a high-precision reference signal of any desired frequency by employing frequency doubling technology based on the instrument line function of the Fourier transform infrared spectrometer, so as to meet the working requirements of the Fourier transform infrared spectrometer.

[0012] This invention also provides a method for generating high-precision reference light for a Fourier transform infrared spectrometer. This method uses the aforementioned system and, based on the instrument's linear function frequency doubling technology, generates a high-precision reference signal for the Fourier transform infrared spectrometer with an arbitrarily variable reference frequency.

[0013] The high-precision reference light generation method and system for Fourier transform infrared spectrometers provided by this invention have at least the following beneficial effects: 1. This invention employs a semiconductor DFB laser frequency stabilization method based on linear absorption frequency modulation spectrum, combined with a method based on the linear function frequency doubling technology of Fourier transform infrared spectrometers, to achieve easy-to-use, low-cost, freely variable reference frequency, and high-precision reference reference generation. This can well meet the instrument application requirements of Fourier transform infrared spectrometers, such as interference data sampling triggering and interferometer moving mirror motion control. 2. This invention uses a DFB laser as the light source, which has significant advantages such as no need for high-voltage driving, small size, compact structure and easy integration, full utilization of the development of semiconductor lasers, and low price. It also effectively overcomes the problems of low frequency stability and low reference frequency of DFB lasers, and has good application value. 3. The high-precision DFB laser frequency stabilization method proposed in this invention can achieve a frequency stability better than 10. -9 DFB laser signal generation; 4. The high-precision reference light generation method for Fourier infrared spectrometers proposed in this invention can be applied to Fourier spectrometers with different wavelengths and spectral resolutions, such as ultraviolet, visible, near-infrared, infrared, and terahertz. In particular, it can meet the application requirements of Fourier spectrometers in low wavelength bands such as ultraviolet, visible, and near-infrared. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of a high-precision reference light generation system for a Fourier transform infrared spectrometer disclosed in an embodiment of the present invention. Implementation

[0015] To facilitate understanding of this research, a more detailed description is provided below with reference to the accompanying drawings and specific embodiments. However, this research can be implemented in many different forms and is not limited to the embodiments described in this specification. Rather, these embodiments are provided to provide a more thorough and comprehensive understanding of the disclosure of this research.

[0016] This invention provides a high-precision reference light generation method for Fourier transform infrared spectrometers and its hardware implementation, such as... Figure 1 As shown, it includes a DFB laser module, a frequency stabilization feedback control module, a current drive module, a temperature control module, and a reference signal generation module.

[0017] 1. DFB laser module The DFB laser module is used to generate high-frequency stable single-wavelength laser signals. The DFB laser module includes a DFB laser, a TEC cooler, and a splitter.

[0018] (1) DFB lasers are used to generate single-wavelength laser signals; 1550nm commercial off-the-shelf DFB fiber laser products can be selected as DFB lasers; (2) The TEC cooler and the DFB laser are integrated. The TEC cooler is used to control the operating temperature of the DFB laser at the optimal temperature by cooling or heating, and to maintain the laser die temperature constant so as to ensure that the operating wavelength of the DFB laser is not affected by temperature changes. (3) The splitter is connected to the DFB laser and is used to split the output light of the DFB laser into two beams with different powers. The beam with lower power is fed into the frequency stabilization feedback control module and used as the frequency stabilization feedback signal light of the DFB laser. The beam with higher power is fed into the reference signal generation module and used to generate the high-precision reference reference signal required for the operation of the Fourier infrared spectrometer.

[0019] 2. Frequency stabilization feedback control module The frequency stabilization feedback control module, connected to the DFB laser module, receives a portion of the laser signal output from the DFB laser module and generates a frequency stabilization feedback control signal for the DFB laser. The module employs a semiconductor DFB laser frequency stabilization method based on linear absorption frequency modulation spectrum to achieve frequency stabilization feedback control of the DFB laser. The frequency stabilization feedback control module includes an RF local oscillator circuit, a gas cell, a photodetector, a mixer circuit, and a frequency stabilization control unit.

[0020] (1) The radio frequency local oscillator circuit connects the mixer circuit and the DFB laser. It has two main functions: first, to provide the radio frequency local oscillator signal required for the operation of the mixer circuit; and second, to provide the radio frequency driving signal for the radio frequency modulation port of the DFB laser, so as to perform frequency modulation on the DFB laser and generate modulated laser output. (2) The gas chamber is connected to a splitter to provide the standard reference frequency required for locking the laser beam. It absorbs a portion of the modulated laser output from the DFB laser, thereby introducing characteristic spectral lines. For a 1550nm DFB laser, the gas in the gas chamber can be acetylene. (3) A photodetector is connected to the gas cell to convert the modulated laser absorbed by the gas cell into an electrical signal. For a 1550nm DFB laser, an InGaAs detector can be used; (4) The mixing circuit connects the radio frequency local oscillator circuit and the photodetector. It is used to mix the local oscillator signal output by the radio frequency local oscillator circuit with the electrical signal output by the photodetector to generate a laser frequency stabilization error signal. (5) The frequency stabilization control unit is connected to the mixing circuit to receive the laser frequency stabilization error signal and provide the drive current regulation signal; the feedback control algorithm of the frequency stabilization control unit adopts a composite control algorithm based on PID algorithm and combined with fuzzy logic to have better response performance and control accuracy. (6) Feedback control algorithm of frequency stabilization control unit, used to realize real-time feedback control of frequency stabilization control unit. The basic idea of ​​feedback control algorithm is to first use fuzzy logic to analyze the laser frequency stabilization error signal, eliminate abnormal false situations such as small fluctuations and transient glitches, and then input the laser frequency deviation information into PID algorithm to make corresponding adjustment strategies, thereby achieving better response performance and control accuracy of frequency stabilization control response, and realizing frequency stabilization of DFB laser.

[0021] 3. Current drive module The current drive module connects the DFB laser module and the frequency stabilization feedback control module. It receives the frequency stabilization feedback control signal output by the frequency stabilization feedback control module, thereby providing the required drive current for the DFB laser module to operate. The current drive module includes a current control unit and a constant current source circuit.

[0022] (1) The current control unit is connected to the frequency stabilization control unit. Based on the driving current regulation signal given by the frequency stabilization control unit, the operating parameters of the constant current source circuit are adjusted in real time, thereby improving the frequency stability of the laser signal output by the DFB laser. (2) The constant current source circuit is connected to the current control unit. Under the control of the current control unit, it is used to provide the high-precision driving current required for the DFB laser to output high-frequency stable laser.

[0023] 4. Temperature control module The temperature control module, connected to the DFB laser module, is used to control the operating temperature of the DFB laser at its optimal level. The temperature control module includes a temperature sensor, a temperature regulation unit, and a TEC drive circuit.

[0024] (1) A temperature sensor is connected to the DFB laser to monitor the operating temperature of the DFB laser in real time; (2) The temperature control unit is connected to a temperature sensor to provide temperature control information. The temperature control unit adopts a temperature control scheme based on the PID algorithm combined with the Kalman recursive algorithm to achieve high-precision, real-time stable control of the DFB laser's operating temperature; (3) The basic idea of ​​the temperature control algorithm of the temperature control unit is that after receiving the real-time working temperature information of the DFB laser, the Kalman recursive algorithm analyzes the working temperature drift of the DFB laser and gives a real-time temperature change prediction. The PID algorithm gives real-time temperature control information based on the DFB working temperature deviation and temperature change prediction given by the Kalman recursive algorithm, thereby realizing high-precision real-time stable control of the DFB working temperature. (4) The TEC drive circuit is connected to the temperature control unit for real-time adjustment of TEC operating parameters; (5) The TEC is connected to the TEC drive circuit. The TEC drive circuit drives the cooling or heating to adjust the working temperature of the laser and maintain the constant temperature of the laser die.

[0025] 5. Reference signal generation module The reference signal generation module, connected to the DFB laser module, is used to detect and receive the high-frequency stable single-wavelength laser output from the DFB laser module, generating a high-precision reference of arbitrary frequency required for the operation of the Fourier transform infrared spectrometer. The reference signal generation module includes a laser interferometer, a photoelectric detection and data acquisition unit, and an FPGA.

[0026] (1) The laser interferometer is connected to the splitter to perform interference modulation on the laser output from the DFB laser to generate high-precision interference light; the laser interferometer is usually designed with the main interferometer of the Fourier infrared spectrometer to obtain the best performance; (2) The photoelectric detection and data acquisition unit is connected to the laser interferometer and is used for photoelectric conversion of the interference light output by the laser interferometer, analog electrical signal conditioning and shaping, data acquisition, etc., and outputs low-frequency cosine signals; (3) The FPGA is connected to the photoelectric detection and data acquisition unit, which uses a frequency doubling technique based on the instrument line function of the Fourier transform infrared spectrometer to perform frequency doubling processing on the low-frequency cosine signal generated by the photoelectric detection and data acquisition unit, generating a high-precision reference signal of arbitrary desired frequency to meet the working requirements of the Fourier transform infrared spectrometer. For Fourier transform infrared spectrometers using a Michelson interferometer, the instrument line function is the Sinc function.

[0027] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A high-precision reference light generation system for a Fourier transform infrared spectrometer, characterized in that, It includes a DFB laser module, a frequency stabilization feedback control module, a current drive module, a temperature control module, and a reference signal generation module; The DFB laser module is used to generate a high-frequency stable single-wavelength laser signal; the DFB laser module includes a DFB laser, a TEC cooler, and a splitter; the DFB laser is used to generate a single-wavelength laser signal; the TEC cooler and the DFB laser are integrated and used to control the temperature of the DFB laser at the optimal temperature; the splitter is connected to the DFB laser and is used to guide the output light of the DFB laser to the frequency stabilization feedback control module and the reference signal generation module respectively; The frequency stabilization feedback control module is connected to the DFB laser module and is used to receive part of the laser signal output by the DFB laser module, thereby generating the frequency stabilization feedback control signal of the DFB laser. The current drive module is connected to the DFB laser module and the frequency stabilization feedback control module. It is used to receive the frequency stabilization feedback control signal output by the frequency stabilization feedback control module, thereby providing the required drive current for the operation of the DFB laser module. The temperature control module is connected to the DFB laser module and is used to control the operating temperature of the DFB laser at the optimal temperature. The reference signal generation module is connected to the DFB laser module and is used to detect and receive the high-stability single-wavelength laser output from the DFB laser module to generate a high-precision reference standard with arbitrary reference frequency required for the operation of the Fourier infrared spectrometer. The reference signal generation module includes a laser interferometer, a photoelectric detection and data acquisition unit, and an FPGA. The laser interferometer is connected to a splitter to perform interference modulation on the laser output from the DFB laser to generate high-precision interference light. The photoelectric detection and data acquisition unit is connected to a laser interferometer and is used for photoelectric conversion of interference light, analog electrical signal conditioning and shaping, data acquisition, and outputting a high-precision cosine signal of a specific frequency. The FPGA is connected to the photoelectric detection and data acquisition unit, which is used to generate a high-precision reference signal of any desired frequency by employing frequency doubling technology based on the linear function of the Fourier transform infrared spectrometer, thus meeting the working requirements of the Fourier transform infrared spectrometer.

2. The high-precision reference light generation system for a Fourier transform infrared spectrometer according to claim 1, characterized in that, The frequency stabilization feedback control module includes an RF local oscillator circuit, a gas chamber, a photodetector, a mixer circuit, and a frequency stabilization control unit. The radio frequency local oscillator circuit connects the mixer circuit and the DFB laser, and is used to provide the radio frequency local oscillator signal required for the operation of the mixer circuit, as well as to modulate the frequency of the DFB laser to generate modulated laser output. The gas cell connection splitter is used to provide the standard reference frequency required for locking the laser beam frequency and to absorb part of the modulated laser output from the DFB laser, thereby introducing characteristic spectral lines. The photodetector is connected to the gas chamber and is used to convert the modulated laser absorbed by the gas chamber into an electrical signal; The mixing circuit connects the radio frequency local oscillator circuit and the photodetector, and is used to mix the local oscillator signal output by the radio frequency local oscillator circuit with the electrical signal output by the photodetector to generate a laser frequency stabilization error signal. The frequency stabilization control unit is connected to the mixer circuit and is used to receive the laser frequency stabilization error signal and provide the drive current regulation signal.

3. The high-precision reference light generation system for a Fourier transform infrared spectrometer according to claim 1, characterized in that, The current drive module includes a current control unit and a constant current source circuit; The current control unit is connected to the frequency stabilization control unit and is used for real-time adjustment of the operating parameters of the constant current source circuit; The constant current source circuit is connected to the current control unit and is used to provide the high-precision drive current required for the DFB laser to output high-frequency stable laser.

4. The high-precision reference light generation system for a Fourier transform infrared spectrometer according to claim 1, characterized in that, The temperature control module includes a temperature sensor, a temperature regulation unit, and a TEC drive circuit. The temperature sensor is connected to the DFB laser and is used to monitor the operating temperature of the DFB laser in real time. The temperature control unit is connected to a temperature sensor to provide temperature control information; The TEC drive circuit is connected to the temperature control unit and is used for real-time adjustment of TEC operating parameters; The TEC is connected to the TEC drive circuit and is used for cooling or heating to keep the operating temperature of the DFB laser constant.

5. A method for generating high-precision reference light for a Fourier transform infrared spectrometer, characterized in that: Using the high-precision reference light generation system for Fourier transform infrared spectrometers as described in any one of claims 1-4, and based on the frequency doubling technique of the instrument's linear function, a high-precision reference signal for Fourier transform infrared spectrometers with arbitrarily variable reference frequency is generated.

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