CN115825004A - Wavelength locking device and method of gas detection tunable semiconductor laser - Google Patents

Abstract

The present disclosure provides a wavelength locking device of a gas detection tunable semiconductor laser, including: the main control MCU is used for generating a voltage scanning signal to the current control module; the current control module is used for supplying energy to the semiconductor laser according to the voltage scanning signal; a semiconductor laser for generating laser light whose wavelength varies periodically; measuring a light path; the special detector is internally packaged with standard gas with preset concentration, and the standard gas is used for enhancing the intensity of a spectrum signal of the gas to be detected absorbed by laser; the signal conditioning module is used for amplifying, filtering and interface matching the detected signal; the AGC automatic gain module is used for adjusting the automatic gain of the detected signal and outputting the adjusted signal to the main control MCU; the master control MCU is also used for generating a temperature control signal according to the voltage signal and outputting the temperature control signal to the temperature control module; and the temperature control module is used for regulating and controlling the working temperature of the semiconductor laser according to the temperature control signal and correcting the central wavelength of the laser generated by the semiconductor laser.

Description

Wavelength locking device and method of gas detection tunable semiconductor laser

Technical Field

The present disclosure relates to the field of gas detection technologies, and in particular, to a wavelength locking method and apparatus for a tunable semiconductor laser for gas detection.

Background

The tunable semiconductor laser absorption spectroscopy (TDLAS) technology has the advantages of high sensitivity, good linearity, high response speed, long detection distance, less interference from other gases and the like, and is widely applied. In order to accurately and stably monitor the gas concentration of the gas detection tunable semiconductor laser, the center wavelength of the laser needs to be stable, but the tunable semiconductor laser is affected by the ambient temperature and the aging of components, so that the output center wavelength position and wavelength range shift is caused, and the accuracy of concentration measurement and the correlation of an inversion algorithm are reduced.

Methods for solving this problem generally include a method using a reference gas cell, a method using a fiber grating, a method using an etalon filter, and the like. The methods using the reference gas cell include a double light path method and a single light path method. The double-optical path method is to divide the output laser into two paths, one path of main optical path is used for gas detection, the other path of wavelength locking optical path is used for laser output wavelength locking, an absorption cell filled with standard gas with higher concentration is placed in a reference optical path, a detector of the reference optical path is used for monitoring the position of a gas absorption line in real time, and once drift occurs, adjustment of laser current is executed, so that the central wavelength of the laser is always stabilized at the gas absorption position. The single light path method can convert the reference light path, intermittently pushes the reference cell into the detection light path, and the detection light path plays a role of the reference light path at this time, and can only adjust and lock the wavelength of the laser at this time, but can not continuously lock the wavelength of the laser. The single light path method also includes that a reference cell is placed in a detection light path, and the reference light path and the detection light path are combined into a whole. The fiber grating method and the etalon interference method are mainly used for locking laser wavelength in optical communication application, are only suitable for locking the wavelength when a laser works at a fixed wavelength, and are not suitable for locking the output wavelength of a continuously scanned laser.

In the field of gas detection, the existing laser wavelength locking technology mainly comprises a method of a double optical path with a reference gas pool, a method of a single optical path with a gas reference pool and a method of a single optical path without a gas reference pool. The dual-optical path reference cell method is used most widely at the earliest time, but a separate wavelength locking optical path and a wavelength locking module are needed, so that the complexity of the system is increased, and the splitting of the wavelength locking optical path can also cause the reduction of the laser power of a detection optical path and the signal-to-noise ratio of the system. The method of the single optical path with the gas reference cell directly obtains the sum of the gas concentration on the measuring optical path and the equivalent concentration of the gas in the reference cell, and the gas in the reference cell commonly used at present is high-concentration gas, which brings errors to the detection of the gas concentration on the measuring optical path. The method that the single light path does not have the gas reference cell is novel, two absorption lines of water vapor commonly existing in the environment are used as the basis for identifying and calculating the wavelength shift of the laser scanning process in the document 'laser wavelength locking system and method for scanning absorption spectrum' (CN 202011503569.1), and the method is only suitable for the condition that the water vapor absorption line exists near the target absorption line of the gas to be detected although the reference cell is not needed.

Disclosure of Invention

In view of the above problems, the present invention provides a wavelength locking device for a tunable semiconductor laser for gas detection, so as to solve the disadvantages of the prior art.

One aspect of the present disclosure provides a wavelength locking device of a gas detection tunable semiconductor laser, including: the device comprises a main control MCU, a current control module, a temperature control module, a semiconductor laser, a measuring light path, a special detector, a signal conditioning module and an AGC automatic gain module; the main control MCU is used for generating a voltage scanning signal to the current control module; the current control module is used for outputting current to the semiconductor laser according to the voltage scanning signal; the semiconductor laser is used for generating laser with periodically changed wavelength; the measuring light path is an open light path containing gas to be measured, so that the laser can detect the gas to be measured through the measuring light path; standard gas with preset concentration is packaged in the special detector and used for converting the laser passing through the measuring light path into a current signal, wherein the laser passes through the standard gas and then reaches a photosensitive surface of the characteristic detector, and the standard gas is used for enhancing the intensity of a spectrum signal of the gas to be measured; the signal conditioning module is used for converting the current signal into a voltage signal and then amplifying, filtering and matching interfaces; the AGC automatic gain module is used for adjusting the automatic gain of the voltage signal and outputting the voltage signal to the main control MCU; the master control MCU is also used for carrying out spectrum signal acquisition, background subtraction, extraction of a gas absorption signal to be detected and central wavelength offset calculation according to the voltage signal, generating a temperature control signal and outputting the temperature control signal to the temperature control module; the temperature control module is used for regulating and controlling the working temperature of the semiconductor laser according to the temperature control signal and correcting the central wavelength of the laser generated by the semiconductor laser.

According to the embodiment of the disclosure, the temperature control module uses an H-bridge circuit to realize the adjustment of the refrigeration and heating power of the TEC in the semiconductor laser.

According to an embodiment of the present disclosure, the apparatus further comprises: and the collimator is arranged between the semiconductor laser and the measuring light path and is used for collimating the laser.

Another aspect of the embodiments of the present disclosure provides a wavelength locking method for a gas detection tunable semiconductor laser, which is applied to the apparatus according to any one of the first aspect, and includes: controlling a semiconductor laser to generate laser with periodically changed wavelength, and enabling the laser to penetrate through the gas to be detected; detecting laser penetrating through the gas to be detected through a special detector, and enabling a main control MCU to obtain a measurement spectrum of the laser, wherein the laser is encapsulated in standard gas with preset concentration in the special detector and then reaches a photosensitive surface of a characteristic detector, and the standard gas is used for enhancing the intensity of a spectrum signal of the gas to be detected; calculating the central wavelength offset of the measurement spectrum and the reference spectrum of the laser by a master control MCU (microprogrammed control unit), and converting the central wavelength offset into an adjustment quantity of a temperature control signal; and adjusting the working temperature of the semiconductor laser based on the temperature control signal and correcting the central wavelength of the laser based on the temperature control signal of the adjustment amount adjusting control module.

According to an embodiment of the present disclosure, before generating the laser, the method includes: and setting the central wavelength and the wavelength scanning range of the light emitted by the semiconductor laser according to the absorption characteristic of the gas to be detected, so that the absorption peak of the gas to be detected is in the center of the wavelength scanning range.

According to an embodiment of the present disclosure, the calculating, by the master control MCU, the central wavelength shift amount of the measurement spectrum and the reference spectrum of the laser includes: acquiring a plurality of sampling points of the measurement spectrum and the reference spectrum; and calculating the offset of sampling points corresponding to the measurement spectrum and the reference spectrum based on a cross-correlation algorithm, and calculating the central wavelength offset based on the offset integration of a plurality of sampling points.

According to an embodiment of the present disclosure, the formula for calculating the offset of the sampling point corresponding to the measurement spectrum and the reference spectrum based on the cross-correlation algorithm and calculating the center wavelength offset based on the offset integration of the plurality of sampling points includes:

wherein f is _b (x) Function representing the reference spectrum, f _r (x) Representing the measured spectrum, R (f) _b ，f _r ) Representing function f _b (x) And f _r (x) X denotes the number of sample points and τ denotes the delay factor.

According to an embodiment of the present disclosure, the method further comprises: judging whether the central wavelength offset exceeds a preset threshold value or not; and when the central wavelength offset does not exceed a preset threshold value, not converting the central wavelength offset into an adjustment quantity of the temperature control signal.

The at least one technical scheme adopted in the embodiment of the disclosure can achieve the following beneficial effects:

the wavelength locking device of the tunable semiconductor laser provided by the embodiment of the disclosure only has a measuring light path, and does not need an independent wavelength locking light path, thereby greatly reducing the complexity of a gas detection system;

the wavelength locking device of the tunable semiconductor laser provided by the embodiment of the disclosure utilizes the specially-made detector, and the detector encapsulates standard gas with a certain concentration in the encapsulation process, so that the application range of wavelength locking can be expanded, the central wavelength of the laser can be locked under the condition that no gas to be detected exists in the region to be detected, the application limitation of the method that the single light path does not have a gas reference pool is broken through, meanwhile, a separate high-concentration gas reference pool does not need to be added in the light path, and the error source of the system is reduced.

Drawings

For a more complete understanding of the present disclosure and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:

FIG. 1 schematically illustrates a schematic diagram of a TDLAS direct absorption technique for detecting gas concentration;

FIG. 2 schematically illustrates a laser wavelength locking system that scans an absorption spectrum;

fig. 3 schematically illustrates a schematic diagram of a wavelength locking device of a gas detection tunable semiconductor laser provided by an embodiment of the present disclosure;

fig. 4 schematically illustrates a wavelength locking method of a gas detection tunable semiconductor laser provided by an embodiment of the present disclosure;

FIG. 5 schematically illustrates a spectrum center wavelength shift diagram provided by an embodiment of the present disclosure;

FIG. 6A is a schematic diagram illustrating the relationship between the position of the absorption peak of the measured spectrum and the ambient temperature when wavelength locking is not performed, provided by an embodiment of the present disclosure;

fig. 6B schematically shows a schematic diagram of measuring a relation between a spectral absorption peak position and an ambient temperature when wavelength locking is performed according to an embodiment of the disclosure.

Detailed Description

Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. It should be understood that the description is illustrative only and is not intended to limit the scope of the present disclosure. In the following detailed description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the embodiments of the disclosure. It may be evident, however, that one or more embodiments may be practiced without these specific details. Moreover, in the following description, descriptions of well-known structures and techniques are omitted so as to not unnecessarily obscure the concepts of the present disclosure.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. The terms "comprises," "comprising," and the like, as used herein, specify the presence of stated features, steps, operations, and/or components, but do not preclude the presence or addition of one or more other features, steps, operations, or components.

All terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art unless otherwise defined. It is noted that the terms used herein should be interpreted as having a meaning that is consistent with the context of this specification and should not be interpreted in an idealized or overly formal sense.

Fig. 1 schematically shows a principle diagram of a TDLAS direct absorption technique for detecting gas concentration.

As shown in fig. 1, fig. 1 is a schematic diagram of a principle of detecting gas concentration by using TDLAS direct absorption technology, which utilizes the absorption of gas molecules to laser with specific wavelength to tune the laser wavelength to the absorption line of the gas to be detected, and uses a photodetector to detect the light intensity of the laser passing through the gas medium, and when the target gas exists in the light path, the light intensity will change along with the gas concentration. The specific process is that the laser is applied with periodic scanning signal to change the laser wavelength, and the scanning is repeated to cover the selected gas absorption line. The light of the laser is divided into two beams, one beam is a measuring light path, the collimated light passes through a gas medium to be measured, and the transmitted light absorbed by the gas to be measured reaches the photoelectric detector 2; the other beam is used for calibrating the laser frequency, reaches the photoelectric detector 1 after passing through the interferometer, realizes the conversion from a time domain (sampling point) to a frequency domain (laser emergent light relative frequency) by using the frequency interval of interference fringes, namely Free Spectrum Range (FSR), is also called wavelength calibration, and then can calculate the average concentration of the gas to be measured by applying Beer-Lambert law.

According to the principle, the central wavelength of the laser must be stable to realize accurate and stable monitoring of the gas concentration, but the tunable semiconductor laser is influenced by the ambient temperature and the aging of components, so that the output central wavelength position and wavelength range can be shifted, the change of the central position of the absorption spectrum target absorption spectrum line of single scanning can be caused, and for the detection technology for carrying out gas concentration inversion by adopting a fixed calibration spectrum signal, the phenomenon can cause the accuracy of concentration measurement and the correlation of an inversion algorithm to be reduced; on the other hand, in the scanning absorption spectrum technology, a method of signal multi-time accumulation is generally adopted to improve the signal-to-noise ratio of signals, the wavelength of single-time scanning absorption spectrum signals participating in accumulation averaging is not aligned due to the change of the output wavelength of a laser, and the spectrum line broadening and the intensity of the accumulated spectrum signals are reduced, so that the detected gas concentration is inaccurate, and gas cannot be detected in serious cases.

Fig. 2 schematically illustrates a laser wavelength locking system that scans the absorption spectrum.

As shown in fig. 2, fig. 2 shows a system of a laser wavelength locking system and method for scanning absorption spectrum (CN 202011503569.1), which is used to solve the problem of how to achieve high-precision and high-reliability locking of the output center wavelength of a semiconductor laser. The working principle is as follows: dividing a detection scanning spectrum signal output by an absorption spectrum detection subsystem into two paths, wherein one path is used for inverting the concentration of target gas; the other path is used as a reference signal to be input into the identification and feedback control subsystem for correcting and locking the laser wavelength drift, a reference light path is not required to be added, and the identification and feedback control of the laser wavelength drift can be completed by using a light path signal of the detection subsystem, so that the system structure is simplified; two water vapor absorption lines which are ubiquitous in the environment are used as the reference for identifying and calculating the wavelength drift of the laser scanning process, the false wavelength drift characteristics caused by noise or interference can be effectively identified, and the reliability and the accuracy of identifying and calculating the wavelength drift of the laser scanning process are higher. Two water vapor absorption lines which are ubiquitous in the environment are used as the basis for identifying and calculating the wavelength drift in the scanning process of the laser, and the method is not required to be used for a reference pool, but is only suitable for the condition that the water vapor absorption lines are near the target absorption line of the gas to be detected.

The embodiment of the disclosure provides a wavelength locking device of a tunable semiconductor laser for gas detection, which can simply and conveniently realize high-precision and high-reliability locking of the output center wavelength of the semiconductor laser. The device only has a measuring light path, and does not need an independent wavelength locking light path, thereby greatly reducing the complexity of the gas detection system. The device utilizes a specially-made detector, and the detector encapsulates standard gas with a certain concentration in the encapsulation process, so that the application range of wavelength locking can be enlarged, the central wavelength of a laser can be locked under the condition that no gas to be detected exists in a region to be detected, the application limitation of the method that a single light path does not have a gas reference pool is broken through, meanwhile, a separate high-concentration gas reference pool does not need to be added in the light path, and the error source of the system is reduced.

Fig. 3 schematically illustrates a schematic diagram of a wavelength locking device of a gas detection tunable semiconductor laser provided by an embodiment of the present disclosure.

As shown in fig. 3, a wavelength locking device of a tunable semiconductor laser for gas detection according to an embodiment of the present disclosure includes: the device comprises a main control MCU, a control module, a semiconductor laser, a special detector and a signal modulation feedback module.

In the embodiment of the disclosure, the device comprises a main control MCU, a current control module, a temperature control module, a semiconductor laser, a measuring light path, a special detector, a signal conditioning module and an AGC automatic gain module; the main control MCU is used for generating a voltage scanning signal to the current control module; the current control module is used for outputting current to the semiconductor laser according to the voltage scanning signal; the semiconductor laser is used for generating laser with periodically changed wavelength; the measuring light path is an open light path containing gas to be measured, so that laser can detect the gas to be measured through the measuring light path; standard gas with preset concentration is packaged in the special detector and used for converting laser passing through a measuring light path into a current signal, wherein the laser passes through the standard gas and then reaches a photosensitive surface of the characteristic detector, and the standard gas is used for enhancing the intensity of a spectrum signal of the gas to be detected; the signal conditioning module is used for converting the current signal into a voltage signal and then carrying out amplification, filtering and interface matching; the AGC automatic gain module is used for automatically adjusting the gain of the voltage signal and outputting the voltage signal to the main control MCU; the master control MCU is also used for carrying out spectrum signal acquisition, background subtraction, extraction of a gas absorption signal to be detected and central wavelength offset calculation according to the voltage signal, generating a temperature control signal and outputting the temperature control signal to the temperature control module; the temperature control module is used for regulating and controlling the working temperature of the semiconductor laser according to the temperature control signal and correcting the central wavelength of the laser generated by the semiconductor laser.

The device also includes: and the collimator is arranged between the semiconductor laser and the measuring light path and is used for collimating the laser.

According to the wavelength locking device of the tunable semiconductor laser for gas detection provided by the embodiment of the disclosure, the main control MCU generates a voltage scanning signal to be connected to the current control module, the current control module adopts a voltage-controlled current source, and outputs a corresponding current to act on the semiconductor laser according to an input voltage value, so that the wavelength output by the semiconductor laser is changed periodically. The master control MCU sends out a laser temperature control signal to the temperature control module, the temperature control module realizes the adjustment of the refrigeration and heating power of the TEC in the semiconductor laser by using the H-bridge circuit, and the semiconductor laser stably outputs laser with the wavelength periodically changing in a specified range under the combined action of the current control module and the temperature control module. The laser emitted by the semiconductor laser passes through the measuring area after being collimated by the collimator and reaches the photosensitive surface of the special detector, the optical signal is converted into an electric signal by the special detector, the electric signal is sent to the signal conditioning module to be converted into a voltage signal, the voltage signal is amplified, filtered and matched with an interface, the voltage signal is sent to the AGC automatic gain module to carry out automatic gain adjustment on the signal, and finally the signal is accessed to the ADC of the main control MCU to carry out data acquisition and processing. The main control MCU is used for collecting spectral signals, deducting background, extracting gas absorption signals to be detected, calculating central wavelength offset, generating laser temperature adjustment signals and outputting the laser temperature adjustment signals to the temperature control module, so that the central wavelength of the laser is accurately locked.

The wavelength locking device of the tunable semiconductor laser for gas detection provided by the embodiment of the disclosure only has a measuring light path, and does not need an independent wavelength locking light path, thereby greatly reducing the complexity of a gas detection system. The special detector is utilized, the detector encapsulates standard gas with a certain concentration in the encapsulation process, so that the application range of wavelength locking can be enlarged, the central wavelength of the laser can be locked under the condition that no gas to be detected exists in a region to be detected, the application limitation of the method that a single light path does not have a gas reference pool is broken through, meanwhile, a separate high-concentration gas reference pool does not need to be added in the light path, and the error source of the system is reduced.

Fig. 4 schematically illustrates a wavelength locking method of a gas detection tunable semiconductor laser provided by an embodiment of the present disclosure.

As shown in fig. 4, a wavelength locking method of a gas detection tunable semiconductor laser according to an embodiment of the present disclosure includes operations S410 to S440.

In operation S410, the semiconductor laser is controlled to generate laser light with a periodically changing wavelength, and the laser light is made to pass through the gas to be measured.

During the detection of the gas to be detected by using the laser, the central wavelength and the wavelength scanning range of the light emitted by the semiconductor laser are set according to the absorption characteristics of the gas to be detected, so that the absorption peak of the gas to be detected is in the center of the wavelength scanning range.

In operation S420, the laser passing through the gas to be detected is detected by the special detector, so that the main control MCU obtains a measurement spectrum of the laser, wherein the laser reaches a photosensitive surface of the characteristic detector after being encapsulated in a standard gas with a preset concentration in the special detector, and the standard gas is used to enhance the intensity of a spectrum signal of the gas to be detected.

In the embodiment, the detector encapsulates standard gas with a certain concentration in the encapsulation process, so that the application range of wavelength locking can be enlarged, the central wavelength of the laser can be locked under the condition that no gas to be detected exists in the region to be detected, the application limitation of the method that a single light path does not have a gas reference pool is broken through, meanwhile, a separate high-concentration gas reference pool does not need to be added in the light path, and the error source of the system is reduced.

In operation S430, the center wavelength shift amount of the measured spectrum and the reference spectrum of the laser is calculated by the main control MCU, and the center wavelength shift amount is converted into an adjustment amount of the temperature control signal.

In this embodiment, the gas absorption spectrum of the laser light may be collected in advance as a reference spectrum. The laser measures the gas to be measured, and the acquired spectrum signal is the measurement spectrum.

In this embodiment, the direction and amount of shift of the center wavelength of the laser output is determined using a cross-correlation algorithm. Specifically, a reference spectrum and a measurement spectrum are utilized to obtain a plurality of sampling points of the measurement spectrum and the reference spectrum, the offset of the sampling points corresponding to the measurement spectrum and the reference spectrum is calculated based on a cross-correlation algorithm, and the central wavelength offset is calculated based on the offset integral of the plurality of sampling points.

The calculation formula for calculating the center wavelength offset includes:

wherein f is _b (x) Function representing reference spectrum, f _r (x) Denotes the measured spectrum, R (f) _b ，f _r ) Representing function f _b (x) And f _r (x) X denotes the number of sample points and τ denotes the delay factor.

According to the property of the cross-correlation function, when the cross-correlation function takes the maximum value, the two groups of spectral data are aligned, and the delay coefficient tau is obtained at the moment _max I.e. the shift of the center wavelengths of the reference spectrum and the measured spectrum. The cross-correlation algorithm can more accurately calculate the wavelength offset by analyzing all sampling points of the two spectra to determine the offset of the center position of the absorption line, rather than simply calculating the offset by using the absorption peak positions of the two spectra. By using the cross-correlation algorithm, not only the relative abscissa shift between the two spectra can be accurately calculated, but also the moving direction (determined by the sign of the delay coefficient τ) of the measurement signal relative to the standard signal can be calculated.

In operation S440, the operating temperature of the semiconductor laser is adjusted based on the temperature control signal of the adjustment amount adjustment control module, and the center wavelength of the laser light is corrected.

According to the offset, the adjustment amount of the temperature can be calculated by combining the corresponding relation between the wavelength of the laser and the temperature, and the temperature adjustment amount is fed back to the temperature control module through the main control MCU, so that the working temperature of the laser is adjusted.

In a specific application, in operation S440, the method may further include S441 and S442.

In operation S441, it is determined whether the center wavelength shift amount exceeds a preset threshold.

When the offset is larger than the set threshold, the offset is fed back to a temperature control module of the laser, and the working temperature of the laser is readjusted

In operation S442, when the central wavelength shift amount does not exceed the preset threshold, the central wavelength shift amount is not converted into an adjustment amount of the temperature control signal.

According to the wavelength locking method of the tunable semiconductor laser for gas detection provided by the embodiment of the disclosure, on one hand, based on the wavelength locking device provided by the embodiment of the disclosure, the detector encapsulates standard gas with a certain concentration in the encapsulation process, so that the application range of wavelength locking can be expanded, the central wavelength of the laser can be locked under the condition that no gas to be detected exists in a region to be detected, the application limitation of the method that a single light path does not have a gas reference pool in the prior art is broken through, meanwhile, a separate high-concentration gas reference pool does not need to be added in the light path, and the error source of the system is reduced; on the other hand, the central wavelength offset calculation method adopted by the embodiment of the disclosure is a cross-correlation operation method, the difference of the abscissa is obtained by calculating the cross-correlation of two spectrum data, and a section of spectrum data is applied, so that the method has a smoothing effect on optical and electronic noises, has higher calculation accuracy, and can ensure high-accuracy locking of laser wavelength.

Fig. 5 schematically illustrates a spectrum center wavelength shift diagram provided by an embodiment of the present disclosure.

As shown in fig. 5, the measurement signal of the laser is shifted from the center wavelength of the standard signal.

In order to more intuitively understand the locking effect of the wavelength locking device of the tunable semiconductor laser in the embodiment, the scanning range of the semiconductor laser is 0.5nm, the number of sampling points in each period is 20000, the part of the laser which does not emit light during sawtooth wave modulation is subtracted, and the number of sampling effective points is 16000.

Fig. 6A schematically illustrates a diagram of measuring a relationship between a spectral absorption peak position and an ambient temperature when wavelength locking is not performed according to an embodiment of the disclosure.

As shown in fig. 6A, when wavelength locking is not performed, the position of the absorption peak of the measurement spectrum increases with an increase in temperature.

Fig. 6B schematically shows a schematic diagram of measuring a relation between a spectral absorption peak position and an ambient temperature when wavelength locking is performed according to an embodiment of the disclosure.

As shown in FIG. 6B, adoptAfter the wavelength locking method of the embodiment is used, the offset swing range of the position of the absorption peak of the measured spectrum is small, the maximum drift 132 point of the central sampling point is calculated according to the scanning range of the light source of 0.5nm and the sampling point of 16000, and the wavelength drift amount is 4.1 multiplied by 10 ^-12 And m, verifying the effectiveness of the wavelength locking method based on the cross-correlation algorithm.

Those skilled in the art will appreciate that various combinations and/or combinations of features recited in the various embodiments and/or claims of the present disclosure can be made, even if such combinations or combinations are not expressly recited in the present disclosure. In particular, various combinations and/or combinations of the features recited in the various embodiments and/or claims of the present disclosure may be made without departing from the spirit or teaching of the present disclosure. All such combinations and/or associations are within the scope of the present disclosure.

While the disclosure has been shown and described with reference to certain exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the disclosure as defined by the appended claims and their equivalents. Accordingly, the scope of the present disclosure should not be limited to the above-described embodiments, but should be defined not only by the appended claims, but also by equivalents thereof.

Claims (8)

1. A wavelength locking device for a gas detection tunable semiconductor laser, comprising:

the device comprises a main control MCU, a current control module, a temperature control module, a semiconductor laser, a measuring light path, a special detector, a signal conditioning module and an AGC automatic gain module;

the master control MCU is used for generating a voltage scanning signal to the current control module;

the current control module is used for outputting current to the semiconductor laser according to the voltage scanning signal;

the semiconductor laser is used for generating laser with periodically changed wavelength;

the measuring light path is an open light path containing gas to be measured, so that the laser can detect the gas to be measured through the measuring light path;

standard gas with preset concentration is packaged in the special detector and used for converting the laser passing through the measuring light path into a current signal, wherein the laser passes through the standard gas and then reaches a photosensitive surface of the characteristic detector, and the standard gas is used for enhancing the intensity of a spectrum signal of the gas to be measured;

the signal conditioning module is used for converting the current signal into a voltage signal and then amplifying, filtering and matching interfaces;

the AGC automatic gain module is used for adjusting the automatic gain of the voltage signal and outputting the voltage signal to the main control MCU;

the master control MCU is also used for carrying out spectrum signal acquisition, background subtraction, extraction of a gas absorption signal to be detected and central wavelength offset calculation according to the voltage signal, generating a temperature control signal and outputting the temperature control signal to the temperature control module;

the temperature control module is used for regulating and controlling the working temperature of the semiconductor laser according to the temperature control signal and correcting the central wavelength of the laser generated by the semiconductor laser.

2. The apparatus of claim 1, wherein the temperature control module uses an H-bridge circuit to enable regulating the cooling and heating power of a TEC in the semiconductor laser.

3. The apparatus of claim 1, further comprising:

and the collimator is arranged between the semiconductor laser and the measuring light path and is used for collimating the laser.

4. A method for wavelength locking of a gas detection tunable semiconductor laser, applied to the apparatus according to any one of claims 1 to 3, comprising:

controlling a semiconductor laser to generate laser with periodically changed wavelength, and enabling the laser to penetrate through the gas to be detected;

detecting laser penetrating through the gas to be detected through a special detector, and enabling a main control MCU to obtain a measurement spectrum of the laser, wherein the laser is encapsulated in standard gas with preset concentration in the special detector and then reaches a photosensitive surface of a characteristic detector, and the standard gas is used for enhancing the intensity of a spectrum signal of the gas to be detected;

calculating the central wavelength offset of the measurement spectrum and the reference spectrum of the laser by a master control MCU (microprogrammed control unit), and converting the central wavelength offset into an adjustment quantity of a temperature control signal;

and adjusting the temperature control signal of the temperature control module based on the adjustment amount, adjusting the working temperature of the semiconductor laser based on the temperature control signal, and correcting the central wavelength of the laser.

5. The method of claim 4, wherein prior to generating the laser light, the method comprises:

and setting the central wavelength and the wavelength scanning range of the light emitted by the semiconductor laser according to the absorption characteristic of the gas to be detected, so that the absorption peak of the gas to be detected is in the center of the wavelength scanning range.

6. The method of claim 4, wherein calculating the center wavelength shift of the measured spectrum and the reference spectrum of the laser by the master MCU comprises:

acquiring a plurality of sampling points of the measurement spectrum and the reference spectrum;

and calculating the offset of sampling points corresponding to the measurement spectrum and the reference spectrum based on a cross-correlation algorithm, and calculating the central wavelength offset based on the offset integrals of a plurality of sampling points.

7. The method according to claim 6, wherein the calculation formula for calculating the offset of the sampling points corresponding to the measured spectrum and the reference spectrum based on the cross-correlation algorithm and calculating the central wavelength offset based on the integral of the offsets of the plurality of sampling points comprises:

wherein f is _b (x) Function representing the reference spectrum, f _r (x) Representing the measured spectrum, R (f) _b ，f _r ) Representing function f _b (x) And f _r (x) X denotes the number of sample points and τ denotes the delay factor.

8. The method of claim 4, further comprising:

judging whether the central wavelength offset exceeds a preset threshold value or not;

and when the central wavelength offset does not exceed a preset threshold, not converting the central wavelength offset into an adjustment quantity of a temperature control signal.

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