CN112556998A - Tunable laser wavelength calibration system and method based on photoacoustic spectroscopy technology - Google Patents
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- 238000004867 photoacoustic spectroscopy Methods 0.000 title claims abstract description 24
- 238000000034 method Methods 0.000 title claims abstract description 13
- 238000005516 engineering process Methods 0.000 title claims abstract description 10
- 238000005086 pumping Methods 0.000 claims abstract description 17
- 150000003384 small molecules Chemical class 0.000 claims abstract description 13
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- 229910001634 calcium fluoride Inorganic materials 0.000 claims description 3
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- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 10
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 7
- 238000013461 design Methods 0.000 description 5
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- HSFWRNGVRCDJHI-UHFFFAOYSA-N alpha-acetylene Natural products C#C HSFWRNGVRCDJHI-UHFFFAOYSA-N 0.000 description 2
- 229910021529 ammonia Inorganic materials 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
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- 230000000694 effects Effects 0.000 description 2
- 125000002534 ethynyl group Chemical group [H]C#C* 0.000 description 2
- 238000001834 photoacoustic spectrum Methods 0.000 description 2
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- G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
- G01M11/00—Testing of optical apparatus; Testing structures by optical methods not otherwise provided for
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- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
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- G01J3/42—Absorption spectrometry; Double beam spectrometry; Flicker spectrometry; Reflection spectrometry
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Abstract
The invention discloses a wavelength calibration system and method of a tunable laser based on a photoacoustic spectroscopy technology, wherein the system comprises the following components: the device comprises a signal generator, a pumping unit, an infrared laser, small molecule gas, an amplifying unit and a computer; the small molecular gas comprises a photoacoustic cell, the photoacoustic cell is in a sealed state and is internally filled with gas, and a sound receiving device is also arranged in the inner cavity of the photoacoustic cell; the radio device is connected with the amplifier and the computer in sequence; the computer is connected with the infrared laser, the computer, the signal generator, the pumping unit and the infrared laser are sequentially connected, and laser output by the infrared laser irradiates gas in the acoustic cell. The instrument can be realized by only one glass cavity, the miniature microphone, the self-made signal amplifier, the oscilloscope or the computer and the like. Small, simple and inexpensive, and it is small, simple and inexpensive.
Description
Technical Field
The invention relates to the technical field of photoacoustic spectroscopy, in particular to a system and a method for calibrating wavelength of a tunable laser based on photoacoustic spectroscopy.
Background
Infrared light is an electromagnetic wave invisible to the naked eye and has a wavelength in the range of 1 mm to 750 nm. The wavelength tunable infrared light has wide application in the aspects of detection, communication, medical treatment, experimental research, military and the like. The infrared light source capable of generating wavelength tunable infrared light mainly comprises: infrared Optical Parametric Oscillators (OPOs), Quantum Cascade Lasers (QCLs), laser Difference Frequency (DFG) infrared sources, and the like. However, the above infrared light sources mainly rely on mechanical control and temperature control to tune the output infrared light wavelength, so that the output infrared light wavelength has a certain error from the actual wavelength. In order to obtain an accurate infrared wavelength, the infrared wavelength output by the laser needs to be calibrated, and usually, the light wave emitted by the laser is measured by an infrared wavelength measuring instrument and then calibrated, for example, the infrared light of the laser is measured and calibrated by a waveScan infrared wavelength measuring instrument manufactured by the company APE, germany. However, such instruments are not only bulky, but also quite expensive. Furthermore, high quality optical elements such as high-reflectivity mirrors, lenses, gratings, etc., as well as photodetectors, control computers, etc., are required, and the instruments thereof are large in size and weight and relatively expensive.
Therefore, there is a need in the industry to develop a method or system for calibrating the wavelength of an infrared laser, which is convenient to operate and low in cost.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a tunable laser wavelength calibration system and method based on the photoacoustic spectroscopy technology, which are convenient to operate and low in cost.
The purpose of the invention is realized by the following technical scheme:
a tunable laser wavelength calibration system based on photoacoustic spectroscopy technology, comprising: the device comprises a signal generator, a pumping unit, an infrared laser, small molecule gas, an amplifying unit and a computer; the small molecular gas comprises a photoacoustic cell, the photoacoustic cell is in a sealed state and is internally filled with gas, and a sound receiving device is also arranged in the inner cavity of the photoacoustic cell; the radio device is connected with the amplifier and the computer in sequence; the computer is connected with the infrared laser, the computer, the signal generator, the pumping unit and the infrared laser are sequentially connected, and laser output by the infrared laser irradiates gas in the acoustic cell.
Preferably, the sound receiving device is a microphone or a piezoelectric ceramic microphone.
Preferably, the amplifying unit includes: the amplifier comprises a first-stage amplifier U1, a second-stage amplifier U2, a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R5, a capacitor C1, a capacitor C2 and a capacitor C3; the resistor R5 is a slide rheostat; two input ends of a first-stage amplifier U1 are connected with a sound receiving device, a forward input end of a first-stage amplifier U1 is connected with an output end through a resistor R1, an output end of the first-stage amplifier U1 is connected with one end of a resistor R2 and a resistor R3 and one end of a capacitor C1, the other end of the resistor R3 is connected with a reverse input end of a second-stage amplifier U2 and one end of a capacitor C2, the other end of the capacitor C2 is connected with the ground, the other end of the capacitor C1 is connected with a same-direction input end of a second-stage amplifier U2 through a resistor R4, one end of a capacitor C3 and one fixed end of a resistor R5, the other fixed end of the resistor R5, a sliding end of the resistor R5 and the other end of the capacitor C3 are connected with an output end of the second-stage amplifier U2, and an; the resistor R2, the resistor R3, the capacitor C1, the capacitor C2 and the connection of the resistors R2, the resistor R3, the capacitor C1 and the capacitor C2 form an RC pi-type filter circuit.
Preferably, the model of the first stage amplifier U1 is AD620, and the model of the second stage amplifier U2 is TLV2711 CDBVR.
Preferably, the small molecule gas pool further comprises an upper cavity, a lower cavity and a cylinder; go up cavity, lower cavity and press from both sides the pressfitting through stainless steel ball mill mouth and connect, the sub-unit connection cylinder of lower cavity, radio reception device sets up at the cylinder, the sub-unit connection optoacoustic cell of cylinder, cylinder and optoacoustic cell intercommunication, the window of going into light of optoacoustic cell side is provided with the calcium fluoride lens, the air flue of optoacoustic cell lower part is connected mechanical pump interface and is had the overhead valve that is used for separating loading and unloading gas portion and optoacoustic cell.
Preferably, a tunable laser wavelength calibration system based on photoacoustic spectroscopy further comprises: a power supply circuit; the power supply circuit is connected with the amplifying unit and the radio device.
Preferably, the power supply circuit comprises a direct current power supply, and the direct current power supply is a direct current stabilized power supply or a dry battery.
A wavelength calibration method of a tunable laser based on a photoacoustic spectroscopy technology comprises the following steps: the pumping unit outputs pumping light to the infrared laser, the infrared laser outputs continuous infrared laser with wavelength under the action of the pumping light, the infrared laser irradiates gas in the photoacoustic cell, if the wavelength of incident light is consistent with the absorption wavelength of gas molecules, the gas molecules absorb the laser to generate periodic pressure fluctuation, the sound receiving device detects the periodic pressure fluctuation of the gas molecules, the periodic pressure fluctuation is amplified by the amplifying unit to obtain photoacoustic signals, the vibration absorption peak position of the photoacoustic signals is compared with the vibration absorption peak position fixed by known molecules, and if the vibration absorption peak position of the photoacoustic signals is inconsistent with the vibration absorption peak position fixed by the known molecules, the output wavelength of the infrared laser is controlled by a computer, so that the calibration of the output wavelength of the infrared laser is realized.
Preferably, when the wavelength generated by the laser is not the wavelength position corresponding to the gas infrared characteristic peak, the absorption of infrared light energy is very small, no pressure disturbance is generated, and the sound receiving device cannot detect the periodic pressure fluctuation of gas molecules.
Compared with the prior art, the invention has the following advantages:
the invention uses tunable IR laser to emit infrared light to irradiate into Gas cell filled with Gas small molecule, to change incident wavelength, when the incident wavelength is matched with the absorption wavelength of Gas small molecule, the pulse incident light is absorbed, the Gas small molecule energy is increased, to generate periodic pressure fluctuation. At this moment, the sound receiving device receives vibration signals of gas molecules, the converter converts sound signals of micro vibration into voltage signals, then the voltage signals are transmitted to the amplifier, the amplifier amplifies the signals and then transmits the signals, and light generated by the optical parametric oscillator is irradiated in a long wave band, so that a photoacoustic spectrogram of the gas is obtained. Finally, the light emitted by the infrared spectrometer in the wave band is calibrated according to the known absorption peak position of the gas molecules. Therefore, the instrument only needs one glass cavity, a miniature microphone, a self-made signal amplifier, an oscilloscope or a computer and the like. Small, simple and inexpensive.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the invention and, together with the description, serve to explain the invention and not to limit the invention. In the drawings:
fig. 1 is a schematic structural diagram of a tunable laser wavelength calibration system based on photoacoustic spectroscopy according to the present invention.
Fig. 2 is a schematic structural diagram of the small molecule gas of the present invention.
Fig. 3 is a circuit diagram of an amplifying unit of the present invention.
FIG. 4(a) is a methane oscillation absorption peak diagram.
FIG. 4(b) is a graph showing the absorption peak of ammonia gas by shaking.
Detailed Description
The invention is further illustrated by the following figures and examples.
The method utilizes the photoacoustic spectroscopy technology to measure and calibrate the wavelength emitted by the infrared wavelength tunable laser through the response of specific gaseous small molecules (such as methane, ammonia and the like) to infrared light with a certain specific wavelength. The specific scheme is as follows:
referring to fig. 1-2, a tunable laser wavelength calibration system based on photoacoustic spectroscopy includes: the device comprises a signal generator 7, a pumping unit 1, an infrared laser 2, small molecule gas 3, an amplifying unit 5 and a computer 6; the small molecule gas 6 comprises a photoacoustic cell 34, the photoacoustic cell 34 is in a sealed state and is internally filled with gas, and a sound receiving device 4 is also arranged in the inner cavity of the photoacoustic cell; the radio device 4 is connected with the amplifier 5 and the computer 6 in sequence; the computer 6 is connected with the infrared laser 2, the computer 6, the signal generator 7, the pumping unit 1 and the infrared laser 2 are sequentially connected, and laser output by the infrared laser 2 irradiates gas in the photoacoustic cell.
In the present embodiment, the sound pickup device 4 is a microphone.
Referring to fig. 2, the main body material of the small molecule gas cell is made of common glass, in order to place the sound receiving device 4, the upper cavity 31 and the lower cavity 32 are connected through stainless steel ball grinding clamps in a pressing mode, the lower part of the lower cavity 32 is connected with a cylinder, the sound receiving device is arranged on the cylinder 33, the lower part of the cylinder 33 is connected with the photoacoustic cell, the cylinder 33 is communicated with the photoacoustic cell 34, and the photoacoustic cell 34 belongs to a cavity type photoacoustic cell 34 which has three resonant modes of radial, intersection and longitudinal. In terms of acoustic wave propagation consumption, the viscous band loss occurs at the side face and the end face in the radial direction and the cross direction, while the acoustic wave of the longitudinal resonance mode is perpendicular to the resonant cavity of the photoacoustic cell 34 and parallel to the end face, so that the loss is generated only at the end face, and the loss is minimal. The side of the photoacoustic cell 34 that is incident light is provided with a calcium fluoride lens that acts as a window lens so that infrared light can be directed into the gas cell for detection and calibration. The gas channel at the lower part of the photoacoustic cell 34 is connected with a mechanical pump interface 36, and an overhead valve 35 for separating the loading and unloading gas part from the photoacoustic cell 34 is arranged. The top valve 35 separates the gas-removable portion at the lower portion from the photoacoustic cell 34, and the upper photoacoustic cell 34 can be sealed under ideal conditions. The bottom interface 36 is externally connected with a mechanical pump and matched with the top valve 35 to pump the gas out of the cavity, so that the high gas tightness and gas loading and unloading of the device are realized. The curved design of the top valve 35 to the bottom port minimizes the size and use of the device. The use of top valve 35 facilitates the loading and unloading of gases and allows the photoacoustic cell 34 to achieve the desired sealed conditions.
In the present embodiment, referring to fig. 3, the amplifying unit 5 includes: the amplifier comprises a first-stage amplifier U1, a second-stage amplifier U2, a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R5, a capacitor C1, a capacitor C2 and a capacitor C3; the resistor R5 is a slide rheostat; two input ends of a first-stage amplifier U1 are connected with the radio device 4, a forward input end of a first-stage amplifier U1 is connected with an output end through a resistor R1, an output end of the first-stage amplifier U1 is connected with one end of a resistor R2 and a resistor R3 and one end of a capacitor C1, the other end of the resistor R3 is connected with a reverse input end of a second-stage amplifier U2 and one end of a capacitor C2, the other end of the capacitor C2 is connected with the ground, the other end of the capacitor C1 is connected with a same-direction input end of a second-stage amplifier U2 through a resistor R4, one end of a capacitor C3 and one fixed end of a resistor R5, the other fixed end of the resistor R5, a sliding end of the resistor R5 and the other end of the capacitor C3 are connected with an output end of the second-stage amplifier U2, and an output end;
the resistor R2, the resistor R3, the capacitor C1 and the capacitor C2 are connected to form an RC pi-shaped filter circuit; the model of the first stage amplifier U1 is AD620, and the model of the second stage amplifier U2 is TLV2711 CDBVR. The AD620 is a low-cost and high-precision amplifier component, can set adjustable gain by only needing an external resistor, and is an ideal choice for precise data acquisition systems such as tiny voltage and sensor interfaces. In order to maximize the gain effect of the amplifier, the amplifying circuit of the device adopts a two-stage amplification design. The AD620 is adopted in the first stage, the VACC operational amplifier is adopted in the second stage, and the design of two-stage amplification enables the gain of the amplifier to reach 400-fold and 1000-fold.
In order to improve various working performances of the amplifying circuit, the amplifying circuit has two innovation points, namely, an RC pi-type filter circuit is innovatively added between two stages of amplification, the risk that a small voltage signal and noise are filtered together when the filter circuit is placed in front of a first stage is eliminated, and the condition that the filter circuit cannot efficiently filter the noise after a second stage is also avoided. The design furthest improves the signal-to-noise ratio on the basis of keeping the original signal. Secondly, the ultra-high gain allows effective and sufficient amplification of the tiny voltage signals.
The second innovation point is that the AD620 part of the amplifying circuit can stably work only by a positive power supply and a negative power supply, and the negative power supply required by the AD620 is directly converted by the positive power supply by uniquely adopting an ICL7660 negative power supply converter, so that the use of multiple (negative) power supplies is reduced, and a better effect is obtained in an experiment.
The data acquisition system at the 6 end of the computer designs two different acquisition systems according to the working conditions of a user: the first data acquisition mode adopts an analog circuit to acquire data, namely, an oscilloscope is used for acquiring signals, and the oscilloscope is connected with a computer 6 through a network cable by a TCP protocol to acquire data. And finally obtaining the photoacoustic spectrogram of the small gas. The acquisition method is suitable for most laboratories in the field of spectroscopy and has great practical applicability. The second acquisition system directly skips the portion of the signal input to the oscilloscope from the amplification circuit. The amplified voltage signal is directly converted into a binary digital signal by an analog-to-digital conversion method by using an AD converter, the binary digital signal is input into the computer 6, and the photoacoustic spectrum of the small gas molecules is acquired by the computer 6.
In this embodiment, the tunable laser wavelength calibration system based on photoacoustic spectroscopy further includes: a power supply circuit; the power supply circuit is connected with the amplifying unit 5 and the sound receiving device 4. The power supply circuit comprises a direct current power supply which is a direct current stabilized power supply. The common direct current power supply is formed, so that the requirement of the amplifier on the working voltage is reduced, and the direct current power supply has super practical significance. In order to make the photoacoustic signal not affected by the voltage fluctuation of the power supply circuit and to make the amplifier circuit in a stable amplification operation state, the output voltage of the dc power supply needs to be stabilized at 5 v.
The wavelength calibration method of the tunable laser based on the photoacoustic spectroscopy technology is applicable to the wavelength calibration system of the tunable laser based on the photoacoustic spectroscopy technology, and comprises the following steps: the pumping unit 1 outputs pumping light to the infrared laser 2, the infrared laser 2 outputs infrared laser with continuous wavelength under the action of the pumping light, the infrared laser irradiates the gas in the photoacoustic cell 34, and if the wavelength of the infrared laser is not consistent with the absorption wavelength of gas molecules, the infrared laser cannot be absorbed; if the wavelength of the laser light is matched with the absorption wavelength of the gas molecules, the infrared laser light is absorbed by the molecules and is excited in a mode of releasing heat energy, the released heat energy enables the gas and the surrounding medium to be periodically heated according to the modulation frequency of the light, so that the gas and the surrounding medium generate periodic pressure fluctuation, the sound receiving device 4 detects the periodic pressure fluctuation, the periodic pressure fluctuation is amplified through the amplifying unit 5 to obtain a photoacoustic signal, and therefore conversion between the optical signal and the acoustic signal (namely, the photoacoustic effect) is achieved. And comparing the vibration absorption peak position of the photoacoustic signal with the vibration absorption peak position fixed by the known molecule, and if the vibration absorption peak of the photoacoustic signal is inconsistent with the vibration absorption peak fixed by the known molecule, controlling the output wavelength of the infrared laser 2 through the computer 6 to realize the calibration of the output wavelength of the infrared laser 2. The obtained photoacoustic signal is the vibration-conversion spectrum of the gas in the photoacoustic cavity, and by comparing the obtained photoacoustic signal with the standard spectrograms of the molecules, the fact whether the wavelength of infrared light is accurate or not, which is absorbed by the photoacoustic spectrum and is emitted by the infrared tunable laser, can be known, so that the wavelength of the scanned light is calibrated.
Because different molecules have the characteristic of selective absorption of infrared light with different wavelengths. The infrared spectrum of gas micromolecules such as methane, ammonia gas and the like has very fine vibration-rotation absorption peaks. Theoretically, the vibration stress peak of each response molecule is a line spectrum, and the resolution ratio is extremely high. When a known simple molecule of gas (e.g., methane, ammonia, ethylene, acetylene, etc.) is placed in the photoacoustic cell 34, the wavelength of the infrared wavelength tunable laser can be calibrated by comparing the vibrational absorption peaks (e.g., fig. 4(a) and 4(b)) with the fixed known molecule. For example, methane and ammonia gas are introduced. The vibration spectrum covers 700-1800cm-1And 2800 and 3600cm-1. An infrared tunable laser of the above range can be corrected by this device. If the mid-infrared light of other wave bands needs to be corrected, other gases can be put into the device, such as: acetylene, ethylene, methyl halide, and the like.
The above-mentioned embodiments are preferred embodiments of the present invention, and the present invention is not limited thereto, and any other modifications or equivalent substitutions that do not depart from the technical spirit of the present invention are included in the scope of the present invention.
Claims (9)
1. A tunable laser wavelength calibration system based on photoacoustic spectroscopy, comprising: the device comprises a signal generator, a pumping unit, an infrared laser, small molecule gas, an amplifying unit and a computer; the small molecular gas comprises a photoacoustic cell, the photoacoustic cell is in a sealed state and is internally filled with gas, and a sound receiving device is also arranged in the inner cavity of the photoacoustic cell; the radio device is connected with the amplifier and the computer in sequence; the computer is connected with the infrared laser, the computer, the signal generator, the pumping unit and the infrared laser are sequentially connected, and laser output by the infrared laser irradiates gas in the acoustic cell.
2. The photoacoustic spectroscopy-based tunable laser wavelength calibration system of claim 1 wherein the sound receiving device is a microphone or a piezo ceramic microphone.
3. The photoacoustic spectroscopy-based tunable laser wavelength calibration system of claim 1, wherein the amplification unit comprises: the amplifier comprises a first-stage amplifier U1, a second-stage amplifier U2, a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R5, a capacitor C1, a capacitor C2 and a capacitor C3; the resistor R5 is a slide rheostat;
two input ends of a first-stage amplifier U1 are connected with a sound receiving device, a forward input end of a first-stage amplifier U1 is connected with an output end through a resistor R1, an output end of the first-stage amplifier U1 is connected with one end of a resistor R2 and a resistor R3 and one end of a capacitor C1, the other end of the resistor R3 is connected with a reverse input end of a second-stage amplifier U2 and one end of a capacitor C2, the other end of the capacitor C2 is connected with the ground, the other end of the capacitor C1 is connected with a same-direction input end of a second-stage amplifier U2 through a resistor R4, one end of a capacitor C3 and one fixed end of a resistor R5, the other fixed end of the resistor R5, a sliding end of the resistor R5 and the other end of the capacitor C3 are connected with an output end of the second-stage amplifier U2, and an;
the resistor R2, the resistor R3, the capacitor C1, the capacitor C2 and the connection of the resistors R2, the resistor R3, the capacitor C1 and the capacitor C2 form an RC pi-type filter circuit.
4. The tunable laser wavelength calibration system based on photoacoustic spectroscopy of claim 3, wherein the model number of the first-stage amplifier U1 is AD620, and the model number of the second-stage amplifier U2 is TLV2711 CDBVR.
5. The photoacoustic spectroscopy-based tunable laser wavelength calibration system of claim 1, wherein the small molecule gas cell further comprises an upper cavity, a lower cavity, and a cylinder; go up cavity, lower cavity and press from both sides the pressfitting through stainless steel ball mill mouth and connect, the sub-unit connection cylinder of lower cavity, radio reception device sets up at the cylinder, the sub-unit connection optoacoustic pond of cylinder, cylinder and optoacoustic pond intercommunication, the one side of going into light of optoacoustic pond side is provided with the calcium fluoride lens, the air flue of optoacoustic pond lower part is connected mechanical pump interface and is had the overhead valve that is used for separating loading and unloading gas portion and optoacoustic pond.
6. The photoacoustic spectroscopy-based tunable laser wavelength calibration system of claim 1, further comprising: a power supply circuit; the power supply circuit is connected with the amplifying unit and the radio device.
7. The photoacoustic spectroscopy-based tunable laser wavelength calibration system of claim 6 wherein the power supply circuit comprises a dc power supply, and the dc power supply is a dc regulated power supply or a dry cell.
8. A wavelength calibration method of a tunable laser based on a photoacoustic spectroscopy technology is characterized by comprising the following steps: the pumping unit outputs pumping light to the infrared laser, the infrared laser outputs continuous infrared laser with wavelength under the action of the pumping light, the infrared laser irradiates gas in the photoacoustic cell, if the wavelength of incident light is consistent with the absorption wavelength of gas molecules, the gas molecules absorb the laser to generate periodic pressure fluctuation, the sound receiving device detects the periodic pressure fluctuation of the gas molecules, the periodic pressure fluctuation is amplified by the amplifying unit to obtain photoacoustic signals, the vibration absorption peak position of the photoacoustic signals is compared with the vibration absorption peak position fixed by known molecules, and if the vibration absorption peak position of the photoacoustic signals is inconsistent with the vibration absorption peak position fixed by the known molecules, the output wavelength of the infrared laser is controlled by a computer, so that the calibration of the output wavelength of the infrared laser is realized.
9. The method for wavelength calibration of a tunable laser based on photoacoustic spectroscopy as claimed in claim 7, wherein when the wavelength generated by the laser is not at the wavelength position corresponding to the infrared characteristic peak of the gas, the absorption of the infrared light energy is very small, no pressure disturbance is generated, and the sound pickup device cannot detect the periodic pressure fluctuation of the gas molecules.
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| CN112986153A (en) * | 2021-03-31 | 2021-06-18 | 华南师范大学 | Formaldehyde gas concentration real-time detection system and method based on photoacoustic spectroscopy technology |
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