A quartz-enhanced photoacoustic spectroscopy detection method and system using optical feedback

Abstract

The application discloses a quartz enhanced photoacoustic spectroscopy detection method and system using optical feedback, and belongs to the technical field of optical feedback. The method comprises the following steps: controlling the phase of optical feedback according to a laser based on a first reflector and a second reflector; matching the cavity film size of a laser and an F-P cavity; establishing stable optical feedback of the laser according to the phase of optical feedback; transmitting the laser passing through a polarizer to a fourth reflector, refracting the laser into the F-P cavity matched with the laser through a CaF2 window mirror, and passing the laser passing through the F-P cavity through the middle of the first resonant tube, the second resonant tube and the prong of the quartz tuning fork, so as to generate a photoacoustic signal based on the stable optical feedback, enhance the photoacoustic signal based on the first resonant tube and the second resonant tube, and detect the spectrum based on the enhanced photoacoustic signal. The application improves the anti-interference of detection.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of optical feedback, and more particularly, to a quartz-enhanced photoacoustic spectroscopy detection method and system using optical feedback. BACKGROUND

[0002] Photoacoustic spectroscopy technology is a laser absorption spectroscopy technology that has developed rapidly in recent years. The technology detects the sound wave signal released by a trace gas after absorbing a specific wavelength laser energy, obtains the spectrum of the trace gas in the characteristic absorption wavelength range, and thus completes the detection of the composition and concentration of the trace gas. Photoacoustic spectroscopy technology is a laser absorption spectroscopy technology with zero background (no signal output when there is no specific absorption), no wavelength selectivity (applicable to all spectral bands from ultraviolet to terahertz light sources), and wide linear response range (at least three orders of magnitude of linear response to the concentration of the trace gas). Benefiting from the rapid development of laser technology and weak signal detection technology in recent years, photoacoustic spectroscopy technology has become an effective method to realize real-time detection of trace gases.

[0003] Quartz-enhanced photoacoustic spectroscopy technology is a trace gas detection technology based on photoacoustic spectroscopy technology and using a quartz tuning fork as an acoustic sensor. Unlike the traditional photoacoustic spectroscopy technology in which photoacoustic energy is accumulated and amplified in an acoustic resonant cavity, the photoacoustic energy in the quartz-enhanced photoacoustic spectroscopy technology is mainly accumulated in a sound measurement module coupled by a quartz tuning fork and a one-dimensional acoustic cavity. Since the quartz tuning fork has a very high quality factor (up to 9000 at normal pressure), the sound measurement module composed of the quartz tuning fork has a good amplification effect on weak photoacoustic signals, thereby achieving high detection sensitivity. In addition, the quartz-enhanced photoacoustic spectroscopy technology also has the advantages of small size, low cost, simple operation, and immunity to environmental noise. However, the quartz-enhanced photoacoustic spectroscopy technology has a high requirement for the laser frequency used, and the stability of the laser frequency needs to be maintained. If the laser frequency is unstable, the frequency of the photoacoustic signal will drift, affecting the accuracy of the analysis results. SUMMARY

[0004] To solve the above problems, the present application provides a quartz-enhanced photoacoustic spectroscopy detection method using optical feedback, comprising:

[0005] A sawtooth wave signal is generated based on a function generator, an electric current signal is generated using the sawtooth wave signal to modulate a driver, the electric current signal generated by the driver is used to drive a laser to generate laser light, the laser light is transmitted to a first mirror, a second mirror and a third mirror in sequence based on a beam splitter, and the phase of the optical feedback is controlled based on the first mirror and the second mirror according to the laser light.

[0006] The laser is transmitted to the first mode matching lens, the second mode matching lens and the third mode matching lens in sequence based on the third mirror, and the cavity membrane size of the laser and the F-P cavity is matched according to the refracted laser based on the first mode matching lens, the second mode matching lens and the third mode matching lens.

[0007] The laser after the third mode matching lens is transmitted to the half-wave plate and the polarizer in sequence, and the feedback rate of the optical feedback of the laser is controlled based on the half-wave plate and the polarizer to establish stable optical feedback of the laser according to the phase of the optical feedback.

[0008] The laser after the polarizer is transmitted to the fourth mirror, the refracted laser is refracted into the F-P cavity matched with the laser through the CaF2 window mirror, the laser after the F-P cavity passes through the middle of the first resonant tube, the second resonant tube and the prong of the quartz tuning fork, so as to generate the photoacoustic signal based on the stable optical feedback, enhance the photoacoustic signal based on the first resonant tube and the second resonant tube, and detect the spectrum based on the enhanced photoacoustic signal.

[0009] Optionally, the method further comprises: a part of the laser after the F-P cavity returns to the light splitting region along the original light path, and another part is refracted to the photodetector, the laser signal is converted into an electric signal through the photodetector, the electric signal converted by the laser is output to the lock-in amplifier, and the electric signal output by the quartz tuning fork and the electric signal of the function generator are simultaneously input to the lock-in amplifier, and the lock-in amplifier demodulates all the input electric signals to determine the signal error.

[0010] Optionally, the wavelength of the laser is 4.59 μm, and the power is 45 mW.

[0011] Optionally, the first mirror and the second mirror are installed on the piezoelectric displacement platform.

[0012] Optionally, the focal lengths of the first mode matching lens, the second mode matching lens and the third mode matching lens are 200 mm, -200 mm and 150 mm respectively.

[0013] Optionally, the F-P cavity comprises: a first high reflectivity mirror and a second high reflectivity mirror with a reflectivity of 99.92%, a cavity fineness of 4000, a cavity mode line width of 125 kHz, a cavity length of 290 mm, a corresponding free spectral range of 500 MHz and a volume of 1.7 L.

[0014] Optionally, the tine of the quartz tuning fork is T-shaped, the natural frequency is 15.82 kHz, the tine spacing is 0.8 mm, the first resonant tube and the second resonant tube have a length of 12.4 mm and an inner diameter of 1.5 mm, the first resonant tube and the second resonant tube are symmetrically arranged on both sides of the quartz tuning fork along the light path, and the first resonant tube and the second resonant tube are kept at a preset distance from the outside of the tine of the quartz tuning fork.

[0015] Optionally, the method further comprises: the phase-locked amplifier demodulates the photoacoustic signal output by the quartz tuning fork and the cavity membrane signal output by the photodetector.

[0016] Optionally, the output frequency of the function generator is 15.82 kHz, which is consistent with the natural frequency of the quartz tuning fork.

[0017] In still another aspect, the application further provides a quartz enhanced photoacoustic spectroscopy detection system using optical feedback, comprising:

[0018] The first signal transmission unit is configured to generate a sawtooth wave signal based on the function generator, modulate a current signal using the sawtooth wave signal, drive the laser to generate laser light based on the current signal generated by the driver, and sequentially transmit the laser light to the first mirror, the second mirror and the third mirror based on the beam splitter, and control the phase of the optical feedback based on the first mirror and the second mirror.

[0019] The second signal transmission unit is configured to sequentially transmit the laser light to the first mode matching lens, the second mode matching lens and the third mode matching lens after being refracted by the third mirror, and match the size of the cavity membrane of the laser and the F-P cavity based on the first mode matching lens, the second mode matching lens and the third mode matching lens.

[0020] The third signal transmission unit is configured to sequentially transmit the laser light after the third mode matching lens to the half-wave plate and the polarizer, control the feedback rate of the optical feedback of the laser based on the half-wave plate and the polarizer, and establish stable optical feedback of the laser based on the phase of the optical feedback.

[0021] The detection unit is configured to transmit the laser light passing through the polarizer to the fourth mirror, refract the refracted laser light through the CaF2 window mirror into the F-P cavity matched with the laser, and pass the laser light through the F-P cavity from the first resonant tube, the second resonant tube and the middle of the tine of the quartz tuning fork, so as to generate a photoacoustic signal based on the stable optical feedback, enhance the photoacoustic signal based on the first resonant tube and the second resonant tube, and detect the spectrum based on the enhanced photoacoustic signal.

[0022] Optionally, the third signal transmission unit is further configured to: return a part of the laser of the preset part of the laser passing through the F-P cavity to the light splitting region along the original light path, refract another part of the laser to the photodetector, convert the laser signal into an electric signal through the photodetector, output the electric signal converted by the laser to the phase-locked amplifier, and simultaneously input the electric signal output by the quartz tuning fork and the electric signal of the function generator to the phase-locked amplifier, demodulate all the electric signals input by the phase-locked amplifier, and determine the signal error.

[0023] Optionally, the wavelength of the laser is 4.59 μm, and the power is 45 mW.

[0024] Optionally, the first mirror and the second mirror are installed on a piezoelectric displacement platform.

[0025] Optionally, the focal lengths of the first mode matching lens, the second mode matching lens and the third mode matching lens are 200 mm, -200 mm and 150 mm, respectively.

[0026] Optionally, the F-P cavity comprises: a first high reflectivity mirror and a second high reflectivity mirror with a reflectivity of 99.92%, a cavity fineness of 4000, a cavity mode line width of 125 kHz, a cavity length of 290 mm, a corresponding free spectral range of 500 MHz, and a volume of 1.7 L.

[0027] Optionally, the fork arms of the quartz tuning fork are T-shaped, the natural frequency is 15.82 kHz, the arm spacing is 0.8 mm, the first resonant tube and the second resonant tube have a length of 12.4 mm and an inner diameter of 1.5 mm, the first resonant tube and the second resonant tube are symmetrically arranged on the two sides of the quartz tuning fork along the light path, and the first resonant tube and the second resonant tube are arranged at a preset distance from the outer side of the fork arms of the quartz tuning fork.

[0028] Optionally, the third signal transmission unit is further configured to: demodulate the photoacoustic signal output by the quartz tuning fork and the cavity film signal output by the photodetector by the phase-locked amplifier.

[0029] Optionally, the output frequency of the function generator is 15.82 kHz, which is consistent with the natural frequency of the quartz tuning fork.

[0030] In still another aspect, the present application also provides a computing device, comprising: one or more processors;

[0031] the processor is configured to execute one or more programs;

[0032] when the one or more programs are executed by the one or more processors, the method as described above is implemented.

[0033] In still another aspect, the present application also provides a computer readable storage medium having a computer program stored thereon, wherein the computer program is executed to implement the method as described above.

[0034] Compared with the prior art, the present application has the following advantages:

[0035] The present application provides a quartz enhanced photoacoustic spectroscopy detection method using optical feedback, comprising: generating a sawtooth wave signal based on a function generator, using the sawtooth wave signal to modulate a driver to generate a current signal, using the current signal generated by the driver to drive a laser to generate laser light, using a beam splitter to sequentially transmit the laser light to a first mirror, a second mirror and a third mirror, and using the first mirror and the second mirror to control the phase of the optical feedback according to the laser light; using the third mirror to refract the laser light and then sequentially transmit the refracted laser light to a first mode matching lens, a second mode matching lens and a third mode matching lens, and using the first mode matching lens, the second mode matching lens and the third mode matching lens to match the size of the cavity membrane of the laser and the F-P cavity according to the refracted laser light; sequentially transmitting the laser light after the third mode matching lens to a half-wave plate and a polarizer, using the half-wave plate and the polarizer to control the feedback rate of the optical feedback of the laser light, and using the phase of the optical feedback to establish stable optical feedback of the laser light; transmitting the laser light after the polarizer to a fourth mirror, refracting the refracted laser light through a CaF2 window mirror into the F-P cavity matched with the laser, and passing the laser light after the F-P cavity through the middle of the first resonant tube, the second resonant tube and the prong of the quartz tuning fork, to generate a photoacoustic signal based on the stable optical feedback, enhance the photoacoustic signal based on the first resonant tube and the second resonant tube, and detect the spectrum based on the enhanced photoacoustic signal. The present application improves the anti-interference of detection. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 The flowchart of the method of the present application is shown in the figure;

[0037] Figure 2 The detection platform diagram of the method of the present application is shown in the figure;

[0038] Figure 3 The structure diagram of the system of the present application is shown in the figure;

[0039] Among them, 1 is a driver, 2 is a QCL laser, 3 is a beam splitter, 4 is a mirror, 5 is a mirror, 6 is a piezoelectric displacement platform, 7 is a mirror, 8 is a first mode matching lens, 9 is a second mode matching lens, 10 is a third mode matching lens, 11 is a half-wave plate, 12 is a polarizer, 13 is a mirror, 14 is a CaF2 window mirror, 15 is an optical trap, 16 is a high-reflectivity mirror, 17 is a high-reflectivity mirror, 18 is an F-P cavity, 19 is a resonant tube, 20 is a resonant tube, 21 is a quartz tuning fork, 22 is a photodetector, 23 is a lock-in amplifier, 24 is a PID module, 25 is a function generator, 26 is a PID module and 27 is a high-voltage amplifier. DETAILED DESCRIPTION

[0040] Reference will now be made to the drawings to describe the exemplary embodiments of the present application in greater detail. The present application can be variously embodied and is not limited to the embodiments described herein, which are provided for the purposes of disclosure and to fully and completely disclose the present application to those skilled in the art. The terms used in the exemplary embodiments of the present application shown in the drawings are terms that are used to describe the exemplary embodiments of the present application and are not intended to limit the present application. In the drawings, the same elements are denoted by the same reference numerals.

[0041] The terms used herein, including technical terms, are used in the same meaning as those of the present application understood by those skilled in the art unless otherwise specified. Also, it is to be understood that the terms defined in commonly used dictionaries are to be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and are not to be interpreted in an idealized or overly formal sense unless otherwise specifically defined herein.

[0042] Embodiment 1:

[0043] The present application proposes a quartz enhanced photoacoustic spectroscopy detection method using optical feedback, as shown in Figure 1 The present application proposes a quartz enhanced photoacoustic spectroscopy detection method using optical feedback, as shown in

[0044] Step 1, a sawtooth wave signal is generated based on a function generator, a current signal is generated using the sawtooth wave signal to modulate a driver, a laser is driven to generate laser light by the current signal generated by the driver, the laser light is sequentially transmitted to a first mirror, a second mirror and a third mirror based on a beam splitter, and the phase of the optical feedback is controlled based on the first mirror and the second mirror according to the laser light;

[0045] Step 2, the laser light is sequentially transmitted to a first mode matching lens, a second mode matching lens and a third mode matching lens after being refracted based on the third mirror, and the cavity membrane size of the laser and the F-P cavity is matched based on the first mode matching lens, the second mode matching lens and the third mode matching lens according to the refracted laser light;

[0046] Step 3, the laser light after the third mode matching lens is sequentially transmitted to a half wave plate and a polarizer, and the feedback rate of the optical feedback of the laser light is controlled based on the half wave plate and the polarizer to establish stable optical feedback of the laser light according to the phase of the optical feedback;

[0047] Step 4, the laser light after the polarizer is transmitted to a fourth mirror, the refracted laser light is refracted into the F-P cavity matched with the laser through a CaF2 window mirror, the laser light after the F-P cavity passes through the middle of the first resonant tube, the second resonant tube and the prong of the quartz tuning fork, the photoacoustic signal is generated based on the stable optical feedback, the photoacoustic signal is enhanced based on the first resonant tube and the second resonant tube, and the spectrum is detected based on the enhanced photoacoustic signal.

[0048] The method further comprises: returning a preset part of the laser passing through the F-P cavity to the light splitting region along the original light path and refracting another part to the photodetector, converting the laser signal into an electric signal through the photodetector, outputting the electric signal converted by the laser to the phase-locked amplifier, and simultaneously inputting the electric signal output by the quartz tuning fork and the electric signal of the function generator to the phase-locked amplifier, demodulating all the input electric signals based on the phase-locked amplifier, and determining the signal error.

[0049] The wavelength of the laser is 4.59 μm, and the power is 45 mW.

[0050] The first mirror and the second mirror are installed on the piezoelectric displacement platform.

[0051] The focal lengths of the first mode matching lens, the second mode matching lens and the third mode matching lens are 200 mm, -200 mm and 150 mm respectively.

[0052] The F-P cavity comprises: a first high reflectivity mirror and a second high reflectivity mirror with a reflectivity of 99.92%, a cavity fineness of 4000, a cavity mode line width of 125 kHz, a cavity length of 290 mm, a corresponding free spectral range of 500 MHz, and a volume of 1.7 L.

[0053] The fork arms of the quartz tuning fork are T-shaped, the natural frequency is 15.82 kHz, the arm spacing is 0.8 mm, the first resonant tube and the second resonant tube have a length of 12.4 mm and an inner diameter of 1.5 mm, the first resonant tube and the second resonant tube are symmetrically arranged on both sides of the quartz tuning fork along the light path, and the first resonant tube and the second resonant tube are arranged at a preset distance from the outer side of the fork arms of the quartz tuning fork.

[0054] The method further comprises: the phase-locked amplifier demodulates the photoacoustic signal output by the quartz tuning fork and the cavity film signal output by the photodetector.

[0055] The output frequency of the function generator is 15.82 kHz, which is consistent with the natural frequency of the quartz tuning fork.

[0056] The method is realized based on a detection platform. Figure 2 As shown in the figure, the detection process comprises:

[0057] 1) The driver (1) is used to drive the laser (2) to generate laser. The function generator (25) generates a sawtooth wave signal to modulate the current signal of the driver (1). The laser is transmitted to the mirror (4) and the mirror (5) through the beam splitter (3), and the mirror (4) and the mirror (5) are placed on the piezoelectric displacement platform (6) to control the phase of the optical feedback. The laser reflected by the mirror (5) is refracted into the first mode matching lens (8), the second mode matching lens (9) and the third mode matching lens (10) through the mirror (7), and the mode matching lens is used to match the cavity size of the laser (2) and the F-P cavity (18).

[0058] 2) The laser transmitted through the third mode matching lens (10) is transmitted to the half wave plate (11) and the polarizer (12), and the half wave plate (11) and the polarizer (12) are used to control the feedback rate of the optical feedback to establish a stable optical feedback.

[0059] 3) The laser transmitted through the polarizer (12) is transmitted to the mirror (13), and the refracted light beam is refracted into the F-P cavity (18) through the CaF2 window mirror (14). The F-P cavity (18) is composed of a high reflection mirror (16) and a high reflection mirror (17), and the laser resonates in the F-P cavity (18) to enhance the laser in the cavity. Another part of the light beam transmits through the CaF2 window mirror (14) to the optical trap (15), and the optical trap (15) is used to block the propagation of the laser to ensure the safety of the experiment.

[0060] 4) The resonant tube (19) and the resonant tube (20) are placed on both sides of the quartz tuning fork (21), so that the laser passes through the resonant tube (19) and the resonant tube (20) and the middle of the fork arm of the quartz tuning fork (21). The gas to be measured interacts with the laser to produce a photoacoustic effect, and the quartz tuning fork (21) converts the mechanical energy converted from the acoustic energy into electrical energy through its piezoelectric effect. The resonant tube (19) and the resonant tube (20) placed on both sides are used to enhance the photoacoustic signal.

[0061] 5) Part of the laser returns to the beam splitter (3) along the original light path, and part of the light is refracted to the photodetector (22) to convert the optical signal into an electrical signal and output to the lock-in amplifier (23). The electrical signal output by the quartz tuning fork (21) is input to the lock-in amplifier (23), and the other signal output by the function generator (25) is input to the lock-in amplifier (23) to demodulate the electrical signal and generate an error signal. Another part of the light returns to the laser (2) through the light beam splitter (3) to establish an optical feedback effect.

[0062] 6) The phase-locked amplifier (23) has a first harmonic error signal input PID module (24) to generate an optical feedback driving current adjustment signal, which is superimposed with the modulation signal from the function generator (25) to act on the driver (1) to adjust the driving current. The phase-locked amplifier (23) has a third harmonic error signal input PID module (26) to generate an optical feedback phase adjustment signal, which acts on the high-voltage amplifier (27) and is output from the high-voltage amplifier (27) to the piezoelectric displacement platform (6). The two feedback adjustment signals together maintain the optical feedback effect, stabilizing the laser power in the F-P cavity (18).

[0063] The QCL laser (2) has a wavelength of 4.59 μm and a power of 45 mW.

[0064] The mirrors (4) and (5) are mounted on the piezoelectric displacement platform (6) to fine-tune the laser phase of the return laser (2).

[0065] The first mode matching lens (8), the second mode matching lens (9), and the third mode matching lens (10) have focal lengths of 200 mm, -200 mm, and 150 mm, respectively, to match the resonant mode of the F-P cavity (18).

[0066] The angle between the CaF2 window mirror (14) and the optical axis of the F-P cavity (18) is 54.5°, close to the size of the Brewster angle.

[0067] The F-P cavity (18) is composed of a high-reflectivity mirror (16) and a high-reflectivity mirror (17) with a reflectivity of 99.92%, a cavity finesse of 4000, a cavity mode linewidth of 125 kHz, and a cavity length of 290 mm, corresponding to a free spectral range of 500 MHz and a volume of 1.7 L.

[0068] The quartz tuning fork (21) has a T-shaped prong with a natural frequency of 15.82 kHz and a prong spacing of 0.8 mm. The resonant tubes (19) and (20) have lengths of 12.4 mm and inner diameters of 1.5 mm. The resonant tubes (19) and (20) are symmetrically placed on both sides of the quartz tuning fork (21) along the optical path, maintaining a small gap with the outer side of the quartz tuning fork prong. Compared with the bare quartz tuning fork, the enhancement factor can reach 60. Further, the phase-locked amplifier (23) demodulates the photoacoustic signal output by the quartz tuning fork (21) and the cavity film signal output by the photodetector (22). The first harmonic signal is used to adjust the QCL laser (2) current, and the third harmonic signal is used to adjust the piezoelectric displacement platform (6) movement, so that the laser output frequency is locked to the F-P cavity (18) resonance frequency, improving the coupling efficiency of the laser to the cavity and enhancing the stability of the cavity film peak.

[0069] The output frequency of the function generator (25) is 15.82 kHz, which is consistent with the natural frequency of the quartz tuning fork (21).

[0070] Specifically, 1) the driver (1) drives the laser (2) to generate laser, which is incident into the F-P cavity (18) through the beam splitter (3), the mirror (4), the mirror (5), the piezoelectric displacement platform (6), the mirror (7), the first mode matching lens (8), the second mode matching lens (9), the third mode matching lens (10), the half wave plate (11), the polarizer (12), the mirror (13) and the CaF2 window mirror (14);

[0071] 2) the laser is resonated in the F-P cavity (18) after being reflected by the CaF2 window mirror (14), forming a stable cavity film signal;

[0072] 3) the sound wave of the gas to be measured is generated in the F-P cavity (18) and converted into an electrical signal by the quartz tuning fork (21);

[0073] 4) the photoacoustic signal output by the quartz tuning fork (21) and the cavity film signal output by the photodetector (22) are sent into the lock-in amplifier (23) to be demodulated with the modulation signal output by the function generator (25);

[0074] 5) the first harmonic signal obtained by demodulation by the lock-in amplifier (23) is sent into the PID module (24), which converts the proportional, integral and differential signals into an adjustment signal, and the adjustment signal of the PID module (24) is connected to the driver (1) to feedback adjust the driving current of the QCL laser (2);

[0075] 6) the third harmonic signal obtained by demodulation by the lock-in amplifier (23) is sent into the PID module (26), which converts the proportional, integral and differential signals into an adjustment signal, and the adjustment signal of the PID module (26) is connected to the high-voltage amplifier (27) to control the movement of the piezoelectric displacement platform (6), so that the distance from the QCL laser (2) to the CaF2 window mirror (14) is an integer multiple of the length of the F-P cavity (18).

[0076] The laser power in the F-P cavity (18) can be represented as:

[0077]

[0078] wherein P0 is the incident light intensity, R B is the reflectivity of the CaF2 window mirror (14), R M is the reflectivity of the high reflector (16) and the high reflector (17), α is the absorption coefficient, and L is the length of the F-P cavity (18).

[0079] The present application narrows the linewidth of the laser, suppresses the output frequency noise of the laser, reduces the frequency drift of the photoacoustic signal, and improves the accuracy of the photoacoustic spectrum detection result;

[0080] The present application uses a T-shaped quartz tuning fork to enhance the photoacoustic signal;

[0081] The present application uses the first and third harmonic signals of the phase-locked amplifier as the adjustment signal, which acts on the laser and the piezoelectric displacement platform respectively, and improves the anti-interference performance of the system.

[0082] Embodiment 2:

[0083] The present application also provides a quartz enhanced photoacoustic spectrum detection system 200 using optical feedback, as shown in Figure 3 , comprising:

[0084] The first signal transmission unit 201 is used to generate a sawtooth wave signal based on a function generator, use the sawtooth wave signal to modulate a driver to generate a current signal, drive the laser to generate laser based on the current signal generated by the driver, and transmit the laser to the first mirror, the second mirror and the third mirror in turn based on the beamsplitter, and control the phase of the optical feedback based on the first mirror and the second mirror;

[0085] The second signal transmission unit 202 is used to refract the laser based on the third mirror and then transmit it to the first mode matching lens, the second mode matching lens and the third mode matching lens in turn, and match the cavity membrane size of the laser and the F-P cavity based on the first mode matching lens, the second mode matching lens and the third mode matching lens according to the refracted laser;

[0086] The third signal transmission unit 203 is used to transmit the laser after the third mode matching lens to the half-wave plate and the polarizer in turn, control the feedback rate of the optical feedback of the laser based on the half-wave plate and the polarizer, and establish the stable optical feedback of the laser according to the phase of the optical feedback;

[0087] The detection unit 204 is used to transmit the laser after the polarizer to the fourth mirror, refract the refracted laser through the CaF2 window mirror into the F-P cavity matched with the laser, and pass the laser after the F-P cavity from the first resonant tube, the second resonant tube and the middle of the prong of the quartz tuning fork, so as to generate the photoacoustic signal based on the stable optical feedback, enhance the photoacoustic signal based on the first resonant tube and the second resonant tube, and detect the spectrum based on the enhanced photoacoustic signal.

[0088] The third signal transmission unit 203 is further configured to: return a part of the laser of the preset part of the laser passing through the F-P cavity to the light splitting region along the original light path and refract another part of the laser to the photodetector, convert the laser signal into an electric signal through the photodetector, output the electric signal converted by the laser to the phase-locked amplifier, and simultaneously input the electric signal output by the quartz tuning fork and the electric signal of the function generator to the phase-locked amplifier, demodulate all the electric signals input by the phase-locked amplifier, and determine the signal error.

[0089] The wavelength of the laser is 4.59 μm, and the power is 45 mW.

[0090] The first mirror and the second mirror are installed on the piezoelectric displacement platform.

[0091] The focal lengths of the first mode matching lens, the second mode matching lens and the third mode matching lens are 200 mm, -200 mm and 150 mm respectively.

[0092] The F-P cavity comprises: a first high reflectivity mirror and a second high reflectivity mirror with a reflectivity of 99.92%, a cavity fineness of 4000, a cavity mode line width of 125 kHz, a cavity length of 290 mm, a corresponding free spectral range of 500 MHz, and a volume of 1.7 L.

[0093] The fork arms of the quartz tuning fork are T-shaped, the natural frequency is 15.82 kHz, the arm spacing is 0.8 mm, the first resonant tube and the second resonant tube have a length of 12.4 mm and an inner diameter of 1.5 mm, the first resonant tube and the second resonant tube are symmetrically arranged on both sides of the quartz tuning fork along the light path, and the first resonant tube and the second resonant tube are arranged at a preset distance from the outer side of the fork arms of the quartz tuning fork.

[0094] The third signal transmission unit 203 is further configured to: the phase-locked amplifier demodulates the photoacoustic signal output by the quartz tuning fork and the cavity film signal output by the photodetector.

[0095] The output frequency of the function generator is 15.82 kHz, which is consistent with the natural frequency of the quartz tuning fork.

[0096] The present application improves the anti-interference of detection.

[0097] Example 3:

[0098] Based on the same inventive concept, the present application further provides a computer device, which comprises a processor and a memory, the memory is used to store a computer program, the computer program comprises program instructions, and the processor is used to execute the program instructions stored in the computer storage medium. The processor can be a central processing unit (CPU), and can also be other general-purpose processors, digital signal processors (DSP), application specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc., which are the computing core and control core of the terminal, and are suitable for implementing one or more instructions, and are specifically suitable for loading and executing one or more instructions in the computer storage medium to implement a corresponding method flow or a corresponding function, so as to implement the steps of the method in the above embodiments.

[0099] Embodiment 4:

[0100] Based on the same inventive concept, the present application further provides a storage medium, specifically a computer readable storage medium (Memory), which is a memory device in the computer device, and is used to store programs and data. It can be understood that the computer readable storage medium herein can include the built-in storage medium in the computer device, and of course can also include the expansion storage medium supported by the computer device. The computer readable storage medium provides a storage space, and the storage space stores the operating system of the terminal. Moreover, one or more instructions suitable for being loaded and executed by the processor are also stored in the storage space, and the instructions can be one or more computer programs (including program codes). It should be noted that the computer readable storage medium herein can be a high-speed RAM memory, or a non-volatile memory such as at least one disk memory. One or more instructions stored in the computer readable storage medium can be loaded and executed by the processor to implement the steps of the method in the above embodiments.

[0101] Those skilled in the art will appreciate that embodiments of the present application can be readily used as software, hardware, or a combination of software and hardware. In a software embodiment, the methods can be tangibly embodied in a machine-readable storage medium having stored thereon instructions that can be used to program a computer to perform any of the methods. The software implementation can be initialized by loading and executing a set of instructions arranged to perform one of the methods into the computer's memory. Alternatively, hard-wired circuitry can be used in place of, or in combination with, software instructions. Thus, the

[0102] The present application is described in reference to the flowchart illustrations and / or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart illustrations and / or block diagrams. Figure 1 one or more functions specified in one or more of the flowchart illustrations and / or block diagrams. Figure 1 means for performing each of the one or more functions specified in the flowchart illustrations and / or block diagrams.

[0103] These computer program instructions can also be stored in a computer- readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instructions which implement the flowchart illustrations and / or block diagrams. Figure 1 one or more functions specified in one or more of the flowchart illustrations and / or block diagrams. Figure 1 means for performing each of the one or more functions specified in the flowchart illustrations and / or block diagrams.

[0104] These computer program instructions can also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the flowchart illustrations and / or block diagrams. Figure 1 one or more functions specified in one or more of the flowchart illustrations and / or block diagrams. Figure 1 means for performing each of the one or more functions specified in the flowchart illustrations and / or block diagrams.

[0105] While preferred embodiments of the application have been described, modifications and variations can be apparent to those skilled in the art once aware of the general underlying concepts. Accordingly, the appended claims are intended to encompass all modifications and variations as falling within the scope of the application.

[0106] It will be apparent to those skilled in the art that various modifications and variations can be made to the present application without departing from the spirit or scope of the application. Thus, it is intended that the present application cover modifications and variations of this application provided they come within the scope of the appended claims and their equivalents.

Claims

1. A quartz-enhanced photoacoustic spectroscopy detection method using optical feedback, characterized in that, The method comprises: Based on the function generator, a sawtooth wave signal is generated, a current signal is generated by modulating the driver using the sawtooth wave signal, the laser is driven to generate laser by the current signal generated by the driver, the laser is transmitted to the first mirror, the second mirror and the third mirror in turn based on the beam splitter, and the phase of the optical feedback is controlled according to the laser based on the first mirror and the second mirror; The laser is transmitted to the first mode matching lens, the second mode matching lens and the third mode matching lens in turn based on the third mirror, and the cavity size of the laser and the F-P cavity is matched according to the refracted laser based on the first mode matching lens, the second mode matching lens and the third mode matching lens; The laser after the third mode matching lens is transmitted to the half-wave plate and the polarizer in turn, and the feedback rate of the optical feedback of the laser is controlled based on the half-wave plate and the polarizer to establish stable optical feedback of the laser according to the phase of the optical feedback; The laser after the polarizer is transmitted to the fourth mirror, the refracted laser is refracted into the F-P cavity matched with the laser through the CaF2 window mirror, and the laser after the F-P cavity passes through the middle of the first resonant tube, the second resonant tube and the prong of the quartz tuning fork, so as to generate the photoacoustic signal based on the stable optical feedback, enhance the photoacoustic signal based on the first resonant tube and the second resonant tube, and detect the spectrum based on the enhanced photoacoustic signal.

2. The method of claim 1, wherein, The method further comprises: a part of the laser after the F-P cavity returns to the beam splitter along the original light path, and another part is refracted to the photodetector, the laser signal is converted into an electric signal through the photodetector, the electric signal converted by the laser is output to the lock-in amplifier, and the electric signal output by the quartz tuning fork and the electric signal of the function generator are simultaneously input to the lock-in amplifier, the input all electric signals are demodulated based on the lock-in amplifier, and the signal error is determined.

3. The method of claim 1, wherein, The wavelength of the laser is 4.59 μm, and the power is 45 mW.

4. The method of claim 1, wherein, The first mirror and the second mirror are installed on the piezoelectric displacement platform.

5. The method of claim 1, wherein, The focal lengths of the first mode matching lens, the second mode matching lens and the third mode matching lens are 200 mm, -200 mm and 150 mm respectively.

6. The method of claim 1, wherein, The F-P cavity comprises: a first high reflectivity mirror and a second high reflectivity mirror with a reflectivity of 99.92%, a cavity fineness of 4000, a cavity mode line width of 125 kHz, a cavity length of 290 mm, a corresponding free spectral range of 500 MHz, and a volume of 1.7 L.

7. The method of claim 1, wherein, The prong of the quartz tuning fork is T-shaped, the natural frequency is 15.82 kHz, the prong spacing is 0.8 mm, the length of the first resonant tube and the second resonant tube is 12.4 mm, the inner diameter is 1.5 mm, the first resonant tube and the second resonant tube are symmetrically arranged on both sides of the quartz tuning fork along the light path, and the first resonant tube and the second resonant tube are kept at a predetermined distance from the outside of the prong of the quartz tuning fork.

8. The method of claim 1, wherein, The method further comprises: the lock-in amplifier demodulates the photoacoustic signal output by the quartz tuning fork and the cavity membrane signal output by the photodetector.

9. The method of claim 1, wherein, The output frequency of the function generator is 15.82 kHz, which is consistent with the natural frequency of the quartz tuning fork.

10. A quartz-enhanced photoacoustic spectroscopy detection system utilizing optical feedback, characterized in that, The system comprises: The first signal transmission unit is configured to generate a sawtooth wave signal based on a function generator, modulate a driver to generate a current signal using the sawtooth wave signal, drive a laser to generate laser light through the current signal generated by the driver, and sequentially transmit the laser light to a first mirror, a second mirror and a third mirror based on a beam splitter. The second signal transmission unit is configured to sequentially transmit the laser light to a first mode matching lens, a second mode matching lens and a third mode matching lens after the laser light is refracted based on the third mirror, and match the laser and a cavity membrane size of an F-P cavity based on the first mode matching lens, the second mode matching lens and the third mode matching lens according to the refracted laser light. The third signal transmission unit is configured to sequentially transmit the laser light after the third mode matching lens to a half-wave plate and a polarizer, control a feedback rate of optical feedback of the laser light based on the half-wave plate and the polarizer, and establish stable optical feedback of the laser light according to a phase of the optical feedback. The detection unit is configured to transmit the laser light after the polarizer to a fourth mirror, refract the laser light after the refracting into the F-P cavity matched with the laser through a CaF2 window mirror, and pass the laser light after the F-P cavity through the middle of a first resonant tube, a second resonant tube and a prong arm of a quartz tuning fork, so as to generate an optoacoustic signal based on the stable optical feedback, enhance the optoacoustic signal based on the first resonant tube and the second resonant tube, and detect a spectrum based on the enhanced optoacoustic signal.

11. The system of claim 10, wherein, The third signal transmission unit is further configured to return a part of the laser light of a preset part of the laser light after the F-P cavity to the beam splitter along an original light path, refract another part of the laser light to a photodetector, convert the laser signal to an electrical signal through the photodetector, output the electrical signal converted by the laser to a lock-in amplifier, simultaneously input an electrical signal output by the quartz tuning fork and an electrical signal of the function generator to the lock-in amplifier, demodulate all the input electrical signals based on the lock-in amplifier, and determine a signal error.

12. The system of claim 10, wherein, The wavelength of the laser is 4.59 μm, and the power is 45 mW.

13. The system of claim 10, wherein, The first mirror and the second mirror are installed on a piezoelectric displacement platform.

14. The system of claim 10, wherein, The focal lengths of the first mode matching lens, the second mode matching lens and the third mode matching lens are 200 mm, -200 mm and 150 mm, respectively.

15. The system of claim 10, wherein, The F-P cavity includes a first high reflectivity mirror and a second high reflectivity mirror with a reflectivity of 99.92%, a cavity fineness of 4000, a cavity mode line width of 125 kHz, a cavity length of 290 mm, a corresponding free spectral range of 500 MHz and a volume of 1.7 L.

16. The system of claim 10, wherein, The prong arm of the quartz tuning fork is T-shaped, has an inherent frequency of 15.82 kHz and a prong arm spacing of 0.8 mm, and the first resonant tube and the second resonant tube have a length of 12.4 mm and an inner diameter of 1.5 mm, are symmetrically arranged on both sides of the quartz tuning fork along the light path, and are kept at a preset distance from the outside of the prong arm of the quartz tuning fork.

17. The system of claim 10, wherein, The third signal transmission unit is further configured to demodulate the optoacoustic signal output by the quartz tuning fork and the cavity membrane signal output by the photodetector by the lock-in amplifier.

18. The system of claim 10, wherein, The output frequency of the function generator is 15.82 kHz, which is consistent with the natural frequency of the quartz tuning fork.

19. A computer device, comprising: comprising: one or more processors; a processor to execute one or more programs; when the one or more programs are executed by the one or more processors, the method as claimed in any one of claims 1-9 is implemented.

20. A computer-readable storage medium, characterized in that, a computer program stored thereon, which, when executed, implements the method as claimed in any one of claims 1-9.

Images