CN210427340U - Cavity ring-down spectrometer system - Google Patents
Cavity ring-down spectrometer system Download PDFInfo
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- CN210427340U CN210427340U CN201921116368.9U CN201921116368U CN210427340U CN 210427340 U CN210427340 U CN 210427340U CN 201921116368 U CN201921116368 U CN 201921116368U CN 210427340 U CN210427340 U CN 210427340U
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Abstract
A cavity ring-down spectrometer system to improve the sensitivity of spectral measurements. The system comprises: the continuous laser, a first light beam splitter coupled with the continuous laser, an acousto-optic modulator and a wavelength meter coupled with the first light beam splitter, a second light beam splitter coupled with the acousto-optic modulator, a third light beam splitter coupled with the second light beam splitter, a ring-down cavity coupled with the third light beam splitter and a computer coupled with the ring-down cavity, the wavelength meter and the continuous laser are respectively arranged at two ends in the ring-down cavityAnd a first reflector and a second reflector are arranged, the output end of the ring-down cavity is provided with a piezoelectric ceramic tube, and the piezoelectric ceramic tube is connected with a computer through a photoelectric conversion device. The technical scheme of the application can realize high-precision continuous wavelength scanning, and the spectral measurement precision can reach 10‑4cm‑1Compared with the prior art, the sensitivity of the spectral measurement is obviously improved.
Description
Technical Field
The application belongs to the scientific research equipment manufacturing field, especially relates to a cavity ring-down spectrometer system.
Background
At present, there are many methods for detecting gas concentration, including acoustic sensors, sensors based on traditional absorption spectroscopy, raman spectroscopy sensors, mass spectrometry sensors, nuclear magnetic resonance sensors, and electrical sensors. Although the existing sensors play an important role in gas detection, the existing sensors generally have the characteristics of low sensitivity, complex operation and the like, so that the application of the sensors to trace gas concentration detection has obvious limitation.
The Cavity ring-down Spectroscopy (CRDS) technique is an absorption Spectroscopy technique that achieves highly sensitive spectroscopic detection by measuring optical loss caused by scattering and absorption of a sample in an optical Cavity. Besides the analysis and detection capabilities of the traditional spectrum technology, the method also has unique advantages: because the laser has more round trip times in the optical cavity and the absorption optical path length is very long, the CRDS technology can obtain very high sensitivity; in addition, the direct measurement parameter of the CRDS technology is not the light intensity absolute intensity change of the laser passing through the substance to be measured, but the light intensity exponential decay rate, so the CRDS technology is not sensitive to the light source intensity fluctuation.
The early intracavity ring-down spectrum mostly adopts pulse laser as a light source, but because the laser linewidth is large, the situation that multiple longitudinal modes are coupled with the optical cavity simultaneously can occur in the laser ring-down process, so that the ring-down curve of the laser becomes the result of superposition of multiple exponential attenuations, and the sample gas absorption coefficient obtained by fitting at the moment has larger deviation (about 1 percent level), thereby reducing the detection sensitivity.
SUMMERY OF THE UTILITY MODEL
An object of the application is to provide a cavity ring-down spectrometer system to improve spectral measurement's sensitivity.
The present application provides in a first aspect an optical cavity ring-down spectrometer system, the system comprising: the device comprises a continuous laser, a first light beam splitter coupled with the continuous laser, an acousto-optic modulator and a wavemeter coupled with the first light beam splitter, a second light beam splitter coupled with the acousto-optic modulator, a third light beam splitter coupled with the second light beam splitter, a ring-down cavity coupled with the third light beam splitter and a computer coupled with the ring-down cavity, the wavemeter and the continuous laser, wherein a first reflecting mirror and a second reflecting mirror are respectively arranged at two ends in the ring-down cavity, a piezoelectric ceramic tube is arranged at the output end of the ring-down cavity, and the piezoelectric ceramic tube is connected with the computer through a photoelectric conversion device;
the continuous laser is used for generating continuous laser under the pumping of the solid laser and outputting the continuous laser to the first light beam splitter;
the first light beam splitter is used for splitting continuous laser generated by the continuous laser into a first light beam and a second light beam through refraction and reflection, the first light beam is output to the acousto-optic modulator, and the second light beam is output to the wavelength meter;
the acousto-optic modulator is used for modulating the first light beam under the modulation of an acoustic signal to obtain modulated light and outputting the modulated light to the second light beam splitter;
the second light beam splitter is used for reflecting the modulated light and outputting the modulated light to the third light beam splitter through a lens;
the third light beam splitter is used for refracting the modulated light output by the lens and outputting the refracted modulated light to the ring-down cavity;
the ring-down cavity is used for ring-down of modulated light input by the third beam splitter under the action of the first reflector and the second reflector and then outputting the modulated light to the photoelectric conversion device;
the photoelectric conversion device is used for converting ring-down optical signals output by the ring-down cavity into electric signals, one path of the electric signals is output to the acousto-optic modulator, and the other path of the electric signals is output to the computer;
the piezoelectric ceramic tube is used for vibrating at a preset frequency under the action of the function generator, so that the longitudinal mode of the ring-down cavity can be matched with the frequency of the modulated light input by the third beam splitter.
Further, the ring-down cavity is provided with a constant-temperature gas channel for inputting constant-temperature gas into the ring-down cavity and outputting the constant-temperature gas from the ring-down cavity.
Further, the wavelength meter is used for monitoring the wavelength of the continuous laser generated by the continuous laser, and a monitoring signal generated by the wavelength meter is output to the computer.
Further, the computer is used for controlling the continuous laser to scan to the laser frequency one by one for measurement under the action of the electric signal output by the photoelectric conversion device and the monitoring signal.
Further, the continuous laser is a continuous ring cavity titanium sapphire laser.
Further, the first and second mirrors have a nominal reflectivity of 99.995% and a radius of curvature of 1 m.
Further, the preset frequency is 100 Hz.
Further, the cavity length of the ring-down cavity is 1.25 m.
Further, the system further comprises a solid state laser for pumping the continuous laser.
Further, the output wavelength of the solid-state laser is 532 nm.
It can be known from the above technical solutions that, because the continuous laser is coupled to the first optical beam splitter, the first optical beam splitter is coupled to the acousto-optic modulator and the wavemeter, the ring-down cavity, the wavemeter and the continuous laser are coupled to the computer, and the computer controls the continuous laser to scan to the laser frequency one by one for measurement under the action of the electrical signal output by the photoelectric conversion device and the monitoring signal output by the wavemeter, the high-precision continuous wavelength scanning can be realized,the spectral measurement precision can reach 10-4cm-1Compared with the prior art, the sensitivity of the spectral measurement is obviously improved.
Drawings
FIG. 1 is a schematic diagram of a cavity ring-down spectrometer system according to an embodiment of the present application;
FIG. 2 is a schematic diagram of a cavity ring down spectrometer system according to another embodiment of the present application;
FIG. 3 is a schematic diagram of a cavity ring down spectrometer system according to another embodiment of the present application;
FIG. 4 is a schematic diagram of a cavity ring down spectrometer system according to another embodiment of the present application.
Detailed Description
In order to make the purpose, technical solution and beneficial effects of the present application more clear and more obvious, the present application is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present application and are not intended to limit the present application.
In the following description, for purposes of explanation and not limitation, specific details are set forth, such as particular system structures, techniques, etc. in order to provide a thorough understanding of the embodiments of the present application. It will be apparent, however, to one skilled in the art that the present application may be practiced in other embodiments that depart from these specific details. In other instances, detailed descriptions of well-known systems, devices, circuits, and methods are omitted so as not to obscure the description of the present application with unnecessary detail.
Fig. 1 is a schematic structural diagram of a cavity ring-down spectrometer system according to an embodiment of the present application, which is described in detail as follows:
the cavity ring-down spectrometer system illustrated in fig. 1 includes a continuous laser 101, a first beam splitter 102 coupled to the continuous laser 101, an acousto-optic modulator 103 and a wavelength meter 104 coupled to the first beam splitter 102, a second beam splitter 105 coupled to the acousto-optic modulator 103, a third beam splitter 106 coupled to the second beam splitter 105, a ring-down cavity 107 coupled to the third beam splitter 106, and a computer 108 coupled to the ring-down cavity 107, the wavelength meter 104, and the continuous laser 101, wherein a first mirror 109 and a second mirror 110 are respectively disposed at two internal ends of the ring-down cavity 107, a piezoelectric ceramic tube 111 is disposed at an output end of the ring-down cavity 107, and the piezoelectric ceramic tube 111 is connected to the computer 108 via a photoelectric conversion device 112, wherein:
the continuous laser 101 is used for generating continuous laser under the pumping of the solid laser and outputting the continuous laser to the first light beam splitter 102;
the first light beam splitter 102 is configured to refract and reflect the continuous laser light generated by the continuous laser 101 into a first light beam and a second light beam, that is, the continuous laser light generated by the continuous laser 101 is refracted to obtain the first light beam, that is, the continuous laser light generated by the continuous laser 101 is reflected to obtain the second light beam, the first light beam is output to the acousto-optic modulator 103, and the second light beam is output to the wavelength meter 104;
the acousto-optic modulator 103 is used for modulating the first light beam under the modulation of the acoustic signal to obtain modulated light and outputting the modulated light to the second light beam splitter 105;
the second light beam splitter 105 is used for reflecting the modulated light and outputting the reflected light to the third light beam splitter 106 through a lens;
the third light beam splitter 106 is used for refracting the modulated light output by the lens and outputting the refracted modulated light to the ring-down cavity 107;
a ring-down cavity 107 for ring-down of the modulated light input from the third beam splitter 106 under the action of the first mirror 109 and the second mirror 110 and outputting the ring-down modulated light to the photoelectric conversion device 112;
the photoelectric conversion device 112 is used for converting the ring-down optical signal output by the ring-down cavity 107 into an electrical signal, wherein one path of the electrical signal is output to the acousto-optic modulator 103, and the other path of the electrical signal is output to the computer 108;
and the piezoelectric ceramic tube 111 is used for vibrating at a preset frequency under the action of the function generator, so that the longitudinal mode of the ring-down cavity 107 can be matched with the input dimmed frequency of the third beam splitter 106.
Further, ring down chamber 107 is provided with a constant temperature gas passage, such as the black circle portion shown in fig. 2, for inputting constant temperature gas into ring down chamber 107 and outputting from ring down chamber 107, and the direction indicated by the arrow represents the direction of the constant temperature gas.
Further, the wavelength meter 104 is used for monitoring the wavelength of the continuous laser light generated by the continuous laser 101, and a monitoring signal generated thereby is output to the computer 108.
Further, the computer 108 is used for controlling the continuous laser 101 to scan to the laser frequency one by one for measurement under the action of the electric signal output by the photoelectric conversion device 112 and the monitoring signal output by the wavelength meter 104, wherein the continuous laser 101 is a continuous ring cavity titanium sapphire laser.
Further, the nominal reflectivity of the first mirror 109 and the second mirror 110 may be 99.995% and the radius of curvature may be 1 meter.
Further, the preset frequency is 100 hz.
Further, the cavity length of ring down cavity 107 is 1.2 meters.
Further, the cavity ring-down spectrometer system further comprises a solid state laser, as shown in fig. 3, for pumping the continuous laser 101.
Further, the output wavelength of the solid state laser may be 532 nm.
As can be seen from the optical cavity ring-down spectrometer system illustrated in fig. 1, since the continuous laser is coupled to the first optical beam splitter, the first optical beam splitter is coupled to the acousto-optic modulator and the wavelength meter, the ring-down cavity, the wavelength meter and the continuous laser are coupled to the computer, and the computer controls the continuous laser to scan to the laser frequency one by one for measurement under the action of the electrical signal output by the photoelectric conversion device and the monitoring signal output by the wavelength meter, the high-precision continuous wavelength scanning can be realized, and the spectral measurement precision can reach 10-4cm-1Compared with the prior art, the sensitivity of the spectral measurement is obviously improved.
FIG. 4 is a schematic diagram of the cavity ring-down spectrometer system according to another embodiment of the present application, which is described in detail below:
the continuous laser 101 may be a model 899-21 continuous ring cavity Tibet laser manufactured by coherent America, IncThe output wavelength of the solid laser (Verdi-18) pump is 532 nm, which covers the spectral range of 700 to 1000 nm, and the wavelength of the continuous laser 101 is monitored by a wavelength meter 104, such as a WA-1500 type wavelength meter. Laser output by the continuous laser 101 passes through the acousto-optic modulator 103, is refracted by the second optical beam splitter 105 and the third optical beam splitter 106 in sequence, and is coupled by the optical fiber coupler, the optical fiber coupler and the two lenses in sequence and then is sent into the ring-down cavity 107. The cavity length of the ring down cavity 107 may be set to 1.25m, the nominal reflectivity of the first mirror 109 and the second mirror 110 at both ends may be 99.995%, and the curvature radius may be up to 1m, and the output end cavity mirror of the ring down cavity 107 is vibrated at a frequency of 100 hz by the piezoelectric ceramic tube 111, so that the longitudinal mode of the ring down cavity 107 can be matched with the frequency of the incident laser light. The light output by the ring-down cavity 107 is received by a photoelectric conversion device 112, such as a silicon diode detector, and then is divided into two paths of electric signals, one path of electric signal passes through an electric comparator, and after a set threshold voltage is exceeded, a trigger source generates a trigger signal to control the acousto-optic modulator 103 to turn off the laser light input from the first optical beam splitter 102; the other path of electric signal, i.e. the detector signal, is sent to a data acquisition card of the computer 108 for data acquisition, the ring-down signal is recorded, and after about 1 millisecond, the acousto-optic modulator 103 is controlled to turn on the laser input from the first beam splitter 102 again. Each ring-down curve recorded by the computer 108 is rapidly subjected to single exponential function fitting by the online computer 108 to obtain ring-down time data and corresponding fitting errors thereof, and the ring-down time data and the fitting errors are stored. The results of the multiple ring downs are averaged to obtain an average ring down time, after which computer 108 again generates a sweep signal to control the continuous laser 101 to sweep to the next laser frequency for measurement. The wavelength of the laser output by the continuous laser 101 is monitored by the wavelength meter 104 and the highly stable etalon, and high-precision continuous wavelength scanning can be realized by the control of the computer 108, and experiments show that the spectral measurement precision of the cavity ring-down spectrometer system illustrated in fig. 4 can reach 10-4cm-1And (4) horizontal.
It should be noted that, since the measured ring-down time may have a significant drift with the increase of the measurement time when the ambient temperature fluctuates, in the cavity ring-down spectrometer system of the above example, in order to improve the influence of the ambient temperature change on the detection sensitivity of the cavity ring-down spectrometer system, a channel for pre-passing the constant temperature gas through the ring-down cavity 107 is designed, so that the constant temperature is maintained in the ring-down cavity 107.
The above embodiments are only used to illustrate the technical solutions of the present application, and not to limit the same; although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; such modifications and substitutions do not substantially depart from the spirit and scope of the embodiments of the present application and are intended to be included within the scope of the present application.
Claims (10)
1. An optical cavity ring-down spectrometer system is characterized by comprising a continuous laser, a first optical beam splitter coupled with the continuous laser, an acousto-optic modulator and a wavemeter coupled with the first optical beam splitter, a second optical beam splitter coupled with the acousto-optic modulator, a third optical beam splitter coupled with the second optical beam splitter, a ring-down cavity coupled with the third optical beam splitter, and a computer coupled with the ring-down cavity, the wavemeter and the continuous laser, wherein a first reflecting mirror and a second reflecting mirror are respectively arranged at two ends in the ring-down cavity, a piezoelectric ceramic tube is arranged at the output end of the ring-down cavity, and the piezoelectric ceramic tube is connected with the computer through a photoelectric conversion device;
the continuous laser is used for generating continuous laser under the pumping of the solid laser and outputting the continuous laser to the first light beam splitter;
the first light beam splitter is used for splitting continuous laser generated by the continuous laser into a first light beam and a second light beam through refraction and reflection, the first light beam is output to the acousto-optic modulator, and the second light beam is output to the wavelength meter;
the acousto-optic modulator is used for modulating the first light beam under the modulation of an acoustic signal to obtain modulated light and outputting the modulated light to the second light beam splitter;
the second light beam splitter is used for reflecting the modulated light and outputting the modulated light to the third light beam splitter through a lens;
the third light beam splitter is used for refracting the modulated light output by the lens and outputting the refracted modulated light to the ring-down cavity;
the ring-down cavity is used for ring-down of modulated light input by the third beam splitter under the action of the first reflector and the second reflector and then outputting the modulated light to the photoelectric conversion device;
the photoelectric conversion device is used for converting ring-down optical signals output by the ring-down cavity into electric signals, one path of the electric signals is output to the acousto-optic modulator, and the other path of the electric signals is output to the computer;
the piezoelectric ceramic tube is used for vibrating at a preset frequency under the action of the function generator, so that the longitudinal mode of the ring-down cavity can be matched with the frequency of the modulated light input by the third beam splitter.
2. The cavity ring down spectrometer system of claim 1, wherein the ring down cavity is provided with a constant temperature gas passage for inputting constant temperature gas into and outputting constant temperature gas from the ring down cavity.
3. The cavity ring down spectrometer system of claim 1, wherein the wavemeter is configured to monitor the wavelength of the continuous laser light produced by the continuous laser, and the resulting monitor signal is output to the computer.
4. The cavity ring down spectrometer system of claim 3, wherein the computer is configured to control the continuous laser to scan one by one at the laser frequency for measurement under the influence of the electrical signal output by the photoelectric conversion device and the monitoring signal.
5. The cavity ring down spectrometer system of claim 1, wherein the continuous laser is a continuous ring cavity titanyl laser.
6. The cavity ring down spectrometer system of claim 1, wherein the first and second mirrors have a nominal reflectivity of 99.995% and a radius of curvature of 1 meter.
7. The cavity ring down spectrometer system of claim 1, wherein the predetermined frequency is 100 hz.
8. The cavity ring-down spectrometer system of claim 1, wherein the ring-down cavity has a cavity length of 1.25 meters.
9. The cavity ring down spectrometer system of any of claims 1-8, further comprising a solid state laser for pumping the continuous laser.
10. The cavity ring down spectrometer system of claim 9, wherein the output wavelength of the solid state laser is 532 nm.
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| CN201921116368.9U CN210427340U (en) | 2019-07-16 | 2019-07-16 | Cavity ring-down spectrometer system |
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| CN201921116368.9U CN210427340U (en) | 2019-07-16 | 2019-07-16 | Cavity ring-down spectrometer system |
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