CN115615953B - Differential absorption laser radar light source for detecting harmful gas in atmosphere environment - Google Patents
Differential absorption laser radar light source for detecting harmful gas in atmosphere environment Download PDFInfo
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- 238000010521 absorption reaction Methods 0.000 title claims abstract description 30
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- 239000007789 gas Substances 0.000 claims abstract description 16
- 238000001514 detection method Methods 0.000 claims abstract description 14
- 239000013078 crystal Substances 0.000 claims abstract description 13
- 238000005086 pumping Methods 0.000 claims description 24
- 230000009977 dual effect Effects 0.000 claims description 22
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 18
- 230000008878 coupling Effects 0.000 claims description 14
- 238000010168 coupling process Methods 0.000 claims description 14
- 238000005859 coupling reaction Methods 0.000 claims description 14
- 230000010355 oscillation Effects 0.000 claims description 14
- VOFUROIFQGPCGE-UHFFFAOYSA-N nile red Chemical compound C1=CC=C2C3=NC4=CC=C(N(CC)CC)C=C4OC3=CC(=O)C2=C1 VOFUROIFQGPCGE-UHFFFAOYSA-N 0.000 claims description 11
- 238000013519 translation Methods 0.000 claims description 8
- 230000005540 biological transmission Effects 0.000 claims description 5
- 239000007787 solid Substances 0.000 claims description 3
- RAHZWNYVWXNFOC-UHFFFAOYSA-N Sulphur dioxide Chemical compound O=S=O RAHZWNYVWXNFOC-UHFFFAOYSA-N 0.000 abstract description 12
- QGJOPFRUJISHPQ-UHFFFAOYSA-N Carbon disulfide Chemical compound S=C=S QGJOPFRUJISHPQ-UHFFFAOYSA-N 0.000 abstract description 11
- 239000006185 dispersion Substances 0.000 abstract 1
- 239000000975 dye Substances 0.000 description 69
- 238000005516 engineering process Methods 0.000 description 9
- 238000000034 method Methods 0.000 description 7
- 238000001228 spectrum Methods 0.000 description 7
- 238000010586 diagram Methods 0.000 description 6
- CBENFWSGALASAD-UHFFFAOYSA-N Ozone Chemical compound [O-][O+]=O CBENFWSGALASAD-UHFFFAOYSA-N 0.000 description 5
- 238000011160 research Methods 0.000 description 4
- 239000000990 laser dye Substances 0.000 description 3
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- 238000007493 shaping process Methods 0.000 description 2
- 238000007614 solvation Methods 0.000 description 2
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Abstract
The invention discloses a differential absorption laser radar light source for detecting harmful gases in the atmosphere, which comprises: the laser pump source, the optical system, the dye laser resonant cavity and the optical frequency doubling system realize the tuning of the output laser wavelength and the generation of the dual-wavelength laser by adjusting the dispersion element in the optical path; and then nonlinear optical frequency multiplication is realized through a frequency multiplication crystal, and the nonlinear optical frequency multiplication is used as a dual-wavelength differential absorption laser radar light source of an ultraviolet band, and can be used for trace detection of atmospheric harmful gases such as sulfur dioxide, carbon disulfide and the like.
Description
Technical Field
The invention belongs to the technical field of dye lasers and lasers, and particularly relates to a differential absorption laser radar light source for detecting harmful gases in an atmospheric environment and a method for generating dual-wavelength lasers.
Background
The combined pollution caused by the atmospheric particulates and ozone has become a major pollution problem in metropolitan areas. Considering the serious harm to human health, ecological system and the like caused by widely distributed atmospheric particulates, ozone, NO 2、SO2 and the like and possibly causing changes of climate warming and the like, the research on optical and physical characteristics of the particulates, ozone, NO 2、SO2 and the like in the atmospheric environment is carried out, and the research on the formation reasons, influence factors and the like is of great significance.
The laser radar applied to the atmospheric environment detection technology is a very common detection instrument, has higher spatial and time resolution, can continuously monitor the vertical distribution of atmospheric pollutants such as atmospheric particulate matters and ozone for a long time, and has been widely applied worldwide. As the most common atmospheric environment detection technology, lidar has different specific applications for different atmospheric pollutants. For aerosols represented by atmospheric particulates, a multi-wavelength polarized laser radar based on Mie scattering is generally adopted; for reactive gases and greenhouse gases in the atmosphere, such as ozone, NO 2、SO2, etc., differential absorption lidar technology is typically used. As an active optical remote sensing technology, the differential absorption laser radar technology has the characteristics of high spatial resolution, high detection sensitivity, large measurement range and the like, can realize the targets which are difficult to realize by conventional technical means such as horizontal and vertical spatial distribution detection of atmospheric trace gas, overhead source exhaust gas monitoring and the like, and has unique application value in the remote sensing monitoring of the concentration of the atmospheric gas.
The research direction of the differential absorption laser radar technology is quite large, the differential absorption laser radar technology is developed until now, the choice of light sources is diversified, and the research of the tunable dual-wavelength laser serving as the laser radar light source is gradually one of the important objects of a plurality of researchers in recent years. Existing ways of generating tunable dual wavelength lasers include nonlinear frequency conversion, active ion level splitting, etc., but these systems are relatively complex in design and more cumbersome to operate. Dye laser-based dual wavelength laser generation methods have been emerging in recent years, but the biggest problem with such methods in practice is that these devices all utilize the same or adjacent spatial gain region of the same dye, making the relative intensities of the two wavelengths of light difficult to control due to mode competition. And the adjustment of the two wavelengths is mutually restricted and cannot be completely independent. In summary, how to accurately select and generate the detection wavelength and reference wavelength required for detection is critical for the overall lidar system.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention provides a differential absorption laser radar light source for detecting harmful gases in the atmosphere environment, which is used for obtaining a laser with double continuous tunable wavelengths and is used as the differential absorption laser radar light source, SO that the detection wavelength and the reference wavelength required by detection can be accurately selected and generated, and the differential absorption laser radar light source is used for effectively detecting the concentration of the harmful gases such as SO 2、CS2 and the like in the atmosphere environment.
In order to achieve the aim of the invention, the invention adopts the following technical scheme:
The invention relates to a differential absorption laser radar light source for detecting harmful gases in the atmosphere, which is characterized by comprising the following components: the device comprises a laser pumping source, an optical system, a dye laser resonant cavity and an optical frequency doubling system; the laser pumping source is a Nd-YAG solid laser in a pulse working mode; the optical system includes: frequency doubling crystal, half wave plate, polaroid, total reflection mirror and cylindrical lens; the dye laser resonator comprises: blazed grating, dye pool and output coupling mirror; the optical frequency doubling system includes: polarizer, transmission reflector, nonlinear frequency doubling crystal, bicolor wave plate and beam combiner;
the laser emitted by the laser pumping source outputs frequency multiplication laser after passing through the frequency multiplication crystal, and after the output energy of the laser is regulated by the half-wave plate and the polaroid in sequence, the laser is subjected to optical path folding by the total reflection mirror to obtain pumping light, and after the pumping light passes through the shaping of the cylindrical lens, linear facula pumping light is formed and irradiated into the dye pool from the side face;
The dye Chi Zhongzhuang is provided with an ethanol solution of nile red as a gain medium of a dye laser resonant cavity, and forms the laser resonant cavity together with a blazed grating and an output coupling mirror, so that the linear facula pumping light generates dye laser in the laser resonant cavity and carries out wavelength tuning, then the dye laser is output from the right side of the output coupling mirror, and finally frequency-doubled laser is output after frequency doubling treatment of a polarizer, a transmission reflector, a nonlinear frequency-doubled crystal, a bicolor wave plate and a beam combiner in sequence, namely the differential absorption laser radar light source.
The differential absorption laser radar light source is also characterized in that: and a full reflection mirror is arranged below the blazed grating of the dye laser resonant cavity, and the full reflection mirror, the dye pool, the blazed grating and the output coupling mirror form a laser resonant cavity in Littman-Metcalf configuration together.
The dye laser in the laser resonant cavity is generated according to the following process:
Rotating dye Chi Shun filled with ethanol solution of nile red clockwise and forming a certain angle with a main optical axis of dye laser, so that a linear laser track and a ring laser track exist in the dye laser resonant cavity at the same time; both remain stable and oscillate back and forth within the cavity, ultimately forming a dual wavelength laser output.
The wavelength tuning of the dual-wavelength dye laser is carried out according to the following steps:
step 1a, changing the incidence angles of a linear laser track and an annular laser track simultaneously by rotating the blazed grating, so as to change the oscillation wavelength of the linear laser track and the annular laser track in the dye laser resonant cavity;
And 2a, keeping the rotation angle of the blazed grating unchanged, and translating the blazed grating from far to near to the dye pool, so that the wavelength interval of the dual-wavelength dye laser is continuously changed within a translation range, and wavelength tuning is realized.
The wavelength tuning of the dual-wavelength dye laser is carried out according to the following steps:
Step 1b, keeping the angle and the position of the blazed grating unchanged, and simultaneously changing the incidence angles of the linear laser track and the annular laser track by rotating the total reflection mirror, so as to change the oscillation wavelength of the linear laser track and the annular laser track in the dye laser resonant cavity;
And 2b, keeping the rotation angle of the blazed grating and the total reflection mirror unchanged, translating the total reflection mirror from far to near to the blazed grating, and continuously changing the wavelength interval of the dual-wavelength dye laser in a translation range so as to realize wavelength tuning.
Compared with the prior art, the invention has the beneficial effects that:
1. The invention utilizes the solvation color development characteristic of the organic laser dye nile red, and can realize the continuous adjustable wavelength dye laser output by combining the tuning of the grating resonant cavity to the laser wavelength. The technology for wavelength tuning through the dispersive element can utilize the motor to control rotation or translation, realizes precise tuning, and is simple to operate and convenient to integrate.
2. The invention utilizes the total internal reflection system formed by the blazed grating, the dye pool and the output coupling mirror, and can realize continuous tunable output of the dual-wavelength dye laser through precise tuning. The means for realizing the dual-wavelength laser output is novel, and compared with other technical means such as nonlinear optics and the like, the dual-wavelength laser is easier to obtain; in addition, by replacing the laser gain medium, namely the laser dye, the dual-wavelength laser output covering the ultraviolet-visible light-near infrared wide spectrum range can be realized, and the application range and the utilization value of the dual-wavelength laser output can not be estimated.
3. The invention can realize frequency doubling and frequency tripling of the output dye laser by utilizing the optical frequency doubling system to obtain the dual-wavelength laser light source with 190-220 nm and 290-330 nm, and the wavelength interval is continuously adjustable within the range of 0.2-2.5 nm, so that the invention can be used for research and development of a differential absorption laser radar complete machine and provides light source technical support for trace detection of harmful gases such as sulfur dioxide, carbon disulfide and the like in the atmospheric environment.
4. The invention has simple integral structure, easy operation, relatively low equipment cost and wide application, and the laser pumping source, the resonant cavity and the optical frequency doubling system can be integrated into a whole.
Drawings
FIG. 1 is a light path diagram of a differential absorption lidar light source according to embodiment 1 of the present invention;
FIG. 2 is a schematic diagram of the trace of an oscillating laser in the resonant cavity of the dye laser according to example 1 of the present invention;
FIG. 3 is a tunable dual wavelength laser spectrum obtained by rotating a grating in example 1 of the present invention;
FIG. 4 is a laser spectrum of the continuous variation of the dual wavelength interval obtained by translating blazed gratings in example 1 of the present invention;
FIG. 5 is a schematic diagram of a light path of a Littman-Metcalf configuration differential absorption lidar light source in example 2 of the present invention;
FIG. 6 is a schematic diagram showing the trajectory of a dual wavelength oscillation laser in a dye laser resonator according to example 2 of the present invention;
FIG. 7 is a tunable dual wavelength laser spectrum obtained by rotating a total reflection mirror in example 2 of the present invention;
FIG. 8 is a graph showing laser spectra of continuous change in the interval of dual wavelengths obtained by translating the total reflection mirror in example 2 of the present invention.
Detailed Description
Example 1: as shown in fig. 1, a differential absorption lidar light source for detection of harmful gases in an atmospheric environment, comprising: the device comprises a laser pumping source 1, an optical system, a dye laser resonant cavity and an optical frequency doubling system; the laser pumping source 1 is a Nd-YAG solid laser in a pulse working mode; the optical system includes: frequency doubling crystal 2, half-wave plate 3, polaroid 4, total reflection mirror 5, column lens 6; the dye laser resonator includes: blazed grating 7, dye pool 8 and output coupling mirror 9; the optical frequency doubling system includes: a polarizer 10, a transmissive mirror 11, a nonlinear frequency doubling crystal 12, a dichroic wave plate 13, and a beam combiner 14;
The laser emitted by the laser pumping source 1 outputs frequency-doubled laser after passing through the frequency-doubled crystal 2, and then the laser is subjected to light path folding by the total reflection mirror 5 to obtain pumping light after being subjected to output energy adjustment of the half wave plate 3 and the polaroid 4, and the pumping light is subjected to shaping by the cylindrical lens 6 to form linear facula pumping light which irradiates into the dye pond 8 from the side face;
The dye pool 8 is filled with ethanol solution of nile red as a gain medium of a dye laser resonant cavity, and forms the laser resonant cavity together with the blazed grating 7 and the output coupling mirror 9, so that the linear facula pumping light generates dye laser in the laser resonant cavity and carries out wavelength tuning, and then is output from the right side of the output coupling mirror 9, and finally outputs frequency multiplication laser after frequency multiplication treatment of the polarizer 10, the transmission reflector 11, the nonlinear frequency multiplication crystal 12, the double-color wave plate 13 and the beam combiner 14 in sequence, namely the differential absorption laser radar light source.
The dual wavelength dye laser in the laser resonator of this example 1 is generated as follows:
The dye pool 8 is filled with a nile red/ethanol solution with proper concentration and is used as a gain medium of a dye laser; the side surface of a 532nm pumping light source irradiates, fluorescence is generated by stimulated radiation in a dye pool 8, stable laser oscillation is formed through feedback of a resonant cavity formed by a blazed grating 7 and an output coupling mirror 9, and dye laser with single wavelength is finally output to the right;
Fig. 2 is a schematic diagram showing the trajectory of the dual-wavelength oscillation laser in the dye laser resonator in example 1. The dye pool 8 filled with the ethanol solution of nile red is rotated clockwise and forms a certain angle with the main optical axis of dye laser, so that a linear laser track 101 and an annular laser track 102 exist in the dye laser resonant cavity at the same time; both remain stable and oscillate back and forth within the cavity, ultimately forming a dual wavelength laser output.
In a specific implementation, the dual wavelength dye laser is wavelength tuned according to the following steps:
Step 1a, changing the incidence angles of the linear laser track 101 and the annular laser track 102 simultaneously by rotating the blazed grating 7, so as to change the oscillation wavelength of the linear laser track 101 and the annular laser track 102 in the dye laser resonant cavity; when the dye pool is horizontally placed, a single laser track exists in the resonant cavity, namely a linear laser track 101; when the dye pool is tilted a small angle clockwise, another laser trace, namely a ring laser trace 102, occurs in the resonant cavity due to total internal reflection TIR, coexisting with the straight laser trace. The two are kept stable in the resonant cavity and oscillate back and forth, and the dual-wavelength laser output is finally formed due to different oscillation track lengths. FIG. 3 is a laser spectrum obtained in the optical path of example 1, with a tuning range of up to 71.2nm, by rotating the grating by 3 degrees to achieve a continuously tunable dual wavelength laser output from 626.6nm to 697.8 nm;
And 2a, keeping the rotation angle of the blazed grating 7 unchanged, and translating the blazed grating from the far to the near dye pool 8, so that the wavelength interval of the dual-wavelength dye laser is continuously changed within the translation range, and wavelength tuning is realized. When the grating is translated from near to far while the rotation angle of the grating is kept unchanged, the oscillation wavelength of the ring laser trace 102 is changed along with the change of the incidence angle of the ring laser trace because the total length of the resonant cavity is increased, so that a closed cavity structure is formed; at the same time, the angle of incidence of the linear laser trace 101 is only dependent on the grating rotation angle and does not change, so its oscillation wavelength is unchanged. Finally, a laser spectrum with continuously changing dual wavelength interval can be obtained from the output, as shown in fig. 4. Through translation, the dual-wavelength laser light source with the wavelength interval continuously changing within the range of 0.7-5 nm can be obtained. After frequency multiplication, the dual wavelength interval is 0.35-2.5 nm, and an important reference basis can be provided for the preparation of the differential absorption laser radar light source.
Example 2: a full reflection mirror 15 is arranged below the blazed grating 7 of the dye laser resonant cavity, and forms a laser resonant cavity with a Littman-Metcalf configuration together with the dye pool 8, the blazed grating 7 and the output coupling mirror 9, as shown in fig. 5.
Wherein, the dual wavelength dye laser in the laser resonant cavity of Littman-Metcalf configuration is generated according to the following procedures:
The dye pool 8 is filled with a nile red/ethanol solution with proper concentration and is used as a gain medium of a dye laser; the side surface of a 532nm pumping light source irradiates, fluorescence is generated by stimulated radiation in a dye pool 8, stable oscillation is carried out in a dye laser resonant cavity, and finally dye laser with single wavelength output to the right is formed;
Fig. 6 is a schematic diagram showing the trajectory of the dual-wavelength oscillation laser in the dye laser resonator in example 2. The dye pool 8 filled with the ethanol solution of nile red is rotated clockwise and forms a certain angle with the main optical axis of dye laser, so that a linear laser track 103 and an annular laser track 104 exist in the dye laser resonant cavity at the same time; both remain stable and oscillate back and forth within the cavity, ultimately forming a dual wavelength laser output.
The wavelength tuning of the dual-wavelength dye laser in the laser resonant cavity of the Littman-Metcalf configuration is carried out according to the following steps:
Step 1b, keeping the angle and the position of the blazed grating 7 unchanged, and simultaneously changing the incidence angles of the linear laser track 103 and the annular laser track 104 by rotating the total reflection mirror 15, so as to change the oscillation wavelength of the linear laser track 103 and the annular laser track 104 in the dye laser resonant cavity; when the dye pool is tilted at a slight angle clockwise, two laser tracks exist in the resonant cavity due to total internal reflection TIR, namely a linear laser track 103 and a ring laser track 104. They remain stable and oscillate back and forth, ultimately forming a dual wavelength laser output. Fig. 7 is a continuously tunable dual wavelength laser output from 634.4nm to 663.3nm achieved by rotating the total mirror 2.1 ° in example 2, with a tuning range covering 29nm.
And 2b, keeping the rotation angle between the blazed grating 7 and the total reflection mirror 15 unchanged, and translating the total reflection mirror 15 from far to near to the blazed grating 7, so that the wavelength interval of the dual-wavelength dye laser is continuously changed within the translation range, and wavelength tuning is realized. The angle between the blazed grating 7 and the total reflection mirror 15 is not changed, the position of the blazed grating 7 is kept unchanged, the distance between the blazed grating 7 and the total reflection mirror 15 is changed by translating the total reflection mirror 15, and a dual-wavelength laser light source with the wavelength interval continuously changed within the range of 1.5-4 nm can be obtained, and the tuning result is shown in figure 8. After frequency multiplication, the dual wavelength interval is 0.75 nm-2 nm, and an important reference basis can be provided for the preparation of a differential absorption laser radar light source.
In summary, according to the differential absorption laser radar light source for detecting harmful gases in the atmosphere and the method for generating dual-wavelength laser, the solvation color development characteristic and excellent laser characteristic of the organic laser dye nile red are utilized, and the wide-range dual-wavelength continuous tunable laser output of 620 nm-700 nm is realized by precise tuning in a total internal reflection system formed by a grating resonant cavity and a dye pool; and meanwhile, the nonlinear optical frequency doubling system is utilized to realize frequency doubling and frequency tripling of output laser, so that a dual-wavelength laser light source of 190-220 nm and 290-330 nm is obtained, the wavelength interval is continuously adjustable within the range of 0.2-2.5 nm, the method can be used for research and development of a differential absorption laser radar complete machine, and important support of light source technology is provided for trace detection of harmful gases such as sulfur dioxide and carbon disulfide in the atmospheric environment.
Claims (5)
1. A differential absorption lidar light source for detection of harmful gases in an atmospheric environment, comprising: the device comprises a laser pumping source (1), an optical system, a dye laser resonant cavity and an optical frequency doubling system; the laser pumping source (1) is an Nd-YAG solid laser in a pulse working mode; the optical system includes: the device comprises a frequency doubling crystal (2), a half-wave plate (3), a polaroid (4), a first total reflection mirror (5) and a cylindrical lens (6); the dye laser resonator comprises: a blazed grating (7), a dye pool (8) and an output coupling mirror (9); the optical frequency doubling system includes: a polarizer (10), a transmission mirror (11), a nonlinear frequency doubling crystal (12), a bicolor wave plate (13) and a beam combiner (14);
the laser emitted by the laser pumping source (1) passes through the frequency doubling crystal (2) and then outputs frequency doubling laser, and then the laser passes through the half-wave plate (3) and the polarizing plate (4) in turn and is subjected to optical path folding by the first total reflection mirror (5) to obtain pumping light, and the pumping light passes through the cylindrical lens (6) to form linear facula pumping light which irradiates into the dye pool (8) from the side face;
the dye pool (8) is internally provided with a Nile red ethanol solution as a gain medium of a dye laser resonant cavity, and forms the laser resonant cavity together with the blazed grating (7) and the output coupling mirror (9), so that the linear facula pumping light generates dual-wavelength dye laser in the laser resonant cavity and carries out wavelength tuning, and then the dual-wavelength dye laser is output from the right side of the output coupling mirror (9), and then sequentially passes through the polarizer (10), the transmission mirror (11), the nonlinear frequency doubling crystal (12), the dual-color wave plate (13) and the beam combiner (14) to carry out frequency doubling treatment, and finally output frequency doubling laser, namely the differential absorption laser radar light source.
2. The differential absorption lidar light source of claim 1, wherein: a second total reflection mirror (15) is arranged below the blazed grating (7) of the dye laser resonant cavity, and the second total reflection mirror, the dye pool (8), the blazed grating (7) and the output coupling mirror (9) form a laser resonant cavity in Littman-Metcalf configuration together.
3. A differential absorption lidar light source according to claim 1 or 2, wherein the dye laser in the laser resonator is generated as follows:
A dye pool (8) filled with ethanol solution of nile red is rotated clockwise and forms a certain angle with a main optical axis of dye laser, so that a linear laser track (101) and a ring laser track (102) exist in a dye laser resonant cavity at the same time; both remain stable and oscillate back and forth within the cavity, ultimately forming a dual wavelength dye laser output.
4. The differential absorption lidar light source of claim 1, wherein the dual wavelength dye laser is wavelength tuned by:
Step 1a, changing the incidence angles of the linear laser track (101) and the annular laser track (102) simultaneously by rotating the blazed grating (7), so as to change the oscillation wavelengths of the linear laser track (101) and the annular laser track (102) in the dye laser resonant cavity;
and 2a, keeping the rotation angle of the blazed grating (7) unchanged, and translating the blazed grating from far to near to the dye pool (8), so that the wavelength interval of the dual-wavelength dye laser is continuously changed within a translation range, and wavelength tuning is realized.
5. The differential absorption lidar light source of claim 2, wherein the dual wavelength dye laser is wavelength tuned by:
Step 1b, keeping the angle and the position of the blazed grating (7) unchanged, and simultaneously changing the incidence angles of the linear laser track (103) and the annular laser track (104) by rotating the second full-reflecting mirror (15), so as to change the oscillation wavelengths of the linear laser track (103) and the annular laser track (104) in the dye laser resonant cavity;
And 2b, keeping the rotation angle of the blazed grating (7) and the second total reflection mirror (15) unchanged, and translating the second total reflection mirror (15) from far to near to the blazed grating (7), so that the wavelength interval of the dual-wavelength dye laser is continuously changed within a translation range, and wavelength tuning is realized.
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| CN114354531A (en) * | 2021-12-30 | 2022-04-15 | 合肥工业大学 | Plastic identification system of double-wavelength coherent light source based on near infrared |
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| CN112202043A (en) * | 2020-08-31 | 2021-01-08 | 西安电子科技大学 | Coumarin C440 and C460 co-doped dye tunable laser |
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| CN115615953A (en) | 2023-01-17 |
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