CN115615953B - Differential absorption lidar light source for detecting harmful gases in the atmosphere - Google Patents
Differential absorption lidar light source for detecting harmful gases in the atmosphere Download PDFInfo
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Abstract
Description
技术领域Technical Field
本发明属于染料激光器及激光技术领域，具体涉及一种用于大气环境中有害气体检测的差分吸收激光雷达光源与产生双波长激光的方法。The invention belongs to the field of dye lasers and laser technology, and in particular 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.
背景技术Background technique
大气颗粒物以及臭氧引起的复合污染已成为大城市区域的主要污染问题。考虑到分布广泛的大气颗粒物、臭氧、NO2、SO2等对人类健康、生态系统等造成的严重危害，并且可能引起气候变暖等一些列的变化，因此对大气环境中颗粒物、臭氧、NO2、SO2等进行光学和物理特性的研究，探究其形成原因与影响因素等，具有十分重要的意义。The combined pollution caused by atmospheric particulate matter and ozone has become the main pollution problem in large urban areas. Considering the serious harm caused by the widespread atmospheric particulate matter, ozone, NO2 , SO2 , etc. to human health, ecosystems, etc., and the possibility of causing a series of changes such as climate warming, it is of great significance to study the optical and physical properties of particulate matter, ozone, NO2 , SO2, etc. in the atmospheric environment, and explore their formation causes and influencing factors.
应用于大气环境检测技术的激光雷达是一种非常常见的检测仪器，它具有较高的空间与时间分辨率，可以长期连续地监测大气颗粒物以及臭氧等大气污染物的垂直分布，已在全世界范围内得到了广泛的应用。激光雷达作为最常见的大气环境检测技术，针对不同的大气污染物有着不同的具体应用。针对以大气颗粒物为代表的气溶胶，一般采用基于Mie散射的多波长偏振激光雷达；而对于大气环境中的反应性气体与温室气体，如臭氧、NO2、SO2等，通常采用的是差分吸收激光雷达技术。作为一种主动式的光学遥感技术，差分吸收激光雷达技术具有空间分辨率高、探测灵敏度高、测量范围大等特点，可以实现大气痕量气体水平和垂直空间分布探测、高架源排放气体监测等常规技术手段难以实现的目标，在大气气体浓度遥感监测中具有独特的应用价值。Laser radar used in atmospheric environment detection technology is a very common detection instrument. It has high spatial and temporal resolution and can monitor the vertical distribution of atmospheric particulate matter and atmospheric pollutants such as ozone for a long time and continuously. It has been widely used throughout the world. As the most common atmospheric environment detection technology, laser radar has different specific applications for different atmospheric pollutants. For aerosols represented by atmospheric particulate matter, multi-wavelength polarization laser radar based on Mie scattering is generally used; while for reactive gases and greenhouse gases in the atmospheric environment, such as ozone, NO2 , SO2 , etc., differential absorption laser radar technology is usually used. As an active optical remote sensing technology, differential absorption laser radar technology has the characteristics of high spatial resolution, high detection sensitivity, and large measurement range. It can achieve the goals that are difficult to achieve with conventional technical means such as horizontal and vertical spatial distribution detection of atmospheric trace gases and monitoring of elevated source emission gases. It has unique application value in remote sensing monitoring of atmospheric gas concentrations.
针对差分吸收激光雷达技术的研究方向有很多，差分吸收激光雷达技术发展至今，其光源的选择也呈现多样化，其中作为激光雷达光源的可调谐双波长激光器的研究近年来逐渐成为众多科研人员重点关注的对象之一。现有的产生可调谐双波长激光的方式包括非线性频率变换、激活离子能级分裂等，但是这些系统的设计相对复杂，操作也更为麻烦。基于染料激光器的双波长激光产生方法是近年来新兴的技术手段，但是这类方法在实施中存在的最大的问题是这些器件都利用同一种染料的同一空间或相邻空间的增益区，由于模式竞争使得两个波长的光相对强度难以控制。并且两个波长的调节相互收到牵制，不能做到完全独立。总而言之，如何准确选择并产生探测所需的探测波长和参考波长是整个激光雷达系统的关键。There are many research directions for differential absorption lidar technology. As differential absorption lidar technology has developed to date, the choice of its light source has also become diversified. Among them, the research on tunable dual-wavelength lasers as lidar light sources has gradually become one of the focuses of many researchers in recent years. Existing methods for generating tunable dual-wavelength lasers include nonlinear frequency conversion, activated ion energy level splitting, etc., but the design of these systems is relatively complex and the operation is more troublesome. The dual-wavelength laser generation method based on dye lasers is an emerging technical means in recent years, but the biggest problem in the implementation of this type of method is that these devices all use the gain region of the same space or adjacent space of the same dye. Due to mode competition, the relative intensity of the two wavelengths of light is difficult to control. And the adjustment of the two wavelengths is mutually restrained and cannot be completely independent. In short, how to accurately select and generate the detection wavelength and reference wavelength required for detection is the key to the entire lidar system.
发明内容Summary of the invention
为了克服现有技术的不足，本发明提出一种用于大气环境中有害气体检测的差分吸收激光雷达光源，以期能得到双波长连续可调谐的激光器，并作为差分吸收激光雷达光源，从而能准确选择并产生探测所需的探测波长和参考波长，用于有效检测大气环境中SO2、CS2等有害气体的浓度。In order to overcome the shortcomings of the prior art, the present invention proposes a differential absorption laser radar light source for detecting harmful gases in the atmospheric environment, in order to obtain a dual-wavelength continuously tunable laser and use it as a differential absorption laser radar light source, so as to accurately select and generate the detection wavelength and reference wavelength required for detection, and effectively detect the concentration of harmful gases such as SO2 and CS2 in the atmospheric environment.
本发明为达到上述发明目的，采用如下技术方案：In order to achieve the above-mentioned object of the invention, the present invention adopts the following technical scheme:
本发明一种用于大气环境中有害气体检测的差分吸收激光雷达光源的特点在于，包括：激光泵浦源、光学系统、染料激光谐振腔以及光学倍频系统；其中，所述激光泵浦源为脉冲工作模式的Nd: YAG固体激光器；所述光学系统包括：倍频晶体、半波片、偏振片、全反镜、柱透镜；所述染料激光谐振腔包括：闪耀光栅、染料池、输出耦合镜；所述光学倍频系统包括：起偏器、透射反射镜、非线性倍频晶体、双色波片以及光束合束器；The differential absorption laser radar light source for detecting harmful gases in an atmospheric environment of the present invention is characterized in that it comprises: a laser pump source, an optical system, a dye laser resonant cavity and an optical frequency doubling system; wherein the laser pump source is a Nd: YAG solid laser in a pulsed working mode; the optical system comprises: a frequency doubling crystal, a half-wave plate, a polarizer, a total reflector, and a cylindrical lens; the dye laser resonant cavity comprises: a blazed grating, a dye pool, and an output coupling mirror; the optical frequency doubling system comprises: a polarizer, a transmission reflector, a nonlinear frequency doubling crystal, a dichroic wave plate, and a beam combiner;
所述激光泵浦源出射的激光经过所述倍频晶体后输出倍频激光，再依次经过所述半波片与偏振片的输出能量调节后，由所述全反镜进行光路折叠得到泵浦光，所述泵浦光经过柱透镜的整型后，形成线状光斑泵浦光从侧面照射入所述染料池中；The laser emitted by the laser pump source passes through the frequency doubling crystal to output a frequency doubling laser, and then passes through the half-wave plate and the polarizing plate in turn to adjust the output energy, and then the total reflector performs optical path folding to obtain pump light, and the pump light is shaped by the cylindrical lens to form a linear spot pump light, which is irradiated into the dye pool from the side;
所述染料池中装有尼罗红的乙醇溶液作为染料激光谐振腔的增益介质，并与闪耀光栅和输出耦合镜共同构成激光谐振腔，使得所述线状光斑泵浦光在所述激光谐振腔内产生染料激光并进行波长调谐后，从输出耦合镜的右侧输出，再依次经过起偏器、透射反射镜、非线性倍频晶体、双色波片以及光束合束器的倍频处理后，最终输出倍频激光，即为差分吸收激光雷达光源。The dye pool contains an ethanol solution of Nile red as the gain medium of the dye laser resonant cavity, and together with the blazed grating and the output coupling mirror, constitutes a laser resonant cavity, so that the linear spot pump light generates dye laser in the laser resonant cavity and after wavelength tuning, it is output from the right side of the output coupling mirror, and then passes through the polarizer, transmission reflector, nonlinear frequency doubling crystal, two-color wave plate and beam combiner in sequence after frequency doubling processing, and finally outputs the frequency doubling laser, which is the differential absorption laser radar light source.
本发明所述的差分吸收激光雷达光源的特点也在于：在所述染料激光谐振腔的闪耀光栅下方设置有全反镜，并与所述染料池、闪耀光栅和输出耦合镜共同构成Littman-Metcalf构型的激光谐振腔。The differential absorption laser radar light source described in the present invention is also characterized in that a total reflection mirror is arranged below the blazed grating of the dye laser resonant cavity, and together with the dye pool, the blazed grating and the output coupling mirror, a laser resonant cavity of the Littman-Metcalf configuration is formed.
所述激光谐振腔内的染料激光是按如下过程产生：The dye laser in the laser resonant cavity is generated according to the following process:
将装有尼罗红的乙醇溶液的染料池顺时针旋转，并与染料激光的主光轴形成一定角度，使得染料激光谐振腔中同时存在直线形激光轨迹与环形激光轨迹；二者在腔内保持稳定并来回振荡，最终形成双波长激光输出。The dye pool containing Nile red ethanol solution is rotated clockwise and forms a certain angle with the main optical axis of the dye laser, so that a linear laser trajectory and a circular laser trajectory exist simultaneously in the dye laser resonant cavity; the two remain stable and oscillate back and forth in the cavity, eventually forming a dual-wavelength laser output.
所述双波长染料激光是按如下步骤进行波长调谐：The dual-wavelength dye laser is wavelength tuned according to the following steps:
步骤1a、通过旋转所述闪耀光栅来同时改变直线形激光轨迹与环形激光轨迹的入射角，从而改变所述直线形激光轨迹与环形激光轨迹在所述染料激光谐振腔中的振荡波长；Step 1a, rotating the blazed grating to simultaneously change the incident angles of the linear laser trajectory and the annular laser trajectory, thereby changing the oscillation wavelengths of the linear laser trajectory and the annular laser trajectory in the dye laser resonant cavity;
步骤2a、保持所述闪耀光栅的旋转角度不变，将其由远到近向所述染料池平移，从而在平移范围内连续改变所述双波长染料激光的波长间隔，以实现波长调谐。Step 2a, keeping the rotation angle of the blazed grating unchanged, and translating it from far to near toward the dye pool, thereby continuously changing the wavelength interval of the dual-wavelength dye laser within the translation range to achieve wavelength tuning.
所述双波长染料激光是按如下步骤进行波长调谐：The dual-wavelength dye laser is wavelength tuned according to the following steps:
步骤1b、保持所述闪耀光栅的角度与位置不变，通过旋转所述全反镜来同时改变直线形激光轨迹与环形激光轨迹的入射角，从而改变所述直线形激光轨迹与环形激光轨迹在所述染料激光谐振腔中的振荡波长；Step 1b, keeping the angle and position of the blazed grating unchanged, and changing the incident angles of the linear laser trajectory and the annular laser trajectory simultaneously by rotating the total reflection mirror, thereby changing the oscillation wavelengths of the linear laser trajectory and the annular laser trajectory in the dye laser resonant cavity;
步骤2b、保持所述闪耀光栅与全反镜的旋转角度不变，将所述全反镜由远到近向所述闪耀光栅平移，从而在平移范围内连续改变所述双波长染料激光的波长间隔，以实现波长调谐。Step 2b, keeping the rotation angle of the blazed grating and the total reflection mirror unchanged, and translating the total reflection mirror toward the blazed grating from far to near, thereby continuously changing the wavelength interval of the dual-wavelength dye laser within the translation range to achieve wavelength tuning.
与现有技术相比，本发明的有益效果在于：Compared with the prior art, the present invention has the following beneficial effects:
1. 本发明利用有机激光染料尼罗红的溶剂化显色特性，结合光栅谐振腔对激光波长的调谐，可以实现波长连续可调的染料激光输出。这种通过色散元件进行波长调谐的技术，可以利用电机操控旋转或平移，实现了精密调谐，且操作简单，便于集成化。1. The present invention utilizes the solvatochromic properties of the organic laser dye Nile Red and combines the tuning of the laser wavelength by the grating resonant cavity to achieve dye laser output with continuously adjustable wavelength. This technology of wavelength tuning through a dispersive element can be controlled by a motor to rotate or translate, achieving precise tuning, and is simple to operate and easy to integrate.
2. 本发明利用闪耀光栅、染料池与输出耦合镜构成的全内反射系统，通过精密调谐可实现双波长染料激光的连续可调谐输出。这种实现双波长激光输出的手段较为新颖，相比于其他技术手段例如非线性光学等更容易得到双波长激光；另外，通过替换激光增益介质即激光染料，可以实现覆盖紫外—可见光—近红外的宽光谱范围的双波长激光输出，其适用范围与利用价值不可估量。2. The present invention utilizes a total internal reflection system composed of a blazed grating, a dye pool, and an output coupling mirror, and can achieve continuous tunable output of a dual-wavelength dye laser through precise tuning. This method of achieving dual-wavelength laser output is relatively novel and is easier to obtain than other technical methods such as nonlinear optics. In addition, by replacing the laser gain medium, i.e., the laser dye, dual-wavelength laser output covering a wide spectral range of ultraviolet-visible light-near infrared can be achieved, and its scope of application and utilization value are immeasurable.
3. 本发明利用光学倍频系统，可实现对输出染料激光的二倍频、三倍频，得到190~220nm以及290~330nm的双波长激光光源，且波长间隔在0.2~2.5nm范围内连续可调，可以用于差分吸收激光雷达整机研发，为大气环境中二氧化硫、二硫化碳等有害气体的痕量检测提供光源技术支持。3. The present invention utilizes an optical frequency doubling system to achieve double and triple frequency of the output dye laser, obtaining a dual-wavelength laser light source of 190-220nm and 290-330nm, and the wavelength interval is continuously adjustable in the range of 0.2-2.5nm. It can be used for the research and development of differential absorption laser radar, and provide light source technology support for trace detection of harmful gases such as sulfur dioxide and carbon disulfide in the atmospheric environment.
4. 本发明整体结构简单，操作容易，激光泵浦源、谐振腔与光学倍频系统可集成为一体，且设备成本相对较低，应用广泛。4. The overall structure of the present invention is simple and easy to operate. The laser pump source, the resonant cavity and the optical frequency doubling system can be integrated into one. The equipment cost is relatively low and it is widely used.
附图说明BRIEF DESCRIPTION OF THE DRAWINGS
图1是本发明实施例1差分吸收激光雷达光源的光路图；FIG1 is a light path diagram of a differential absorption laser radar light source according to Embodiment 1 of the present invention;
图2是本发明实施例1中染料激光器谐振腔中的振荡激光轨迹示意图；FIG2 is a schematic diagram of the oscillating laser trajectory in the resonant cavity of the dye laser in Example 1 of the present invention;
图3是本发明实施例1中通过旋转光栅得到的可调谐双波长激光光谱；FIG3 is a tunable dual-wavelength laser spectrum obtained by rotating the grating in Example 1 of the present invention;
图4是本发明实施例1中通过平移闪耀光栅得到的双波长间隔连续改变的激光光谱；FIG4 is a laser spectrum with a continuously changing dual-wavelength interval obtained by translating the blazed grating in Example 1 of the present invention;
图5是本发明实施例2中Littman-Metcalf构型的差分吸收激光雷达光源的光路图；5 is a light path diagram of a differential absorption laser radar light source of a Littman-Metcalf configuration in Example 2 of the present invention;
图6是本发明实施例2中染料激光谐振腔中双波长振荡激光的轨迹示意图；FIG6 is a schematic diagram of the trajectory of the dual-wavelength oscillating laser in the dye laser resonant cavity in Example 2 of the present invention;
图7是本发明实施例2中通过旋转全反镜得到的可调谐双波长激光光谱；FIG7 is a tunable dual-wavelength laser spectrum obtained by rotating the total reflection mirror in Example 2 of the present invention;
图8是本发明实施例2中通过平移全反镜得到的双波长间隔连续改变的激光光谱图。FIG8 is a laser spectrum diagram of a dual-wavelength interval continuously changed by translating a total reflection mirror in Example 2 of the present invention.
具体实施方式Detailed ways
实施例1：如图1所示，一种用于大气环境中有害气体检测的差分吸收激光雷达光源，包括：激光泵浦源1、光学系统、染料激光谐振腔以及光学倍频系统；其中，激光泵浦源1为脉冲工作模式的Nd: YAG固体激光器；光学系统包括：倍频晶体2、半波片3、偏振片4、全反镜5、柱透镜6；染料激光谐振腔包括：闪耀光栅7、染料池8、输出耦合镜9；光学倍频系统包括：起偏器10、透射反射镜11、非线性倍频晶体12、双色波片13以及光束合束器14；Embodiment 1: As shown in FIG1 , a differential absorption laser radar light source for detecting harmful gases in an atmospheric environment comprises: a laser pump source 1, an optical system, a dye laser resonant cavity and an optical frequency doubling system; wherein the laser pump source 1 is a Nd: YAG solid laser in a pulsed working mode; the optical system comprises: a frequency doubling crystal 2, a half-wave plate 3, a polarizer 4, a total reflector 5, and a cylindrical lens 6; the dye laser resonant cavity comprises: a blazed grating 7, a dye pool 8, and an output coupling mirror 9; the optical frequency doubling system comprises: a polarizer 10, a transmission reflector 11, a nonlinear frequency doubling crystal 12, a two-color wave plate 13 and a beam combiner 14;
激光泵浦源1出射的激光经过倍频晶体2后输出倍频激光，再依次经过半波片3与偏振片4的输出能量调节后，由全反镜5进行光路折叠得到泵浦光，泵浦光经过柱透镜6的整型后，形成线状光斑泵浦光从侧面照射入染料池8中；The laser emitted by the laser pump source 1 passes through the frequency doubling crystal 2 to output the frequency doubling laser, and then passes through the half-wave plate 3 and the polarizer 4 in turn to adjust the output energy, and then the total reflector 5 folds the optical path to obtain the pump light. After the pump light passes through the cylindrical lens 6, it forms a linear spot pump light and irradiates into the dye pool 8 from the side.
染料池8中装有尼罗红的乙醇溶液作为染料激光谐振腔的增益介质，并与闪耀光栅7和输出耦合镜9共同构成激光谐振腔，使得线状光斑泵浦光在激光谐振腔内产生染料激光并进行波长调谐后，从输出耦合镜9的右侧输出，再依次经过起偏器10、透射反射镜11、非线性倍频晶体12、双色波片13以及光束合束器14的倍频处理后，最终输出倍频激光，即为差分吸收激光雷达光源。The dye pool 8 is filled with an ethanol solution of Nile red as the gain medium of the dye laser resonant cavity, and together with the blazed grating 7 and the output coupling mirror 9, constitutes a laser resonant cavity, so that the linear spot pump light generates dye laser in the laser resonant cavity and after wavelength tuning, it is output from the right side of the output coupling mirror 9, and then passes through the polarizer 10, the transmission reflector 11, the nonlinear frequency doubling crystal 12, the two-color wave plate 13 and the beam combiner 14 for frequency doubling processing, and finally outputs the frequency doubling laser, which is the differential absorption laser radar light source.
本实施例1中的激光谐振腔内的双波长染料激光是按如下过程产生：The dual-wavelength dye laser in the laser resonant cavity in this embodiment 1 is generated according to the following process:
染料池8中装有适当浓度的尼罗红/乙醇溶液，作为染料激光器的增益介质；经过532nm抽运光源的侧面照射，在染料池8中受激辐射产生荧光，经过闪耀光栅7与输出耦合镜9构成的谐振腔反馈形成稳定的激光震荡，最终向右输出单一波长的染料激光；The dye pool 8 is filled with a Nile red/ethanol solution of appropriate concentration as the gain medium of the dye laser; after being irradiated from the side by a 532nm pumping light source, stimulated radiation in the dye pool 8 generates fluorescence, which is fed back through the resonant cavity formed by the blazed grating 7 and the output coupling mirror 9 to form a stable laser oscillation, and finally outputs a single wavelength dye laser to the right;
如图2所示，为实施例1中染料激光谐振腔中双波长振荡激光的轨迹示意图。将装有尼罗红的乙醇溶液的染料池8顺时针旋转，并与染料激光的主光轴形成一定角度，使得染料激光谐振腔中同时存在直线形激光轨迹101与环形激光轨迹102；二者在腔内保持稳定并来回振荡，最终形成双波长激光输出。As shown in Fig. 2, it is a schematic diagram of the trajectory of the dual-wavelength oscillating laser in the dye laser resonant cavity 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 the dye laser, so that a linear laser trajectory 101 and a ring laser trajectory 102 exist in the dye laser resonant cavity at the same time; the two remain stable in the cavity and oscillate back and forth, and finally form a dual-wavelength laser output.
具体实施中，双波长染料激光是按如下步骤进行波长调谐：In a specific implementation, the wavelength of the dual-wavelength dye laser is tuned according to the following steps:
步骤1a、通过旋转闪耀光栅7来同时改变直线形激光轨迹101与环形激光轨迹102的入射角，从而改变直线形激光轨迹101与环形激光轨迹102在染料激光谐振腔中的振荡波长；当染料池水平放置时，谐振腔中存在唯一一种激光轨迹，即直线形激光轨迹101；当染料池沿顺时针倾斜微小角度时，谐振腔中由于全内反射TIR，出现另一种激光轨迹，即环形激光轨迹102，与直线形激光轨迹并存。二者在谐振腔内保持稳定并来回振荡，由于振荡轨迹长度不同，最终形成双波长激光输出。图3是在实施例1的光路中得到的激光光谱，通过旋转光栅3°可以实现从626.6nm至697.8nm连续可调谐的双波长激光输出，调谐范围高达71.2nm；Step 1a, by rotating the blazed grating 7 to simultaneously change the incident angles of the linear laser track 101 and the annular laser track 102, thereby changing the oscillation wavelengths of the linear laser track 101 and the annular laser track 102 in the dye laser resonant cavity; when the dye pool is placed horizontally, there is only one laser track in the resonant cavity, namely the linear laser track 101; when the dye pool is tilted clockwise at a small angle, another laser track appears in the resonant cavity due to total internal reflection TIR, namely the annular laser track 102, coexisting with the linear laser track. The two remain stable and oscillate back and forth in the resonant cavity, and due to the different lengths of the oscillation tracks, a dual-wavelength laser output is eventually formed. Figure 3 is the laser spectrum obtained in the optical path of Example 1. By rotating the grating 3°, a continuously tunable dual-wavelength laser output from 626.6nm to 697.8nm can be achieved, and the tuning range is up to 71.2nm;
步骤2a、保持闪耀光栅7的旋转角度不变，将其由远到近向染料池8平移，从而在平移范围内连续改变双波长染料激光的波长间隔，以实现波长调谐。当保持光栅旋转角度不变，将其由近到远平移时，由于增加了谐振腔总长，导致为了形成闭合的腔结构，其中环形激光轨迹102的入射角必然发生改变，因此其振荡波长也随之变化；与此同时，直线形激光轨迹101的入射角只与光栅旋转角度有关，并不发生改变，因此其振荡波长不变。最终可从输出端得到双波长间隔连续改变的激光光谱，如图4所示。通过平移，可以得到波长间隔在0.7~5nm范围内连续改变的双波长激光光源。经过倍频后，其双波长间隔为0.35~2.5nm，可为差分吸收激光雷达光源的制备提供重要参考依据。Step 2a, keep the rotation angle of the blazed grating 7 unchanged, and translate it from far to near toward the dye pool 8, so as to continuously change the wavelength interval of the dual-wavelength dye laser within the translation range to achieve wavelength tuning. When the grating rotation angle is kept unchanged and translated from near to far, the total length of the resonant cavity is increased, resulting in the formation of a closed cavity structure, in which the incident angle of the annular laser track 102 must change, so its oscillation wavelength also changes accordingly; at the same time, the incident angle of the linear laser track 101 is only related to the grating rotation angle and does not change, so its oscillation wavelength remains unchanged. Finally, a laser spectrum with a continuously changing dual-wavelength interval can be obtained from the output end, as shown in Figure 4. By translation, a dual-wavelength laser light source with a wavelength interval that continuously changes in the range of 0.7~5nm can be obtained. After frequency doubling, its dual-wavelength interval is 0.35~2.5nm, which can provide an important reference for the preparation of differential absorption laser radar light sources.
实施例2：在染料激光谐振腔的闪耀光栅7下方设置有全反镜15，并与染料池8、闪耀光栅7和输出耦合镜9共同构成Littman-Metcalf构型的激光谐振腔，如图5所示。Embodiment 2: A total reflection mirror 15 is arranged below the blazed grating 7 of the dye laser resonant cavity, and together with the dye pool 8, the blazed grating 7 and the output coupling mirror 9, forms a laser resonant cavity of Littman-Metcalf configuration, as shown in FIG5 .
其中，Littman-Metcalf构型的激光谐振腔内的双波长染料激光是按如下过程产生：The dual-wavelength dye laser in the laser resonator of the Littman-Metcalf configuration is generated according to the following process:
染料池8中装有适当浓度的尼罗红/乙醇溶液，作为染料激光器的增益介质；经过532nm抽运光源的侧面照射，在染料池8中受激辐射产生荧光，在染料激光谐振腔中稳定振荡，最终形成向右输出单一波长的染料激光；The dye pool 8 is filled with a Nile red/ethanol solution of appropriate concentration as the gain medium of the dye laser; after being irradiated from the side by a 532nm pumping light source, stimulated radiation in the dye pool 8 generates fluorescence, which oscillates stably in the dye laser resonant cavity, and finally forms a dye laser with a single wavelength output to the right;
如图6所示，为实施例2中染料激光谐振腔中双波长振荡激光的轨迹示意图。将装有尼罗红的乙醇溶液的染料池8顺时针旋转，并与染料激光的主光轴形成一定角度，使得染料激光谐振腔中同时存在直线形激光轨迹103与环形激光轨迹104；二者在腔内保持稳定并来回振荡，最终形成双波长激光输出。As shown in Fig. 6, it is a schematic diagram of the trajectory of the dual-wavelength oscillating laser in the dye laser resonant cavity 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 the dye laser, so that a linear laser trajectory 103 and a ring laser trajectory 104 exist in the dye laser resonant cavity at the same time; the two remain stable in the cavity and oscillate back and forth, and finally form a dual-wavelength laser output.
Littman-Metcalf构型的激光谐振腔中双波长染料激光是按如下步骤进行波长调谐：The wavelength tuning of the dual-wavelength dye laser in the laser resonator of the Littman-Metcalf configuration is carried out according to the following steps:
步骤1b、保持闪耀光栅7的角度与位置不变，通过旋转全反镜15来同时改变直线形激光轨迹103与环形激光轨迹104的入射角，从而改变直线形激光轨迹103与环形激光轨迹104在染料激光谐振腔中的振荡波长；当染料池沿顺时针倾斜微小角度时，谐振腔中由于全内反射TIR同时存在两种激光轨迹，即直线形激光轨迹103与环形激光轨迹104。它们保持稳定并来回振荡，最终形成双波长激光输出。图7为实施例2中通过旋转全反镜2.1°实现的从634.4nm至663.3nm的连续可调谐双波长激光输出，调谐范围覆盖29nm。Step 1b, keep the angle and position of the blazed grating 7 unchanged, and change the incident angles of the linear laser track 103 and the annular laser track 104 at the same time by rotating the total reflection 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; when the dye pool is tilted clockwise at a small angle, two laser tracks, namely the linear laser track 103 and the annular laser track 104, exist simultaneously in the resonant cavity due to total internal reflection TIR. They remain stable and oscillate back and forth, eventually forming a dual-wavelength laser output. Figure 7 shows a continuously tunable dual-wavelength laser output from 634.4nm to 663.3nm achieved by rotating the total reflection mirror 2.1° in Example 2, and the tuning range covers 29nm.
步骤2b、保持闪耀光栅7与全反镜15的旋转角度不变，将全反镜15由远到近向闪耀光栅7平移，从而在平移范围内连续改变双波长染料激光的波长间隔，以实现波长调谐。不改变闪耀光栅7与全反镜15的角度，且保持闪耀光栅7的位置不变，通过平移全反镜15，改变其与闪耀光栅7之间的距离，可以得到波长间隔在1.5nm~4nm范围内连续改变的双波长激光光源，其调谐结果如图8所示。经过倍频后，其双波长间隔为0.75nm~2nm，同样可为差分吸收激光雷达光源的制备提供重要参考依据。Step 2b, keep the rotation angle of the blazed grating 7 and the total reflection mirror 15 unchanged, and translate the total reflection mirror 15 from far to near to the blazed grating 7, so as to continuously change the wavelength interval of the dual-wavelength dye laser within the translation range to achieve wavelength tuning. Without changing the angle between the blazed grating 7 and the total reflection mirror 15, and keeping the position of the blazed grating 7 unchanged, by translating the total reflection mirror 15 and changing the distance between it and the blazed grating 7, a dual-wavelength laser light source with a wavelength interval continuously changing in the range of 1.5nm~4nm can be obtained, and the tuning result is shown in Figure 8. After frequency doubling, the dual wavelength interval is 0.75nm~2nm, which can also provide an important reference for the preparation of differential absorption laser radar light source.
综上所述，本申请一种用于大气环境中有害气体检测的差分吸收激光雷达光源与产生双波长激光的方法，利用有机激光染料尼罗红的溶剂化显色特性与优秀的激光特性，在光栅谐振腔与染料池构成的全内反射系统中，通过精密调谐，实现620nm~700nm的大范围双波长连续可调谐激光输出；同时利用非线性光学倍频系统实现对输出激光的二倍频、三倍频，得到190~220nm以及290~330nm的双波长激光光源，且波长间隔在0.2~2.5nm范围内连续可调，可以用于差分吸收激光雷达整机研发，为大气环境中二氧化硫、二硫化碳等有害气体的痕量检测提供光源技术的重要支持。In summary, the present application provides a differential absorption laser radar light source and a method for generating dual-wavelength laser for detecting harmful gases in an atmospheric environment. The method utilizes the solvatochromic properties and excellent laser properties of the organic laser dye Nile Red to achieve a wide range of 620nm~700nm dual-wavelength continuously tunable laser output through precise tuning in a total internal reflection system consisting of a grating resonant cavity and a dye pool. At the same time, a nonlinear optical frequency doubling system is used to achieve double and triple frequency of the output laser to obtain a dual-wavelength laser light source of 190~220nm and 290~330nm, and the wavelength interval is continuously adjustable in the range of 0.2~2.5nm. The method can be used for the research and development of a differential absorption laser radar system, and provide important light source technology support for trace detection of harmful gases such as sulfur dioxide and carbon disulfide in the atmospheric environment.
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