一种新的USED CARS相位匹配实现技术

相位匹配是相干反斯托克斯拉曼散射(CARS)测温的关键技术之一，针对现有非稳腔空间增强探测(USED)相位匹配方式中存在的背景辐射大、光路调试不灵活以及斯托克斯光利用率低的不足，提出了一种新的USED CARS相位匹配实现方案：即设计一个与斯托克斯光斑大小相当、呈45°斜角的斜反镜，用于反射全部斯托克斯光，并以斜反镜代替传统USED CARS中的环反镜，让泵浦光从斜反镜后方射入，从而形成USED相位匹配方式。新的USED CARS相位匹配方案中：由于斜反镜面积相对于环反镜大为减小，使得因反射而进入光路的背景辐射大幅降低;斜反镜本身可作为光路调节元件，因而增加了光路调试灵活度;斯托克斯光被斜反镜全部反射用于产生CARS信号，提高了其利用效率。基于平面火焰炉稳态火焰开展的测温实验结果表明：新的USED CARS相位匹配方案不但克服了传统USED CARS中存在的不足，而且具有更小的标准差，是一种更为有效的相位匹配方法。

New Implementation Technique of USED Phase Matching for CARS

Phase matching is one of the key techniques in temperature measuring by coherent anti-Stokes Raman scattering (CARS). In order to overcome the disadvantages of large background radiation, inconvenient adjusting and low-usage of Stokes laser energy in traditional unstable-resonator spatially enhanced detection (USED) phase matching, new implementation technique of USED CARS phase matching is researched. A piece of oblique reflector, which is as big as the Stokes spot and with an angle of 45 degrees, was used to replace the annular reflector in traditional USED to reflect the Stokes fully. Then, pump laser shines from the back of the oblique reflector to satisfy USED phase matching with reflected Stokes. In the new USED CARS phase matching, background radiation caused by reflecting was weakened for the area of oblique reflector is smaller than that of annular reflector; Furthermore, oblique reflector can be used as an adjusting component in experiments which can make beam path adjusting more easier; Finally, Stokes laser was in high-usage for it was fully reflected by the oblique reflector. Temperature measuring results on laminar flame suggest that new USED CARS phase matching has lower standard deviation and it is a more effective phase matching method.