[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.