连续激光光腔衰荡法精确测量高反射率

提出了基于宽谱半导体激光器连续激光光腔衰荡法测量高反射率的方法,给出了方波调制连续激光光腔衰荡法理论。采用锁相技术记录光腔输出信号一次谐波的振幅和相位,由振幅和相位随调制频率的变化曲线分别拟合衰荡时间。给出了不同腔长下两种拟合方式分别得到的衰荡时间,最终确定腔镜反射率为99.70%,误差小于0.01%。由频域拟合方式得到反射率结果,使可靠性得到提高。与脉冲激光光腔衰荡法相比,采用连续半导体激光器作光源,大大降低了成本,且由于光束质量高,更有利于提高测量精度。

Continuous-Wave Cavity Ring-Down Technique for Accurate Measurement of High Reflectivity

A continuous-wave cavity ring-down spectroscopy (CW-CRDS) technique employing a broad-band diode laser is developed for the high reflectivity measurement. The theory of square-wave modulated CW-CRDS is presented. Both amplitude and phase shift of the first harmonic of the CRDS signal, measured at an appropriate frequency range, are detected by a lock-in method and fitted to obtain the ring-down time and the reflectivity. The measurements are repeated with different cavity spacings and the reflectivities are determined by the frequency-domain fitting methods. The reflectivity of the cavity mirror is determined to be 99.70%±0.01%. The agreement among the reflectivities determined with the frequency-domain fitting techniques indicates the high reliability of the CW-CRDS technique. Compared with the pulsed CRDS approach, the CW-CRDS technique is simple, low-cost and highly precise due to the use of a CW diode laser with high beam quality.