采用双离子溅射的方法，在硅、石英基底上制备了单层Ta2O5、SiO2及双层Ta2O5/SiO2光学薄膜。结合Cauchy色散模型，利用石英基底上单层Ta2O5及双层Ta2O5/SiO2薄膜透射光谱曲线，采用改进的遗传单纯形混合算法，获得了Ta2O5和SiO2薄膜材料在400~700 nm波段的光学常数。结果表明，理论分析值与实验测量值取得了很好的一致性，拟合出的单层Ta2O5薄膜折射率误差小于0.001，膜层厚度误差不超过1 nm；双层Ta2O5/SiO2薄膜最大折射率误差小于0.004，最大厚度误差小于2.5 nm。此外，还对400 ℃高温环境下双层Ta2O5/SiO2薄膜的微观结构、应力、表面形貌及光学性能变化进行了研究。

An optical feedback cavity ring-down technique (OF-CRD), in which the retro-reflection of the ring-down cavity (RDC) is re-injected into the oscillator cavity of a Fabry-Perot diode laser and causes the spectral fluctuation of the diode laser, is developed for ultra-high reflectivity measurement of optical mirrors. Due to the optical feedback-induced spectral fluctuation, the spectral line of the diode laser is occasionally in resonance with one or more RDC modes, resulting in an enhancement of the coupling efficiency of the laser power into the RDC and the occurrence of resonance peaks in the amplitude of the CRD output signal. These resonance peaks are employed in a CRD experimental setup for high reflectivity measurement of optical mirrors at 1064 nm. In the CRD setup, a pair of cavity mirrors, with reflectivities higher than 99.99%, is used. The reflectivity of both cavity mirrors is determined to be 99.99606% with an uncertainty of only 0.00003%. With a folded cavity configuration, the reflectivities of three mirrors with incident angles of 0, 22.5, and 45 degrees, are measured, and the results are 99.9459±0.0004%, 99.9755±0.0005%, and 99.9621±0.0006%, respectively.