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.

根据光腔衰荡光谱(CRDS)技术原理,建立了直型光腔下3.3 μm波长反射率测试实验装置。测试了一对反射率为99%的腔镜,测试精度为10-4。利用该装置得到不同腔长下激光在腔内振荡的时间衰减曲线。根椐衰减曲线计算得到腔镜反射率,分析其均方根误差为2.25×10-4。就透镜位置变化以及在光路中加光阑的方式改变腔内模式,研究其对衰荡实验的影响。实验发现,透镜的相对位置在20 mm调节范围内得到的反射率测试均方根误差为2.55×10-5。另外发现使用加在光路中的光阑可以改善光腔模式匹配,减小衰减时间的拟合误差。

根据光腔衰荡光谱技术(CRDS)原理,使用中红外光参变振荡器(OPO)为光源建立了直腔与折叠腔相结合的中红外波段3.6 μm 反射率测量实验装置,用于研究中红外波段的高反射膜反射率,测试精度为10-4。使用直型衰荡光腔测试了三对不同薄膜材料设计镀制的高反射腔镜的反射率,并选择了一对腔镜用于实验装置中。采用该装置精确测试了不同薄膜材料镀制的高反射膜的反射率,包括YbF3/ZnS,YbF3 /ZnSe多层膜,以及由银加保护膜镀制的反射镜。研究表明,中红外波段介质膜的反射率可达到R>0.9990,其中由YbF3/ZnSe镀制在硅基底上的多层介质膜3.6 μm反射率可达到99.96％。