Tunable Optical Filters for Wavelength Division Multiplexing by Using High-Precision Single-Crystal Piezoelectric Actuators

本课题的研究目的是利用高精度LiNbO_3压电致动器开发一种适用于波分复用的高性能可调谐滤光片。本课题的研究结果如下：(1)设计并制作了一种内置在一对光纤连接器卡箍内的法布里-珀罗可调谐光滤波器。在光纤的抛光端形成高反射率的介电镜，形成一个Fabry-Perot标准子，腔长由两个由140个<s:1>旋转y型切割LiNbO_3单晶制成的压电致动器来改变。得到了自由光谱范围为14nm、精细度为140 nm、频宽为0.1nm的可调谐滤光片。然而，观察到少量的迟滞，这可能是由卡箍和金属套筒之间的摩擦引起的。(2)提出了另一种法布里-珀罗可调谐滤波器，该滤波器采用一对带有介电镜的石英片作为标准子。这些反射镜被放置在准直光束的路径上，标准子间距由140个<s:1>旋转y型切割LiNbO_3单晶制成的弯曲或拉伸驱动器控制。这些过滤器工作良好，但需要进一步研究以提高过滤器的性能。

The purpose of this research project is to develop a high-performance tunable optical filters suitable for wavelength division multiplexing by using high-precision LiNbO_3 piezoelectric actuators. The results obtained in this project are as follows :(1) A Fabry-Perot tunable optical filter built in a pair of optical-fiber connector ferrules has been designed and fabricated. Dielectric mirrors of high reflectivity are formed on a polished end of fibers to form a Fabry-Perot etalon, and the cavity length is varied by two piezoelectric actuators made of 140ﾟ rotated Y-cut LiNbO_3 single crystals. A tunable optical filter having a free spectral range of 14nm, a finesse of 140, and a FWHM of 0.1nm has been obtained. However, a small amount of hysteresis is observed that might be caused by friction between the ferrules and a metallic sleeve.(2) Another type of Fabry-Perot tunable filter that employs a pair of quartz plates with dielectric mirrors as an etalon is presented. The mirrors are placed in a path of a collimated optical beam, and the etalon spacing is controlled by a bending or a stretching actuator made of 140ﾟ rotated Y-cut LiNbO_3 single crystals. These filters work well, but further investigation is required to improve the filter performance.