Micromachined Optical Matrix Switch for WDM Optical Communication Networks

本研究的目的是利用微机械加工技术制作适用于波分复用(WDM)光通信网络的N×N光矩阵开关。该开关由一个芯片上的N×N个可移动反射镜和2N个用于光纤对准的V型槽组成。来自N个输入光纤的光束在适当的位置被N个反射镜反射，以将光束连接到N个输出光纤。(1)微机械加工预对准微镜和V型槽用湿法各向异性刻蚀单晶硅同时制备出垂直于衬底的薄微镜和具有精确45度角的V型槽。通过在V型槽中插入纤维，可以很容易地实现猪尾巴。由于由晶体的图形取向确定了精确的取向，因此插入损耗小于1d B。采用干法各向异性腐蚀和湿法各向异性腐蚀相结合的方法，获得了较高的微镜堆积密度。由于输入输出端之间的距离变小，耦合损耗减小。(2)自锁存电磁致动器和阵列致动器通过电磁/永磁体的组合拉动固定在动镜上的坡莫合金片。永磁体使镜子能够进行自锁操作。因为能量耗散只发生在从一种状态转换到另一种状态时，所以我们可以最小化能量消耗。制作了与阵列反射镜匹配的阵列线圈。平面线圈直径500~800微米，厚度20~50微米。在线圈中产生2A的脉冲电流就可以产生足够的磁场来驱动。(3)光学评价。单模光纤的插入损耗为0.8dB，开关速度为2ms，对比度为50db，工作寿命超过2000万次。

The purpose of this research is to fabricate an N x N optical matrix switch by micromachining technologies for WDM (wave division multiplex) optical communication networks. The switch consists of N x N movable mirrors on a chip and 2N V-grooves for optical fiber alignment. The optical beams from N input fibers are reflected by N mirrors at appropriate positions to connect light beams to N output fibers. We have obtained the following results :(1) Pre-aligned micromirrors and V-grooves by micromachiningThin micromirrors that are vertical to the substrate and V-grooves that have exact 45 degree angles were fabricated simultaneously by wet anisotropic etching of single crystal silicon. Easy pig-tailing was possible by inserting fibers in V-grooves. The insertion loss was less than 1 dB because of precise alignment determined by crystal graphic orientation. Higher packing density of micromirrors was achieved by combining dry anisotropic etching and wet anisotropic etching subsequently. The coupling loss decreased because the distance between input and output ports became shorter.(2) Self-latching electromagnetic actuation and arrayed actuatorA permalloy piece attached to the moving mirror was pulled by a combined electro/permanent magnet. The permanent magnet enabled the self-latching operation of the mirror. Because energy dissipation occurs only at the switching from one state to another, we could minimize the energy consumption. Arrayed coils that match the arrayed mirrors were fabricated. The planar coil was 500-800 micrometers in diameter and 20-50 micrometers in thickness. We could generate enough magnetic field for actuation with 2 A pulse current in the coil.(3) Optical evaluationA 2 x 2 elementary switch was fabricated and tested. It had insertion loss of 0.8 dB with single mode fibers, switching speed of 2 ms, contrast of 50 dB and lifetime of more than 20 million operations.