VERTICAL MIRRORS FABRICATED BY DEEP REACTIVE ION ETCHING FOR FIBEROPTIC SWITCHING APPLICATIONS

We report on vertical mirrors fabricated by deep reactive ion etching of silicon, The mirror height is 75 mu m, covering the fiber core of a single-mode fiber when the latter is placed into a groove of equal de pth and etched simultaneously with the mirror, To obtain a uniform etc h depth, etching is stopped on a buried oxide layer, Using the buried oxide as a sacrificial layer allows to fabricate mirrors with suspensi on and actuation structures as well as fiber-alignment grooves in one and the same processing step. A minimal mirror thickness of 23 mu m wa s achieved, resulting in an aspect ratio higher than 30, The verticali ty was better than 89.3 degrees, In the upper part of the mirror a sur face roughness below 40 nm rms was obtained, At a wavelength of 1300 n m the reflectivity of the aluminum-coated mirrors was measured to be h igher than 76%. Using a reactive ion etched mirror we have fabricated an optical fiber switch with electrostatic actuation, The coupling los s in the bar state of two packaged prototypes was between 0.6 and 1.7 dB and between 1.4 and 3.4 dB in the cross state, The switching time i s below 0.2 ms.