Micro-opto-mechanical 2×2 switch for single-mode fibers based on plasma-etched silicon mirror and electrostatic actuation

This paper reports on a new optical 2×2 switch for single-mode fibers. The switching principle is based on a vertical micro-mirror which can be moved into the optical path to switch light between two pairs of fibers. The micromirror switch is designed for by-pass applications. When power is turned off the mirror spring back into its rest position and brings the switch into its bar state. This operation is very reliable, since the moving parts do not get into contact. Fabrication is based on the silicon micromachining technology, which allows to integrate the switching mirror, its electrostatic actuator and the alignment grooves for the fibers on the same chip. The mechanical switching principle brings with it a number of optical advantages such as a high crosstalk attenuation above 50 dB and wavelength and polarization insensitivity. At a wavelength of 1310 nm a minimum insertion loss of 0.6 dB was measured in the bar state, i.e. when the mirror is out of the optical path. In the cross state the light is reflected on the gold coated micro-mirror which has a reflectivity of about 80%. The insertion loss of the bar state was thus higher and a minimum value of 1.6 dB could be obtained. The switching time was well below 1 ms