Phase-shifter using submicron silicon waveguide couplers with ultra-small electro-mechanical actuator

Phase shifter is an important part of optical waveguide circuits as used in interferometer. However, it is not always easy to generate a large phase shift in a small region. Here, a variable phase-shifter operating as delay-line of silicon waveguide was designed and fabricated by silicon micromachining. The proposed phase-shifter consists of a freestanding submicron-wide silicon waveguide with two waveguide couplers and an ultrasmall silicon comb-drive actuator. The position of the freestanding waveguide is moved by the actuator to vary the total optical path. Phaseshift was measured in a Mach-Zehnder interferometer to be 3.0π at the displacement of 1.0 urn at the voltage of 31V. The dimension of the fabricated device is 50μm wide and 85μm long.