Air-Spaced Cylindricalprisms for Fast Thermo-Optic Switching

This paper reports a design of double micromachined silicon cylindrical prisms separated by a thin air gap to enable fast thermo-optic switching. The fabricated structure has obtained an extinction ratio of 29.8 dB. This design is advantageous over conventional micromechanical switches for the absence of mechanical stability problems. The use of total internal reflection significantly enhances the sensitivity of switching to small refractive index change of only 5.2 times 10^-3, which allows an on-off switching at 2.2 mus by localized heating through a thermal resistor patterned on top of the prism.