An efficient total-internal-reflection optical switch based on reverse breakdown of pn junction and thermo-optic effect in silicon

Abstract

We propose and experimentally demonstrate a new type of silicon total-internal-reflection (TIR) optical switch by embedding of pn junction providing both function of a reflector and a thermo-optic heater simultaneously. The TIR switch is composed of asymmetrically y-branched multimode waveguides with a waveguide width of 5 μm for a switching node. The incident light is tapered from singlemode waveguides for the fundamental mode propagation and normally reflected without bias at the pn diode based on free carrier plasma dispersion effect. The switching operation is achieved by thermo-optic effect which can compensate the decreased refractive index at the doped region based on reverse breakdown of pn junction. At the rest of switch, extinction ratio of 8 dB and insertion loss of 5.6 dB are achieved with a 3° and 1-μm-thick reflector, By applying-50 V to pn diode, we achieved the perfect switching operation with an extinction ratio of 11.6 dB, an insertion loss of-4.1 dB and a thermal heating power of 152.5 mW.