Ultra-compact, self-holding asymmetric Mach-Zehnder interferometer switch using Ge2Sb2Te5 phase-change material

An asymmetric Mach-Zehnder interferometer optical switch using phase-change material (PCM) is reported. In this switch, two Ge2Sb2Te5 thin films, each 1 mu m in diameter, are deposited on a Si waveguide, and are used as phase shifters. The PCM can be reversibly switched between the amorphous and crystalline states. The difference in refractive index between the two states is very large, typically more than 2. Therefore, an optical switch using the PCM can be very small. The switching operation is successfully demonstrated by laser pulse irradiation. The maximum extinction ratio is 26.7 dB, and 2.2-nm peak wavelength shift is verified.