Figure of merit of phase change materials for Mach-Zehnder interferometer-based and directional-coupler-based optical switches

For further improvement of phase change material switches, relationships between optical characteristics of phase change materials(PCM) and the performance of optical switches were investigated. PCM optical switch is optimized for the both states of the insertion loss to be balanced. With optimized three-channel directional coupler switch, the refractive index difference between amorphous and crystalline state was inversely proportional to the insertion loss.