Compact and fast-response optical switch based on complex refractive index engineering

Abstract

The optical switch is a crucial device in integrated photonic circuits. Among the various types of optical switches available, the on–off Mach–Zehnder interferometer is one of the most widely used structures. However, compared with other structures, such as a microring, the large footprint of a Mach–Zehnder interferometer significantly restricts the integration density. In this paper, we propose a compact Mach–Zehnder interferometer based on complex refractive index engineering. By manipulating the complex index of the material in the structure, the lateral size of the device can be compressed down to only 3.25 µm. Moreover, the reducing of the space between heaters and waveguides leads to a fast response of only 1.9 µs. Our work offers a new, to the best of our knowledge, approach of a compact integrated optical switch, and opens a new avenue for application of absorbing materials.