Optical switch based on multimode interference coupler

An optical switch based on the multimode interference (MMI) coupler is demonstrated in this letter. The device is designed and fabricated in polymeric materials and the thermooptic (TO) effect of polymers, which has a negative TO coefficient, is employed to change the self-imaging effect of a side-heated MMI coupler and realize optical switching. The switching power is only 22 mW. The experimental results show that the crosstalk of the switch is about -20 dB at both the cross and bar states.

I. Introduction

In RECENT years, there has been growing interest in multimode interference (MMI) waveguide couplers [1]–[11]. Fig. 1. Schematic diagram of the MMI-based optical switch. The channel waveguide is composed of polymeric materials and the heater is set on the polymeric films. Fig. 2. Operation principle of the side-heated MMI coupler. The simulation is done by using the BPM. Fig. 3. Simulated operation of the MMI-based optical switch: (a) the cross state in which no electric power is applied and (b) the bar state in which the heater is powered. A lot of optical components based on MMI couplers was reported, including optical power splitters [5], [6], couplers [7], optical filters [8], optical multiplexers/demultiplexers [9], variable optical attenuators [10], as well as optical switches [11], [12]. In those optical switches [11], [12], MMI couplers were commonly used as a passive part, i.e., a 3-dB coupler and/or an interference coupler. In this letter, we demonstrate a novel optical switch, in which the MMI coupler is used as the central part and the thermooptic (TO) effect is applied to change the self-imaging effect of the side-heated MMI coupler and then achieve optical switching.