Switching Operation in Tunable Add-Drop Multiplexer With Si-Grating Waveguides Featuring Ferroelectric Liquid Crystal Cladding

We propose a tunable add–drop multiplexer in a silicon waveguide Mach–Zehnder interferometer that has a sampled grating structure and ferroelectric liquid crystal (FLC) cladding, which we fabricated. The effective coupling coefficient that was decreased by the sample grating structure led to a narrow stop bandwidth in the grating waveguide. The FLC material caused a change in the Bragg conditions for lightwave propagation in the waveguide according to the direction of the electric field applied to FLC. The switching operation of the fabricated device, which separated the input and reflected signals without a circulator, was successfully demonstrated. The time response, dependence on voltage, and memory operation of the fabricated device based on FLC characteristics are also reported.

I. Introduction

The continuous increase in telecommunications traffic, which has included data communication with smart phones and tablet devices, will require photonic networks that are high speed, have large capacity, and are flexible. Wavelength channels in wavelength division multiplexing (WDM) systems in photonic networks can be routed and reconfigured optically at nodes, which avoids energy intensive and extensive optical-to-electrical conversion and electrical switching. Tunable optical filters, wavelength selective switches, and reconfigurable optical add-drop multiplexers are crucial components in such photonic nodes to control optical paths.