High-Efficiency Silicon Photonic Modulator Using Coupled Bragg Grating Resonators

Abstract

In this, we propose a novel design of a silicon photonic modulator that has a high modulation efficiency and that is tolerant to temperature variations. A series of phase-shifted Bragg gratings are placed in each arm of a Mach–Zehnder interferometer in order to provide enhanced phase modulation. The slow light effect in these ultra-compact coupled resonators improves phase modulation efficiency compared to conventional silicon phase shifters. These Bragg grating cavities are designed such that the optical bandwidth is increased compared to other coupled resonators, such as micro-rings. This improved bandwidth reduces the temperature sensitivity of the devices. We present in detail how to optimize these modulators considering properties, such as modulation efficiency ( Vπ × L ), optical modulation amplitude, and optical bandwidth ( $\Delta \lambda _{BW}$ ); the latter property determines the operating temperature range (Δ T ). As examples, we present two designs that meet different target specifications for short-reach or long-haul applications. We further provide a model, based on the coupled mode theory, to investigate the dynamic response of the proposed modulators. A large signal analysis is performed using finite-difference time domain in order to simulate on/off keying modulation and eye diagrams up to 110 Gb/s.