A Segmented Heater-Driven, Low-Loss, Reconfigurable Photonic Phase-Change Material-Based Phase Shifter

TL;DR

This paper introduces a novel segmented heater design for PCM-based photonic phase shifters, enabling hundreds of precise, low-loss phase levels with improved linearity and control over traditional uniform heater configurations.

Contribution

The work presents a new segmented heater architecture that achieves multilevel phase shifting with enhanced linearity and reduced insertion loss compared to conventional designs.

Findings

Segmented heater enables hundreds of well-spaced phase levels.

Achieves a low insertion loss of 0.6 dB.

Demonstrates superior performance over uniform heater designs.

Abstract

Phase-change material (PCM)-based non-volatile multilevel phase shifters are key components in photonic integrated circuits. Electrically, multiple phase levels can be encoded by controlling the heater power and employing different microheater architectures to induce varying degrees of PCM amorphization. However, encoding a large number of levels is not straightforward. In this work, we first investigate a phase shifter structure based on a GeSe PCM integrated on top of a silicon-on-insulator waveguide, employing a simple rectangular-shaped heater under pulse-width modulation (PWM). We numerically demonstrate that multilevel phase shifts can be achieved because of non-uniform heating in the GeSe PCM layer. However, the resulting phase levels for this basic configuration are highly non-linear because of the uniform power dissipation along the light propagation direction characterized by the same cross-section. To overcome this limitation, we designed a novel PCM-based phase shifter with a segmented heater whose width gradually increases along the light propagation direction. This configuration enables the encoding of hundreds of well-spaced phase levels between 0 and $\pi$, facilitated by smoother amorphization arising from the combined effects of non-uniform heating across segments and within each segment, while achieving an insertion loss of only 0.6 dB in the worst case. Furthermore, when evaluating both heater architectures under pulse amplitude modulation (PAM) at a fixed pulse duration, we observe behavior consistent with the trends observed for PWM, confirming the superior performance of the segmented heater design.