Reversible single-pulse laser-induced phase change of Sb$_2$S$_3$ thin films: multi-physics modeling and experimental demonstrations

TL;DR

This paper investigates the physics of laser-induced reversible phase changes in Sb$_2$S$_3$ thin films, combining modeling and experiments to determine energy thresholds and effects of material properties for optical switching applications.

Contribution

It provides a comprehensive multi-physics analysis of laser-induced phase transitions in Sb$_2$S$_3$, including thresholds, effects of polycrystallinity, and strategies for thick layers, advancing understanding for photonic device integration.

Findings

Identified laser energy thresholds for amorphization and recrystallization.

Showed impact of polycrystallinity and anisotropy on switching thresholds.

Addressed challenges in amorphizing thick Sb$_2$S$_3$ layers.

Abstract

Phase change materials (PCMs) have gained a tremendous interest as a means to actively tune nanophotonic devices through the large optical modulation produced by their amorphous to crystalline reversible transition. Recently, materials such as Sb$_2$S$_3$ emerged as particularly promising low loss PCMs, with both large refractive index modulations and transparency in the visible and NIR. Controlling the local and reversible phase transition in this material is of major importance for future applications, and an appealing method to do so is to exploit pulsed lasers. Yet, the physics and limits involved in the optical switching of Sb$_2$S$_3$ are not yet well understood. Here, we investigate the reversible laser-induced phase transition of Sb$_2$S$_3$, focusing specifically on the mechanisms that drive the optically induced amorphization, with multi-physics considerations including the optical and thermal properties of the PCM and its environment. We theoretically and experimentally determine the laser energy threshold for reversibly changing the phase of the PCM, not only between fully amorphous and crystalline states but also between partially recrystallized states. We then reveal the non-negligible impact of the material's polycrystallinity and anisotropy on the power thresholds for optical switching. Finally, we address the challenges related to laser amorphization of thick Sb$_2$S$_3$ layers, as well as strategies to overcome them. These results enable a qualitative and quantitative understanding of the physics behind the optically-induced reversible change of phase in Sb$_2$S$_3$ layers.