  Phase change materials (PCMs) have long been used as a storage medium in
rewritable compact disk and later in random access memory. In recent years, the
integration of PCMs with nanophotonic structures has introduced a new paradigm
for non-volatile reconfigurable optics. However, the high loss of the
archetypal PCM Ge2Sb2Te5 in both visible and telecommunication wavelengths has
fundamentally limited its applications. Sb2S3 has recently emerged as a
wide-bandgap PCM with transparency windows ranging from 610nm to near-IR. In
this paper, the strong optical phase modulation and low optical loss of Sb2S3
are experimentally demonstrated for the first time in integrated photonic
platforms at both 750nm and 1550nm. As opposed to silicon, the thermo-optic
coefficient of Sb2S3 is shown to be negative, making the Sb2S3-Si hybrid
platform less sensitive to thermal fluctuation. Finally, a Sb2S3 integrated
non-volatile microring switch is demonstrated which can be tuned electrically
between a high and low transmission state with a contrast over 30dB. Our work
experimentally verified the prominent phase modification and low loss of Sb2S3
in wavelength ranges relevant for both solid-state quantum emitter and
telecommunication, enabling potential applications such as optical field
programmable gate array, post-fabrication trimming, and large-scale integrated
quantum photonic network.
