Sb2S3 as a low-loss phase-change material for mid-IR photonics

We study the mid-IR optical properties of Sb 2 S 3 – a phase-change material (PCM) with high potential for mid-IR integrated photonics. We show that Sb 2 S 3 exhibits a high refractive index contrast Δn ≈ 1 between its two phases and an extinction coefficient k below 10 −2 at mid-IR wavelengths (up to ∼10 µm). We study the impact of 100 nm Sb 2 S 3 cladding on SiGe-on-Si waveguides and experimentally show that it brings additional propagation loss below 1 dB/cm in the 3.3–3.9 µm wavelength range in both phases. These findings pave the way for new uses of Sb 2 S 3 in mid-IR integrated photonics.