Non-Volatile Reconfigurable Transmissive Notch Filter Using Wide Bandgap Phase Change Material Antimony Sulfide

Abstract

Reconfigurable free-space metasurfaces with subwavelength-scale tunable nano-scatterers can manipulate light for many applications ranging from bio-medical imaging, light detection and ranging to optical computing. Several endeavors have been made to achieve tunable metasurfaces using thermo-optic, electro-optic effects, liquid crystals, and phase change materials (PCMs). PCMs stand out, particularly for low-tuning frequency and low-power consumption applications, thanks to their non-volatile nature and drastic index modulation, leading to zero-static power and a small footprint. Antimony sulfide (Sb2S3) is an emerging low-loss PCM with the widest bandgap reported so far, enabling operation at low wavelengths down to similar to 600 nm in the visible spectrum. In addition, Sb2S3 has slow crystallization speed, which enables amorphization of large-volume Sb2S3 without unintentional recrystallization. This makes Sb2S3 suitable for application in reconfigurable metasurfaces, where the switching area (usually > hundreds of mu m(2)) is significantly larger than photonic integrated circuits (tens of mu m(2)). Herein, we experimentally demonstrate an electrically tunable notch filter at a wavelength of similar to 1150 nm on a Sb2S3-cladded silicon-on-sapphire platform. The notch filter is enabled by a 2-dimensional symmetry-protected quasi-bound-state-in-the-continuum (quasi-BIC) metasurface. We experimentally observed a quality factor of up to similar to 200 and demonstrated reversible tuning of a record large volume (4.5 mu m(3)) of Sb2S3. Thanks to the large modulation provided by Sb2S3, we observed a resonance shift as high as similar to 4 nm in situ using a doped silicon microheater. Our work paves the way for compact and low-power nonvolatile notch filters. Moreover, due to the low loss of Sb2S3 in the visible, this work also lays the foundation for phase-only modulation in the visible using PCMs.