The dramatic optical property change of optical phase change materials (O-PCMs) between their amorphous and crystalline states potentially allows the realization of reconfigurable photonics devices with low power consumption, such as optical switches and routers, reconfigurable meta-optics, displays, and photonic memories. However, conventional O-PCMs, such as VO2 and Ge2Sb2Te5, are inherently plagued by their excessive optical losses even in dielectric states, limiting their optical performance and hence application space. In this talk, we present the development of a new group of O-PCMs and their implementations in novel photonic devices. Ge-Sb-Se-Te (GSST), obtained by partially substituting Te with Se in traditional GST alloys, feature unprecedented broadband optical transparency covering the telecommunication bands to LWIR. Capitalizing on the dramatically-enhanced optical performance, novel non-volatile, reconfigurable on-chip photonics devices and architectures are demonstrated. GSST-integrated Si photonics based on the material innovation and novel “non-perturbative” designs exhibit significantly improved switching performance over state-of-the-art GST-based approaches. The technology is further scalable to realize non-blocking matrix switches with arbitrary network complexity, paving the path towards high performance reconfigurable photonics chips.
Optical phase change materials (O-PCMs) are a unique class of materials which exhibit extraordinarily large optical property change (e.g. refractive index change > 1) when undergoing a solid-state phase transition. These materials, exemplified by Mott insulators such as VO2 and chalcogenide compounds, have been exploited for a plethora of emerging applications including optical switching, photonic memories, reconfigurable metasurfaces, and non-volatile display. These traditional phase change materials, however, generally suffer from large optical losses even in their dielectric states, which fundamentally limits the performance of optical devices based on traditional O-PCMs. In this talk, we will discuss our progress in developing O-PCMs with unprecedented broadband low optical loss and their applications in novel photonic systems, such as high-contrast switches and routers towards a reconfigurable optical chip.
We demonstrate designs of dielectric-filled anti-reflection coated (ARC) two-dimensional (2D) metallic photonic
crystals (MPhCs) capable of omnidirectional, polarization insensitive, wavelength selective emission/absorption. Up to
26% improvement in hemispherically averaged emittance/absorptance below the cutoff wavelength is observed for
optimized hafnium oxide filled 2D tantalum (Ta) PhCs over the unfilled 2D Ta PhCs. The optimized designs possess
high hemispherically averaged emittance/absorptance of 0.86 at wavelengths below the cutoff wavelength and low
hemispherically averaged emittance/absorptance of 0.12 at wavelengths above the cutoff wavelength, which is extremely
promising for applications such as thermophotovoltaic energy conversion, solar absorption, and infrared spectroscopy.