The dramatic optical property change of optical phase change materials (O-PCMs) allows the realization of tunable optical and photonic devices with enhanced optical functionalities, such as reconfigurable optics, optical switches and routers, and photonic memories. Recently we developed a new class of non-volatile O-PCM, Ge-Sb-Se-Te (GSST), which features unprecedented broadband optical transparency (1-18.5 micron), large optical contrast (dn = 2) and significantly improved glass forming ability. Leveraging the remarkable material property and advanced design methods, we develop a suite of reconfigurable, all-dielectric metasurface optics with unprecedented performance. In one example, a focal length tunable transmissive metalens is demonstrated showing diffraction-limited imaging performance and complete optical function switching during the phase transition, which sets the foundation for ultra-compact, solid-state, tunable meta-optical systems.
On-chip optical isolators constitute an essential building block for photonic integrated circuits. Monolithic magnetooptical isolators on silicon, while featuring unique benefits such as scalable integration and processing, fully passive operation, large dynamic range, and simple device architecture, had been limited by their far inferior performances compared to their bulk counterparts. Here we discuss our recent work combining garnet material development and isolator device design innovation, which leads to a monolithic optical isolator with an unprecedented low insertion loss of 3 dB and an isolation ratio up to 40 dB. To further overcome the bandwidth and polarization limitations, we demonstrated broadband optical isolators capable of operating for both TM and TE modes. These results open up exciting opportunities for scalable integration of nonreciprocal optical devices with chip-scale photonic circuits.
The development of low-loss optical phase change materials (O-PCMs) promises to enable a plethora of nonvolatile integrated photonic applications. However, the relatively large optical constants change between different states of calls for a set of new design rationales. Here we report a non-perturbative design that enables low-loss device operation beyond the traditional figure-of-merit limit. The basic design rationale is to engineer the light propagation path through the OPCMs when it is in the low-loss amorphous state, and divert light away from the lossy crystalline state leveraging the large mode modification induced by the O-PCM phase transition. Following this approach, we demonstrate broadband photonic switches with significantly enhanced performances compared to current state-of-the-art.
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. Traditional O-PCMs suffer from large optical losses even in their dielectric states, which fundamentally limits the performance of optical devices based on the materials. To resolve the issue, we have recently demonstrated a new O-PCM Ge-Sb-Se-Te (GSST) with broadband low loss characteristics. In this talk, we will review an array of reconfigurable photonic devices enabled by the low-loss O-PCM, including nonvolatile waveguide switches with unprecedented low-loss and high-contrast performance, free-space light modulators, bi-stable reconfigurable metasurfaces, and transient couplers facilitating waferscale device probing and characterizations.
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