Optical phase change materials (O-PCMs), a unique group of materials featuring exceptional optical property contrast upon a solid-state phase transition, have found widespread adoption in photonic applications such as switches, routers and reconfigurable meta-optics. Current O-PCMs, such as Ge–Sb–Te (GST), exhibit large contrast of both refractive index (Δn) and optical loss (Δk), simultaneously. The coupling of both optical properties fundamentally limits the performance of many applications. Here we introduce a new class of O-PCMs based on Ge–Sb–Se–Te (GSST) which breaks this traditional coupling. The optimized alloy, Ge2Sb2Se4Te1, combines broadband transparency (1–18.5 μm), large optical contrast (Δn = 2.0), and significantly improved glass forming ability, enabling an entirely new range of infrared and thermal photonic devices. We further demonstrate nonvolatile integrated optical switches with record low loss and large contrast ratio and an electrically-addressed spatial light modulator pixel, thereby validating its promise as a material for scalable nonvolatile photonics.

Uniquely furnishing giant and nonvolatile modulation of optical properties and chalcogenide phase change materials (PCMs) have emerged as a promising material to transform integrated photonics and free-space optics alike. The surge of interest in these materials warrants a thorough understanding of their characteristics specifically in the context of photonic applications. This article seeks to clarify some commonly held misconceptions about PCMs and offer a perspective on new research frontiers in the field.

This review summarized the recent advances made in the task-specific design and synthesis of metalloporphyrin-based porous organic polymers (POPs) and their functionalization for conversion of CO2 into cyclic carbonates.

The retention-of-state functionality provided by memories is fundamental to any Turing machine and neural network, hence is critical for any information system today. While emerging optical machine learning accelerators and photonic neuromorphic computing paradigms provide promising signal processing and computing performance, the lack of a photon-photon force in the universe makes storing optical information challenging. Fortunately, phase change materials provide such a missing memristive nonvolatile function via their reconfigurable crystalline structure and allow for rapid optical READ paradigms. However, demonstrations of photonic memory are limited by high optical loss, low state-cyclability, and rely on cumbersome non-CMOS like optical programmability. To overcome all three shortcomings and unlock the full potential of optical information storage and access, here we introduce a photonic random-access memory featuring vanishing low optical loss, demonstrate more than half a million switching cycles, a 100x improvement over state-of-art, and realize electrical programmability on-chip. The exceedingly low optical absorption (0.0015 dB/μm) is achieved via a novel broadband transparent phase change material, Ge2Sb2Se5 integrated atop a nanophotonic waveguide of a silicon chip. We show a highly efficient signal modulation (0.2 dB/μm) achieved by realizing a newly designed paired micro-heaters along both sides of waveguide, which allows for electronic-standard programmability of these photonic memories. When interrogated by an optical beam, they offer picosecond-short memory READ latency. Furthermore, we demonstrate a partial amorphization scheme realizing multi-state memory levels on a single heater enhancing footprint efficiency. Lastly, we verify the energy and switching speed and show how each trades-off with heater-to-waveguide proximity and signal strength, respectively. Such as CMOS-near electronically programmed and optical read photonic random-access memory with low-optical loss yet efficient programmability can become a crucial building block for network edge AI system of the looming industry 4.0 era.

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