Photonic integrated circuits (PICs) as potential candidate to overcome the “von Neumann bottleneck” of current electronic technologies beyond Moore’s law gain increasing applications in fields of optical communication, data exchange and highperformance interconnect networks etc. Currently, elementary active devices such as photonic switches and modulators play essential roles in light-flow control of optical interconnection network, but suffer from high static power consumption because of volatile control and large footprint that is hard to integrate. In this trend, optical phase change materials (OPCMs) based active devices emerge as promising solutions due to advantages of large optical contrast between the amorphous and crystalline states, optically or electrically switchable and non-volatile control, easy to integration etc. In this paper, we propose a non-volatile O-PCMs photonic switch by integrating a thin film of germanium antimony telluride (GST) alloy on top of a micro-ring resonator. As confirmed by our analytical and computational results, upon an amorphous-to-crystalline phase change, two output ports of the O-PCM microring switch exhibit gigantic transmission contrast with a ratio up to highest 47:1. Further, the O-PCM based photonic switch also demonstrates extremely low extinction ration to 13.58 dB and 14.40 dB for both output ports from 1.5 μm to 1.6 μm.
Over the past decade, major progress in emerging mid-infrared (IR) sources and detectors leads to increased interests for various IR-based applications, such as trace-gas detection, biological and medical sensing, and environmental monitoring. However, a limiting factor in the middle and long wave IR range is the lack of suitable materials that are transparent, low cost, lightweight and easy to fabricate. Here, we numerically demonstrate the artificially constructed Huygens meta-surface with versatile mid-IR wavefront control, by hybridizing the dielectric meta-atoms of high-permittivity chalcogenide on fluoride substrates. Based on the double-elements Huygens meta-atom design for linear phase tuning, transmission is enhanced substantially with high-efficiency (85%) by concentrating beam propagation into the first diffraction order similar as traditional blazed grating but with ultra-thin thickness (λ/8). Further, based on centrosymmetric deflection to produce a local and highly focused propagation mode, a Bessel beam generator is demonstrated (λ=5.22 μm, NA = 0.5) by coding a well-defined phase map into dielectric meta-atoms. As a result, the proposed dielectric metasurface with nanometer level thickness shows great prospects in the field of integrated photonics.
The combination of phase change materials and metasurfaces has enabled myriads of versatile platforms for dynamic wave control, especially for various applications in integrated photonics and optoelectronics. In this paper, an electrically reconfigurable metasurface is demonstrated to work as a terahertz (THz) broadband digital switch by integration of vanadium dioxide (VO2). In such integrated optoelectronic frameworks, active and bistable digital control of optical responses is enabled by applying electrical stimuli to vertically cascaded metasurfaces with broadband behaviors for Joule heating that causes phase change and state switching. Before and after phase change, a high contrast ratio of transmittance is demonstrated within a broad THz range up to 400 GHz. Essentially, fast switching can be guaranteed compared with current devices based on thin film phase change materials, due to the local electrical heating that proves inherently efficient and faster to trigger the phase transition process. As a result, such active optoelectronic framework based on phase change materials may pave a new way for emerging integrated devices such as photoelectric switch, photonic memory, signal processing and so on
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