可调谐超构表面为纳米光子器件赋予了更多的自由度与灵活度，在过去十几年中得到了快速发展。在众多调谐机制中，电调超构表面更容易与半导体集成电路结合，是光电器件小型化发展的重要研究方向。本文综述了过去十几年来主要的电调超构表面设计路线。根据调谐机制将电调超构表面分为电控载流子激发调控、液晶调控、电光晶体调控以及微机电系统调控四种设计方案。总结了不同方案的物理机制、调谐方法、研究现状以及优缺点。最后，讨论了不同调谐方案的应用前景并展望了电调超构表面未来的发展趋势。

Plasmonic devices using periodic metallic nanostructures have recently gained tremendous interest for color filters, sensing, surface enhanced spectroscopy, and enhanced photoluminescence, etc. However, the performance of such plasmonic devices is severely hampered by the solid substrates supporting the metallic nanostructures. Here, a strategy for freestanding metallic nanomembranes is introduced by taking advantages of hollow substrate structures. Large-area and highly uniform gold nanomembranes with nanohole array are fabricated via a flexible and simple replication-releasing method. The hollow structures include a hollow core fiber with 30 μm core diameter and two ferrules with their hole diameter as 125 and 500 μm, respectively. As a proof-of-concept demonstration, 2 times higher sensitivity of the bulk refractive index is obtained with this platform compared to that of a counterpart on a solid silica substrate. Such a portable and compact configuration provides unique opportunities to explore the intrinsic properties of the metal nanomembranes and paves a new way to fabricate high-performance plasmonic devices for biomolecule sensing and color filter.

We demonstrate that ferroferric-oxide (Fe3O4) nanoparticles exhibit nonlinear saturable absorption property at 1.55 μm, and fabricate two filmy saturable absorbers by embedding the nanoparticles into a polyvinyl alcohol (PVA) film or polyimide (PI) film separately. In the Fe3O4-PVA (Fe3O4-PI) Q-switched fiber laser, the pulse repetition rate increases from 8.5 kHz (5.5 kHz) to 28 kHz (49 kHz) and the pulse duration decreases from 23.5 μs (47 μs) to 6 μs (3.5 μs) by varying the pump power from 25 mW (23 mW) to 150 mW (650 mW). Experiment results indicate that PI-based saturable absorbers can afford larger powers than PVA-based saturable absorbers, which can be attributed to the higher fusion point of the PI film. The Fe3O4-PI saturable absorber exhibits features of high damage threshold, low cost, and good flexibility, which could be applied in fields of near-infrared pulse generation and frequency conversions.