采用钛蓝宝石飞秒激光加工系统在融石英表面诱导表面周期性微纳结构，研究了激光诱导表面周期结构的形成过程以及激光能量密度、脉冲数、光斑大小和脉冲的空间间隔对融石英表面激光诱导表面周期结构的形貌的影响。实验结果表明，飞秒激光在融石英表面可以诱导出周期性的亚波长结构，主要以垂直于激光偏振方向的光栅状结构为主，其周期在百纳米量级且具有更好的可复现性。在激光光斑控制在1 μm附近时，所得到的形貌具有较高的规则性。根据实验结果设计了聚焦高斯光斑低通量的加工方式。所制备的光栅结构具有200~300 nm的周期，平均深度约为300 nm。

We report on subwavelength reflective gratings for hyperspectral applications operating in a very large spectral band (340–1040 nm). Our study concerns a blazed-binary grating having a period of 30 μm and composed of 2D subwavelength structures with size from 120 nm to 350 nm. We demonstrate the manufacturing of the gratings on 3″ wafers by two lithography technologies (e-beam and nanoimprint) followed by classical dry etching process. Optical measurements show that the subwavelength grating approach enables a broadband efficiency, polarization behaviour and wavefront quality improvement with respect to the requirements for the next generation of spectro-imagers for Earth observation missions. An outlook towards spherical substrate based on nanoimprint lithography is also reported with the results of mixed features replication (holes and pillars in the range of 160–330 nm) on a 540 mm concave substrate which demonstrate uniformity and accuracy capabilities over 3″ surface.

Plasmonic structural colors have plenty of advantages over traditional colors based on colorants. The pulsed laser provides an important method generating plasmonic structural colors with high efficiency and low cost. Here, we present plasmonic color printing Al nanodisc structures through curvature-driven shape transition. We systematically study the mechanism of morphologic evolution of the Al nanodisc below the thermal melting threshold. A multi-pulse-induced accumulated photothermal effect and subsequent curvature-driven surface atom diffusion model are adopted to explain the controllable shape transition. The shape transition and corresponding plasmonic resonances of the nanodisc can be independently and precisely modulated by controlled irradiations. This method opens new ways towards high-fidelity color prints in a highly efficient and facile laser writing fashion.

We propose and experimentally demonstrate a wideband linear polarization converter in a reflection mode operating from 2.4 to 4.2 THz with conversion efficiency of more than 80%. Our device can expand the applications to a higher frequency band. A numerical simulation is performed for this metamaterial converter, which shows a good agreement with experimental results. Importantly, a concise and intuitive calculating model is proposed for the Fabry–Pérot cavity. The theoretical results indicate that the underlying reason for the enhanced polarization conversion is the additional phase difference induced by the resonance of the meta-structure and multiple reflections within the Fabry–Pérot cavity.

In this Letter, a photonic crystal (PC) flat lens with a scatterer-size gradient is proposed, which simultaneously achieves imaging of the point source and sub-wavelength focusing of the plane wave in the first, second, and fifth bands. The imaging of the point source breaks through the diffraction limit in the second and fifth bands. The PC flat lens with the scatterer-size gradient is expected to be used in a new multifunctional optical imaging and focusing device, which improves the application potential of a PC flat lens.

We present a perfect graphene absorber with a compound waveguide grating at the near-infrared. The analytical approach is mainly based on the coupled leaky mode theory, which turns the design of the absorber to finding out the required leaky modes supported by the grating structure. Perfect absorption occurs only when the radiative loss of the leaky mode matches the intrinsic absorption loss, which is also named the critical coupling condition. Furthermore, we also demonstrate that the critical coupling of the system can be robustly controlled, and the perfect absorption wavelength can be easily tuned by adjusting the parameters of the compound waveguide grating.