Optically Controlled Terahertz Dynamic Beam Splitter with Adjustable Split Ratio

High-efficiency, four-channel beam splitter based on a fishnet-shaped continuous metasurface

Beam splitters play important roles in several optical systems. Due to the growing demand for the miniaturization of optical systems, it is necessary to design beam splitters with nanoscale dimensions to miniaturize the essential components for integrated optical circuits. In this work, we propose and numerically demonstrate a broadband, high efficient, and four-channel beam splitter based on a fishnet-shaped metasurface. The proposed structure is constructed of cruciform AlSb nanoantennas on the PDMS substrate. The simple design can split a beam of light into four beams with equal intensity, it achieves a conversion efficiency above 83%, and an anomalous transmission intensity exceeding 0.8 for the wavelength range of 761-835 nm. In this wavelength range, the beam splitting angle changes from 46.45° to 53.68°. Moreover, the four-channel beam splitter is tunable when the metasurface is designed as a discrete structure. At the wavelength of 874 nm, the beam splitting angle can be adjusted from 56.34° to 46.39° as the period increases from 1050 nm to 1207 nm by stretching the substrate. The presented metasurface might enable promising applications in integrated optical devices, owing to its advantages of multi-channel, wide broadband, high efficiency, and large beam split angle.

Design of Multifunctional Tunable Metasurface Assisted by Elastic Substrate

Metasurfaces with both multifunctionality and tunability hold great application potential in next-generation optical devices. In this paper, we propose a stretchable metasurface composed of arrays of identical dielectric rectangular resonators embedded in the polydimethylsiloxane (PDMS) substrate. It is shown that the metasurface possesses three functions at the operating wavelength of 532 nm. The switching of functions can be implemented by changing the period Px of the metasurface, induced by stretching the PDMS substrate along the x-direction. When the period Px is less than the operating wavelength of 532 nm, the behavior of metasurface can switch between transmissive window and reflective mirror. When the period Px of the metasurface varies from 532 nm to 700 nm, the metasurface act as a dynamic equal-power beam splitter with conversion efficiency higher than 90%, and the corresponding splitting angle can be adjusted from 90° to around 49.5°. Moreover, we achieve the switching of transmissive window/reflective mirror/split-ratio-variable splitter based on the metasurface consisting of arrays of identical L-shaped resonators embedded in the PDMS substrate.

Generation of arbitrarily directed split beams with a reflective metasurface

We present a new, to the best of our knowledge, formalism in the design of metasurface beamsplitters with arbitrarily chosen split beam directions. This technique is based on the well-established array theory; in particular the Fourier transform method of array synthesis, to cast an obliquely incident plane wave to multiple designer-selected scattering directions. To show the efficacy of this approach, a beamsplitting metasurface reflector is designed and verified experimentally and numerically. The metasurface is fabricated by screen-printing patterns of metallic rectangular-shaped resonators of conductive ink onto a ground plane-backed substrate. The beamsplitting characteristics are quantified using a simple free-space transmit/receive horn system operating at 10.525 GHz. It is shown that the presented design technique accurately predicts the scattering properties of the fabricated metasurface and is a useful method for electromagnetic wave manipulation.