Appl. Phys. Lett. 111, 071101 (2017)

Credit: AIP Publishing LLC

A broadband non-polarizing beam splitter for terahertz (THz) waves that features a controllable splitting ratio has been developed by researchers from China, Saudi Arabia and the USA. The device is based on an all-dielectric metasurface made of an array of miniature silicon cylinders on a silicon substrate. The cylinders were arranged into an array with a period of 150 μm. The thickness of the substrate was 1.8 mm, and the height of the cylinders was 200 μm. The radius of the cylinders increased from 33 μm at the centre of the metasurface to 74 μm at the edge. A THz beam at normal incidence to the metasurface is split into two diffracted beams. The ratio of the power in the split beams can be controlled by shifting the lateral position of the metasurface relative to the incident beam. When the beam struck the centre line of the metasurface, a split ratio of 1:1 was obtained, whereas it was 1:300 for an offset position of x = 12 mm. The splitter works over a frequency range from 0.65 to 0.95 THz.