Thermally tunable terahertz vortex beam generator based on an InSb metasurface

In this work, a thermally tunable dielectric metasurface (DMS) composed of InSb cylindrical micropillars is proposed to generate vortex beam in the terahertz region. The full 2 pi phase shift could be realized at resonance frequency for the incident linearly polarized wave by changing the diameter of InSb cylindrical micropillars. In addition, the resonance frequencies vary with the temperatures of the InSb cylindrical micropillars. More specifically, the resonance frequency will be moved from 0.69 to 1.65 THz when the temperature increases from 240 K to 340 K, and the corresponding transmission coefficients are higher than 0.5. Vortex beams carrying orbital angular momentums with different topological charges at 1.27 THz (T = 300 K) and thermally tunable vortex beams with topological charge m = -2 can be achieved. The results showed that the generated vortex beams have high mode purity under different external environment temperatures. The vortex beam generator can reconstruct the operating frequency without changing the physical size, which has great potential in terahertz imaging, detecting, and communication. (C) 2021 Optical Society of America