Terahertz pulse generation and focusing with InAs nonlinear metalens

Dr. Hyunseung Jung1, Dr. Sadhvikas Adamame1, Dr. Ting Shan Luk1, Dr. Thomas Harris1, Dr. Igal Brener1, Prof. Oleg Mitrofanov2
1Sandia National Labs, Albuquerque, USA. 2UCL, London, United Kingdom


A new class of nonlinear terahertz (THz) metasurfaces, which not only define the THz beam structure but also generate THz pulses of desired structure, have been demonstrated recently. These metasurfaces take advantage of the optical nonlinearity in nano-scale metallic or dielectric elements. They can generate THz transients at the nano-scale with control over their amplitude, phase and polarization. However, the efficiency of THz generation is still below conventional THz pulse sources. Here, we present a binary-phase nonlinear metasurface made of InAs nanoscale resonators and thin (130 nm) areas of uniform (unpatterned) InAs for simultaneous generation of THz pulses and manipulation of their phase. We demonstrate that the metasurface serves as an efficient THz emitter and a lens with a short focal length (4-6 mm) and high NA (~ 0.5). The InAs metasurface platform can pave the way for efficient structured THz beam generation with additional functionalities, including beam focusing and steering without the need for THz optics.