Metalens-coupled terahertz NbN hot electron bolometer mixer
D. Ren (TU Delft - ImPhys/Adam group)
J.R.G. Silva (SRON–Netherlands Institute for Space Research)
S. Cremasco (Student TU Delft)
Z.H. Zhao (TU Delft - ImPhys/Adam group)
W. Ji (TU Delft - ImPhys/Adam group)
J.B.P. de Graaff (TU Delft - ImPhys/El Gawhary group)
A.J.L. Adam (TU Delft - ImPhys/Adam group)
J.R. Gao (SRON–Netherlands Institute for Space Research, TU Delft - ImPhys/Adam group)
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Abstract
Enabled by planarized phase engineering, metalenses based on metasurfaces offer compact and scalable solutions for applications such as sensing, imaging, and virtual reality. They are particularly attractive for multi-pixel, large-scale heterodyne focal plane arrays in space observatories, where a flat metalens array on a silicon wafer can replace individual lenses, greatly simplifying system integration and beam alignment. In this work, we demonstrate a superconducting niobium nitride (NbN) hot electron bolometer (HEB) mixer coupled to a silicon-based metalens operating at terahertz frequencies. The metalens phase profile was derived from a finite-size Gaussian beam source using the Rayleigh–Sommerfeld diffraction integral, and its focusing behavior was validated through 2D simulation. Experimentally, the metalens-coupled NbN HEB receiver exhibited a noise temperature of 1800K at 1.63THz. The power coupling efficiency from free space to the mixer via the metalens was measured to be 25%. Measured far-field beam profiles are Gaussian-like with sidelobes below −14dB. These results demonstrate the feasibility of integrating metalenses with HEB mixers for THz detection, offering a scalable path for compact focal plane arrays in space-based THz instrumentation.