Metalens-coupled terahertz NbN hot electron bolometer mixer

TL;DR

This paper demonstrates the first integration of a silicon-based metalens with a superconducting NbN hot electron bolometer mixer for terahertz detection, achieving promising performance metrics for space-based THz applications.

Contribution

It introduces a novel coupling of a metalens with a superconducting NbN HEB mixer at terahertz frequencies, enabling compact and scalable THz detection systems.

Findings

Noise temperature of 1800 K at 1.63 THz

Power coupling efficiency of 25% from free space to the mixer

Gaussian-like far-field beam profiles with sidelobes below -14 dB

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, for the first time, a superconducting niobium nitride (NbN) hot electron bolometer (HEB) mixer coupled with 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 1800 K at 1.63 THz. 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 -14 dB. 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.