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.

In this talk, we discuss the effect of plasmonic resonances on the Fisher information in the far field. We consider a metallic nanowire embedded in a silicon substrate, illuminated by a dark-field focused spot, and we investigate how its position can be estimated from the scattered far-field intensities. The Fisher information is computed for both lateral and longitudinal displacements of the nanowire, and the dependence on the illumination frequency is analyzed. We compute the complex resonance frequencies of the nanowires and show that frequencies near the real part of the plasmonic resonance frequency enhance the Fisher information. However, at the resonance frequency itself, the Fisher information drops sharply, leading to an Information Dark State in which the position of the nanowire becomes nearly undetectable. This effect is analyzed and illustrated for both gold and silver nanowires.