Optical Characterisation of a Camera module Developed for Ultra-low NEP TES Detector Arrays at FIR Wavelengths

Here we report on the optical design and on the spectral-spatial characterisation of a small 16 pixel camera. The prototype uses TES detectors with NEPs ~10 -16 W/Hz 0.5 which have been fabricated with near identical optical coupling structures to mimic their much lower NEP counterparts (~10 -19 W/Hz 0.5 ). This modification, which is achieved through changing only the pixel thermal conductance, G , has allowed us to perform spectral/spatial cryogenic testing using a 100mK ADR to view room temperature thermal sources. The measurements show a flat spectral response across the waveband and minimal side lobe structure in the antenna patterns down to 30dB.