Ultra-low-noise absorber-coupled TES detectors for infrared astronomy

We present recent progress in the development of ultra-low-noise Transition-Edge Sensors (TESs) pixels designed for far-infrared (~30-300µm) astronomical instruments. The TES sensitivity is maximized using phononic filters, which are sub-wavelength coherent filters that provide broadband rejection of thermal phonons emitted at the TES critical temperature, Tc~100mK. The phononic filter isolation legs are compact, ~50 µm. In a absorber-coupled bolometer suspended by four legs, the thermal conductance is reduced to achieve an NEP of less than 0.3 aW/rtHz, which is sufficient for balloon- and space-based imaging and low-resolution spectrometer instruments with cold optics. We discuss the phononic filter and TES design, the performance of the phononic-isolated TES pixels, and the advantage of these highly-sensitive absorber-coupled TES bolometers for astronomical instruments.