Nanomechanical radiation sensing at the fundamental temperature fluctuation noise limit - Raphael St-Gelais

Thermal-based radiation sensors have been used for decades for long-wavelength detection (infrared and terahertz), but performance still falls short of the fundamental limit imposed by the fluctuation noise of thermal photons. This performance gap largely results from non-fundamental imperfections, such as Johnson- Nyquist electrical noise, occurring in existing thermal-based sensing elements such as thermopiles, bolometers, or pyroelectrics. In recent years, temperature-sensitive nanomechanical resonators have been proposed as an alternative to alleviate this limitation since mechanical resonant sensors can in-principle be immune from electrical noise. Based on this approach, we have used silicon nitride membrane resonators to detect 0.5 - 3 terahertz light with a noise equivalent power NEP = 36 pW/√Hz and a detectivity D^*=3.4x10⁹cm⋅√Hz/W that outperform the best commercially available room-temperature on-chip THz detectors (i.e., pyroelectrics). I will present progress from our group in this direction, alongside our general efforts on radiative thermal transport in nanomechanical resonators including near-field thermal radiation and passive radiative cooling.