Speaker
Description
The frequency band above few kHz remains a largely unexplored frontier in gravitational wave observation, with many important and interesting new-physics phenomena lying in the region such as axion super-radiance and primordial black holes. We present a proposal for a versatile platform for detecting high-frequency gravitational waves and vector dark matter using a nanomechanical membrane resonator integrated into a moderate-finesse ($\mathcal{F}\sim 10$), 100 m-long optical cavity to overcome the shot noise limitation at the resonance frequency at these higher frequencies. This design leverages the radiation-pressure force to enable in situ tuning of the membrane's resonance frequency by nearly a factor of two, allowing a frequency coverage from 0.5 to 40 kHz by using only six different membranes. The detector is capable of achieving a peak strain sensitivity of $2\times 10^{-23}/\sqrt{\text{Hz}}$ at 40 kHz at comparable mirror sizes to those currently used in LIGO. Using a silicon membrane and a gallium-arsenide input mirror additionally provides sensitivity to vector dark matter via differential acceleration from their differing atomic-to-mass number ratios. The projected reach surpasses the existing limits in the range of $2\times 10^{-12}$ to $2\times 10^{-10} \text{eV}/c^2$ for a one-year measurement. Current activities towards the realization of a NEST (Nano-membrane Experiment for Space-time Tremors) prototype focus on the fabrication and characterization of the cm$^2$-scale nanomechanical membranes with ultra-low mechanical loss.