Speaker
Description
Calibrating ultra-sensitive THz/meV detectors in cryogenic environments is a challenging pursuit, as conventional fiber optics suffer greatly from loss and tunable sources are limited. A system composed of a high-frequency photomixer coupled to a hollow cylindrical waveguide is being developed to deliver tunable frequency THz photons to cryogenic sensors. This work is motivated by the need to calibrate superconducting quasiparticle-amplifying transmons (SQUATs), which are sensitive to single THz photons and meV phonons, lending to their future use in searches for QCD axion and light-dark matter candidates as well as neutrino detection. The system will also be useful for the end-to-end calibration of the Broadband Reflector Experiment for Axion Detection (BREAD). This talk reports on the performance of waveguide-coupled photomixers, showing the validation of our experimental THz transmission results with photonic simulations using Ansys Lumerical. Various frequency- and time-domain simulations have been done to quantify the effects of geometric and material properties of waveguides on THz-regime transmission, informing the development of our experimental setup. Room temperature tests have been conducted that validate the efficacy and alignment constraints of waveguides in this system, providing both theoretical and experimental benchmarks. We also report on the progress of our first cryogenic tests in a dilution refrigerator.
