A TUNABLE, ACOUSTICAL PHONON DETECTOR USING Tm2+ IN CaF2

Abstract
The sensitivity and versatility of a phonon detector based on the optical detection of the spin population difference of an impurity ion through the spin-phonon interaction is demonstrated. Phonons generated at 1.4°K by a variety of transducers using at most several milliwatts of rf power at 9.5 GHz were detected. Phonons generated at the 2nd and 3rd harmonics were also detected.