Megahertz monocrystalline optomechanical resonators with minimal dissipation

We present detailed experimental and theoretical results for novel micro-optomechanical resonators, representing a significant improvement in the performance of such structures. These devices exhibit eigenfrequencies (f_r) approaching 4 MHz, reflectivities exceeding 99.98% at 1064 nm, and mechanical quality factors (Q) of 0.8 × 10⁵ (measured at 20 K and 2.5 × 10^-7 millibar pressure); yielding a Q·f_r product of 3.1 × 10¹¹ Hz, while enabling a finesse of approximately 20,000 when used as an end mirror in an impedance-matched Fabry-Perot optical cavity. These results represent a breakthrough in the development of optomechanical devices applicable to the emerging field of quantum optomechanics.