Phononically shielded multi-wavelength photonic-crystal membrane for cavity quantum optomechanics

We propose and design a stoichiometric silicon-nitride membrane resonator featuring highly reflective at multi-wavelengths and high mechanical quality factor. The membrane resonator has a thickness of 100 nm and 2D-photonic and phononic crystal patterns. By designing concentric holes of suitable radius on both sides of the membrane, high reflectivity at multi-wavelengths can be achieved. In particularly, the simulation shows that high reflectivity can be realized at telecommunications wavelength and alkaline atoms absorption lines, with reflectivity of 99.76% at 852 nm, and 99.98% at 1054 nm, and 99.96% at 1566 nm, respectively. The designed device can find useful applications in cavity optomechanical system to realize quantum frequency conversion and precise quantum measurement, and other field of quantum information processing tasks.