Optimized optomechanical crystal cavity with acoustic radiation shield
  We present the design of an optomechanical crystal nanobeam cavity that combines finite-element simulation with numerical optimization, and considers the optomechanical coupling arising from both moving dielectric boundaries and the photo-elastic effect. Applying this methodology results in a nanobeam with an experimentally realized intrinsic optical Q-factor of 1.2x10^6, a mechanical frequency of 5.1GHz, a mechanical Q-factor of 6.8x10^5 (at T=10K), and a zero-point-motion optomechanical coupling rate of g=1.1MHz. 
Jasper Chan, Amir H. Safavi-Naeini, Jeff T. Hill, Sean Meenehan, and   Oskar Painter
physics.optics quant-ph