High-reflectivity, high-Q micromechanical membranes via guided   resonances for enhanced optomechanical coupling
  Using Fano-type guided resonances (GRs) in photonic crystal (PhC) slab structures, we numerically and experimentally demonstrate optical reflectivity enhancement of high-Q SiNx membrane-type resonators used in membrane-in-the-middle optomechanical (OM) systems. Normal-incidence transmission and mechanical ringdown measurements of 50-nm-thick PhC membranes demonstrate GRs near 1064 nm, leading to a ~ 4\times increase in reflectivity while preserving high mechanical Q factors of up to ~ 5 \times 10^6. The results would allow improvement of membrane-in-the-middle OM systems by virtue of increased OM coupling, presenting a path towards ground state cooling of such a membrane and observations of related quantum effects. 
Catvu H. Bui, Jiangjun Zheng, S. W. Hoch, Lennon Y. T. Lee, J. G. E.   Harris, and Chee Wei Wong
physics.optics quant-ph