Strong optomechanical interaction in a bilayer photonic crystal

We fabricated bilayer photonic crystal (PhC) as large as 20×30 μm possessing 200-nm-thick slabs and a 200-nm-thick air gap. Input power dependence of reflectance spectra indicates air gap reduction by 3.6 nm. Combining it with finite element method calculation we estimate optomechanically generated force per unit stored energy as 0.4 μN/pJ, exhibiting strong optomechanical coupling. RF spectrum of reflected light reveals intensity modulation by thermal vibration of bilayer PhC, which also shows strong interaction of optical resonance mode and mechanical mode of bilayer PhC