High quality mechanical and optical properties of commercial silicon nitride membranes

We have measured the optical and mechanical loss of commercial silicon nitride membranes. We find that 50nm thick, 1mm2 membranes have mechanical Q106 at 293K, and Q107 at 300mK, well above what has been observed in devices with comparable dimensions. The near-IR optical loss at 293K is less than 2×10−4. This combination of properties make these membranes attractive candidates for studying quantum effects in optomechanical systems.