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 50 nm thick, 1 mm(2) membranes have mechanical Q > 10(6) at 293 K, and Q > 10(7) at 300 mK, well above what has been observed in devices with comparable dimensions. The near-IR optical loss at 293 K is less than 2x10(-4). This combination of properties make these membranes attractive candidates for studying quantum effects in optomechanical systems. (C) 2008 American Institute of Physics.