Phys. Rev. Lett. 116, 147202 (2016)

Credit: APS

Many goals of the optomechanics community involve quantum mechanics, for example, squeezing of optical and mechanical modes, or ground-state cooling. These types of experiment are technically non-trivial and are typically conducted at cryogenic temperatures due to limitations of optomechanical resonators currently available. Now, Richard Norte, João Moura and Simon Gröblacher, working at Delft University of Technology in The Netherlands, have proposed and demonstrated an on-chip mechanical resonator with suitable characteristics for room-temperature optomechanical experiments to reach the quantum regime. Mechanical quality factors as high as 108 were reached by using ultrathin (down to 15 nm thickness) Si3N4 membrane 'tethers' under high tensile stress, close to breaking point (6.4 GPa). Previous works have noted difficulty in simultaneously achieving high mechanical quality and strong optical reflectivity required for room-temperature optomechanical quantum regime experiments. Typically, high optical reflectivity requires sufficiently thick dielectric media, limiting the mechanical characteristics. The team solved this problem by incorporating hole-array photonic crystal 'mirrors' with a reflectivity of >99%, which are tethered by stressed SiN beams. The team hopes that the concept will be applied to silicon-based quantum networks operating at room temperature.