Opto-electromechanical Systems for Detection of RF Waves
Wednesday, 05 Feb. 2014, 15:00 - 16:00
Presenter: Tolga Bagci; QUANTOP, Niels Bohr Institute – University of Copenhagen, DK
Host: M. Aspelmeyer
Where: Schrödingerroom, 4th floor, Boltzmanngasse 5, 1090 Wien
Hybrid opto-electromechanical systems have recently emerged as promising candidates for combining the superior features of optical systems and the functionality of electrical devices. In that sense, high-Q mechanical resonators provide a convenient link between optical and electrical domains. For example, quantum noise-limited optical detection can be applied to rf/microwave electrical signals through a nanomechanical transducer. In this talk, several experiments we have performed towards the goal of realizing an opto-electromechanical device, will be described. I will first talk about the optical investigation of capacitive coupling with aluminum and graphene coatings on bare SiN membranes. Then I will discuss the readout (both optical and electrical) of strong coupling between an electrical LC circuit and a metal-coated nanomechanical membrane. By using the coupled system and Michelson interferometric detection, we have shown low-noise optical detection of 0.7 MHz rf voltage signals through the mechanical transducer. We find voltage sensitivities as low as 60 pV/rtHz, coming equally from the membrane thermal noise (which is suppressed by the cooperativity) and the quantum shot noise of the optical interferometric readout. This performance competes with the current state of the art op-amps at room-temperature. We expect that together with further optimization and extension to higher frequency and bandwidth, our device will have a potential in replacing expensive cryogenic amplifiers in demanding applications like NMR imaging and astrophysics.