Researchers Deploy Novel Phonon Laser to Control Mode Competition
21 November 2013
Researchers at the Physical Measurement Laboratory (PML) and the Joint Quantum Institute (JQI) have been successful in observing and controlling a process known as mode competition using a novel "phonon laser" devised by them, the National Institute of Standards and Technology (NIST).
Mode competition is a process that takes place in optical lasers but has never been detected in similar optomechanical oscillator systems, or phonon lasers.
The phonon laser devised by the scientists features a Fabry-Perot optical cavity, placed into a vacuum environment, in which one mirror is a thin silicon nitride membrane with an appropriated pattern. The membrane was in particular designed to create a sub-wavelength diffraction grating producing a reflectivity of 99.4%, which was made possible thanks to the NIST nanofabrication facility (CNST).
Alongside the membrane's optical role in the cavity, it also has properties of a mechanical oscillator supporting hundreds of drumhead modes with frequencies greater than 130 kHz. When light is applied to the cavity, the circulating power aggravates significantly to correlate with the motion of the membrane. When detuned to the high-frequency field of a cavity resonance, the radiation pressure linked to the circulating power generates mechanical gain. The mode begins to oscillate if the gain is strong enough to prevail over the damping peculiar to a particular mechanical mode of the membrane. The motion of the membrane is examined by a supplementary interferometer beam which does not interfere with the cavity tracking its displacement over time.