OPTONANOMECH · Operation of Cavity Optomechanics in Fluids for Ultrasensitive Mass Detection

In cavity nanomechanics, researchers are racing towards the mechanical quantum ground states, however, it remains unclear how these interesting system could be usable in real applications. This project proposes that the cavity nanomechanics could find important use 
in a broad range of applications in chemical and biological detection. The use of cavity nanomechanics as sensitive mass detection could potentially replace mass spectrometers in portable detection systems. These devices are light based force devices. They use recirculating 
light to enhance the interaction of light and mechanical structure achieving an improvement of orders of magnitude in the intrinsic 
sensitivity compared with the commonly used free-space interferometer. 
 The high displacement sensitivity translates to high mass sensistivity if the devices are employed in a sensing environment. The nanomechanical component of the cavity optomechanics provide extremely high mass sensitivity in mass sensing due to their excellent combination of small mass, high frequency and high mechanical quality factor. Zeptogram mass sensing has been achieved at low 
temperature and in vacuum, however, the mass sensitivity in ambient air is much lower due to air damping.
 In this project, the active oscillation resulting from regenerative cavity back-action brings about a new concept for ultrasensitive 
mass detection. In contrast to passive resonators, these active oscillators do not require external ac stimulation and can be self-sustained. 
With the proposed resonator (2GHz), the theoretical mass sensitivity in vacuum is predicted to be 10-24g, close to the mass of a H atom. Under ambient conditions, the practical sensitivity will be compromised by air damping of the mechanical oscillator, the readout noise of 
the device systems and the molecular dynamic noise. Nevertheless, previous analysis shows that mass sensitivity on the order of 10-21g is possible with the optomechanical oscillators