aus Bonn

Abstract

In this thesis we report on two matters, (i) time-resolved single particle bio-sensing using a cavity enhanced refractive index sensor with unmatched sensitivity, and (ii) the theoretical analysis of parametric normal mode splitting in cavity optomechanics, as well as the quantum limit of a displacement transducer that relies on multiple cavity modes. It is the unifying element of these studies that they rely on a high-Q optical cavity transducer and amount to a precision measurement of an optical frequency. In the first part, we describe an experiment where a high-Q toroidal microcavity is used as a refractive index sensor for single particle studies. The resonator supports whispering gallery modes (WGM) that feature an evanescent fraction, probing the environment close to the toroid’s surface. When a particle with a refractive index, different from its environment, enters the evanescent field of the WGM, the resonance frequency shifts. Here, we monitor the shift with a frequency resolution of ∆ν/ν = 7.7 · 10 −11 at a time resolution of 100 µs, which constitutes a ×10 improvement of the sensitivit