Cavity QED with Diamond Nanocrystals and Silica Microspheres

Normal mode splitting is observed in a cavity QED system, in which nitrogen vacancy centers in diamond nanocrystals are coupled to whispering gallery modes in a silica microsphere. The composite nanocrystal-microsphere system takes advantage of the exceptional spin properties of nitrogen vacancy centers as well as the ultra high quality factor of silica microspheres. The observation of the normal mode splitting indicates that the dipole optical interaction between the relevant nitrogen vacancy center and whispering gallery mode has reached the strong coupling regime of cavity QED

aus Bonn

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