Microcavities for Ultrasensitive Spectroscopy

Spectroscopy is often performed on emission or absorption centers that due to sample preparation are located within a thin film or located in proximity to a dielectric interface. However, locating emission or absorption centers near reflecting interfaces can strongly effect their interaction with the electromagnetic field. In recent years, there have been several reports of the observation of a change in the angular distribution of emission due to cavity confinement. In addition, changes in the radiative lifetime have also been reported. A review of spontaneous emission from planar microstructures has recently been presented by Deppe et. al.1 The perturbation of the radiative properties of centers can be predicted using quantum electrodynamics for the electromagnetic modes of the discontinuous media. In fact, it is possible to design a specific structure to enhance the mode amplitude, and therefore, the interaction at the position of a radiative center. This approach can be used for ultrasensitive spectroscopy. Furthermore, emission or excitation angle can be used to selectivity cause enhancement at a particular frequency or position within a planar structure.