Two-photon fluorescence excitation using an integrated optical microcavity: a promising tool for biosensing of natural chromophores.

Application of an integrated optics (IO) microcavity (MC) for evanescent excitation of two-photon excited fluorescence (TPF) is demonstrated. The MC provides a high local intensity, which is required for the TPF, because of resonant enhancement of the intracavity power and a strong two-dimensional confinement of the guided mode. Numerical estimations show a large increase, by more than a factor of 10(4) of the TPF intensity at the MC compared to a conventional straight waveguide.

Spectral-purity-enhancing layer for multilayer mirrors.

We demonstrate, both theoretically and experimentally, that special spectral-purity-enhancing multilayer mirror systems can be designed and fabricated to substantially reduce the level of out-of-band radiation expected in an extreme ultraviolet lithographic tool. A first proof of principle of applying such spectral-purity-enhancement layers showed reduced out-of-band reflectance by a factor of five, while the in-band reflectance is only 4.5% (absolute) less than for a standard capped multilayer.

Visualizing the whispering gallery modes in a cylindrical optical microcavity.

Whispering gallery modes in cylindrical integrated optics microcavities have, for what is to our knowledge the first time, been mapped with a photon scanning tunneling microscope. Optical images were obtained with a spatial resolution of 50 nm. By combination of information on the spatial optical distributions with wavelength-dependent measurements, an unexpectedly rich variety of intracavity phenomena, such as polarization conversion and interference of copropagating and counterpropagating modes, could be directly observed.

Integrated optical microcavities for enhanced evanescent-wave spectroscopy.

The use of integrated optical microcavities (MCs) for enhanced optical spectroscopy and sensing is investigated. The MC sustains high- Q whispering-gallery modes, in which the energy of the optical field can be efficiently stored. The resulting enhanced field can be used to probe fluorescent molecules in the cladding of the MC.

Sensor based on an integrated optical microcavity.

A novel integrated optical sensor based on a cylindrical microcavity (MC) is proposed. A MC sustains so-called whispering-gallery modes (WGMs), in which the energy of the optical field can be efficiently stored. By monitoring the scattering intensity from the MC, one can detect minute changes in the refractive index of the WGM, for instance, as a result of analyte adsorption.