In this paper, we review experiments performed with silica microspheres as optical resonators. We
introduce our approach to utilize scanning optical near-field probes as nano scatterers and nano emitters.
Applications of mode mapping techniques to improve selective coupling to high-Q modes and to study
Raman lasing are presented. Furthermore, we analyze the emission properties of a single nano emitter
interacting with resonator modes and demonstrate long-distance energy transfer between two nano emitters.
The controlled splitting of a high-Q mode by a single Rayleigh scatterer is also demonstrated.
In this paper we discuss different configurations of experiments where two nanoemitters are coupled through exchange of photons via shared cavity modes. We introduce an experimental setup where we combine microspheres as optical resonators with the techniques of scanning confocal and scanning near-field microscopy. The emission of fluorescence light from a single nanoemitter in high-Q whispering-gallery modes is demonstrated. Also first experiments with a novel type of stable active nanoprobe are reported. These results demonstrate the feasibility of experiments where optical modes mediate interactions between few quantum emitters in a controlled manner.
We report the observation of conical emission induced by cross-phase-modulation when a strong beam copropagates with a weak beam through dimethylsulfoxide. Laser beams at 1064 nm and 597 nm, in the transparency window of the material, were used. The phenomenon is understood in terms of a nonlinear spatial modulation of the refractive index.
We developed a new technique which allows measurements of the relative amplitudes of the third- and fifth-order susceptibilities, as well as their relative phases. Preliminary results for a semiconductor doped glass that illustrate the theoretical predictions are presented.
We measured the coupling of the florescence from semiconductor nano-crystals and sub-micron sized dye-doped beads to high-Q whispering gallery modes (WGM) of a microsphere resonator. With Q-factors as high as 109 the florescence could be extracted in a controlled way via a prism coupler. We observed nearly 100 % modulation in
the spectrum which reflects the coupling to the WGMs. With the help of a beam scanning confocal microscope we were able to address a single 500 nm sized dye-doped bead on the sphere’s surface and to collect and analyze its florescence in a well defined manner via the prism coupler.
We report optical gain at 382 nm and 414 nm from Nd3+ doped fluoroindate glasses after excitation with lasers operating either at 583 nm or 532 nm. Stimulated emission due to a frequency upconversion process results in increase of the emitted light intensity and emission line narrowing. Large optical gain is measured by pump-and-probe spectroscopy using samples with various Nd3+ concentrations.