Stable High-Q Bouncing Ball Modes inside a Fabry-Perot Cavity

We discover that stable high-Q bouncing ball modes with tight lateral confinement and whole-body light-matter interaction can exist in an imperfectly aligned, wedged plano-plano FP (WFP) cavity by simply introducing a vertical dielectric interface (DI) between two media with different refractive indices. Compared to a pure WFP cavity without the DI, which is known to have a low-Q factor and a finesse of 10-300 due to the large diffraction and geometrical walk-off losses, our WFP-DI cavity exhibits a high-Q factor of similar to 10(5), a finesses of similar to 3000, and a mode size (or diameter) down to 2 mu m. Furthermore, optical properties of our WFP-DI cavity, including stability, loss, dependences of the Q-factor, and the effective mode area on the DI refractive index contrast and the mirror tilt angle are systematically investigated using numerical methods. Finally, we experimentally demonstrate WFP-DI dye lasers in the total internal reflection (TIR) and non-TIR cases. A lasing threshold of 1-2 mu J/mm(2) is achieved, which is 7-40x lower than the pure WFP laser without the DI and agrees well with the theoretical predications. Our results suggest that the WFP-DI cavity provides a promising technology platform for miniaturized photonic devices, optofluidic lasers, and microfluidics for biological/chemical analysis.