Spherical Cavity Glass Lasers for Multiwavelength Emission

Abstract

This review takes a look at small-sized resonators, especially, spherical glass lasers of micrometer size. Two optical coupling techniques developed in our laboratories are described: (1) terrace microspheres (high-refractive index glass spheres having a light entrance portion made from organic–inorganic hybrid materials) and (2) a half-polished fiber coupler. We tried to pump several tens of micrometer-sized high-index glass spheres (nD=1.93) in BaO–TiO2–SiO2 glass system and containing a few ppm of Nd3+ for laser demonstrations. Using two optical coupling techniques with CW Ti:sapphire laser, we carried out overlapped emission of both of the wavelength regions originating from Raman scattering (840–890 nm) and fluorescence of Nd3+ (860–940 nm). A potential for a multiwavelength laser having >100 emission peaks was demonstrated with thresholds of several mW order.