Laser emission from dye-doped polystyrene microsphere

Micro dielectric spheres are known to act as efficient optical resonators. According to the Lorenz-Mie scattering theory, micro spheres of the order of the several tenth of micrometer in diameters have very narrow resonances in the visible frequency region. Such cavity resonance modes of a micro sphere are called electromagnetic whispering gallery modes (WGM´s) or morphology dependent resonance modes (MDR´s). Because of the extremely high quality factor (Q-value) of the resonances, the spherical cavity structure has a strong potentiality for various applications of photonic devices. For example, such as low threshold laser. Here we present two methods to control resonance of micro spherical cavity lasers. One is the control of the lasing mode by the injection of the monochromatic beam. Second is the mode elimination by using the doping of the gain medium in stratified structure