Polymer whispering gallery mode lasers

We study the emission properties of dye doped polymer microspheres. Under the weak excitation condition, emission exhibits resonant features characteristic to the spherical cavity modes, By the systematic analyses with the Lorenz-Mie calculation. we determine the mode indices of all the resonance lines, From the line width analyses, we determine the effective concentration of dye molecules, Under the pulsed pumping, we observe lasing. Spheres with dye molecule in the entire sphere show complicated spectra indicating the multi-mode lasing, We demonstrate the mode elimination by using a stratified structure, A 20 mu m diameter sphere which has the dye doped shell shows very simple lasing by the lowest order number modes of spherical cavity mode, A small sphere of 5 mu m in diameter shows single mode lasing behavior. The observed spontaneous coupling coefficient is about 30% which agrees with the calculated value. (C) 1998 Elsevier Science B.V.