Laser oscillations of resonance modes in a thin gain-doped ring-type cylindrical microcavity

We studied the lasing characteristics of resonance modes in a thin dye-doped dielectric ring cavity made on the inner wall of a cylindrical capillary. Lasing spectra corresponding to the whispering gallery modes (WGMs) and waveguide modes were addressed by investigating the spectral changes before and after a liquid was inserted into the capillary. The cavity quality factors of waveguide modes increased while those of WGMs did not alter as the refractive index of inner region increased. By observing a red shift of lasing envelope when a liquid was inserted, we could address the lasing peaks were waveguide modes coming from the total internal reflections at the both boundaries of the ring cavity. (C) 2004 Elsevier B.V. All rights reserved.