We propose and demonstrate the use of polarization to determine the threshold of an optical microcavity when the output power versus pump power does not show a sharp threshold. A lasing threshold is observed via a sharp transition in the polarization and a simultaneous reduction in emission linewidth. We find that dipole angular diffusion in a dye gain medium has a significant effect on the polarization of the emission. A theoretical model including the diffusion process is presented. Quantitative agreement with the measurements is obtained.
ASJC Scopus subject areas
- Atomic and Molecular Physics, and Optics