Effects of radiation trapping on mode competition and dispersion in the ring laser

By considering the phenomena of radiation trapping, corrections are obtained in the third order Lamb coefficients for the amplitude and frequency ring laser equations. The corrected coefficients allow the correct prediction of the shape of the experimentally measured Lamb dip. They also allow the prediction of mode competition between the oppositely directed traveling waves near the Doppler center. As found experimentally, this competition region is predicted to increase with increasing pressure. Expressions are given for the Lamb coefficients that are obtained from an exact third order integration.