Abstract

A parametric study of intracavity absorption by a gas-phase broadband absorbing species has been carried out using a cw dye laser. Absorption by ozone in the weak visible Chappuis band system guaranteed that the intracavity absorption linewidth was much greater than the multimode dye laser emission bandwidth, providing an essentially constant optical loss for all the oscillating longitudinal cavity modes. High spectral resolution of the dye laser emission showed the change in mode intensity due to the presence of additional loss was best characterized by the absorptance (Δl/l₀). Use of this form allowed quantification of the absorption via a modified Beer-Lambert relationship. Enhancement of absorption over conventional techniques was observed to be strongly dependent on the laser power, having a value in excess of a factor of 600 near the lasing threshold. Comparison is made to narrowband intracavity absorption by the visible bands of NO₂, providing the first direct quantitative observation of both broadband and narrowband intracavity absorbers with the same experimental apparatus. In addition to providing another direct sensitive optical detection method in laboratory studies of O₃, the results yield further information for the comprehensive theoretical analysis of standing-wave multimode dye lasers.

© 1987 Optical Society of America