Amplification and excited state absorption in longitudinally pumped laser dyes

Direct measurements of optical gain using a probe laser beam for the laser dye cresyl violet perchlorate (CVP) in methanol solution using longitudinal pumping at two different wavelengths are described. An analysis of these longitudinal pumping experiments is developed and analytical expressions relating measured gain to the measured pump laser transmission are presented. This analysis is developed in terms of relevant optical cross sections including the influence of excited state absorption. The results demonstrate the influence of excited state absorption at the pump wavelength on pumping efficiency and on the gain per pass at the probe laser wavelength.