Spectral characterization of a tunable alexandrite laser by rubidium absorption at 780 nm

Rubidium vapor was used to characterize the output of a tunable, pulsed alexandrite laser operating at 780 nm. Rubidium spectra were obtained at temperatures of 23, 50, 110, and 140°C. Excellent agreement was obtained with computer-synthesized spectra which yielded values for the effective laser bandwidth at different operating conditions. The model assumed a Voigt profile for the rubidium
5^{2}P_{3/2} \leftarrow 5^{2}S_{1/2}
transition and a Gaussian profile for the laser pulse. The model also showed that the laser output was spectrally compact with no evidence of energy outside the narrow 780 nm central feature.