Detailed single-shot spectral diagnostics of Q-switched solid state lasers

A measurement station to examine the longitudinal mode structure of Q-switched solid state lasers on a single pulse basis is presented. The key component is a Fabry-Perot interferometer (FPI) providing a high finesse to not only display the full spectral emission bandwidth but also resolve single modes of high gain laser media such as Nd : YVO4. In addition the setup allows one to link relative pulse energy data to each recorded fringe pattern. It is then used to quantify the spectral information of three lasers with a cavity length of up to 200 mm to evaluate correlations among pulse stability, pulse repetition frequency and spectral emission characteristics. The optical approach implies a decaying finesse from approximately 250 to 60 across the measurement range. Therefore the setup can only partially resolve single longitudinal modes of lasers with a cavity length greater than 130mm but still gives a qualitative picture of the emission bandwidth that allows a deeper understanding of the spectral characteristics and thus points the direction for performance improvement.