Spectral fluctuations of a high repetition rate dye laser through a flowing gain medium

In this paper, wavelength and bandwidth fluctuations of a Rhodamine 6G dye laser, transversely pumped by CVL, through a flowing gain medium are investigated. The gain medium mass flow rates were varied in the range 1-6 l min(-1) (LPM). Analysis of the wavelength and bandwidth fluctuations of the dye laser was carried out using a high resolution Fabry-Perot etalon based setup and composite images generated from spectral profiles. The wavelength varied within 0.0290, 0.0240, 0.0200, 0.0120, 0.0110 and 0.0200 nm while the bandwidth was within 1.340, 0.912, 0.679, 0.301, 0.296 and 0.509 GHz at flow rates of 1.0, 2.0, 3.0, 4.0, 5.0 and 6.0 LPM, respectively. The minimum fluctuations, which depend on the experimental conditions, were observed at similar to 5 LPM. Spectral fluctuations at particular flow rates depend mainly on the microscopic fluctuations in the temperature and flow velocity inside the boundary layers.