Numerical and experimental estimates of inhomogeneities in dye laser gain medium

Abstract

In this paper the flow behaviour in a converging diverging curve duct used in a high stability dye laser pumped by CVL is presented at different bulk flow velocities for dye gain medium length of 25mm. The flow behaviours using a prototype flow duct are studied numerically and experimentally using a dye solvent mixture of 70% glycol and 30% ethanol. A non-linear CFD turbulence model is used to get enhanced numerical results for accelerating curved flow. The numerically estimated average values of turbulent kinetic energy and its dissipation rate at different flow rates are compared with the intensity variation of He–Ne laser passing through the flow. The flow field tends to become more stable at higher Reynolds number and at lowest hydraulic diameter (CVL pump position). The average variation of flow and temperature inhomogeneities in boundary layer at CVL pump position reduces with the increase in flow rate. It is shown by using He–Ne laser on dye flow test cell that the intensity variation of transmitted laser light in boundary layer (dye gain sector) reduces with increase in bulk flow speed up to about 8m/s and then increases. The variation in dye laser bandwidth and wavelength is correlated with flow and temperature induced inhomogeneities for different flow speed.