On the flow and thermal characteristics of high Reynolds numbers (2800-17000) dye cell: simulation and experiment

TL;DR

This study investigates the flow and thermal effects on wavelength fluctuations in high Reynolds number dye cells, combining simulations and experiments to identify controlling parameters for stable laser operation.

Contribution

It introduces a new dimensionless parameter, l_plus, to correlate eddy sizes with wavelength fluctuations and provides guidelines for dye cell design at high PRR.

Findings

Wavelength fluctuations are influenced by temperature gradients at low flow rates.

Turbulence Reynolds number and eddy sizes affect fluctuations at high flow rates.

Controlling ReT and l_plus can stabilize wavelength fluctuations.

Abstract

This paper presents computational and experimental studies on wavelength/frequency fluctuation characteristics of high pulse repetition rate (PRR: 18 kHz) dye laser pumped by frequency doubled Nd:YAG laser (532 nm). The temperature gradient in the dye solution is found to be responsible for wavelength fluctuations of the dye laser at low flow rates (2800<Red<5600). The turbulence Reynolds number (ReT) and the range of eddy sizes present in the turbulent flow are found to be responsible for the fluctuations at high flow rates (8400<Red<17000). A new dimensionless parameter, dimensionless eddy size (l_plus), has been defined to correlate the range of eddy sizes with the experimentally observed wavelength fluctuations. It was found that fluctuations can be controlled by keeping ReT~10 and l_plus max~1. The simulated result explains the experimental observation and provides a basis for designing the dye cells for high PRR pumping.