Design of the dye cell of a dye laser to facilitate repetitive operation in the single longitudinal mode

A dye cell was designed and fabricated to facilitate high repetition rate single longitudinal mode (SLM) operation with low viscosity solvents such as ethanol. The flow circulation (vortex) in the dye cell was eliminated by reducing the flow cross section from 10 to 5 mm(2) with optimized flow entry. The physical dimension of dye cell is very important for short cavity SLM lasers in terms of keeping the cavity length small. Flow visualization of various geometries in the dye cell was carried out using commercial computational fluid dynamics (CFD) software. It was found that the slit as well as tubular entry to the dye cell of cross section 1 x 10 mm(2) shows flow circulation (a vortex) near the entry to the dye cell. The SLM was obtained from a 10 mm(2) flow cross section dye cell with a high viscosity solvent such as binary solvent (200 cP) or glycerol (1400 cP) with a higher bandwidth. The pulse to pulse fluctuations in the bandwidth and wavelength are generally associated with dye flow instabilities. These flow related instabilities reduced with higher viscosity solvents, which results in an increased bandwidth of the SLM dye laser (by nearly 40%). A specially designed dye cell was fabricated and used for SLM operation at two different pump lasers having different pulse repetition rates ranging from 20 to 6000 Hz. SLM operation was demonstrated for longitudinal pumping of the dye cell with low viscosity solvents. Time averaged SLM line widths of 400 and 175 MHz were obtained with a copper vapor laser (CVL) and Nd:YAG laser, respectively. A single pulse line width of 315 MHz was obtained with a CVL pumped dye laser.