An analysis of turbulence in the dye medium of a high-repetition-rate narrowband dye laser is presented, and it is shown that the output bandwidth is proportional to the turbulence length scale, which depends on the Reynolds number. The length scale and the bandwidth both first decrease and then increase as the Reynolds number is increased from -200 to -20,000. The observed bandwidth, as we report and as in the published literature, confirms the validity of the analysis. A Rhodamine 6G grazing-incidence grating, stable dye laser transversely pumped by a copper-vapor laser was used in the experiments.
A copper vapour laser is a gas discharge laser that requires fast, high-voltage, high-repetition-rate excitation pulses. In this paper, energy deposition studies in a typical copper vapour laser are reported under various pulse excitation schemes and under different operating conditions of the laser. The energy deposited in the laser tube is calculated by processing the measured voltage and current waveforms on the laser tube. This method has advantages over the calorimetric measurement method because it gives time-resolved energy deposition in the laser tube during the excitation pulse. Three different charge transfer circuits are used for pulse excitation: one is based on a thyratron switch, the second one on a magnetic pulse compressor switch and the third one on an insulated-gate bipolar transistor assisted by a magnetic pulse compressor. From studies of these circuits, it is found that the conventional thyratron-based capacitor-to-capacitor charge transfer circuit has the highest overall efficiency of energy deposition but it has the lowest energy deposition efficiency in the initial 100 ns of the pulse.
The paper presents the design and performance of a transversely pumped, narrow bandwidth, high wavelength stability tunable dye laser that neither uses low expansion coefficient materials for construction nor incorporates any active control on the wavelength or the dye solution and environmental temperature as generally used in such lasers. The scheme essentially involves designing the mechanical assembly in such a way that, when bolted together it forms a massive monoblock, enclosing all the optical components and the dye laser axis within itself. This ensures the environmental temperature changes can only affect the output characteristics over long time scale. Short term (pulse to pulse) fluctuations in wavelengths and bandwidths, generally associated with the dye flow instabilities, were minimized by using a specially designed a dye cell made of a near 360°-curved rectangular duct, in which the turbulent flow is transformed itself into laminar flow as it reaches the dye laser axis. The laser was operated with Rhodamine 6G-ethanol-ethylene glycol solution, pumped by a copper vapor laser operating at 5.6 kHz. The dye laser output, consisting of three axial modes, separated by about 990 MHz, was stable over the observation period of about 90 min. Maximum long term (>1 h) fluctuation in Δν/ν was about ±3.6×10−6. The bandwidth of the individual mode varied between 245 MHz to 315 MHz.
A compact externally heated discharge tube of 25-mm internal diameter is described. The oven made of alumina tube, tungsten heater, and graphite felt insulation, takes about 45 min at 1.5-kW heater input power to reach temperatures in excess of 1500 °C. Its use with a copper vapor laser is demonstrated. The laser gives output power of 500 mW at 500-Hz repetition rate.
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