Volume 76, number 2 OPTICS COMMUNICATIONS 1.5 April I990 A HIGH POWER DYE LASER PUMPED BY A CROWBAR MODE FLASHLAMP J. GASSEN, D. MOLLER, P. VON BRENTANO and A.P. GEORGIADIS ’ Institut ftir Kernphysik, Universitiit zu K&I. 5000 Cologne 41, Fed. Rep. Germany Received 9 November 1989 A flashlamp pumped dye laser system is described. The flashlamp works in the crowbar mode and was especially developed for this laser system. The laser has been operated with rhodamine 6G (AZ 600 nm) and coumarine 1H (1~470 nm) with an output energy of up to 1 J per pulse. With a single etalon a linewidth of 0.2 nm was achieved in a pulse of 3-6 us length. The maximum repetition rate is 2 pps, limited by the high voltage power supply. 1. Introduction Stimulated emission of light from organic dye so- lutions was observed for the first time in 1966 [ 1,2]. From this time on dye lasers [ 31 became a fasci- nating tool in experimental physics as a result of their tunability and wide wavelength range. A lot of im- provements of their performance were made such as reducing the linewidth [ 41 and increasing the output power. Besides many other applications dye lasers are today a standard tool in atomic and molecular spectroscopy [ 5,6 1. The laser described in the present report was de- veloped for the special application of a Lamb shift measurement using a laser resonance technique [ 7- 1 11. For these experiments, a tunable laser with a power density of 10 MW/cm2 in a 1 mm2 focus is required. The width of the wavelength has to be less than 0.3 nm combined with a minimum tunability range of 6 nm. It is convenient to have a pulse length of several microseconds. With these requirements a flashlamp pumped dye laser was indicated. The de- velopment started initially from a commercial laser #I, but all components have been replaced dur- ing the long optimization process of the laser construction. ’ Institute of Electronic Structure and Laser, Herakhon 711 10, Crete, Greece. #’ Electrophotonics, Mod. 23. 2. The laser head The pump cavity (fig. 1) is formed by two ad- justable half elliptical dielectric coated mirrors. In consideration of the dye used different mirrors with specific coatings were employed. Therefore, the coating is adapted to the absorption range of the dye and so it has a reflectivity of more than 99% for the specific wavelength range for maximum absorption of the dye. The flashlamp is situated in one focal line, while the dye cuvette is in the second focus. The quartz flashlamp is surrounded by a quartz tube to allow cooling of the lamp with deionized water. This quartz tube also has a dielectric coating to reduce the uv-radiation from the flashlamp. 3. The electrical set-up To get the desired high power output from the laser it is necessary to discharge 500 J electrical energy through the flashlamp. Therefore a 2 uF capacitor is loaded up to 23 kV with a repetition rate of 2 pps from a high voltage power supply. A selfmade spark gap triggered by a 16 kV pulse of a car ignition coil closes the main discharge circuit and the capacitor is discharged through the flashlamp (fig. 2 ). Air flows through the spark gap, which besides cooling the main electrodes, allows an easy adjustability of the voltage working range by control of the air pressure. A pseudo-simmering circuit over a 1 MQ resistor pro- 0030-4018/90/$03.50 0 Elsevier Science Publishers B.V. (North-Holland ) 131