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Low-energy electron-beam-pumped lasers

Low energy electron beams with particle energies of typically 10 to 20 keV are used for pumping gas lasers. Extremely thin (300 nm) ceramic (SiNx) membranes are used as entrance foils for the electron beam. Laser gas pressure up to several atmospheres is possible using this technique if the dimension of one side of the foil is restricted to about 1 mm. Energy loss of the electrons in the foil is less than 10%. The short range of the low energy electrons in the laser medium leads to a high specific power deposition. In transverse geometry the beam pumped volume is cylindrical with typically 1 to 3 mm diameter. This is well matched with the diameter of optical modes in stable optical cavities. The new pumping method is demonstrated using the 1.73 micrometers 5d[3/2]1-6p[5/2]2 XeI laser line in Ar-Xe laser gas mixtures at pressures between 130 and 650 mbar. Laser effect was observed for Xe concentrations between 0.1 and 1%. A low threshold pumping power of 5.5 W and a maximum output power of 6 mW at 13 W pumping power were measured. Scaling to higher power and shorter wavelength laser systems is discussed.