The active material (10) is pumped by the light (11) of a gas discharge lamp (12). Thus higher power levels can be attained with the laser and the useful life of the gas discharge lamp (12) is prolonged if the gas discharge lamp (12) is excited at high frequency. The active material (10) is pumped by the light (11) of a gas discharge lamp (12). Thus higher power levels can be attained with the laser and the useful life of the gas discharge lamp (12) is prolonged if the gas discharge lamp (12) is excited at high frequency.