Mode locked pulsed dye laser

Apparatus using dye lasers for the production of pulsed light at a desired wavelength wherein the dye cells (4, 5) are fed with a weak beam of a narrow desired wavelength and pumped at another wavelength, thus producing an amplified output at the desired wavelength, the apparatus having a special aptitude in certain medical treatments. A metal vapour laser is employed using copper and gold active media in spatially separated regions, with the strong copper output at 511 nm and 578 nm being passed through a wavelength selective mirror (1) to pump two dye cells (4, 5) which are locked to the weaker 628 nm output obtained from the gold vapour discharge.