Experimental evidence of an x-ray laser.

A three-stage neodymium:glass laser has been used to produce collimated x-radiation from an aqueous copper(II) sulfate gel. The 1.06-mum Q-switch pulse from the neodymium laser was focused by a cylindrical lens to a horizontal line traversing a microscope slide sandwich that contained a thin film of gel. The emission from the gel was detected as a 0.2-mm spot on shielded, standard x-ray photographic film at distances that varied from 30 to 110 cm from the sandwich. Spot size did not increase with distance, suggesting coherence of the x-rays.