Surface Lasers

Abstract

Room‐temperature visible laser action is reported in PrCl₃ and PrBr₃. Optical pumping directly into the upper laser level is accomplished by a wavelength‐tunable dye laser. Threshold is less than 1 μJ. Superradiant laser action within physical dimensions of a few microns is generated by focusing the excitation light on the cleaved crystal surface. Use as an active element in integrated optics networks is indicated with over 10⁶ individual lasers per square inch.