OBSERVATION OF LASER OSCILLATION FROM CAGA2S4-EU2+

The first observation of laser oscillation from a single crystal of Ca Ga2S4 . Eu2+ (1 at%) is described in this report. A liquid nitrogen co oled thin platelet (0.8 mm thick), whose one flat surface was coated w ith aluminum to increase the reflectivity, was excited from the other uncoated side with a pulsed dye laser beam having a photon energy of a round 2.48 eV. When the input power density exceeded a threshold value of similar to 10MW/cm(2), a directional beam having a sharp spectral line at around 2.19 eV emerged from the sample. This laser was found t o have interesting wavelength tunability extending to similar to 200 A ngstrom, possibly related to the broad gain spectrum of Eu2+ emission in this material.