SPECTROSCOPY AND GREEN UP-CONVERSION LASER-EMISSION OF ER(3-DOPED CRYSTALS AT ROOM-TEMPERATURE())

The spectroscopic parameters of Er3+-doped crystals were determined wi th regard to the upconversion laser parameters of the green transition S-4(3/2) --> I-4(15/2), The influence of excited-state absorption on this laser channel was determined. Furthermore, upconversion pump mech anisms using ground-state and excited-state absorption around 810 and 970 nm were investigated by direct measurements of excited-state absor ption. The spectroscopic results confirm the pulsed room-temperature l aser experiments on the S-4(3/2) --> I-5(5/2) transition. The lasers b ased on Er:LiYF4, Er:Y3Al5O12, and Er:Lu3Al5O12 were directly excited into the upper laser level by an excimer laser pumped dye laser in the blue spectral range. In Er:LiYF4, Er:KYF4, and Er:Y3Al5O12, laser act ion was achieved with two-step upconversion pumping by a Ti:sapphire l aser and a krypton ion laser. In the case of the fluorides, the additi onal pumping with the krypton ion laser was not necessary. The laser e mission wavelengths were 551 nm for Er:LiYF4, 561 nm for Er:Y3Al5012 a nd Er:Lu3Al5O12, and 562 nm for Er:KYF4. In addition, green quasi-cw l aser emission of Er:LiYF4 pumped with an argon-ion laser was realized at room temperature.