Visible laser emission of Pr3+ in various hosts

We report on the first observation of low temperature pulsed blue and orange laser emissions in P~~+:YAG. Furthermore, we compare these results with similar observations in YLiF4 and YAlO3 doped crystals. Pulsed laser oscillations were obtained in crystals with uncoated surfaces by direct excitation of one of the relevant Stark components of the PO, 3 ~ 1 or 3 ~ 2 states. A careful1 spectroscopic analysis of all these systems allows to clearly identify the laser transitions as arising from the PO metastable state, the lifetime of which has been measured using a nanosecond pumped dye laser. Introduction. The renewal of interest in studying praseodymium (Pr3+)-doped solid state materials is due to the emission spectrum of this ion extending from ultraviolet [I] to near infrared [2]. Laser action in several pr3+-doped crystals: YLF [3], YAP [4], YAG [S] as well as FY3+-doped fibres has recently been reported. The need for compact, integrated laser sources in the bluegreen part of the spectrum has led to development of up-conversion laser using two-photon pumping schemes, excited state absorption or energy transfer, to generate laser emission at wavelengths shorter than those used for pumping [6]. Clearly, of practical significance are one-colour IR laser diode pumped devices of this type. Our recent studies put into evidence efficient one-colour up-conversion of IR photons to blue emission in Pr3+-doped YAG and YLF crystals [7]. In this paper, we compare the first observation of low temperature pulsed blue and orange laser emission in ~ r 3 + : YAG reported recently [8] with similar observations in YLF and YAP doped crystals. Experimental. The samples used are YAG: 0.6at%~r3+, YAP: 0.lat%Pr3+ and YLF: 0.24at%~r3+. Their thickness is 2.53 mm, 4.97 mm and 4 mm respectively. They are optically polished without Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jp4:19944130 C4-542 JOURNAL DE PHYSIQUE IV any coating on the surfaces. They are mounted in a liquid He clyostat with a gas heating system to allow temperature variation from 4.4 K to 300 K. The crystals were excited longitudinally by a pulsed Coumarin 480 dye laser ( 10 ns pulse, 0.1 cm-1 band width ) pumped by a tripled Nd: YAG or an excirner laser. Results. Each crystal was excited selectively in one of the Stark components of the 3 ~ 2 , 3 ~ 1 or 3p0 states. Then fluorescence occurs from the PO metastable level which decay is mostly radiative. The gain was high enough that only with optically polished plane parallel ends, providing = 4% Fresnel reflections from the crystalme interface, laser emission was achieved at cryogenic temperatures. The table 1 summarizes the PO spectroscopic properties (position and lifetime), the excitation and laser emission wavelengths for each