This communication describes a new method for producing stable, high concentrations of Sc 2+ in optically clear CaF 2 crystals. We have achieved Sc 2+ concentrations as high as 3 × 10 18 cm −3 without degradation of optical quality. We have converted as much as 5% of the scandium dopant to the divalent state. The concentration of divalent scandium is stable during room temperature storage for periods of at least one year.

This communication describes a new method for producing stable, high concentrations of Sc2+ in optically clear CaF2 crystals. We have achieved Sc2+ concentrations as high as 3 × 1018 cm−3 without degradation of optical quality. We have converted as much as 5% of the scandium dopant to the divalent state. The concentration of divalent scandium is stable during room temperature storage for periods of at least one year.

A Dy:YLF laser operating on the /sup 6/H/sub 11/2/ to /sup 6/H/sub 13/2/ transition at 4.34 mu m and using a laser pumping scheme is reported. This pumping scheme is necessitated by the short upper-laser-level lifetime and the small effective stimulated-emission cross section. A suitable laser for this application is the Er:YLF laser operating at 1.73 mu m. A simple model that approximates Dy:YLF laser performance well is presented. Results on laser performance, including a determination of the slope efficiency and threshold as a function of the output mirror reflectivity and a correlation of the pulse length with the laser output energy, are reported. Overall laser efficiency is found to be limited primarily by the ratio of the pump wavelength to laser output wavelength and the terminated four-level laser operation.< >

We report the first observation of cw lasing at 2.78 μm in an erbium doped fluorozirconate (ZBLAN) single-mode host fiber, pumped by a laser diode array emitting at 792 nm. An erbium doped fluorozirconate single-mode cw fiber laser at 2.71 μm pumped a tunable argon laser at 476.5 and 501.7 nm was recently reported by Allain et al.1 Brierley and France2 earlier reported a cw laser at 2.7 μm, also pumped by a tunable argon laser, in an erbium doped multimode fiber. Excited state absorption (ESA) of the pump beam by the terminal laser level population was the proposed mechanism for overcoming unfavorable branching ratios and also allowing cw lasing on a normally self-terminating transition.3 In contrast to the argon laser, diode pumping has the advantages of much higher efficiency and compactness.

: A flashlamp pumped titanium sapphire laser has been operated with efficiencies approaching 1% using a fluorescent converter. Performance of specific fluorescent converters is described, and ways to further increase the efficiency at the titanium sapphire laser are discussed. (EG)

Reports for the first time laser emission at 2.3 mu m from a thulium-doped fluorozirconate fibre pumped by a pulsed alexandrite laser at 0.786 mu m. Threshold occurs at 25 mu J incident on the focusing lens. This wavelength is in the 2-3 mu m ultra-low loss region of fluorozirconate fibres. Further improvement is expected to result in Cw operation using diode laser pumping.<>

Continuous-wave laser emission at 2.02 µm has been generated at room temperature using a 12% Tm3+:YAG monolithic laser rod longitudinally pumped by a laser diode. This is the first report of a cw room-temperature 2-µm Tm3+ laser pumped by a laser diode. Previous researchers have pumped this transition at room temperature using other laser sources1 and achieved cw operation at 77 K.2 In addition, the present experiments demonstrate the generation of two (2-µm) laser photons for each absorbed (785-nm) pump photon. The threshold for laser emission is 17.2 mW, and the slope efficiency with laser diode pumping is 56 %. The high efficiency of this system Is due to a cross-relaxation process that has been previously studied in laser emission at 2.1 µm in Tm:Ho:YAQ.3

Using excitation via an upconversion process to populate the upper laser level, laser emission at 1.73 μm from the 4S3/2 → 4I9/2 transition has been observed in 4% and 8% Er:LiYF4 (Er:YLF) at room temperature. Laser emission at 1.68 μm from the erbium 4I9/2 → 4I13/2 transition was also observed in both samples.

Cascade laser emission at 2.31 and 2.08 µm is observed in Tm3+,Ho3+:LiYF4 (YLF) at room temperature using a laser diode pump source. The laser emission at 2.31 µm is from the 3H4 → 3H5 transition in thulium, and the emission at 2.08 µm is from the 5I7→5I8 transition in holmium. The laser transition in holmium has been previously reported with laser diode pumping in another laser host yttrium aluminum garnet (YAG)1,2,3.

Since operation of Nd:YAG lasers, especially at 1.06 μm, is well known, this paper compares the operation of several different Nd lasers with Nd:YAG. Lasers were operated on both the 4F3/2 to 4/11/2 transition, nominally 1.06 μm, and the 4F3/2 to 4/13/2 transition, nominally 1.33 μm. Lasers were operated to the extent possible continuously, normal mode, and Q-switched. A comparison of the operation of Nd:YAG, Nd:YLF, Nd:BEL, and Nd:Cr:GSGG was performed on this basis. Results of this comparison will be presented.

We have achieved efficient room-temperature flash-lamp-pumped laser operation in titanium-doped sapphire. The laser has a threshold of 20 J, a slope efficiency of 0.5%, an output energy in excess of 300 mJ, and a tuning range (with our present optics) of 720-920 nm. Ways of reducing the lasing threshold and increasing slope efficiency are discussed.

Development of the Ti:Al2O3 laser(1) has mainly been confined to laser pumping, because of its short (3.2 μsec) spontaneous emission lifetime, Esterowitz, et.al.,(2) reported successful flashlamp pumping of Ti:Al2O3, with efficiency enhanced by using a dye surrounding the laser rod to convert near UV light from the flashlamp into blue-green fluorescent overlapping the titanium absorption band (Fig. 1). The present work describes successful attempts to substantially increase the flashlamp pumped efficiency, and to better characterize flashlamp pumped behavior. In preliminary results a slope efficiency of approximately 3×10-4 was obtained(2), in our most recent results we have increased the flashpumped efficiency to 2×10-2.