Roger E. Allen

cw and pulsed 2.8 μm laser emission from diode‐pumped Er3+:LiYF4 at room temperature

Laser emission at 2.8 μm from an Er3+:LiYF4 sample longitudinally pumped with a multiple stripe laser diode array is observed for the first time. The threshold for pulsed laser emission is 33 μJ and for cw laser emission 147 mW. cw laser action in this normally self‐terminating laser transition is attributed to a cooperative up‐conversion process.

Room temperature Dy:YLF laser operation at 4.34 mu m

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. >

Flash-lamp-pumped Ti:Al 2 O 3 laser using fluorescent conversion

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.

Comparison of Nd 1.06 and 1.33 µm operation in various hosts

Performances of Nd in various hosts including Nd:YAG, Nd:YLF, Nd:BEL, and Nd:Cr:GSGG were characterized and compared for operation on the nominal 1.06 μm and 1.33 μm transitions. Comparison included continuous mode operation, normal mode operation, Q -switched operation, and gain measurements. Continuous lasing of Nd:Cr:GSGG under lamp pumping is reported for what may be the first time. Characterization included operation with different mirror reflectivities to obtain the internal losses, measurement of the upper laser level lifetime, measurement of the beam quality of the lasers operating under nominally similar circumstances, and measurement of the wavelength. These measurements should provide a comparison of the various Nd hosts under similar circumstances for a wide variety of operational modes and at both wavelengths of interest.

Diode‐pumped single‐mode fluorozirconate fiber laser from the 4I11/2→4I13/2 transition in erbium

Diode‐pumped cw lasing at 2.71, 2.75, and 2.78 μm from an erbium‐doped ZBLAN single‐mode fiber is reported for the first time. A threshold of 4 mW absorbed power at 792 nm was obtained for the 2.71 μm transition. 3% slope efficiency was obtained with an 80% reflecting output mirror. cw lasing was also observed from the fiber when a tunable pump was scanned across most of the 4I15/2→4I9/2 absorption band. cw lasing observed when pumping around 820 nm indicates that excited‐state absorption of the pump from the 4I13/2 may not be necessary for cw operation. However, excited‐state absorption of the pump around 810 nm from the 4I11/2 may limit performance.

Operation of an Er:YLF laser at 1.73 µm

The performance, characterization, and optimization of an Er:YLF laser operating at 1.73 μm is described. The lifetimes of the upper and lower laser level were measured which allowed the optimum Er concentration and the ultimate performance to be predicted. In addition, the pulse-forming network and the mirror transmissivity were optimized. The laser output energy in the normal mode and the Q -switched mode as well as the Q -switched pulselength were measured. In a separate, more efficient, laser arrangement, an output energy of 55 mJ was obtained with an overall efficiency of 0.0024.

Diode-Pumped 2 μm Holmium Laser

A high-efficiency laser diode array pumped Nd:YAG solid-state laser has recently been demonstrated.[1] We report for the first time a diode array pumped rare-earth laser other than Nd. Laser action was observed on the trivalent Holium \({5_{{I_7}}} \to {5_I}_{_8}\), 2.1 μm transition. Laser sources in this wavelength region are required in infrared optical fiber communication systems.

Upconversion Pumped Laser at 1.73 µm in Er:LiYF4 at Room Temperature

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 from Laser Diode Pumped Tm,Ho:LiYF4 at Room Temperature

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.

Flashlamp Pumped Ti:Al2O3 Laser Studies

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.