Leon Esterowitz

Efficient, broadly tunable, laser-pumped Tm:YAG and Tm:YSGG cw lasers

Broadly tunable cw laser emission is reported in Tm:YAG and Tm:YSGG at room temperature with Ti:sapphire laser pumping. The Tm(3+)(3)F(4) ? (3)H(6) transition is tuned continuously over the ranges 1.87-2.16 microm in YAG and 1.85-2.14 microm in YSGG. Smooth tuning results from overlapping transitions between phonon-broadened crystal field Stark levels.

Broadly tunable infrared parametric oscillator using AgGaSe2

The first successful operation of a AgGaSe2 infrared parametric oscillator is reported. Continuous tuning ranges of 1.6–1.7 μm, 6.7–6.9 μm, and 2.65–9.02 μm were achieved using 1.34‐μm neodymium and 2.05‐μm holmium pump lasers. Pulse energies exceeding 3 mJ, peak powers near 100 kW, and conversion efficiencies of 18% were obtained. Operation of the parametric oscillator was possible well below the 13–40 MW/cm2 surface damage threshold of this nonlinear material.

Efficient 1.94-/spl mu/m Tm:YALO laser

Laser emission from Tm:YALO is observed over the range 1.93-2.00 /spl mu/m. A model including reabsorption loss and polarization effects, predicting the output wavelength as a function of laser parameters, is used to design a Tm:YALO laser with output restricted to 1.94 /spl mu/m, without employing a tuning element. This laser is potentially useful for medical applications, offing to the strong absorption coefficient at 1.94 /spl mu/m in liquid water (twice that of the 2.02-/spl mu/m Tm:YAG laser and four times that of the 2.09-/spl mu/m Ho:YAG laser). >

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.

Blue light emission by a Pr : LiYF4 − laser operated at room temperature

Room‐temperature operation of a solid‐state laser has been achieved for the first time in the blue region using Pr : YLF. The 0.2% Pr : YLF crystal was longitudinally pumped at 444 nm using a pulsed dye laser. Laser emission was observed at 479 nm and required a pump‐energy density of 8 J/cm2 at threshold.

Intracavity-pumped 2.09-μm Ho:YAG laser

The 2.09-μ Ho:YAG 5I7 → 5I8 laser transition is intracavity pumped by a Tm:YAG laser. Separate Tm:YAG and Ho:YAG crystals share a single laser cavity, the Tm:YAG crystal is pumped at 785 nm, and the resulting 2.01-μm Tm3+ laser emission pumps the Ho:YAG crystal. The slope efficiency of the 2.09-μm Ho3+ laser output is 42% of the absorbed 785-nm pump power.

Efficient resonantly pumped 2.8-μm Er 3+ :GSGG laser

Efficient cw operation of the Er(3+):GSGG (4)I(11/2)?(4)I(13/2) laser transition at 2.8 microm is demonstrated at room temperature. The (4)I(11/2) upper laser state is directly pumped at 0.97 microm. The slope efficiency for the 2.8-microm laser is 36%, indicating a greater than unity quantum efficiency. This excess efficiency results from the recycling of population through upconversion out of the lower laser state.

Growth, spectroscopy, and lasing of titanium-doped sapphire

The growth, spectroscopy, and lasing of titanium-doped sapphire are discussed. Particular attention is given to the problems of achieving high-quality laser material and to the identification and elimination of defects that currently limit Ti:Al 2 O 3 laser performance.

Auger‐limited carrier lifetimes in HgCdTe at high excess carrier concentrations

The performance of n‐type Hg0.8Cd0.2Te (PC) detectors under high optical flux densities was investigated. Detector photoconductivity and response time were measured, in the presence of 10.6‐μm laser radiation. Flux densities, φ, were varied over four orders of magnitude up to a maximum level of φ=1021 photons/cm2 sec. For high flux levels the photoconductivity varies as the cube root of the incident flux and the detector response time varies as φ−2/3. It is concluded that the observed saturation in photoconductivity is due to the decrease in carrier lifetime with carrier concentration. The dominant recombination mechanism at high flux levels was determined to be Auger recombination.

Efficient room-temperature operation of a flash-lamp-pumped, Cr,Tm:YAG laser at 2.01 μm

We report what is to our knowledge the first room-temperature operation of an efficient flash-lamp-pumped Cr,Tm:YAG laser at 2.014 microm. Thresholds as low as 43 J, output energies exceeding 2 J, and slope efficiencies as high as 4.5% have been achieved using a compact diffuse-reflecting pump cavity. These efficiencies are an order of magnitude higher than those previously reported for a 2.01-microm Cr,Tm:YAG laser operated at cryogenic temperatures.