Charles L. Marquardt

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 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.

High-efficiency 2.09 μm flashlamp-pumped laser

Utilizing the results of Cr3+→Tm3+ transfer efficiency studies, we have demonstrated that YAG is the preferred host for the Cr:Tm:Ho laser, and that highest efficiencies are obtained at relatively low Cr3+ concentrations. We have achieved a slope efficiency of 5.1% from a flashlamp‐pumped room‐temperature 2 μm laser.

Hole self trapping and recombination luminescence in AgCl at low temperatures

Abstract Experimental correlations are established among steady state optical and ESR spectra and transient luminescence and optical absorption. These correlations support the existence of self-trapped holes in the form of substitutional Ag2+ in AgCl and imply that intrinsic electron-hole recombination is the source of a strong emission band around 2.4 eV.

Tunable, continuous-wave laser action using (F 2 + )A centers in lithium-doped KCl

Continuous-wave, broadly tunable laser action is reported for an (F2+)A center in lithium-doped KC1. The laser is continuously tunable from about 2.00 to 2.50 microm, is highly efficient, has a low threshold for absorbed power, and retains its laser capability after several weeks of storage at room temperature.

Efficient room-temperature operation of Cr3+-sensitized, flashlamp-pumped, 2µm lasers

Utilizing the results of Cr3+ → Tm3+ transfer efficiency studies, we have demonstrated that yttrium aluminium garnet (YAG) is the preferred host for room-temperature, flashlamp-pumped solid-state lasers operating in the 2.0 µm spectral range. We report data on two different sensitizer-activator combinations in YAG and yttrium scandium gallium garnet (YSGG) laser materials: one is doped with Cr:Tm:Ho and operates on the Ho3+5I7 →5I8 transition at 2.097 µm; the other is doped only with Cr:Tm, which lases on the Tm3+3F4 →3H6 transition at 2.014 µm. We have achieved a slope efficiency of 5.1% with the Cr:Tm:Ho:YAG laser, which is the highest slope efficiency yet reported for a room-temperature, flashlamp-pumped, 2 µm solid-state laser. We have measured thresholds as low as 38 J and output energies >1.5 J for that system. We also report the first room-temperature operation of an efficient flashlamp-pumped Cr:Tm:YAG laser at 2.014 µm. Thresholds as low as 43 J, output energies exceeding 2 J, and slope efficiencies as high as 4.5% have been achieved. This is an order of magnitude higher than the efficiency previously reported for a 2.01 µm Cr:Tm:YAG laser operated at cryogenic temperatures. These two efficient 2 µm laser systems (Cr:Tm:Ho:YAG and Cr:Tm:YAG) are discussed in terms of their potential for Q-switched operation.

On the role of copper in the darkening of silver‐halide photochromic glass

A photoinduced ESR signal has been detected in silver‐halide photochromic glasses. It is shown to arise from Cu++ ions distributed among distorted cation sites in the silver‐halide phase. Correlation with optical absorption data suggests that the photoinduced Cu++ may be directly responsible for a significant fraction of the photochromic darkening.

Broadly tunable laser action beyond 3 μm from (F 2 + )A centers in lithium-doped KI

Laser action has been achieved by using lithium (F2+)A centers in KI. The laser is continuously tunable from 2.59 to 3.65 μm; the 1.73-μm line from a pulsed Er:YLF laser is used as pump source.

Hydrazinelike Defect, N2H4+, in Irradiated Ammonium Halides. I Production and Characterization

The hydrazinelike defect in irradiated ammonium halides has been studied using electron paramagnetic resonance. The results suggest that this defect is an N2H4+ molecular ion at a normal ammonium ion lattice site. In NH4Cl and NH4Br it freezes in the lattice in such a way that the p orbitals in which the unpaired spin is localized are aligned along a 〈110〉 direction. The defect appears to be produced as a result of chemical decomposition of NH3X centers (X=halogen) through the competetive processes: NH3X→NH2++X−+H0 and NH3X→NH20+X−+H+. Products of these reactions then combine to form N2H4+ in the following way: NH20+NH2+→N2H4+. The N2H4+ subsequently undergoes decomposition at higher temperatures, its stability at any given temperature being also influenced by impurities.

Hydrazinelike Defect, N2H4+, in Irradiated Ammonium Halides. II. Theoretical Analysis

An LCAO–MO energy level diagram and bond length estimates are used to describe a planar ethylenic molecule model for the N2H4+ defect at an NH4+ site in ammonium halides. The unpaired spin orbital is found to be an antibonding combination of 2p orbitals on each nitrogen perpendicular to the molecular plane. The model is then further specified and used to analyze the low‐temperature EPR data for NH4Cl in detail, from which hyperfine, bond length, and bond angle parameters are extracted and compared with LCAO–MO calculations. Thereby, more information about the defect and confirmation of the model are obtained. Satellite intensity and linewidth angular variations in the high‐temperature spectra are explained, and the relation of high‐ to low‐temperature spectra is discussed.