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Continuous wave (cw) operating temperature of 223 K was achieved with molecular beam epitaxy grown separate confinement buried heterostructure (SCBH) PbTe diode lasers with PbEuSeTe electrical and optical confinement layers. This is the highest cw operating temperature reported for midinfrared diode lasers. The active region of the SCBH diode lasers varies laterally to form a crescent-shaped waveguide with a maximum thickness of 0.15 μm and a lateral width of 2 μm. Exceptionally low threshold currents of 102 mA at 200 K, 166 mA at 210 K, and 249 mA at 215 K were measured.

Buried-heterostructure tunable PbEuSeTe/PbTe lasers were fabricated using a two-stage molecular beam epitaxy growth procedure. Improvements in the processing technique yielded lasers that show performance characteristics significantly better than those reported previously. A continuous wave (cw) operating temperature of 203 K was realized, which is the highest cw operating temperature ever reported for lead-chalcogenides diode lasers. This laser exhibited exceptionally low-threshold currents of 1.4 mA at 90 K and 43 mA at 160 K with single-mode operation for injection currents up to 30Ith and 0.18 mW power at 100 K. The usefulness of the laser, when operating cw at 200 K, was demonstrated by the ability to perform high-resolution spectroscopy of a low-pressure CO2 gas sample.

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Polymethylmethacrylate (PMMA) is a convenient solvent for studies of the fluorescence, phosphorescence, and triplet-triplet absorption of a number of aromatic hydrocarbons and N-heterocyclic compounds. Theoretical assignments of some triplet states are discussed briefly. Triplet lifetimes of the solutes have been determined at 77 and 293 K by phosphorescence decay measurements and by kinetic spectrophotometry. Non-exponential decays of compounds with triplet lifetimes less than 0.1 s at 293 K have been attributed to diffusion-controlled quenching reactions occurring in low viscosity regions in the polymer.