Wavelengths beyond 2 μm have long been employed in spectroscopy, materials processing, military systems, and laboratory or remote monitoring. As a result of recent progress in potentially ultralow-loss fluoride fibers, new applications in mid-IR (2-4-μm) lightwave communications are now receiving serious consideration. At present, the minimum loss in experimental fluoride fibers, just below 1 dB/km, occurs near 2.5 μm. Most previous device work, however, has been concentrated in the region beyond 4 μm, where sources include either molecular or cooled injection lasers, and receivers contain cooled detectors or detector arrays. Although cryogenic component temperatures may be acceptable for some applications, practical lightwave systems will likely demand semiconductor devices capable of efficient operation at or close to room temperature. In these conditions, laser threshold and efficiency are strongly affected by Auger recombination processes, and narrow band gap detectors suffer from large dark currents. This discussion will emphasize the limits these effects are expected to place on injection lasers and photodetectors operating in the 2-4-μm wavelength range.
© 1987 Optical Society of AmericaPDF Article