| Mid-infrared (2--20 mum) lasers have important applications in industrial process control, bio-medical diagnostics, environmental monitoring, remote sensing, and defense. The Sb-based semiconductor laser is among the most advanced 2--5-mum laser technologies developed recently. However, an impediment to its commercial application is the inadequate lasing efficiency above 200 K. The objective of this dissertation is to investigate this low efficiency problem. Prior to this work, evidences suggested that carrier density was the sole factor affecting efficiency at high temperature. The results here suggest a more complex process involving intervalence band spectral features and carrier relaxation dynamics. Solving these specific problems can lead to high-temperature Sb lasers.;An experimental system and procedure was developed for accurate measurement of the internal loss and internal quantum efficiency as a function of temperature. Lasers with different active structures were studied. Unusual behavior never reported before was observed. One type of laser exhibited a rapid increase followed by a decrease of the internal loss with increasing temperature. The other type exhibited a nearly constant internal loss. In both cases, carrier density was determined from photoluminescence, and evidences indicate that other factors besides carrier density were responsible for their complex behavior. The low internal loss at high temperature indicates that high power scaling was possible. This was demonstrated with a device with AR/HR-coated facets, which yielded a peak power of 0.3 W with 2.5-mus pulse width at 190 K. This result is among the highest power reported for diode-pumped Sb laser at this wavelength and temperature range.;Three modeling programs, eight-band k·p model, two-dimension thermal model, and two-dimension waveguide model were developed for data analysis and laser design. All three were based on the finite-element method. The eight-band k·p model can calculate the energy levels, wavefunction, bandstructure, gain, interband absorption, internal loss, and photoluminescence spectrum. The two-dimension thermal model can calculate the dynamic temperature profile of the lasers. The two-dimension waveguide model can calculate the optical field inside the laser and the far field pattern of the light beam. The results from these models were compared extensively with experiments and good agreement was obtained. |
