Antimonide type-II "W" lasers

Abstract

This chapter has reviewed the various classes of antimonide Type-II "W" lasers developed to date and the status of their performance, as well as factors limiting their operating temperature, output power, spectral purity, and beam quality. Since the "W" concept was first introduced in 1995, dramatic progress has been made by both optically-pumped devices and their electrically-injected counterparts. Recent results from the latest embodiments of the "W"-ICL configuration have been especially encouraging. PCDFB designs that maintain coherent output from very wide stripes open a promising avenue to "W" devices exhibiting both much higher powers and good beam qualities. Nonetheless, further issues must be resolved before "W" diodes can operate efficiently in CW mode at higher temperatures. Carrier transport should benefit from the incorporation of smoothing transition regions and appropriate doping profiles. Less straightforward to address are the dominance of Auger non-radiative decay and greater-than-expected internal losses at higher operating temperatures, which induce high lasing thresholds and reduced differential efficiencies. Systematic variation of the design parameters may elucidate the fundamental limitations and suggest solutions. Optimization of the heat sinking, especially using epitaxial-sidedown mounting, should close the gap between pulsed and CW performance levels. While there is still substantial room for improving the current generation of antimonide Type-II "W" devices, we envision that they will ultimately play a valuable role in addressing the need for convenient and low-cost mid-IR sources. © 2006 Springer-Verlag London Limited.