ABSTRACT
Semiconductor lasers are devices for oscillation or amplification of an optical wave based on the stimulated emission of photons through optical transition of electrons in a semiconductor. The idea was proposed early in 1957 [1]. Soon after the construction of the fundamental theory of lasers by Schawlow and Townes [2] in 1958, followed by the experimental verifications of laser oscillation in a ruby laser and a He-Ne laser in 1960, the pioneering work on semiconductor lasers was performed [3-5]. In 1962, pulse oscillation at a low temperature in the first semiconductor laser, a GaAs laser, was observed [6-8]. In 1970, continuous oscillation at room temperature was accomplished [9-11]. Since then, remarkable development has been made by the great efforts in different areas of science and technology. Nowadays, semiconductor lasers [12-20] have been employed practically as one of the most important optoelectronic devices and are widely used in a variety of applications in many areas.
