摘要
Lasers are devices that produce light by stimulatedemission （SE） which amplifies light coherently. They aredistinguished from other light sources by their beamswith good coherence, directionality, high brightness andspectral purity. As such, lasers have widespread appli-cations, including scientific research, industry, medicineand military defense, and actually become ubiquitous inour daily life. Despite of the diversity in laser classifica-tion, compact lasers are dominantly made from semi-conductors. Especially, electrically driven semiconductorlasers are indispensable components for optical commu-nication.
