Introduction to Semiconductor Lasers

Abstract

Every laser consists of or involves -- principle -- vital parts or mechanisms: an active medium that allows light ampli.cation and some form of feedback, e.g. realized in the form of an optical resonator. In a semiconductor laser, the fundamental principle of the active medium is the recombination of electron--pairs in a suitable layer of semiconductor medium embedded in a chip forming an optical cavity for optical fields propagating within. Inversion of this medium may be achieved by optical or electronic pumping via an optical pump beam or directly via electrical contacts by applying a current. Once the pump beam or the current exceeds a characteristic threshold intensity spontaneous emission processes are exceeded by stimulated emission and lasing starts. In the following we will give a brief overview of typical semiconductor active media and resonator structures employed in modern semiconductor lasers.