ABSTRACT
Lasers are based on self-oscillations of light emitting systems through stimulated emission. To gain enough to overcome absorption, inversion of the quantum states is needed between which the laser transition occurs. Light coupling from external sources is an already available technical solution, which will continue to be the preferred configuration if the heat from high-power lasers is left outside the densely packed chip and if the laser light may be split and distributed around the chip dimension by a photonic waveguide network. Many direct semiconductors have proven to be excellent laser materials in diode lasers, where carrier injection is provided from forward-biased p/n junctions. The success of hybrid laser integration had a large influence on the acceptance of silicon photonics but also inspired new research on monolithic integration approaches. Electrically stimulated lasers have the higher practical importance in semiconductors.
