H01S 5/3401

Structure or shape of the active region; Materials used for the active region comprising quantum well or superlattice structures, e.g. single quantum well lasers [SQW-lasers], multiple quantum well lasers [MQW-lasers] or graded index separate confinement heterostructure lasers [GRINSCH-lasers] {having no PN junction, e.g. unipolar lasers, intersubband lasers, quantum cascade lasers}