ABSTRACT
The active layer in a semiconductor laser is a lower bandgap material sandwiched between two layers of a higher-bandgap semiconductor. The relative permittivities of the core and cladding layers are, however, opposite, that is, the refractive index (RI) is higher for the core layer. This difference in RIs leads to the optical connement of the generated light. The electromagnetic (EM) wave is essentially guided and the core layer acts as a waveguide for the light. The waveguiding may also extend in two directions, as in a buried heterostructure laser.
