Electric-field control of the occupancy of the upper laser subband in quantum-well structures with asymmetric barriers designed for unipolar laser operation.

Experimental and theoretical studies of triple-quantum-well structures implementing a prototype active element for a novel type of unipolar laser were carried out. Such a laser, whose design was suggested by us previously, is based on highly asymmetric quantum wells (with barriers of noticeably different heights). It is shown that application of an external electric field to the structures under study leads to an effect similar to the dimensionality-switching effect in a structure with optimum parameters. Despite the fact that barrier thicknesses in the structures under study exceed considerably the values corresponding to the optimum structure, the matrix-element product that determines the gain remains sufficiently large (175–200 Ų as compared to 250 Ų in the optimum structure) in a wide range of electric fields. [ABSTRACT FROM AUTHOR]