Abstract
Asymmetric quantum wells possess large optical nonlinearities1 useful for a number of applications, including modulators, optical switches, and wavelength converters. Second-order nonlinearities due to intersubband transitions have been demonstrated in both GaAs-based and InP-based quantum wells. The measured nonlinear optical susceptibilities for second harmonic generations of mid-infrared radiation were 2 to 3 orders of magnitude larger than that of bulk GaAs.2 For near-infrared applications, interband processes should also be considered. For high wavelength conversion efficiencies in near-infrared, the ratio (F.M.) between the nonlinear optical susceptibility and the interband absorption coefficient has to be large. In type-I quantum wells, F.M. is limited because the spatial distributions of the ground state electron and the heavy-hole wave functions are similar. Type-II asymmetric quantum wells, on the other hand, can achieve large F.M. resulting from relatively small overlap between the lowest-level electron wave function and the uppermost heavy, hole wave function.3 Type-II quantum wells found in lattice-matched material systems have limited choices of band-gap energies and band offsets. In this paper we discuss the realization of type-II quantum wells in a strain- compensated system.
© 1995 Optical Society of America
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