Abstract

A new class of quantum well semiconductors exhibiting electric field tunable nonlinear optical properties (second and third harmonic generation and multiphoton ionization) has been demonstrated using band gap engineering and molecular beam epitaxy. By careful control of the layer thicknesses and composition, we have implemented coupled quantum well structures (Fig. 1) with extremely large second and third order nonlinear susceptibilities and have been able to observe for the first time third harmonic generation and multiphoton ionization in a quantum well structure. Recent second harmonic generation and optical rectification experiments in stepped quantum wells have found large values of |χ⁽²⁾| at λ = 10 µm.^[1,2] A unique feature of our present structures (Fig. 1) is that the intersubband transitions can be strongly Stark-shifted so that the nonlinear susceptibilities can be resonantly enhanced or quenched by application of a small voltage.

© 1992 IQEC