Abstract

Substantial effort has been recently dedicated to the study of the far-IR nonlinear optical properties of the intersubband transitions (IST’s), especially in the areas of IR detection¹ and frequency conversion, based on the second-order susceptibility.^2–4 The third-order susceptibility research was mostly limited to the saturation-type nonlinearity χ⁽³⁾ (ω; ω; −ω; ω), which is inherently slow and is always accompanied by significant absorption, making practical applications difficult.⁵

© 1993 Optical Society of America