We discuss peculiarities of the nonlinear optical processes utilizing intersubband nonlinearities in high band offset
heterostructures formed by three nearly lattice matched binaries, InAs, GaSb, AlSb, and their alloys. We show that these
materials offer unique benefits for nonlinear optics due to great flexibility in designing optical interaction schemes in a
wide frequency range and very large values of the nonlinear susceptibilities even involving short-wavelength transitions.
The resulting nonlinear conversion efficiency for the second-harmonic or sum-frequency generation is in the mW/W<sup>2</sup>
range even for very short coherence lengths of the order of several &mgr;m.