Quantum-well shape optimization for intersubband-related electro-optic modulation properties

A method is described for the optimized design of quantum-well structures, in respect to maximizing the second-order susceptibilities relevant for electro-optic applications. It relies on applying the isospectral (energy structure preserving) transformations to an initial Hamiltonian, in order to generate parameter(s) controlled family of Hamiltonians that (i) are isospectral to the initial one and, (ii) have the potential variation proportional to the effective mass variation, being thus realizable by graded ternary alloys like ${\mathrm{Al}}_{x}{\mathrm{Ga}}_{1\ensuremath{-}x}\mathrm{As}.$ By changing the values of control parameters one changes the potential shape and thus the values of matrix elements relevant for the susceptibility to be maximized. The use of the method is demonstrated by designing optimal quantum wells for the Stark effect or quantum interference derived electro-optical effects.