Nonlinear optical devices based on a transparency in semiconductor intersubband transitions

We propose nonlinear optical devices for the near and mid infrared range that use an absorption transparency along with a resonantly enhanced second order susceptibility for efficient frequency conversion or parametric amplification, The susceptibilities have been calculated for an asymmetric GaAs/AlGaAs double quantum well structure that utilizes coherent resonant tunneling to create Fano-type interferences. Our calculations show that nonlinear susceptibilities of the order of chi((2)) = 10(-7) m/V are feasible at the transparency frequency of a singly resonant transition at 5 mu m. Second harmonic conversion efficiency and parametric gain depend on the ratio of coupling strength to the dephasing rare and can be tuned by changing the width of the tunneling barrier.