Nonlinear optical rectification in asymmetric coupled quantum wells

The optical rectification (OR) in the asymmetric coupled quantum wells (ACQWs) is calculated theoretically. The dependence of the OR on the width of the right-well and the barrier is studied. The analytical expression of the optical rectification coefficient is obtained by using the compact density-matrix approach and the iterative method, and the numerical calculations are presented for a typical GaAs/Al_xGa_1 − xAs ACQW. The results obtained show that the OR efficient can reach the magnitude of 10⁻⁴ m/V in this ACQW system, which is 1-2 orders higher than that in single quantum systems. Moreover, the OR coefficient is strongly dependent on the widths of the barrier and the right-well of the ACQWs. An appropriate choice for the width of the barrier and the right-well of the ACQWs can induce a larger OR coefficient.