An ultra-high level second-order nonlinear optical susceptibility in strained asymmetric GaN–AlGaN–AlN quantum wells: Towards all-optical devices and systems

In this paper an asymmetric structure for enhancement of second-order nonlinear optical susceptibility in the strained asymmetric GaN–AlGaN–AlN quantum well (QW) is proposed. In this structure, the strain-induced spontaneous and piezoelectric effects have been taken into account, and the second-order optical susceptibility of the δ-doped step QW structure is analyzed by considering the Shrödinger–Poisson self-consistent for different Al mole fraction x, step position, and pump photon energy hω. The magnitude of the second-order susceptibility of the simulated results for the proposed structure show an enhancement more than 400 times compared traditional strained QWs. Our simulations show that with increasing well width in the case of constant step width, peak of the second-order susceptibility is increased as well as resonant wavelength is decreased. Also, it is shown that for a given well and step widths there is an optimum mole fraction corresponding to maximum second-order susceptibility. Finally in the case of constant well width and mole fraction of the step, with increasing step width the second-order susceptibility is decreased.