摘要： Within the framework of the effective-mass envelope-function theory , the field-dependent intersubband optical properties of a Al_0.4Ga_0.6As/Al_0.2Ga_0.8As/GaAs step quantum well are investigated theoretic ally based on the periodic boundary condition. A very large Stark shift occurs when the lowest subband electron remains confined to the small well while the hig her subband electron confined to the big well. The optical nonlinearity in a step well due to resonant intersubband transition(ISBT) is analyzed using a density matrix approach. The second-harmonic generation coefficient χ⁽²⁾_2ω and nonlinear optical rectification χ⁽²⁾₀ have also been investigated theoretically. The results show that the ISBT in a step well can generate very large second order optical nonlinearities,χ⁽²⁾₀ and χ⁽²⁾_2ω can be tuned by the electric field over a wide range.

Abstract: Within the framework of the effective-mass envelope-function theory , the field-dependent intersubband optical properties of a Al_0.4Ga_0.6As/Al_0.2Ga_0.8As/GaAs step quantum well are investigated theoretic ally based on the periodic boundary condition. A very large Stark shift occurs when the lowest subband electron remains confined to the small well while the hig her subband electron confined to the big well. The optical nonlinearity in a step well due to resonant intersubband transition(ISBT) is analyzed using a density matrix approach. The second-harmonic generation coefficient $\chi$⁽²⁾_2$\omega$ and nonlinear optical rectification $\chi$⁽²⁾₀ have also been investigated theoretically. The results show that the ISBT in a step well can generate very large second order optical nonlinearities, $\chi$⁽²⁾₀ and $\chi$⁽²⁾_2$\omega$  can be tuned by the electric field over a wide range.

中图分类号:  (Quantum wells)

• 78.67.De

42.65.Ky (Frequency conversion; harmonic generation, including higher-order harmonic generation) 78.20.Ls (Magneto-optical effects) 71.18.+y (Fermi surface: calculations and measurements; effective mass, g factor)