Linear and nonlinear intersubband electroabsorptions in a modulation-doped quantum well

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Abstract
The linear and nonlinear optical-absorption coefficients and changes in refractive indices due to intersubband optical transitions in a modulation-doped quantum well with an applied electric field are derived theoretically based on the density-matrix formalism. The calculations of electron energy levels and envelope wave functions in a double-confinement quantum-well structure are discussed with electric-field and screening effects. The electric-field, screening, and tunneling effects on the electronic properties (electron energy levels and envelope wave functions) and optical properties (linear and nonlinear optical-absorption coefficients and changes in refractive indices) are discussed with detailed numerical results. The comparisons between theoretical results and the corresponding experimental data show good agreement. The results presented here will be useful for high-speed intersubband infrared photodetectors and electro-optical modulators.