CALCULATION OF THE 2ND-ORDER OPTICAL NONLINEAR SUSCEPTIBILITIES IN BIASED ALXGA1-XAS QUANTUM-WELLS

The second-order optical nonlinear susceptibilities chi(2) of biased Al(x)Ga1-xAs quantum wells (QW's) are theoretically estimated. The contributions of Wannier excitonic states and nonexcitonic excited states to chi(2) are discussed. It is shown that the transitions between a Wannier excitonic state and nonexcitonic excited states contribute dominantly to chi(2) of biased Al(x)Ga1-xAs QW's. The chi(2) values are calculated for various QW widths and electric fields. The strong resonance of exciton energy and pumping-light energy, the strong oscillator strength of Wannier exciton states, and the large dipole of Wannier excitons result in large chi(2) values greater than 5 x 10(-10) m/V for QW's with well widths of less than 70 angstrom. Because QW's have large chi(2) values in the wavelength range near 1.55 mum, they are good candidates for nonlinear optical devices for communication systems.