Modeling and optimization of the excitonic diffraction grating.

Periodical spatial modulation of the excitonic resonance in a quantum well could lead to the formation of a new highly directional and resonant coherent optical response-resonant diffraction. Such excitonic diffraction gratings were demonstrated in epitaxially grown quantum wells patterned by low-dose ion beam irradiation before or after the growth. In this paper we present a theoretical model of the resonant diffraction formation based on the step-by-step approximation of the Maxwell equation solution.

Ion-beam-assisted spatial modulation of inhomogeneous broadening of a quantum well resonance: excitonic diffraction grating.

We propose a method of spatial modulation of inhomogeneous broadening of a quantum-well excitonic resonance based on local generation of defects produced by a focused ion beam. The method is applied to fabrication of excitonic diffraction grating in a single quantum-well InGaAs/GaAs structure by irradiating the sample with a beam of 35-keV He ions of exposure doses <10  cm. The spectrum of resonant diffraction on such a structure is narrower than that of reflectivity and decreases much faster with increasing temperature.

Motional enhancement of exciton magnetic moments in zinc-blende semiconductors.

We report a remarkable enhancement of the magnetic moments of excitons as a result of their motion. This surprising result, which we have observed in magneto-optical studies of three distinct zinc-blende semiconductors, GaAs, CdTe, and ZnSe, becomes significant as the kinetic energy of the exciton becomes comparable with its Rydberg energy and is attributed to motionally induced changes in the internal structure of the exciton. The enhancement of the magnetic moment as a function of the exciton translational wave vector can be represented by a universal equation.