Optical: systems and elements – Optical modulator – Light wave temporal modulation
Patent
1996-11-21
1998-05-05
Font, Frank G.
Optical: systems and elements
Optical modulator
Light wave temporal modulation
359245, G02F 103
Patent
active
057483590
ABSTRACT:
An imaging system for transferring an infrared (IR) image to a visible image. The imaging system includes a polarization rotator that rotates the polarization of a visible light beam in response to absorptions of radiation from the IR image. A polarizer outputs components of the visible light beam as a function of the amount of absorbed radiation from the IR image. The polarization rotator is formed from a multiple quantum well structure grown on a semiconductor substrate with a thermally induced uniaxial, in-plane, compressive strain. The multiple quantum well structure includes a heterostructure of undoped barrier layers and doped quantum well layers. The strain causes the quantum well layers to have anisotropic radiation absorption characteristics. In particular, orthogonal components of the visible light parallel to and perpendicular to the strain will experience different degrees of absorption. The dopant in the quantum well layers is sufficient to bleach the lowest exciton resonances, thereby reducing absorption of the light beam. IR absorption from the image decreases the bleaching and increases the ability of the quantum well layers to promote exciton transitions. As such, the polarization of the light beam rotates as a function of the amount of IR absorbed from the image.
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Shen et al, "Optical anisotropy in GaAs/Al.sub.x Ga.sub.1-x As multiple qtum wells under thermally induced uniaxial strain", Pysical Review B47 pp. 13933-13936, 15 May 1993.
Dutta Mitra
Pamulapati Jagadeesh
Shen Paul H.
Wraback Michael
Anderson William H.
Font Frank G.
Ratliff Reginald A.
The United States of America as represented by the Secretary of
Zelenka Michael
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