Infrared/optical imaging techniques using anisotropically strained doped quantum well structures

US5748359A · kind A · utility

Assignee

• The United States of America as represented by the Secretary of the Army · US

Inventors

• Paul H. Shen · North Potomac, US
• Mitra Dutta · Tinton Falls, US
• Michael Wraback · Germantown, US
• Jagadeesh Pamulapati · Eatontown, US

Key dates

• Filing date: Nov 21, 1996
• Grant date: May 5, 1998
• Expiry date: Nov 21, 2016

Classification

• Technology area (CPC G): Physics
• CPC primary: G02F2203/07
• WIPO field: Optics
• WIPO sector: Instruments

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, …