Abstract: An AlGaN composition is provided comprising a group III-Nitride active region layer, for use in an active region of a UV light emitting device, wherein light-generation occurs through radiative recombination of carriers in nanometer scale size, compositionally inhomogeneous regions having band-gap energy less than the surrounding material. Further, a semiconductor UV light emitting device having an active region layer comprised of the AlGaN composition above is provided, as well as a method of producing the AlGaN composition and semiconductor UV light emitting device, involving molecular beam epitaxy.

Abstract: An AlGaN composition is provided comprising a group III-Nitride active region layer, for use in an active region of a UV light emitting device, wherein light-generation occurs through radiative recombination of carriers in nanometer scale size, compositionally inhomogeneous regions having band-gap energy less than the surrounding material. Further, a semiconductor UV light emitting device having an active region layer comprised of the AlGaN composition above is provided, as well as a method of producing the AlGaN composition and semiconductor UV light emitting device, involving molecular beam epitaxy.

Abstract: In a preferred embodiment, a light emitting device comprising: a polar template; a p-type layer grown on the polar template; the p-type layer having a first polarization vector; the first polarization vector having a first projection relative to a growth direction; an n-type layer grown on the p-type layer; the n-type layer having a second polarization vector; the second polarization vector having a second projection relative to said growth direction that is larger than the first projection of the first polarization vector for the p-type layer; the n-type layer and p-type layer forming an interface; whereby the first polarization vector in the p-layer and second polarization vector in the n-layer create a discontinuity at the interface resulting in a negative charge appearing at the interface.

Abstract: A method and device for generating terahertz radiation comprising a polar crystal material layer operative to emit terahertz radiation; the polar crystal material layer comprising a plurality of stacking faults; the stacking faults lying substantially perpendicular to the polar axis and forming boundaries at which the internal electric polarization terminates leading to charges accumulating at the boundaries, and creation of internal electric fields oriented along the polar axis; a pulsed radiation source for creating photogenerated carriers in the polar crystal material; whereby the photogenerated carriers accelerate in the internal electric fields associated with the termination of the internal electric polarization by the stacking faults to thereby generate terahertz radiation.

Abstract: An AlGaN composition is provided comprising a group III-Nitride active region layer, for use in an active region of a UV light emitting device, wherein light-generation occurs through radiative recombination of carriers in nanometer scale size, compositionally inhomogeneous regions having band-gap energy less than the surrounding material. Further, a semiconductor UV light emitting device having an active region layer comprised of the AlGaN composition above is provided, as well as a method of producing the AlGaN composition and semiconductor UV light emitting device, involving molecular beam epitaxy.

Abstract: Methods and devices for creating an anisotropic strain in a semiconductor quantum well structure to induce anisotropy thereof are disclosed herein. Initially, a substrate is provided, and a quantum well structure formed upon the substrate. A first crystalline layer (e.g., a GaAs layer) having a first crystalline phase can then be deposited upon the quantum well structure. Thereafter, a second crystalline layer (e.g., a GaN layer) having a second crystalline phase and a thickness thereof can be formed upon the first crystalline layer to thereby induce an anisotropic strain in the quantum well structure to produce a quantum well device thereof. Additionally, the second crystalline layer (e.g., GaN) can be formed from a transparent material and utilized as an anti-reflection layer. By properly choosing the thickness of the second crystalline layer (e.g., a GaN layer), a desired anisotropic strain as well as a desired anti-reflection wavelength can be achieved.

Abstract: Methods and devices for creating an anisotropic strain in a semiconductor quantum well structure to induce anisotropy thereof are disclosed herein. Initially, a substrate is provided, and a quantum well structure formed upon the substrate. A first crystalline layer (e.g., a GaAs layer) having a first crystalline phase can then be deposited upon the quantum well structure. Thereafter, a second crystalline layer (e.g., a GaN layer) having a second crystalline phase and a thickness thereof can be formed upon the first crystalline layer to thereby induce an anisotropic strain in the quantum well structure to produce a quantum well device thereof. Additionally, the second crystalline layer (e.g., GaN) can be formed from a transparent material and utilized as an anti-reflection layer. By properly choosing the thickness of the second crystalline layer (e.g., a GaN layer), a desired anisotropic strain as well as a desired anti-reflection wavelength can be achieved.

Abstract: A terahertz electromagnetic energy detector comprises a (100) oriented multiple quantum well thermally bonded to a first transparent substrate having a direction dependent thermal coefficient of expansion such that this coefficient matches the thermal coefficient of expansion of MQW in one direction but different form the direction-dependent thermal coefficient of expansion of the MQW in a perpendicular direction. The resultant internal thermally induced anisotropic strain leads to a polarization dependence of the optical absorption that is strongest near the lowest heavy-hole and light-hole exciton peaks. A second transparent substrate is placed beneath the first transparent substrate and is oriented so that its thermal coefficients of expansion act in a direction perpendicular to those of the first transparent substrate so that the accumulated phase retardation of the optical wave associated with birefringence of the substrate is effectively cancelled.

Abstract: A high contrast ultrahigh speed optically-addressed ultraviolet light modulator exploits the optical anisotropy in a ZnO film epitaxially grown on (01 {overscore (1)}2) sapphire. This device, which could also be realized in a ZnO bulk crystal or similar wide bandgap material, achieves both high contrast and high speed by exploiting the anisotropic bleaching of the anisotropic absorption and concomitant ultrafast polarization rotation near the lowest exciton resonances produced by femtosecond ultraviolet pulses. The resultant modulation in a preferred embodiment is characterized by a contrast ratio of 70:1, corresponding to a dynamic polarization rotation of 12°, and decays to a quasi-equilibrium value within 100 ps.

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.