US Government As Represented by the Secretary of the Army

Mitra Dutta

Michael A Stroscio

Jagadeesh Pamulapati

Paul H Shen

Hongen Shen

Weimin Zhou

Gerald J Iafrate

Ki Wook Kim

Arthur D Ballato

Michael Wraback

Yicheng Lu

Serge Luryi

Gregory L Belenky

Vladimir V Mitin

Mikhail Kisin

Rimvydas Mickevicius

Yuri M Sirenko

John A Kosinski

Kwong-Kit Choi

Doran Dakota Smith

Richard H Wittstruck

Joel R Shappirio

Harold L Grubin

Viatcheslav Kochelap

Jun He

Gerald J Lafrate

Paul Hongen Shen

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.

Creation of anisotropic strain in semiconductor quantum well

Intersubband semiconductor lasers (ISLs) are of great interest for mid-infrared (2-20 &#x3bc;m) device applications. These semiconductor devices have a wide range of applications from pollution detection and industrial monitoring to military functions. ISLs have generally encountered several problems which include slow intrawell intersubband relaxation times due to the large momentum transfer and small wave-function overlap of the initial and final electron states in interwell transitions. Overall, the ISL's of the prior art are subject to weak intersubband population inversion. The semiconductor device of the present invention provides optimal intersubband population inversion by providing a double quantum well active region in the semiconductor device. This region allows for small momentum transfer in the intersubband electron-phonon resonance with the substantial wave-function overlap characteristic of the intersubband scattering.

Intersubband semiconductor lasers with enhanced subband depopulation rate

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. A transverse electric and electromagnetic field is applied across the plane of the quantum well layers to ionize the excitons, which produces an anisotropic bleaching and concomitant line broadening of the anisotropic excitonic absorption. This phenomenon results in a polarization rotation of the transmitted optical field such that light passing through the device may be detected by a photosensitive polarization detector. The device is capable of effectively measuring the phase and frequency of terahertz energy over a wide bandwidth.

Method and apparatus for detection of terahertz electric fields using polarization-sensitive excitonic electroabsorption

An optical signal processor is implemented as a monolithically integrated semiconductor structure having optical waveguide devices forming beam splitters, optical amplifiers and optical phase shifters. The monolithic structure photonically controls a phased-array microwave antenna. Phase-locked master and slave lasers generate orthogonal light beams having a difference frequency that corresponds to the microwave carrier frequency of the phased-array antenna. The lasers feed the signal processor, which performs beam splitting, optical amplifying and phase shifting functions. A polarizer and an array of diode detectors convert optical output signals from the signal processor into microwave signals that feed the phased-array antenna. The optical waveguides of the signal processor are fabricated in a single selective epitaxial growth step on a semiconductor substrate.

Microwave system

A semiconductor waveguide modulator that is polarization insensitive/independent at bias variations for any chosen wavelength. The modulator of the present invention employs a novel type of strained semiconductor quantum well (QW) structure that exhibits bias independent, heavy-hole and light hole degeneracy. This effect is achieved by inserting one or two thin layers of highly tensile, strained materials in a specific position within the QW. By adjusting the thickness and the position of the highly tensile strained layers, the quantum confined Stark effect (QCSE) for the heavy hole and light hole can be engineered separately to control the bias dependent polarization properties. The present invention has applications, for example, in optoelectronic devices in the areas of telecommunications, optical signal processing, scanning and displays.

Polarization insensitive/independent semiconductor waveguide modulator

Monolithically integrated signal processing circuit having active and

A mesoscopic structure is fabricated such that the desired dominant modes of the acoustic phonons in the structure have wavelengths such that the length of a half-integral number of wavelengths equals the length of the structure through which the desired electron wave is propagating. A manner of achieving this object is to provide for a material in a quantum wire and a material at the end of the quantum wire such that the two materials have such different properties (as disclosed hereinafter) to abruptly dampen the phonon modes at the interface between the two materials. With such an interface, a clamped boundary condition will occur and the modes of amplitude can be assumed to vanish at the interface. Such a case applies at some metal-semiconductor interfaces. In particular, for a mesoscopic device having wire-like regions which terminate on a variety of metal regions (regions used as contacts, gates, barriers, etc.), it is satisfactory to apply clamped boundary conditions. At these boundaries, the acoustic modes will have nodes instead of the anti-nodes that are established in the case of an open boundary.

Mesoscopic electronic devices with tailored energy loss scattering

An MQW is fabricated such that at a particular level of purely mechanical ress/strain the optical properties of the MQW are altered by breaking the heavy and light hole degeneracy (splitting of the heavy and light holes in the valence band) of the MQW in the E-k domain. In a preferred embodiment of the invention ring electrical contacts are disposed on the MQW and the entire MQW structure, including electrical contacts is mounted on a piezoelectric substrate, with the proper crystallographic orientation and strain induced orientation, via an epoxy. In operation, a bias is applied to the MQW structure and the piezoelectric substrate. The bias causes quantum decoupling of the heavy and light holes; however, the bias also will cause the piezoelectric material to move, which will induce a strain on the MQW structure. This strain will, in turn, also induce a decoupling of the heavy and light holes, but to a greater degree than the decoupling induced by the electrical bias and therefore, the absorption of the MQW will altered, thereby polarizing optical signal incident to (or through) the device.

Dynamic modulation of quantum devices

Method for making monolithically integrated signal processing circuit

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.

Infrared/optical imaging techniques using anisotropically strained doped

A carrier transport media is doped with impurities or includes barrier structures within or on the carrier transport media and a sinusoidally alternating external electric field(s) with frequencies equal to the Bloch frequency divided by an integer is applied to the carrier transport media to alter the effective barriers of the impurities or barrier structures to an arbitrarily large potential compared to the zero field barrier potential. The various impurities or barrier structures are band engineered and deposited, grown or implanted in the carrier transport media and can take any form such as barrier layers in or on the transport media, laterally induced barriers, and impurities or defects in the carrier transport media. The application of time-dependent external fields across a length of nanoscale or mesoscopic structure leads to an effective renominalization of the barrier potential strengths when the frequency of the applied electric field multiplied by an integer is equal to the Bloch frequency. Under these conditions the transmission probability is altered and the current ratio, i.sub.2 /i.sub.1, will be modulated strongly.

Field controlled current modulators based on tunable barrier strengths

A semiconductor lasing device is formed by disposing a quantum well or quum wire array between positive and negative ohmic contacts such that different potentials are applied along the array to establish a transverse electromagnetic (TEM) mode of the optic signal (i.e. where the field components lie in a plane perpendicular to the direction of propagation). Thus, the light confinement l will be on the order of the electron confinement a. By applying different potentials via the positive and negative ohmic contacts to multiply connected waveguides, the established TEM mode does not have a cut-off frequency, and therefore, the gain of device can be greatly enhanced while still providing increased anisotropy and a low threshold current.

TEM mode quantum wire or well structure

A submatrix of semiconductor material contains plural electron conduction annels in either or both series and parallel arrangements. Electrons in the channels are confined by the submatrix and a surrounding main matrix provides photon confinement within the submatrix for nonequilibrium phonons which are mutually interchanged between channels. The confinement enhances the efficiency of energy and momentum transfer by means of nonequilibrium phonons. Embodiments of the invention as a transformer, bistable switch, controlled switch and amplifier are disclosed.

Interchannel nonequilibrium confined-phonon exchange device

A multiple quantum well layer is sandwiched between two core waveguide layers, which are, in turn, sandwiched by two cladding layers. This layering is deposited on a substrate with a metal contact and the top cladding layer is formed so as to form at least two parallel channels with metal contacts. The refractive indices of the various materials comprising the layers are chosen such that the cladding layers and the multiple quantum well layer have refractive indices which are less than the refractive index of the core waveguide layers, but which are different from one another. In operation, an electric field is applied to the structure via metal contacts on the parallel channels. Depending on the magnitude of the electric field the optical signal may be switched from one channel to the other channel and depending on the magnitude and direction of the electric field and the intensity of the optical signal, the optical signal may be switched from the upper waveguide to the lower waveguide.

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Matawan, NJ, United States of America

Mitra Dutta