With Traveling Wave-type Tube Patents (Class 330/43)
  • Patent number: 6369648
    Abstract: A linearized traveling wave tube amplifier with average power limiter is disclosed. The device includes an average power limiter for the purpose of preventing a TWT from operating at output powers higher than the required operating point. The device includes a detector for dynamically producing a detector signal proportional to an average power of an input signal and substantially independent from a peak power of the input signal, and an attenuator, in communication with the detector and the amplifier, for dynamically attenuating the input signal according to the detector signal. The limiter allows the TWTs to be optimized for performance at the required operating point, resulting in higher efficiency, and eliminates the need to size the amplifier for a power level any larger than the required operating point which reduces the cost and complexity of the system.
    Type: Grant
    Filed: April 21, 1999
    Date of Patent: April 9, 2002
    Assignee: Hughes Electronics Corporation
    Inventor: George F. Kirkman
  • Patent number: 6369511
    Abstract: A travelling-wave tube amplifier comprises a travelling-wave tube, a plurality of collector electrodes, a plurality of collector leads and at least one magnetic core. The travelling-wave tube causes interaction between an electron beam and an input high frequency signal to amplify the high frequency signal, and outputs the amplified high frequency signal. The plurality of the collector electrodes capture the electron beam which was subjected to velocity modulation by the interaction. The plurality of the collector electrodes are electrically connected to a power source via the plurality of the collector leads. The at least one magnetic core comprises a through hole. Any two of the plurality of the collector leads go through the through hole in one of the magnetic cores. Currents flowing through the two collector leads through the through hole in the magnetic core generate magnetic fluxes in the magnetic core. The directions of the generated magnetic fluxes are reversed from each other.
    Type: Grant
    Filed: November 2, 1999
    Date of Patent: April 9, 2002
    Assignee: NEC Corporation
    Inventors: Jun' ichi Matsuoka, Kouji Okamoto, Junichi Kobayashi
  • Patent number: 6360084
    Abstract: An RF transmitter, such as a radar transmitter or a communications amplifier, is provided that includes a plurality of RF power tube sections each sharing a common collector. The RF tube sections may comprise Klystron tubes, TWT tubes or other RF power tubes known in the art. A common modulator is also typically provided to modulate electron beams produced in each of the plurality of tube sections. The RF transmitter according to the present invention is considerably lighter and smaller relative to known multi-band RF transmitter structures that employ separate collectors and modulators. An associated RF amplification method that employs a common collector is also provided.
    Type: Grant
    Filed: November 3, 1999
    Date of Patent: March 19, 2002
    Assignee: The Boeing Company
    Inventor: Andrew G. Laquer
  • Patent number: 6353525
    Abstract: A power unit for a grid pulsed O-type microwave tube (1) having a cathode (2) and a collector (3), comprises a cathode unit (5) and a collector unit (6), each having two output terminals (7, 8; 9, 10). A first and a second capacitor (C1, C2) are connected between the output terminals of the respective unit (5, 6). One output terminal (7) of the cathode unit (5) is connected to the cathode (2) of the tube (1), while the other (8) is connected to a ground terminal. One output terminal (9) of the collector unit (6) is connected to the collector (3) of the tube (1), while the other (10) is interconnected with that one (7) of the output terminals of the cathode unit (5) that is connected to the cathode (2) of the tube (1). To minimize crosstalk caused by the collector unit (6) across the first capacitor (C1), the output terminals (9, 10) of the collector unit (6) are connected to said second capacitor (C2) via non-capacitive impedances (Z1, Z2), and to said ground terminal via decoupling capacitors (C31, C32).
    Type: Grant
    Filed: March 9, 2000
    Date of Patent: March 5, 2002
    Assignee: Telefonaktiebolaget LM Ericsson (publ)
    Inventor: Jan Allansson
  • Patent number: 6346853
    Abstract: A predistortion linearizer circuit comprising an amplitude distorting part (AM/AM) and a phase distorting part (AM/PM). At least the phase distorting part (AM/PM) comprises broadband biasing means (51) and a non-linear transmission line (L51/D51 to L55/D55) responsive to them. The biasing means (51) are arranged to bias the non-linear transmission line (L51/D51 to L55/D55) to a substantially phase distorting area. The characteristics of the circuit can be changed by adjusting a biasing voltage (VB1) or by switching some of the diodes (D54, D55) inactive by activation signals (VA1, VA2). The amplitude distorting part (AM/AM) and the phase distorting part (AM/PM) can be similar in structure, but the diodes (D51 to D55) are partly forward-biased, whereby the losses caused by them decrease the amplitude of the signal.
    Type: Grant
    Filed: May 22, 2000
    Date of Patent: February 12, 2002
    Assignee: Ylinen Electronics Oy
    Inventors: Pekka Kangaslahti, Sami Kalajo
  • Patent number: 6177836
    Abstract: A feed-forward linearization of a traveling wave tube amplifier linearizes the transfer function of the tube through a linearization voltage derived at baseband from the instantaneous amplitude of the input signal to control the cathode voltage causing induced phase modulation to offset the normal amplitude modulation to phase modulation conversion distortion. The feed forward linearization control results in reduced distortion for improved phase linearization of the tube over the operating range of the tube.
    Type: Grant
    Filed: May 7, 1999
    Date of Patent: January 23, 2001
    Assignee: The Aerospace Corporation
    Inventors: Albert M. Young, Samuel Seth Osofsky
  • Patent number: 6049249
    Abstract: Apparatus compensating for gain variations versus frequency of a traveling wave tube (TWT) is disclosed. The apparatus provides an RF interaction circuit section designed with specified mismatches causing internal reflections of the RF waves, such that the overall gain response is flattened out or inverted.
    Type: Grant
    Filed: September 8, 1997
    Date of Patent: April 11, 2000
    Assignee: Hughes Electronics Corporation
    Inventors: Ivo Tammaru, James W. Hansen
  • Patent number: 5940025
    Abstract: A radar transmitter for producing a radar signal in response to a radar trigger signal fed thereto. The transmitter includes a radio frequency oscillator for producing a signal having a radio frequency carrier to be used in each transmitted radar signal. The signal produced by the oscillator is amplified by a radio frequency amplifier. In response to the system trigger signal, the transmitter is configured in a normal operating mode to operate with three noise cancellation loops; i.e., an automatic level control loop (ALC); an amplitude modulation noise cancellation loop (AM noise cancellation loop); and a phase modulation noise (PM noise cancellation loop). In response to the system trigger signal, the normal operating mode is preceded with two calibration modes: an AM noise calibration mode used to determine a nominal operating point for the AM noise calibration mode; and a subsequent phase modulation (PM) noise calibration mode used to establish a nominal operating point for the PM noise calibration mode.
    Type: Grant
    Filed: September 15, 1997
    Date of Patent: August 17, 1999
    Assignee: Raytheon Company
    Inventors: Mark A. Koehnke, W. Roger Melick, Raoul E. Plutchak, Stephen Rego, Steve B. Santangelo
  • Patent number: 5862462
    Abstract: A satellite is formed with a signal translation and amplification system which includes at least one communication path. Each communication path includes a plurality of radiation-cooled TWTs powered by a single EPC. Also included in the communication path is a high efficiency radiation panel capable of transmitting heat generated by said TWTs and EPC into space; as well as a radiating collector which is directly applied to each TWT, and is capable of transmitting heat generated by said TWT into space.
    Type: Grant
    Filed: July 12, 1996
    Date of Patent: January 19, 1999
    Assignee: Space Systems/Loral, Inc.
    Inventors: Randall D. Tyner, Donald C. Briggs, Daniel E. Collins, William R. Avellino
  • Patent number: 5838195
    Abstract: Second harmonic distortion of a traveling wave tube amplifier with a bandwidth exceeding one octave is efficiently minimized by generating a low-power second harmonic signal, modifying it by an adaptive filter, and adding the modified second harmonic signal to the fundamental frequency input signal to the TWT. The adaptive filter is controlled by a feedback loop from the output of the TWT and is arranged to minimize the correlation between the generated second harmonic signal and the second harmonic content of the TWT output. Intermodulation distortion is eliminated in a similar manner.
    Type: Grant
    Filed: August 6, 1996
    Date of Patent: November 17, 1998
    Assignee: Northrop Grumman Corporation
    Inventors: Thomas E. Szmurlo, Mitchell F. Radich, Warren E. Guthrie
  • Patent number: 5834971
    Abstract: Multiple gain stages are provided in a single traveling wave tube amplifier (TWTA). Each gain stage comprises an interaction circuit, an associated RF input, and an associated RF output. The gain stages are separated by a drift length that is selected to achieve a desired interaction between gain stages. In one embodiment that uses only one TWT, couplers, and adjustment blocks external to the TWT, feed-forward and feedback connections remove intermodulation distortion introduced by the TWTA.
    Type: Grant
    Filed: November 8, 1995
    Date of Patent: November 10, 1998
    Assignee: Hughes Electronics
    Inventors: David B. Giguere, Paul A. Gianfortune
  • Patent number: 5789978
    Abstract: A Ku-band integrated pre-distortion type linearizer bridge circuit for use in linearizing the performance of a traveling wave tube amplifier. The linearizer bridge circuit comprises linearizer bridge that embodies a phase shifter and a fixed delay in a linear arm, and a Schottky diode distortion generator and a PIN diode attenuator in a nonlinear arm. The output of the linearizer bridge is coupled through an output amplifier and an output attenuator. The RF output signal from the linearizer bridge circuit is coupled to the traveling wave tube amplifier. A control circuit is coupled to the phase shifter, the nonlinear Schottky diode distortion generator circuit, and the PIN diode attenuator, and receives on and off input command signals, and outputs a bilevel telemetry signal that is used as a mode indicator for ground command control.
    Type: Grant
    Filed: November 25, 1996
    Date of Patent: August 4, 1998
    Assignee: Space Systems/Loral, Inc.
    Inventors: Weimin Zhang, Mark Adams, Cindy Yuen
  • Patent number: 5773933
    Abstract: A broadband, traveling wave amplifier which includes a target anode and an lectron gun for bombarding the anode with an electron beam having an amplitude proportional to that of an input signal. The electron gun includes a NEA semiconductor cold cathode having an electron emitting surface and a modulation structure for modulating the emitted electron beam with an input signal to be amplified. The electron gun and the anode are configured as parallel strip transmission lines having the same phase velocity. The target anode may be a reversed-biased stripline diode, Schottky barrier stripline diode, or metal/semiconductor/metal stripline structure.
    Type: Grant
    Filed: March 29, 1996
    Date of Patent: June 30, 1998
    Assignee: The United States of America as represented by the Secretary of the Navy
    Inventor: Max N. Yoder
  • Patent number: 5649310
    Abstract: A satellite is formed with a signal translation and amplification system which includes at least one communication path. Each communication path includes a plurality of radiation-cooled TWTs powered by a single EPC. Also included in the communication path is a high efficiency radiation panel capable of transmitting heat generated by said TWTs and EPC into space; as well as a radiating collector which is directly applied to each TWT, and is capable of transmitting heat generated by said TWT into space.
    Type: Grant
    Filed: June 15, 1994
    Date of Patent: July 15, 1997
    Assignee: Space Systems/Loral, Inc.
    Inventors: Randall D. Tyner, Donald C. Briggs, Daniel E. Collins, William R. Avellino
  • Patent number: 5604402
    Abstract: A harmonic gyro-TWT is provided that has only one possible mode of operation. The harmonic gyro-TWT comprises a waveguide and an electron beam projected through the waveguide and encircling an axis of the waveguide. A plurality of evenly spaced electrical conductors are disposed within the waveguide parallel to the axis and spaced a fixed distance from an inner wall of the waveguide. The electrical conductors are connected together at an end of the waveguide. The electrical conductors are excited in phase with an AC signal connected between the electrical conductors and the inner wall of the waveguide. As a result, a multipole field having an order equal to twice the number of electrical conductors is defined within the waveguide. A plurality of support rails couple the inside surface of the waveguide to each respective one of the plurality of electrical conductors.
    Type: Grant
    Filed: January 31, 1995
    Date of Patent: February 18, 1997
    Assignee: Litton Systems, Inc.
    Inventor: Robert S. Symons
  • Patent number: 5568014
    Abstract: According to this invention, a traveling-wave tube amplifier includes a traveling-wave tube having a multistage depressed collector and a power supply for applying operation voltages to the traveling-wave tube. A body voltage (Vb) for a cathode of the traveling-wave tube is set to be lower than a small-signal synchronous voltage (Vbs) at which a small-signal gain of the traveling-wave tube is maximized. As a result, a tube efficiency (.eta.t) of the traveling-wave tube can be increased and an efficiency of the traveling-wave tube amplifier can be increased as compared with a conventional device.
    Type: Grant
    Filed: December 8, 1993
    Date of Patent: October 22, 1996
    Assignee: Kabushiki Kaisha Toshiba
    Inventors: Yasuhiro Aoki, Kiyoshi Momota, Tetsuo Yamamoto, Hideki Ide, Hiroshi Onihashi
  • Patent number: 5500621
    Abstract: A travelling-wave tube (TWT) for a satellite communication system includes a cathode current regulator which compares a sensed I.sub.K signal with a cathode current reference to form an cathode current error signal, and controls the cathode current in response to the cathode current error signal. Helix arc protection is provided by a helix current shut-down, which compares the helix current with a particular reference, and shuts the TWT supply down when helix current flows. Desirable high efficiency TWTs have a small input drive range between maximum TWT output and a defocussed condition, in which beam current flows in the helix. Sudden changes in path attenuation may result in an RF overdrive condition, and cause helix current flow, and undesirably shut down the TWT. A helix current limiter senses the helix current, and compares it with a reference which represents less helix current than that which causes shutdown, to produce a helix current error signal.
    Type: Grant
    Filed: April 3, 1995
    Date of Patent: March 19, 1996
    Assignee: Martin Marietta Corp.
    Inventors: Allen Katz, Herbert J. Wolkstein, James J. Meighan, III
  • Patent number: 5402085
    Abstract: The voltage variation between the electrodes of the tube of a microwave amplifier (1) causing a phase Shift of the output wave from the microwave amplifier (1), the process according to the invention consists of creating a phase shift of the wave entering the tube of the microwave amplifier (1) that is substantially proportional to the voltage variation and in the direction opposite the phase shift of the output wave caused by this voltage variation.
    Type: Grant
    Filed: April 20, 1993
    Date of Patent: March 28, 1995
    Assignee: Thomson-CSF
    Inventor: Gilles Cote
  • Patent number: 5291146
    Abstract: The RF amplifier has a single waveguiding structure extending longitudinally in a direction of propagation of electromagnetic waves, in which density of an injected current flow is not RF modulated, and a transverse E-field component vector of the electromagnetic waves interacts with the electron flow by electron transit time effects. The waveguiding structure comprises a metallic top strip 1 and a metallic ground strip 2 held apart by two ceramic supports 3 which integrate the two strips into a vacuum tight enclosure together with two RF transparent dielectric windows 4 and 5 which represent the amplifier input and output respectively. Electron flow is generated in a linear current injection system by electronic emitters providing a cathodic source of electron flow which is injected into the waveguiding structure, with a flow vector orientation transverse to the direction of propagation of said electromagnetic waves.
    Type: Grant
    Filed: October 7, 1992
    Date of Patent: March 1, 1994
    Assignee: The United States of America as represented by the Secretary of the Air Force
    Inventor: Walter Friz
  • Patent number: 5227701
    Abstract: An electron tube for achieving high power at high frequency with high efficiency, including an input coupler, a ribbon-shaped electron beam and a traveling wave output coupler. The input coupler is a lumped constant resonant circuit that modulates a field emitter array cathode at microwave frequency. A bunched ribbon electron beam is emitted from the cathode in periodic bursts at the desired frequency. The beam has a ribbon configuration to eliminate limitations inherent in round beam devices. The traveling wave coupler efficiently extracts energy from the electron beam, and includes a waveguide with a slot therethrough for receiving the electron beam. The ribbon beam is tilted at an angle with respect to the traveling wave coupler so that the electron beam couples in-phase with the traveling wave in the waveguide. The traveling wave coupler thus extracts energy from the electron beam over the entire width of the beam.
    Type: Grant
    Filed: May 18, 1988
    Date of Patent: July 13, 1993
    Inventor: Peter M. McIntyre
  • Patent number: 5125417
    Abstract: A process and device for generating conjugated micrometer to radio frequency range electromagnetic waves and for their amplification. The conjugated waves are generated by establishing in a plasma two waves of the desired frequency, essentially identical in wavelength at in opposite directions and by directing a third electromagnetic wave of essentially the same frequency so that this will enter the plasma at a predetermined wavelength, resulting in a fourth conjugated electromagnetic wave.A high magnification of the intensity of the conjugated wave can be attained. Such conjugated waves can be used in human medicine for concentrating waves at a tumor site. Devices of the invention can be used for the intensification of other waves, such as radar frequency waves.
    Type: Grant
    Filed: June 29, 1988
    Date of Patent: June 30, 1992
    Inventor: Isaiah Nebenzahl
  • Patent number: 5124664
    Abstract: A klystron device comprises an array of cold-cathode field emission elements arranged to form a distributed amplifier which further comprises a modulation strip line and a catcher strip line. A collector electrode is spaced from the catcher strip line. The device may include a deflector for returning electrons emitted by the elements back to the modulation strip line so that the device acts as an oscillator.
    Type: Grant
    Filed: November 27, 1990
    Date of Patent: June 23, 1992
    Assignee: The General Electric Company, p.l.c.
    Inventors: Neil A. Cade, David F. Howell
  • Patent number: 5103187
    Abstract: This amplifier stage comprises a microwave tube wherein an electron beam (3) is made to interact with a microwave having a frequency variable within a given useful range, the velocity of the electrons of the beam being determined by a cathode voltage (V.sub.k) applied to the tube and the microwave being propagated in said delay structure (4) that imposes a phase velocity close to the velocity of the electron beam on said microwave. The cathode voltage is a variable voltage, regulated as a function of said frequency, said voltage varying with the frequency to modify the velocity of the electrons of the beam in such a way that, for every frequency of said useful range of frequencies, the corresponding velocity of these electrons remains essentially, but not precisely, identical to the phase velocity of the microwave. Thus, the dispersivity in frequency of the delay structure is compensated for, and the output power delivered by the tube is thus kept essentially constant.
    Type: Grant
    Filed: April 1, 1991
    Date of Patent: April 7, 1992
    Assignee: Thomson-CSF
    Inventors: Alain Durand, Olivier Rabot
  • Patent number: 5059917
    Abstract: A rectangular light pipe (38) and associated optical elements (36), (40) are used to produce an overlapped combination of an array of aberrated laser beams (32), (34) inside a phase conjugate mirror (42). The beam array (32), (34) is focussed onto the entrance face (38a) of the light pipe (38) in such a way that each beam (32), (34) spreads by diffraction and internal reflections to fill the exit face (38b) of the light pipe (38). An image of the exit face (38b), which is completely filled by the overlapped beams (32), (34), is focussed into the phase conjugate mirror (42) such as to produce an overlap spot (46) size which is independent of beam aberation level. The apparatus preserves the linear polarization of the input beams (32), (34), has low optical loss, and may be incorporated into a 2 pass (50), (74) or 4 pass (80) phase conjugate master-oscillator power amplifier.
    Type: Grant
    Filed: April 20, 1990
    Date of Patent: October 22, 1991
    Assignee: Hughes Aircraft Company
    Inventor: Ronald R. Stephens
  • Patent number: 5038076
    Abstract: A radio frequency amplifier having a slow wave structure supported adjacent an electron beam by a support structure. The support structure includes at least one structural support member, having a supporting rod, and a dielectric material disposed on an outer surface portion of the supporting rod. The dielectric material is different from the material of the supporting rod. More particularly the dielectric material is electrically insulating having either a resistivity which reduces upon impingement of electrons from the electron beam or a secondary emission ratio that is substantially unity. The supporting rod has high thermal conductivity and is preferably boron nitride. The dielectric material is preferably titania, magnesia or beryllia.
    Type: Grant
    Filed: May 4, 1989
    Date of Patent: August 6, 1991
    Assignee: Raytheon Company
    Inventors: Burton H. Smith, Colin Bowness, Andras Dallos
  • Patent number: 5029297
    Abstract: The device here disclosed comprises an optical amplifier coupled to direct optical energy into a passive waveguide for transmission through the waveguide to its other end. A photodetector, positioned relative to the passive waveguide, detects the presence of optical energy in the passive waveguide. The photodetector in the structure illustrated is positioned downstream from the optical amplifier and spatially positioned with respect to the optical amplifier to receive optical energy only from the waveguide. The photodetector does not receive optical energy directly from the optical amplifier. A small fraction of the optical energy carried by the passive waveguide is received and detected by the photodetector.
    Type: Grant
    Filed: October 13, 1989
    Date of Patent: July 2, 1991
    Assignee: AT&T Bell Laboratories
    Inventors: Thirumala R. Halemane, Thomas L. Koch, Steven K. Korotky
  • Patent number: 5027079
    Abstract: This invention relates to an Erbium doped fiber amplifier having improved operating characteristics. Parameters which determine the operating characteristics of an erbium doped fiber amplifier are the concentration of erbium in the core of a fiber; the ratio of the radius of the core of the fiber doped with erbium relative to the radius of the core of the fiber, and, the length of the fiber. It is now recognized that improved fiber amplifier performance can be obtained by varying the core-cladding refractive index difference of the fiber. The various parameters are here defined for providing an erbium doped fiber amplifier having optimum gain characteristics.
    Type: Grant
    Filed: July 31, 1990
    Date of Patent: June 25, 1991
    Assignee: AT&T Bell Laboratories
    Inventors: Emmanuel Desurvire, Clinton R. Giles, John L. Zyskind
  • Patent number: 5025142
    Abstract: A light waveform shaping apparatus comprises; a beam splitting means for branching an input optical signal into two optical signals; a photoelectric converter for converting one of the two branched optical signals into an electrical signal; an optical amplifier whose gain is adjustable by a controlling electrical signal, for amplifying an optical signal; an input optical path for introducing the other branched optical signal to the optical amplifier; and an electrical circuit for introducing the electrical signal from the photoelectric converter to the optical amplifier; wherein the optical and controlling electrical signals are supplied to the optical amplifier at a predetermined timing of generally coincident arrival.
    Type: Grant
    Filed: May 19, 1989
    Date of Patent: June 18, 1991
    Assignee: Hamamatsu Photonics Kabushiki Kaisha
    Inventors: Shinichiro Aoshima, Tsuneyuki Urakami, Yutaka Tsuchiya
  • Patent number: 5023563
    Abstract: A method is disclosed of employing free electron lasing action at a first frequency to achieve gain in output power at a second frequency. In a broadest sense, an electron beam is driven with an electromagnetic wave at said first frequency in a first stage, having a first spatial period, to cause bunching of the electron beam. The electrons in the beam are oscillated with a second stage, having a second spatial period, to generate electromagnetic wave power from said beam at the second frequency.In a specific embodiment, the second frequency is near a harmonic of said first frequency. And in a particular implementation, the first stage is provided by a free electron laser having a first wiggler with a first spatial period, the second stage is a second wiggler having a second spatial period and a drift region is disposed between the first and second stages.
    Type: Grant
    Filed: September 24, 1990
    Date of Patent: June 11, 1991
    Assignee: Hughes Aircraft Company
    Inventors: Robin J. Harvey, A. Jay Palmer
  • Patent number: 5021742
    Abstract: This invention relates to a laser amplifier which achieves substantially enhanced gains by diverging the laser beam in a gain medium having a substantially rectangular shape. In particular, at least one laser beam is passed through a lens or other suitable means to cause it to diverge at a predetermined angle and the diverging beam or beams are caused to pass through the gain medium in a manner such that a beam makes only a single pass through any section of the medium, with the total number of passes through the medium by the beam(s) applied to the medium being an even number. The angle at which the beam diverges should be such as to maintain a near optimum laser power extraction efficiency for the beam. If a single beam is supplied to the medium, it makes an even number of passes through the medium with mirrors, prisms, or other suitable means being provided as the beam exits the medium after each pass except the last pass to fold the beam back into the medium for a subsequent pass.
    Type: Grant
    Filed: September 19, 1988
    Date of Patent: June 4, 1991
    Assignee: Science Research Laboratory, Inc.
    Inventor: Jonah H. Jacob
  • Patent number: 5019787
    Abstract: An optical amplifier comprising a substrate of a semiconductor material having a pair of opposed surfaces and a body of semiconductor material on one of the surfaces. The body includes a pair of clad layers of opposite conductivity types having an intermediate quantum wall region therebetween. The clad layers are of a semiconductor material which form a heterojunction with the material of the quantum well region. The clad layers and quantum well region forms a waveguide which extends along the body. A gain section is in the body along the waveguide. The gain section includes a capping layer over the outermost clad layer, a contact on the capping layer and a contact on the other surface of the substrate to allow a voltage to be applied across the gain section. The gain section is adapted to generate light in the active region when a voltage is applied thereacross. A light input section having a grating extending across the body is at one end of the gain section.
    Type: Grant
    Filed: October 30, 1989
    Date of Patent: May 28, 1991
    Assignee: David Sarnoff Research Center, Inc.
    Inventors: Nils W. Carlson, Gary A. Evans, Jacob M. Hammer, Michael Ettenberg
  • Patent number: 5017885
    Abstract: An improved optical amplifier is disclosed with reduced signal-induced, deleterious, nonlinear effects, such as crosstalk, inter-modulation distortion and other saturation-induced effects. The invention comprises an optical amplifier with a compensation loop, such as a feed-forward or a feed-backward loop. This loop provides additional pumping to the gain medium associated with the amplifier, thereby compensating for what would otherwise be deleterious, signal-induced variations in the gain of the optical amplifier.
    Type: Grant
    Filed: September 28, 1990
    Date of Patent: May 21, 1991
    Assignee: AT&T Bell Laboratories
    Inventor: Adel A. M. Saleh
  • Patent number: 5015964
    Abstract: A semiconductor travelling wave optical amplifier in presented in a new configuration. An amplifier chip (20) has the rear facet (23) provided with a reflective coating. Optical signals are input and amplified signals are output via optical fibers (21, 35, 30) and directional coupler (24). A single fiber-to-amplifier alignment is required between fibre tail (25) and the front facet (22) is provided with a very low reflectivity coating. In this configuration the amplification is increased in comparison with the conventional in-line amplifier configuration.
    Type: Grant
    Filed: March 16, 1990
    Date of Patent: May 14, 1991
    Assignee: British Telecommunications Public Limited Company
    Inventor: Michael J. O'Mahony
  • Patent number: 5014015
    Abstract: An ultra-short optical pulse source uses a gain-switched laser diode with a dispersive delay line to compress the optical pulse output from the laser diode, the gain-switched laser diode having particular spectral characteristics. The gain-switched laser diode may be tested by energizing it with a continuous wave signal at or near the lasing threshold level. The resulting spectrum is examined for the presence of satellite spectral intensity features. Those gain-switched laser diodes that exhibit a spectrum having all satellite spectral features below a predetermined level with respect to the intensity of a principal spectral component are selected for use in the ultra-short optical pulse source.
    Type: Grant
    Filed: December 5, 1989
    Date of Patent: May 7, 1991
    Assignee: Tektronix, Inc.
    Inventor: R. Thomas Hawkins, II
  • Patent number: 5008717
    Abstract: Modulation-doped quantum well heterostructures are cascaded in a semiconductor device to achieve high speed operation while obtaining large index of refraction or absorption coefficient changes for modulating lightwave signals without significant increases in the operating potentials over prior quantum well structures. Each modulation-doped quantum well heterostructure exhibits substantially equal boundary conditions in an unbiased condition for efficient cascading or stacking. Each quantum well has associated with it a barrier layer to minimize leakage current. As a result, each quantum well has associated with it a separate charge reservoir. This aspect contributes to the speed of the cascaded structure. When incorporated within a waveguide structure, cascaded modulation-doped quantum well heterostructures can act as an external modulator, or as an intra-cavity wavelength tuning element, or as an intra-cavity modulator, or even as an optically-pumped laser.
    Type: Grant
    Filed: March 3, 1989
    Date of Patent: April 16, 1991
    Assignee: AT&T Bell Laboratories
    Inventors: Israel Bar-Joseph, Tao-Yuan Chang, Daniel S. Chemla
  • Patent number: 5006813
    Abstract: A nonlinear optical receiver includes a source of coherent light of frequency .omega. for illuminating a spatial region. The portion of the source light which is reflected from objects within the spatial region constitutes a signal beam. A reference beam of coherent light of frequency .omega. is also provided. A photorefractive element receives the signal and reference beams and amplifies the signal beam by two-wave mixing.The receiver may include a first polarizer, having a first polarization direction, placed between a cubic photorefractive element and the signal and reference beams, and a second polarizer, having a second polarization direction perpendicular to the first polarization direction, placed so that the amplified signal beam must pass therethrough. A frequency shifting element, such as a Bragg cell modulator, is used to change the frequency of the reference beam.
    Type: Grant
    Filed: February 10, 1986
    Date of Patent: April 9, 1991
    Assignee: Rockwell International Corporation
    Inventors: Mohsen Khoshnevisan, Pochi A. Yeh
  • Patent number: 5005175
    Abstract: This invention is a rare earth doped optical amplifier with increased gain and lowered pump thresholds. The amplifying scheme is based on a 3 level lasing system rather than the more prevalent 4 level lasing system. Additionally, the transmission mode of the optical fiber at the pump wavelength has a radius which is substantially equal to or greater than the radius of the distribution profile of the rare earth ions in the fiber amplifier core. With the inventive amplifier, a gain of 37 dB and a saturation power of 11.3 dBm has been obtained with only 54 mW of launch power at .lambda.=1.49 .mu.m.
    Type: Grant
    Filed: November 27, 1989
    Date of Patent: April 2, 1991
    Assignee: AT&T Bell Laboratories
    Inventors: Emmanuel Desurvire, Clinton R. Giles, Jay R. Simpson, John L. Zyskind
  • Patent number: 5003268
    Abstract: An optical signal sampling apparatus for high-speed gating of an optical signal in the form of repetitive waveforms comprises an input optical path for introducing the optical signal to an optical amplifier; the optical amplifier whose gain is adjustable by a gating electrical signal, for amplifying the optical signal; a driving circuit for providing, in response to a sampling signal, the optical amplifier with the gating electrical signal having a series of pulses which are gradually shifted on a time axis with respect to the repetitive waveforms of the optical signal; and an output optical path for introducing an output optical signal from the optical amplifier.
    Type: Grant
    Filed: April 25, 1989
    Date of Patent: March 26, 1991
    Assignee: Hamamatsu Photonics Kabushiki Kaisha
    Inventor: Yutaka Tsuchiya
  • Patent number: 4993813
    Abstract: An optical amplifier includes a plurality of amplifiers which are disposed between a first reflective mirror and a second reflective mirror of an optical resonator arranged with the first reflecting mirror and the second reflecting mirror in face-to-face relationship and are adapted to amplify light through induced emission; and a beam combining and separating device which is adapted to combine the light made incident thereupon from the plurality of amplifiers and cause the light to emerge therefrom in the direction of the second reflecting mirror and is also adapted to separate the light from incident thereupon after being reflected by the second reflecting mirror and cause the light to emerge therefrom in the respective directions of the amplifiers. As the combination and separation of the light are repeatedly effected, a beam of light having high energy amplified by the amplifiers is obtained.
    Type: Grant
    Filed: November 21, 1989
    Date of Patent: February 19, 1991
    Assignee: Fuji Photo Film Co., Ltd.
    Inventor: Hiroyuki Hiiro
  • Patent number: 4995100
    Abstract: An AGC for a laser amplifier uses a control tone modulated onto the optical signals. During use the modulation on the optical signals is superimposed on the drive current for the laser. The AGC derives a control signal by detecting the modulation in the drive current, multiplying it by the drive current. The drive current for the laser is adjusted to keep the control signal constant. In a preferred embodiment a low level sensor detects when the control tone falls below a threshold level and switches the circuit to a default configuration. The default configuration provides a distress signal to indicate a fault and to identify the affected amplifier. This preferred embodiment is particularly suitable for submarine telecommunications capable which include a plurality of inaccessible amplifiers.
    Type: Grant
    Filed: March 2, 1989
    Date of Patent: February 19, 1991
    Assignee: British Telecommunications public limited company
    Inventors: William A. Stallard, Andrew D. Ellis, Derek Malyon
  • Patent number: 4992750
    Abstract: Novel designs for an efficient coupling mechanism for the conversion of typical profile laser beams into Jo profile beams are presented. Five specific embodiments are provided which employ non-linear optical mechanisms in the conversion process.
    Type: Grant
    Filed: July 18, 1989
    Date of Patent: February 12, 1991
    Inventor: B. W. Stewart
  • Patent number: 4991921
    Abstract: An optical modulating device is disclosed which has, on a substrate directly or via a lower cladding layer, an optical waveguide layer, an upper cladding layer of a refractive index smaller than that of the optical waveguide layer and a pair of electrodes for applying an electric field across the substrate and the upper cladding layer and in which the absorption coefficient for incident light of a fixed intensity incident to the optical waveguide layer is varied by the electric field applied across the pair of electrodes to perform the modulation of the light and the modulated light is emitted from a light emitting end face of the optical waveguide layer. In accordance with the present invention, a pn junction is formed in the upper cladding layer and at least one buffer layer of an energy gap smaller than that of the upper cladding layer but larger than that of the optical waveguide layer is interposed between the upper cladding layer and the optical waveguide layer.
    Type: Grant
    Filed: November 27, 1989
    Date of Patent: February 12, 1991
    Assignee: Kokusai Denshin Denwa Kabushiki Kaisha
    Inventors: Masatoshi Suzuki, Hideaki Tanaka, Shigeyuki Akiba, Yuichi Matsushima
  • Patent number: 4993031
    Abstract: Raman cell beam combining apparatus for combining a seed beam with a pump beam being introduced into the Raman cell, and employing a segmented mirror for substantially correcting the relative tilt of individual incremental portions of the wavefront of the pump beam with respect to the wavefront of the seed beam, and such mirror having an array of flat non-coplanar wavefront shifting elements positioned parallel with respect to each other.
    Type: Grant
    Filed: March 1, 1990
    Date of Patent: February 12, 1991
    Assignee: The United States of America as represented by the Secretary of the Air Force
    Inventor: Frederic H. White, III
  • Patent number: 4989216
    Abstract: A double conjugate laser beam amplifier which twice conjugates the laser ut beam and provides an output beam in exactly the same direction and of the same polarization as the input beam while retaining the alignment stability of singly conjugated amplifiers even when the thin film polarizer between two conjugate amplifiers is not stable. A half-wave voltage at a Pockels cell positioned on the beam axis immediately prior to the polarizer controls whether the oscillator beam is transmitted through the polarizer or is reflected off the polarizer toward a first conjugate amplifier for amplification and retroflection back through the first conjugate amplifier and the polarizer into a second conjugate amplifier for further amplification and retroreflection back and is reflected off the polarizer a second time. The double conjugate amplifiers may be cascaded to both increase output and laser beam pulse repetition rate.
    Type: Grant
    Filed: April 18, 1990
    Date of Patent: January 29, 1991
    Assignee: The United States of America as represented by the Secretary of the Army
    Inventors: Suresh Chandra, Geraldine H. Daunt
  • Patent number: 4987376
    Abstract: A compact, powerful, single slab laser oscillator-amplifier system immersed in a high pressure gas which acts as a Raman shifting medium to shift the oscillator output wavelengths from the 1060-3000 nm range to the 1100-14000 nm range. The Raman shifting gas is conained within the casing (29) which also encloses a laser oscillator defined along the long axis of the slab laser medium (1) between dielectric mirror (2) and partially reflecting mirror (3). An electro-optic switch (7) is provided and slab (1) is pumped via a pump light source (22) while being cooled by Peltier stack (26). The slab also includes dielectric mirror (12) and anti-reflection coating (13) which act in conjunction with the slab laser medium (1) and the mirrored substrate (10) to form the amplifier portion of the system. Light passed from the oscillator through prism (4) is reflected by bevelled portion (9) of mirror (10) and directed to slab (1) where it is amplified and reflected by mirror (12).
    Type: Grant
    Filed: November 18, 1988
    Date of Patent: January 22, 1991
    Assignee: Australian Electro Optics Pty Ltd.
    Inventor: John L. Hughes
  • Patent number: 4982166
    Abstract: Apparatus for combining two laser beams each having a power level into a common colinear laser beam having a power level that is the sum of the power levels of the two laser beams comprising a support, a polarization selective device disposed on the support having a first surfaces upon which a first of the laser beams impinges for transmitting the first laser beam with substantially full power transmission along an axis and having a second surface upon which the second laser beam impinges for reflecting the second laser beam with substantially full power along the axis, resulting in a common colinear beam along the axis, and suitable optical and/or mechanical devices disposed on the support for providing the first and second laser beams to the polarization selective device, the first and second laser beams being substantially orthogonally polarized with respect to each other.
    Type: Grant
    Filed: March 1, 1989
    Date of Patent: January 1, 1991
    Inventor: Clifford E. Morrow
  • Patent number: 4979234
    Abstract: The span of an optical dispersion-limited fiber for propagating optical pulses is improved by simultaneously chirping and amplifying the stream by means of a saturated semiconductor laser amplifier. The chirp causes a compression of the pulses as they propagate through an initial portion of the fiber, whereby the span of the fiber is increased.
    Type: Grant
    Filed: December 20, 1988
    Date of Patent: December 18, 1990
    Assignee: AT&T Bell Laboratories
    Inventors: Govind P. Agrawal, Nils A. Olsson
  • Patent number: 4978208
    Abstract: A spatial light modulator includes a photosensor diode and a photoemitting diode array, each having two semiconductive layers of opposite electrical polarities, and which are sandwiched together with layers of the same polarity (P or N) in electrical contact with each other. Transparent electrode layers are formed on the opposite surfaces of the photosensor diode and photoemitting diode array respectively, in electrical contact with the layers of the opposite polarity. The individual photoemitting diodes are electrically and optically isolated from each other. With a voltage applied across the electrodes which causes the photosensor diode to be reverse biased and the photoemitting diodes to be forward biased, the photoemitting diode array generates a visual display which is a reproduction of a light image incident on the photosensor diode. The photosensor diode may be replaced by a single layer of a photoconductive material.
    Type: Grant
    Filed: July 24, 1989
    Date of Patent: December 18, 1990
    Assignee: Hughes Aircraft Company
    Inventors: Tsung-Yuan Hsu, Shin-Tson Wu, Robert Y. Loo
  • Patent number: 4976539
    Abstract: A diode laser array comprises a substrate of a semiconductor material having first and second opposed surfaces. On the first surface is a plurality of spaced gain sections and a separate distributed Bragg reflector passive waveguide at each end of each gain section and optically connecting the gain sections. Each gain section includes a cavity therein wherein charge carriers are generated and recombine to generate light which is confined in the cavity. Also, the cavity, which is preferably a quantum well cavity, provides both a high differential gain and potentially large depth of loss modulation. Each waveguide has a wavelength which is preferably formed by an extension of the cavity of the gain sections and a grating. The grating has a period which provides a selective feedback of light into the gain sections to supporting lasing, which allows some of the light to be emitted from the waveguide normal to the surface of the substrate and which allows optical coupling of the gain sections.
    Type: Grant
    Filed: August 29, 1989
    Date of Patent: December 11, 1990
    Assignee: David Sarnoff Research Center, Inc.
    Inventors: Nils W. Carlson, Gary A. Evans, Charlie J. Kaiser
  • Patent number: 4975655
    Abstract: Photons of an electromagnetic source wave are frequency-upshifted as a plasma is rapidly created around the path of this propagating source wave. The final frequency can be controlled by adjusting the gas density. A controlled time-varying frequency (chirped) pulse can be produced by using a controlled spatially varying gas density. The plasma must be created in a time which is short compared to the transit time of the light through the plasmas region. For very fast creation over one to at most a few light periods of an overdense plasma, static magnetic fields with short wavelengths are created.
    Type: Grant
    Filed: June 14, 1989
    Date of Patent: December 4, 1990
    Assignee: Regents of the University of California
    Inventors: John M. Dawson, Scott C. Wilks, Warren B. Mori, Chandrasekhar J. Joshi, Andrew M. Sessler