Patents by Inventor Won-Tien Tsang

Won-Tien Tsang has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • Patent number: 7031612
    Abstract: An optical transponder/transceiver for intermediate range (e.g., 10-50 km) optical communication applications utilizes an electroabsorption modulated laser for the transmitting device. Preferably, the laser operations at a wavelength of approximately 1310 nm and comprises an electroabsorption modulated Fabry-Perot laser.
    Type: Grant
    Filed: July 17, 2001
    Date of Patent: April 18, 2006
    Assignee: Multiplex, Inc.
    Inventors: Kang-Yih Liou, Tawee Tanbun-Ek, Won-Tien Tsang, Liang David Tzeng
  • Patent number: 6597718
    Abstract: An electroabsorption modulated laser (EML) is formed to include a Fabry-Perot lasing section, in place of the conventional DFB lasing section. When operated at a wavelength of 1310 nm, the wider spectral bandwidth of the FP device (containing several longitudinal modes) is of no concern, since 1310 nm is the zero dispersion wavelength of most conventional transmission fibers. A selective area growth process is used to simultaneously form the MQW active regions of both the FP and EA sections of the EML device, and an isolation trench may be formed between the sections to reduce the effects of electrical crosstalk.
    Type: Grant
    Filed: July 17, 2001
    Date of Patent: July 22, 2003
    Assignee: Multiplex, Inc.
    Inventors: Tawee Tanbun-Ek, Won-Tien Tsang, Liang David Tzeng
  • Publication number: 20020060824
    Abstract: An optical transponder/transceiver for intermediate range (e.g., 10-50 km) optical communication applications utilizes an electroabsorption modulated laser for the transmitting device. Preferably, the laser operations at a wavelength of approximately 1310 nm and comprises an electroabsorption modulated Fabry-Perot laser.
    Type: Application
    Filed: July 17, 2001
    Publication date: May 23, 2002
    Inventors: Kang-Yih Liou, Tawee Tanbun-Ek, Won-Tien Tsang, Liang David Tzeng
  • Publication number: 20020009114
    Abstract: An electroabsorption modulated laser (EML) is formed to include a Fabry-Perot lasing section, in place of the conventional DFB lasing section. When operated at a wavelength of 1310 nm, the wider spectral bandwidth of the FP device (containing several longitudinal modes) is of no concern, since 1310 nm is the zero dispersion wavelength of most conventional transmission fibers. A selective area growth process is used to simultaneously form the MQW active regions of both the FP and EA sections of the EML device, and an isolation trench may be formed between the sections to reduce the effects of electrical crosstalk.
    Type: Application
    Filed: July 17, 2001
    Publication date: January 24, 2002
    Inventors: Tawee Tanbun-Ek, Won-Tien Tsang, Liang David Tzeng
  • Patent number: 6108362
    Abstract: A tunable semiconductor laser comprises a gain section having an MQW active region, a uniform pitch grating DFB region, and first waveguide. A composite reflector, including a second MQW region and a second waveguide, forms a cavity resonator with the DFB region. A voltage applied to the composite reflector induces a quantum confined stark effect, thereby allowing the wavelength to be altered. In one embodiment, the current drive to the active region and the shape of the first waveguide (e.g., a raised-sine function) are mutually adapted so that N longitudinal modes have essentially the same threshold gain and so that the DFB region spanned by the first waveguide is segmented into N zones, each zone providing optical feedback at a different wavelength corresponding to a different longitudinal mode.
    Type: Grant
    Filed: October 17, 1997
    Date of Patent: August 22, 2000
    Assignee: Lucent Technologies Inc.
    Inventors: Laura Ellen Adams, Clyde George Bethea, Wei-Chiao Fang, Gerald Nykolak, Roosevelt People, Arthur Mike Sergent, Tawee Tanbun-Ek, Won-Tien Tsang
  • Patent number: 5834792
    Abstract: The disclosed novel doping method makes it possible to tailor the effective activation energy of a dopant species in semiconductor material. The method involves formation of very thin layers of .delta.-doped second semiconductor material in first semiconductor material, with the second material chosen to have a bandgap energy that differs from that of the first material. Exemplarily, in a Be-doped GaAs/AlGaAs structure according to the invention the effective activation energy of the dopant was measured to be about 4 meV, and in conventionally Be-doped GaAs it was measured to be about 19 meV. The invention can be advantageously used to dope III-V and II-VI semiconductors. In some cases it may make possible effective doping of a semiconductor for which prior art techniques are not satisfactory.
    Type: Grant
    Filed: August 25, 1993
    Date of Patent: November 10, 1998
    Assignee: Lucent Technologies Inc.
    Inventors: John Edward Cunningham, Won-Tien Tsang
  • Patent number: 5606573
    Abstract: A method and apparatus for control of lasing wavelength in distributed feedback lasers using an improved waveguide. The waveguide comprises a periodic structure or grating and an active stripe which is oriented at a nonzero angle .THETA. with respect to a line perpendicular to the lines of the grating. Incremental changes in the operating wavelength of a plurality of lasers can be achieved by forming the active stripe of each waveguide of each laser at a different angle .THETA.. This method and apparatus provides a fine degree of control over the operating wavelength of distributed feedback lasers and is particularly useful in high capacity optical communications networks.
    Type: Grant
    Filed: February 29, 1996
    Date of Patent: February 25, 1997
    Assignee: Lucent Technologies Inc.
    Inventor: Won-Tien Tsang
  • Patent number: 5548607
    Abstract: The disclosed integrated modulator/laser (I-MOD/DFB) combination comprises an active region that extends the full length of the combination without variation of layer thickness and/or composition. Because of this constancy of the active region parameters the relevant bandgap energy is the same in the laser portion of the combination as in the modulator portion thereof. The combination typically comprises a distributed feedback structure (e.g., a "grating"). In preferred embodiments the feedback structure is selected such that .lambda..sub.e >.lambda..sub.o (typically .lambda..sub.e -.lambda..sub.o in the range 20-70 nm), where .lambda..sub.e is the laser output wavelength, and .lambda..sub.o is the wavelength of the gain peak of the laser medium. The active region can be a bulk active region but preferably is a quantum well active region. Optionally an I-MOD/DFB combination according to the invention can comprise an absorbing region, e.g.
    Type: Grant
    Filed: June 8, 1994
    Date of Patent: August 20, 1996
    Assignee: Lucent Technologies, Inc.
    Inventor: Won-Tien Tsang
  • Patent number: 5440575
    Abstract: Disclosed are high reliability semiconductor lasers that need not be maintained inside a hermetic enclosure. Such lasers can advantageously be used in a variety of applications, e.g., in optical fiber telecommunications, and in compact disc players. Such "non-hermetic" lasers comprise facet coatings that comprise a dielectric layer that has very low water saturation value. In preferred embodiments this dielectric layer is SiO.sub.x (1.ltoreq.x<2), deposited by a molecular beam method. Deposition conditions are selected to result in a dense material that is largely free of particulates and blisters, and is substantially impermeable to moisture. Among the deposition conditions is substantially normal beam incidence, and a relatively low deposition rate. Deposition is advantageously carried out under relatively high vacuum conditions. A quantitative method of determining the water level in a SiO.sub.x film is disclosed.
    Type: Grant
    Filed: April 6, 1994
    Date of Patent: August 8, 1995
    Assignee: AT&T Corp.
    Inventors: Naresh Chand, Robert B. Comizzoli, John W. Osenbach, Charles B. Roxlo, Won-Tien Tsang
  • Patent number: 5407531
    Abstract: A device fabrication method includes an etching step for compound III/V semiconductor materials such as gallium arsenide or indium phosphide. The step is carried out in the chamber of a growth reactor under conditions that are compatible with a subsequent growth step performed in the same reactor. Specifically, etching is performed in a so-called pulsed mode wherein each etching interval is followed by an interval in which etching is interrupted. Moreover, a Group III species such as indium is introduced into the chamber during each etching interval to enhance the smoothness of the etched surface.
    Type: Grant
    Filed: February 15, 1994
    Date of Patent: April 18, 1995
    Assignee: AT&T Corp.
    Inventors: Tien-Heng Chiu, Won-Tien Tsang
  • Patent number: 5346581
    Abstract: In a preferred embodiment, the disclosed method of making a compound semiconductor (e.g., InP, GaAs) device comprises etching of a semiconductor body by exposure of the body to a chemical beam or beams that comprise an etching medium (e.g., PCl.sub.3, AsCl.sub.3) and a precursor chemical (e.g., trimethylindium, trimethylgallium), followed by chemical beam epitaxy (CBE) growth of semiconductor material on the etched surface without exposure of the semiconductor body to the ambient atmosphere. Presence of the precursor chemical in the etching beam can result in significantly improved surface morphology, with attendant high quality re-growth. Multiple etching/growth sequences are facilitated by the almost instantaneous (e.g., about 1s) switching between the etching and growth modes that is possible in a reactor according to the invention.
    Type: Grant
    Filed: April 1, 1993
    Date of Patent: September 13, 1994
    Assignee: AT&T Bell Laboratories
    Inventor: Won-Tien Tsang
  • Patent number: 5224113
    Abstract: In accordance with the present invention a semiconductor laser is provided with a cavity having decreasing loss with increasing wavelength in order to reduce temperature dependence. Such decreasing loss canbe obtained by providing the laser cavity with reflecting means or gratings which favor longer wavelengths. Decreasing loss can be provided, for example, by provision of appropriate multilayer reflection coatings or by longitudinal gratings. The coatings advantageously have peak reflectivity centered at the lasing wavelength corresponding to maximum operating temperature. The result in long wavelength InGaAs lasers is an improvement in the threshold temperature coefficient from about 50K to about 85K. In addition, the improved lasers exhibited a decreased rate of quantum efficiency degradation with temperature.
    Type: Grant
    Filed: December 20, 1991
    Date of Patent: June 29, 1993
    Assignee: AT&T Bell Laboratories
    Inventor: Won-Tien Tsang
  • Patent number: 5208824
    Abstract: DFB lasers with advantageously structured grating region are disclosed. The grating region comprises one or more thin semiconductor layers (to be referred to as "QWs"), with the QWs varying periodically in the longitudinal direction of the laser. In an exemplary preferred embodiment the AWs are patterned during grating etch, with the topmost grating QW being covered with a layer of substantially the substrate composition. The structure inter alia facilitates defect-free epitaxial growth on the corrugated etched surface and also facilitates growth of the coupling coefficient .kappa.. Furthermore, lasers according to the invention can be partially or purely gain coupled, resulting in desirable wavelength discrimination.
    Type: Grant
    Filed: December 12, 1991
    Date of Patent: May 4, 1993
    Assignee: AT&T Bell Laboratories
    Inventor: Won-Tien Tsang
  • Patent number: 5153693
    Abstract: A bipolar transistor which is inherently bistable, is disclosed. This bipolar transistor has a structure such that the corresponding band diagram includes a first potential barrier within the collector, at or adjacent the base-collector interface. In addition, the band diagram also includes at least a second potential barrier within the collector.
    Type: Grant
    Filed: July 19, 1990
    Date of Patent: October 6, 1992
    Assignee: AT&T Bell Laboratories
    Inventors: Won-Tien Tsang, Ming-Chiang Wu
  • Patent number: 5115294
    Abstract: A new MSM photodetector, including a photoabsorbing layer of ternary or quaternary III-V compound semiconductor material, is disclosed. This new photodetector is significant because it exhibits a relatively small dark current and a correspondingly large signal-to-noise ratio. Moreover, the photodetector is readily integrable with electronic integrated circuits and is relatively easy to fabricate.
    Type: Grant
    Filed: August 14, 1991
    Date of Patent: May 19, 1992
    Assignee: AT&T Bell Laboratories
    Inventors: Aasmund S. Sudbo, Won-Tien Tsang, Long Yang
  • Patent number: 4831628
    Abstract: A method of selective area epitaxial growth using a scanning ion beam is described.
    Type: Grant
    Filed: November 10, 1986
    Date of Patent: May 16, 1989
    Assignee: American Telephone and Telegraph Company, AT&T Bell Laboratories
    Inventor: Won-Tien Tsang
  • Patent number: 4785454
    Abstract: A light transmitter comprising a cleaved-coupled cavity laser and stabilization means to maintain the laser in single longitudinal mode operation is described.
    Type: Grant
    Filed: May 13, 1983
    Date of Patent: November 15, 1988
    Assignee: American Telephone and Telegraph Company, AT&T Bell Laboratories
    Inventors: Nils A. Olsson, Won-Tien Tsang
  • Patent number: 4784967
    Abstract: A method of fabricating a field-effect transistor is disclosed wherein only two masking steps are used in the development of the device. The semiconductor wafer used in the process has a non-alloyed contact at its top surface, that is, a contact which does not require alloying temperatures in excess of 200 degrees C. The first mask is used to create conventional mesa structures which isolate each individual field-effect transistor from its adjacent neighbors. A second mask is utilized to define the source and drain electrodes and also to create a gap through which the gate electrode structure is fabricated. By using a single mask for creation of both the source and drain electrodes and the gate structure, very close tolerances are obtained between the gate structure and the source and drain regions.
    Type: Grant
    Filed: December 19, 1986
    Date of Patent: November 15, 1988
    Assignee: American Telephone and Telegraph Company, AT&T Bell Laboratories
    Inventors: John E. Cunningham, Erdmann F. Schubert, Won-Tien Tsang
  • Patent number: 4780748
    Abstract: A field-effect transistor is created on a GaAs semi-insulating substrate using molecular beam epitaxy by fabricating a delta-doped monolayer with a silicon dopant between two undoped GaAs layers grown over the semi-insulating substrate. A plurality of delta-doped monolayers are grown over the surface of the upper undoped layer interleaved with layers of GaAs having a thickness equal to or less than the tunneling width of electrons in GaAs. A channel is etched through the plurality of delta-doped monolayers to permit a gate electrode to contact the upper undoped GaAs layer. Source and drain electrodes are deposited over the delta-doped monolayers on each side of the channel.
    Type: Grant
    Filed: June 6, 1986
    Date of Patent: October 25, 1988
    Assignee: American Telephone & Telegraph Company, AT&T Bell Laboratories
    Inventors: John E. Cunningham, Erdmann F. Schubert, Won-Tien Tsang
  • Patent number: 4772934
    Abstract: A non-alloyed ohmic contact in gallium arsenide is described wherein a plurality of delta-doped monolayers are placed at a predetermined distance from each other and from the metal to semiconductor interface of the contact. The predetermined distance is chosen to keep the tunneling barrier extremely thin. In the embodiment shown, silicon is used as a dopant in the gallium arsenide material but other elements from groups II, IV and VI of the periodic table of elements may be used in other III-V semiconductor substrates.
    Type: Grant
    Filed: June 6, 1986
    Date of Patent: September 20, 1988
    Assignee: American Telephone and Telegraph Company, AT&T Bell Laboratories
    Inventors: John E. Cunningham, Erdmann F. Schubert, Won-Tien Tsang