At&t Bell Laboratories

Bell Telephone Laboratories

American Telephone & Telegraph Co., At&t Bell Laboratories

Lucent Technologies Inc.

At+t Corp.

Multiplex, Inc.

Won-Tien Tsang

Ralph A Logan

John E Cunningham

Federico Capasso

Erdmann F Schubert

Tawee Tanbun-Ek

Alfred Yi Cho

Nils A Olsson

Liang David Tzeng

John William Osenbach

Albert Lee Hutchinson

Gerald Nykolak

Laura Ellen Adams

Kang-Yih Liou

Barry Franklin Levine

Arthur Mike Sergent

Clyde George Bethea

Clyde G Bethea

Charles B Roxlo

Naresh Chand

Roosevelt People

Tien-Heng Chiu

Ming-Chiang Wu

Robert B Comizzoli

Wei-Chiao William Fang

Gareth F Williams

Jan P Van Der Ziel

Aasmund S Sudbo

Long Yang

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.

Optical transponders and transceivers

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.

Electroabsorption-modulated fabry perot laser

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.

Broadband tunable semiconductor laser source

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.

Articles comprising doped semiconductor material

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.

Method and apparatus for control of lasing wavelength in distributed

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 &gt;.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., an ion implanted region between the laser section and the modulator section. Combinations according to the invention typically are easier to manufacture than prior art combinations, and are advantageously used in e.g., optical fiber communication systems.

Article comprising an integrated laser/modulator combination

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&lt;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.

Article comprising a semiconductor laser with stble facet coating

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.

Method of fabricating a compound semiconductor device

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.

Semiconductor laser having reduced temperature dependence

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.

Article comprising a DFB semiconductor laser

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.

Circuit including bistable, bipolar transistor

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.

Optoelectronic integrated circuit

A method of selective area epitaxial growth using a scanning ion beam is described.

Denices fabricated using method of selective area epitaxial growth using

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.

Method for fabricating a field-effect transistor with a self-aligned gate

A light transmitter comprising a cleaved-coupled cavity laser and stabilization means to maintain the laser in single longitudinal mode operation is described. '

Growing community of inventors

New Providence, NJ, United States of America

Won-Tien Tsang