Bell Telephone Laboratories

At&t Bell Laboratories

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

Peter W Smith

Walter J Tomlinson, Iii

David A Miller

Daniel S Chemla

Detlef Christoph Gloge

Edwin Leroy Chinnock

Obert R Wood, Ii

Arthur Ashkin

John E Bjorkholm

Alexander E Kaplan

Edward H Turner

The invention is a controlled laser having an optical resonator, a laser gain medium placed inside the optical resonator, the laser gain medium being capable of emitting light and of lasing with the light, a multiple layer heterostructure placed inside the optical resonator, and means for varying an optical absorption of the multiple layer heterostructure for the light in order to control an optical gain of the optical resonator, and thereby control lasing of the laser gain medium. Passive mode locking is achieved by the light emitted by the gain medium controlling the optical absorption of the multiple layer heterostructure. Active mode locking and modulation are achieved by controlling the optical absorption of the multiple layer heterostructure by applying an electric field to the multiple layer heterostructure. Control of laser gain by an external light source is achieved by controlling the optical absorption of the multiple layer heterostructure by illuminating it with light from the external light source. An embodiment of the multiple layer heterostructure fabricated as a GaAs-AlGaAs multiple quantum well with a Type I superlattice band structure is a passive mode locker for a semiconductor diode laser.

Laser controlled by a multiple-layer heterostructure

A nonlinear optical apparatus is provided with a multiple layer heterostructure made from alternate layers of a charge carrier semiconductor material having a narrow bandgap energy, and a charge barrier material having a wider bandgap energy than the charge carrier material. The layers are deposited one upon the other in substantially flat planes forming a series of potential barriers. The potential barriers are capable of confining charge carriers which arise within the layers of the charge carrier semiconductor material to remain substantially therein. The optical absorption coefficient of the multiple layer heterostructure exhibits at least one sharp resonant optical absorption peak near the semiconductor material bandgap absorption. A light source is restricted to provide a beam of light photons of energy near the energy of the sharp resonant optical absorption peak for promoting production of charge carriers within the charge carrier semiconductor material. The light photons are directed into the multiple layer heterostructure so that the light photons may saturate the optical absorption coefficient and thereby cause the index of refraction of the multiple layer heterostructure to vary with incident light intensity.

Nonlinear optical apparatus

A four-wave mixer which uses a multiple quantum well structure as a nonlinear optical material is provided. There are provided means for providing a first beam of light which propagates through said multiple quantum well structure, and means for providing a second beam of light which also propagates through said multiple quantum well structure and substantially overlaps said first beam of light within said MQW structure. At least one ouput phase conjugate beam of light is produced by interaction of said first and said second beams of light with said multiple quantum well structure. An alternate embodiment has two counterpropagating pump beams and a probe beam of light which produce a backward scattered phase conjugate beam of light.

Degenerate four-wave mixer using multiple quantum well structures

Several types of nonlinear characteristics are provided in an optical device wherein at least two optical materials are constructed to provide a waveguide structure. At least one of the materials has a dominant nonlinear characteristic over the length of the waveguide that is commonly referred to as the Kerr effect. The index of refraction in this material is a function of the light intensity in the waveguide. By selecting materials that provide either positive or negative Kerr coefficients, and by constructing the device with the nonlinear material either as the core or as the cladding layer, power output versus input characteristics that exhibit both limiting and amplification can be provided. A bistable characteristic is provided in one of the embodiments by terminating the waveguide structure with a mirror. Specific embodiments using carbon disulfide and polydiacetylene as the nonlinear materials are disclosed.

Nonlinear and bistable optical waveguide devices

The present invention relates to a nonlinear optical time-division multiplexer and demultiplexer formed from a cascaded plurality of triggerable optical switching elements. In accordance with the present invention, an exemplary triggerable optical switching element comprises a nonlinear optical material disposed in, for example, a ring resonator arrangement. The nonlinear optical material exhibits an index of refraction which is a function of the intensity of the light passing therethrough. An exemplary switching element is responsive to two separate optical pulse streams, where neither pulse stream comprises a sufficient intensity to cause the element to switch. A trigger pulse is utilized which comprises a sufficient intensity to stimulate switching the output from a first optical pulse stream to a second optical pulse stream. An external synchronization means may be employed to adjust the arrival of the trigger pulse in the nonlinear material so as to allow the time-division multiplexing or demultiplexing to be achieved.

Nonlinear all-optical time division multiplexer and demultiplexer

The present invention relates to a high speed optical switch and the use of such switches to form a time division demultiplexer. The optical switch comprises a length of linear material (12) including an outer surface on a portion of which is formed a layer of nonlinear material (11) to form a nonlinear interface (10) at the boundary of the two materials. An input data light beam (14) is propagated in the linear material with a predetermined intensity and angle of incidence on the nonlinear interface to, by itself, cause total reflection of the input beam. A control light beam (11) is also selectively energized and directed at the nonlinear interface with an intensity and angle of incidence to cause a portion of the input data beam to be formed into a self-focused channel or beam propagating in the nonlinear material. The self-focused beam can then be detected at an edge of the nonlinear material.

High speed optical switch and time division optical demultiplexer using

The invention provides apparatus comprising at least two beams of coherent radiation directed so as to intersect and form a standing wave pattern having a period .LAMBDA. in an optically responsive medium. The optically responsive medium is a colloidal suspension of dielectric particles in a liquid medium, the dielectric particles and liquid having different indices of refraction, and the diameter of the particles being less than or approximately equal to the period .LAMBDA.. The dielectric particles are arranged into a grating by the electric fields carried by the beams of coherent radiation. In an embodiment of the invention, the dielectric particles are small dielectric spheres. The dielectric particles and the liquid may have approximately equal mass densities. A third beam of light may generate an output beam of light by degenerate four-wave mixing processes incorporating a dielectric grating made by the electric fields carried by the beams of coherent radiation.

Optical grating using a liquid suspension of dielectric particles

Many prior art bistable optical devices require resonant optical cavities and are therefore limited in their operation due to the long lifetimes associated with their high-finesse cavities. A bistable optical device that does not use a resonant cavity is disclosed wherein a nonlinear medium whose index of refraction increases with increased light intensity is arranged to have input and output faces into which and out of which a laser beam having a nonuniform spatial profile can be propagated. A mirror having a predetermined area of reflectivity is positioned with respect to the output face of a nonlinear medium so as to reflect only the light energy that propagates in an area at the output face that is approximately equal to the area which the beam presents at this face when the beam is propagating at a critical power level, that is, when the beam is self-trapped.

Nonlinear optical device using self-trapping of light

An optical apparatus which provides a nonlinear characteristic between input and output amplitude levels is disclosed. A single frequency linearly polarized single mode light beam having amplitude variations that are to be acted upon is coupled to a Fabry-Perot interferometer (10) having two mirrored ends (11 and 12) and substantially filled with an electrooptic material (13) having electrodes (14 and 15). A beam splitter (21) is positioned and oriented so as to deflect optical energy that is reflected from the cavity into a photodetector circuit (22 and 23) whose output voltage is applied to the electrodes of the electrooptic material. Adjustment of the cavity length provides a wide range of nonlinear characteristics including some that permit the apparatus to be used as a bistable memory element and others which permit the device to be used as a clipper for all input power levels below a predetermined threshold level.

Nonlinear optical apparatus using fabry-perot resonators

A nonlinear interferometer apparatus is disclosed wherein a Fabry-Perot cavity is substantially filled with an electro-optic material having terminals to which a potential can be applied. A single frequency, single mode, linearly polarized source of optical radiation is coupled into the cavity and a beam splitter at the output of the cavity deflects a portion of the optical energy coming from the cavity. This deflected portion of output optical energy is incident on a photodetector whose output is amplified and connected to the terminals of the electro-optic material. The resulting device exhibits differential gain, and can function as an optical switch, limiter or optical memory element. With sufficient amplification of the detector output, an optical quantizer is provided. By properly adjusting the cavity length and providing a substantially constant optical signal to the input end of the cavity, an amplified replica of an amplitude modulated optical signal applied to the photodetector appears at the output end of the cavity.

Interferometer apparatus using electro-optic material with feedback

Preionization is achieved in transverse-discharge gaseous lasers by means of the Malter effect. In two embodiments, the preionization is achieved either with a metal electrode which is the cathode during preionization and then is the anode during the subsequent pumping phase, or by means of a separate set of preionization electrodes. These preionization cathodes are metal electrodes, such as aluminum or tantalum electrodes, exhibiting high secondary electron emission by the Malter effect. High-field electron emission from these preionization cathodes is inherently possible because of a thin insulating layer on the surface. This layer separates positive ions attracted to the surface from the conducting metal and thereby creates a very high field gradient over a very short distance. In a preferred embodiment, uniform initial ionization is created during the preionization phase of operation; and the excitation is supplied by an electric field which is lower than that required to sustain the discharge; and the active medium is enclosed in an optical waveguide free of interfering structure.

Transverse-excitation laser with preionization

Particular apparatuses implement a method of breaking a rod of brittle material, such as a glass optical fiber, so as to yield a mirrorlike surface across the entire rod end. A decreasing tensile stress is achieved across the cross section of the rod, which at all points is greater than zero but less than the threshold stress at which a mist zone forms, by simultaneously applying longitudinal tension to the rod and bending it in a tool that laterally moves a section of the fiber while holding sections to either side in friction-type clamps. A convenient hand tool for breaking optical fibers uses pivoting clamps which serve to increase tensile stress as bending is increased. Scoring is done before or after the above-mentioned tool operations.

Apparatus for breaking brittle rods or fibers

A method of breaking a rod of brittle material, such as a glass optical fiber, so as to yield a mirrorlike surface across the entire rod end is described. This is achieved by establishing a decreasing tensile stress across the cross section of the rod which, at all points, is greater than zero but less than the threshold stress at which a mist zone forms. This is conveniently achieved by simultaneously applying longitudinal tension to the rod and bending it. A convenient hand tool for breaking optical fibers is also described.

Growing community of inventors

Colts Neck, NJ, United States of America

Peter W Smith