Lucent Technologies Inc.

At&t Bell Laboratories

At+t Corp.

American Telephone and Telegraph, Co.

Jane E Zucker

Mujibun Nisa Khan

Wayne Harvey Knox

Alan H Gnauck

Thomas L Koch

Rodney C Alferness

Uziel Koren

Steven K Korotky

Tao-Yuan Chang

Michael D Williams

Stephen Cason Shunk

Margarita M Mihailidi

An optical waveguide for use in an optoelectronic integrated circuit and the associated method of manufacturing such a waveguide. The waveguide is formed by the successive layering of varied waveguide materials on a III-V semiconductor substrate, thereby producing a slab waveguide. The various layers within the slab waveguide are relatively thick, thereby producing a slab waveguide that is sized to be more compatible with an optical fiber and therefore more readily coupled to an optical fiber. The larger slab waveguide structure broadens the fundamental mode of the optical signal. However, multiple modes are also produced in the thicker slab waveguide that include higher order modes. A ridge structure is etched into the slab waveguide, wherein the width and height of the ridge structure are selected to impose lateral confinements on the higher order slab modes. The result is a waveguide that has a broadened fundamental mode yet is essentially single-mode. The resulting broadened fundamental mode is closer in symmetry to the mode of standard optical fibers, thereby enabling the waveguide to be more efficiently coupled to an optical fiber.

Single-mode waveguide structure for optoelectronic integrated circuits

An optoelectronic modulator modulates an optical signal in response to an electromagnetic signal. The optoelectronic modulator includes a waveguide for conveying the optical signal, where the waveguide has an associated width, core thickness, and waveguide-electrode separation, and includes a optical index of refraction with respect to the optical signal and a microwave index of refraction with respect to the electromagnetic signal; and where the microwave index of refraction substantially matches the optical index of refraction for velocity-matching the optical signal and the electromagnetic signal through the waveguide. The waveguide may be disposed on an n-type doped substrate, may include a quantum well region disposed on the substrate, and may have a predetermined width for providing the matching of refractive indices.

Traveling wave quantum well waveguide modulators using velocity matching

An optical switch array in an M.times.N configuration has a set of M input digital optical Y-branches; a set of N output digital optical Y-branch; and at least one S-bend interconnect waveguide connecting at least one input digital optical Y-branch to at least one output digital optical Y-branch, with the S-bend interconnect waveguide being adiabatically tapered for providing adiabatic modal evolution between the at least one input and output digital optical Y-branches. Each of the set of N output digital optical Y-branches has an associated branch separation point; and an output port of the at least one tapered S-bend interconnect waveguide is connected substantially adjacent to a respective branch separation point of a respective one of the set of N output digital optical Y-branch. Compact digital optical switch arrays can be fabricated using such adiabatically tapered S-bend interconnects to eliminate the overlap sections of intermediate digital optical switch elements of the digital optical switch array, and thus to reduce the overall length of the digital optical switch array for providing improved propagation characteristics.

Adiabatic tapered S-bends for compact digital switch arrays

An optical switch provides improved high speed digital optical switching with a compact and fabrication tolerant configuration, and includes a first waveguide portion, a plurality of intermediate waveguide portions connected to the first portion, with each intermediate portion associated with a first angle .theta..sub.1 where the first angle .theta..sub.1 is less than about 2.0.degree.; and a plurality of branch waveguide portions, with each branch waveguide portion connected to a respective intermediate waveguide portion and associated with a second angle .theta..sub.2 where the second angle .theta..sub.2 is less than .theta..sub.1 and is less than about 0.3.degree..

Compact and fabrication tolerant high speed digital optical Y-switches

Conventional microfabrication techniques in conjunction with the precise growth of layers of single crystalline materials by epitaxial growth techniques allow the creation of electro-optic microstructures which achieve high reflectivity with only few periods of layer pairs. Standard lithographic techniques are utilized to fabricate quantum wells which are confined on both sides by air, acrylic resin, or vacuum. The quantum wells are fabricated from spatially and compositionally modulated III-V superlattices in which alternate layers of the structures are sacrificed by selective etching. The structures are patterned such that the quantum wells are suspended between support posts.

Free standing quantum well structure

External modulation is accomplished in a dual waveguide device wherein substantially identical input optical beams are supplied to the waveguides and wherein each waveguide through its electrode is subject to individual, mutually exclusive control. Modulation signals are applied to each waveguide via its separate electrode. Control signals are applied to each waveguide for adjusting the modulation chirp parameter to a desired fixed, non-zero value. Typically, the desired value of the chirp parameter is one which provides the lowest fiber dispersion penalty for the system. Modulated lightwave signals emerging from the waveguides are combined to form a single output signal suitable for transmission over an optical fiber. In one embodiment, Mach-Zehnder interferometer having separately controllable waveguides has its input coupled to a CW laser. Both III-V semiconductor and Ti:LiNbO.sub.3 Mach-Zehnder interferometers have been utilized as external modulators in accordance with the principles of the present invention.

Tunable chirp, lightwave modulator for dispersion compensation

A polarization independent guided wave semiconductor device is realized wherein the waveguide region of the device includes one or more strained quantum well layers wherein strain is designed to be tensile in nature so that energy subbands in the quantum well or wells are displaced by a predetermined amount in a direction opposite to that for the quantum size effect. Polarization independence is achieved when, for a lightwave signal having an incident mean photon energy below the absorption bandedge of the strained quantum well layer or layers, the ratio of the oscillator strengths versus the wavelength detuning for heavy and light holes in a first polarization (TE) is substantially equal to a similar ratio computed in a second polarization (TM). Wavelength detuning is understood to be the difference between the wavelength of operation and the wavelength of an exciton resonance peak. Passive and active or actively controllable waveguides and waveguide devices are described.

Polarization-independent semiconductor waveguide

Polarization independence and higher intrinsic speed resulting from lowered device capacitance are achieved in a modulation-doped semiconductor heterostructure wherein a transfer barrier region including a graded bandgap semiconductor layer facilitates flow of carriers (electrons) from a doped reservoir to a narrow bandgap active region while an isolation barrier region confines carrier flow to be substantially within the graded bandgap region and the associated active region to minimize leakage current. The present modulation-doped heterostructure exhibits substantially equal end-boundary conditions in an unbiased condition for efficient cascading or stacking with additional modulation-doped heterostructures. Several embodiments of the present invention are described in which grading in the transfer barrier region is shown to include substantially continuous compositional grading, stepwise compositional grading, and superlattice grading. In these embodiments, the thickness of the active region is determined in proportion to the size of the optical effect which is to be produced.

Semiconductor device including cascadable polarization independent

A grating coupler is combined with a quantum well index modulator and an optical waveguide to alter the reverse or forward coupling characteristics between two different propagation modes of the system.

Growing community of inventors

Aberdeen, NJ, United States of America

Jane E Zucker