Abstract: 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..

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.