Abstract: The present invention relates to a waveguide taper. The waveguide taper has a first end and a second end for being coupled with a fiber. The core has an overall width that progressively increases from the waveguide end toward the fiber end such that the width of the fiber end of the taper corresponds to the diameter of the core of the fiber. Side-gaps are disposed in the sides of the core and extend into the core but not across the entire width of the core. The depth of the side-gaps progressively increases from the waveguide end to the fiber end of the taper. In one embodiment, the side-gaps may be aperiodically and/or randomly disposed along the length of the taper and the side-gaps can be disposed at different angles to a direction of light propagation along a length of the core.

Abstract: In accordance with the invention, a new type of monolithic optical waveguide filter comprises a chain of optical couplers of different effective lengths linked by differential delays of different lengths. The transfer of the chain of couplers and delays is the sum of contributions from all possible optical paths, each contribution forming a term in a Fourier series whose sum forms the optical output. A desired frequency response is obtained by optimizing the lengths of the couplers and the delay paths so that the Fourier series best approximates the desired response. The filter is advantageously optimized so that it is insensitive to uncontrolled fabrication errors and is short in length. The wavelength dependence of practical waveguide properties is advantageously incorporated in the optimization. Consequently, the filter is highly manufacturable by mass production. Such filters have been shown to meet the requirements for separating the 1.3 and 1.551 .mu.

Abstract: The invention relates to a fixed gap waveguide taper. The waveguide taper has a first end and a second end for being coupled to a fiber. The waveguide taper includes a plurality of segments extending from the first end toward the second end. The segments include a gap portion and a core portion. In the present invention, the gap portion remains fixed at a constant length s throughout the entire waveguide taper. In contrast, the core section of the segment varies from the waveguide end of the taper toward the fiber end of the taper. In particular, the core section in each of the segments progressively decreases in length from the waveguide end toward the fiber end of the taper. Accordingly, the length of the segment .LAMBDA. progressively decreases from the waveguide end toward the fiber end of the taper.

Abstract: A waveguide Bragg reflector is made by forming periodic grooves in either the undercladding or the core, applying a high index coating on the grooved surface and selectively removing the coating from the horizontal surfaces while leaving the coating on the vertical surfaces. The waveguide is then completed.

Abstract: A new electro-optic sampling probe with femtosecond resolution suitable for ultra-fast electro-optic sampling. The new probe is several times thinner and has a dielectric constant four times less than the best reported conventional bulk LiTaO.sub.3 probes. In addition, the ultimate bandwidth is 50 percent greater than an equivalent LiTaO.sub.3 probe. The probe is a thin film of Al.sub.x Ga.sub.1-x As used in both total internally reflecting and free-standing geometries. Here x is chosen for sufficient transmission of the crystal to the wavelength of the laser source being used for electro-optic sampling. The thickness of the film is a small fraction of the thickness of prior art probes and is chosen, for speed and sensitivity of electro-optic sampling, to be thin compared to the spatial extent of the laser pulse. The thin film probe eliminates many of the problems associated with the use of bulk crystals as electro-optic sensors.

Abstract: A solution of H.sub.2 O.sub.2 and EDTA selectively etches GaAs-containing Group III-V compounds in the presence of other Group III-V compounds. Illustratively, Al.sub.y Ga.sub.1-y As (y.ltoreq.0) is selectively etched in the presence of Al.sub.x Ga.sub.1-x As(x>y), and InGaAs is selectively etched in the presence of either InAlAs or InP.

Abstract: An etching process is described for etching aluminum containing III-V semiconductor compounds. The etch solution contains dichromate ion in acid aqueous solution in which the acid is either phosphoric acid or sulfuric acid. The etch solution is highly selective in that it etches the aluminum containing III-V semiconductor compounds without etching significantly other III-V semiconductor compounds not containing aluminum exposed to the same etching solution. the etching process is extremely useful in fabricating a variety of III-V semiconductor devices including heterojunction bipolar transistors, heterojunction field effect transistors and self-enhanced electro optic devices.

Abstract: A photoelectrochemical etching process is described for n-type and semi-insulating III-V semiconductor compounds that contain aluminum or indium (AlGaAs, InGaAs) in which a non-aqueous electrolyte is used. High etch rates are achieved without harm to exposed metallization or p-layers. An exemplatory application is the separation of chips (e.g., LED chips) after wafer processing.