Abstract: A method of fabricating an expanded beam optical waveguide device (e.g., a laser), comprises the steps of (a) forming a first semiconductor waveguide region having first and second sections of different thickness and an intermediate vertical taper section of varying thickness coupling the first and second sections to one another, the first waveguide region being effective to expand the size of the beam as it propagates from the first section to the second section, (b) forming a second semiconductor region (e.g., a laser active region) on the first waveguide region, (c) etching the second region so as to form an essentially vertical first surface of length A-B which extends obliquely across the propagation axis of the device, (d) forming a third semiconductor region (e.g.

Abstract: A multifrequency laser (MFL) eliminates nonlinearities produced in the "shared" waveguide of the MFL laser (the section in which all the lightwaves from all the lasers pass) by either making the shared waveguide as short as possible to mimimize the production of mixing product signals or using a channel spacing that is unequal such that any mixing product signals formed from the multifrequency optical laser signal do not overlap in frequency with any of the signals of the multifrequency optical laser signal.

Abstract: An improved wavelength tunable transmitter comprises a waveguide grating router coupled to a truncated Mach-Zehnder interferometric modulator. Light from the second order Brillouin zones of a waveguide grating router having substantially the same phase are captured and coupled to first and second transmission paths comprising the truncated Mach-Zehnder interferometer, the transmission paths then being altered relative to each other and recombined to produce a modulated output signal. With this configuration, a compact tunable transmitter is provided exhibiting bandwidth and chirp control features comparable with those of a traditional Mach-Zehnder interferometer.

Abstract: A laser transmitter based on a star coupler includes a separate controlled output port. An interferometric modulator is incorporated inside a laser cavity by means of a star coupler and enables modulation of the laser signal, independent of the means of wavelength selection used to determine the frequency of the laser.

Abstract: A method and apparatus for guiding optical signals in a laser cavity to determine the oscillation frequency or frequencies of a laser by controlling the lengths of waveguide grating arms.

Abstract: A single-mode stabilized laser comprises a laser cavity having a round trip time .tau..sub.r and a linewidth enhancement parameter .alpha.; and a frequency routing device formed in the laser cavity comprising controllable frequency selective pathways such that selective gating of the frequency selective pathways causes selected lasing frequencies to be supported in the laser cavity separated by a frequency spacing .DELTA.F.sub.C, .DELTA.F.sub.C =1/.tau..sub.r. The frequency routing device has an optical grating having unequal length waveguides to form paths. The optical grating has arms, a time delay .tau..sub.f between the longest path and the shortest path, and a grating bandwidth .DELTA.F.sub.F, .DELTA.F.sub.F =1/.tau..sub.f, at least one of (1) .alpha. and (2) .tau..sub.r and .tau..sub.f having sufficient value to stabilize the laser in single-mode operation.

Abstract: A laser mounting configuration and method that enables a laser to be mounted onto a substrate in an orientation that passively aligns the laser with and adjacent optical fiber or optical waveguide. In an application with an optical fiber, a structure is formed in the substrate to retain the optical fiber at a fixed position. Ridges are formed in the substrate at a known orientation with respect to where the optical fiber is held. When the laser is applied to the substrate, the ridges on the substrate engage grooves formed on the bottom of the laser, thereby orienting the laser. In an application with an optical waveguide, a trench is formed in the substrate. The optical waveguide is formed partially within the trench so that the core of the waveguide is at the same height as the active layer of the laser when the laser lays flush on the substrate. Alignment stops are formed on the substrate at predetermined positions with respect to the waveguide.

Abstract: A method for forming an optical grating within a waveguide integrated on a substrate includes the step of depositing on a substrate successive layers of material constituting a waveguide such that the waveguide has a periodically varying width along a portion of its longitudinal axis. The deposition may be accomplished by depositing by selective area epitaxy at least some of the successive layers through a mask having a periodically varying width along at least one edge. The successive layers deposited through the mask may constitute a plurality of quantum well layers separated from each other by barrier layers which collectively form a multiple quantum well stack.

Abstract: A polarization compensated waveguide grating router is formed by reducing the thickness of the cladding material deposited over segments of waveguide cores to be on the order of the height of the vertical extension of the optical field of the waveguide. The resulting "air-patch" segments increase the birefringence in the patch segments of the waveguides. By using an air-patch length which is inversely proportional to the length of each waveguide, the correct phase relationship can be maintained between the different waveguides to produce an InP-based router which is polarization independent.

Abstract: A multi-frequency optical signal source is adapted to include a plurality of power splitters, each connected to obtain a portion of an electrical data signal used to modulate a different one of the plurality of input optical sources; a plurality of delay means, each connected to an output of a different power splitter, each delay means providing a different predetermined signal delay; and an electrical signal combiner having a plurality of inputs, each input connected to a different output of the respective delay means, for electrically combining a portion of the modulation signal received from the connected delay means to form a combined electrical signal at an output of the electrical signal combiner, the output of the combiner being connected to control biasing of the optical output amplifier. The resulting multi-frequency optical signal source exhibits reduced signal distortion and crosstalk by keeping the carrier density constant in its shared optical output amplifier.

Abstract: A method for forming a reflective digitally tunable laser using selective area epitaxy is disclosed. The laser comprises passive waveguides and a plurality of optical amplifiers. The waveguides and optical amplifiers are formed by depositing multiple quantum wells having a suitable bandgap. According to the method, the multiple quantum wells forming both the passive waveguides and the optical amplifiers are deposited simultaneously using a dielectric mask. The mask comprises dual, rectangularly-shaped strips of dielectric material, spaced to form a gap. The multiple quantum wells grown in the gap are suitable for use as optical amplifiers, and those grown outside of the gap are suitable for use as passive waveguides.

Abstract: Semi-insulating epitaxial layers of Group III-V based semiconductor compounds are produced by a MOCVD process through the use of organic titanium-based compounds. Resistivities greater than 1.times.10.sup.7 ohm/cm have been achieved.

Abstract: Semi-insulating epitaxial layers of Group III-V based semiconductor compounds are produced by an MOCVD process through the use of bis arene titanium sources, such as cyclopentadienyl cycloheptatrienyl titanium and bis (benzene) titanium.

Abstract: High resistivity Ti-doped Group III-V-based MOCVD layers are used to constrain current to flow through the active region of a variety of devices such as CSBH and DCPBH lasers.

Abstract: Low loss semiconductor waveguides for supporting propagation of optical signals over a wide range of wavelengths are achieved by growing at least two epitaxial layers of dopant material contiguous along a major surface of each layer to form a heterointerface therebetween. At least one of the epitaxial layers includes a sufficient concentration of semiconductor material to cause strain via lattice mismatch substantially at and near the heterointerface. The strain induces a change in refractive index such that the heterointerface exhibits a substantially higher refractive index than a portion of each epitaxial layer proximate to the heterointerface. The resulting waveguide is capable of supporting propagation of optical signals substantially along the heterointerface. In one example, contiguous epitaxial layers of InP and InGaP form a waveguide for optical signals at wavelengths greater than 0.93 .mu.m. The concentration of Ga in the InGaP epitaxial layer is varied from 10.sup.18 to 10.sup.20 cm.sup.