Abstract: Optical structures useful in splitters, couplers, combiners, and switches are provided. An example optical structure has a Y-branch configuration that includes a linear taper segment and two branching waveguides. A straight section extends between the linear taper segment and the two branching waveguides to reduce losses during splitting/combining operation. The straight section may be used in Y-branch configurations having a blunt section, as well as configurations without a blunt section. Straight sections formed of a single segment and of multiple segments are shown, and the straight sections may be formed of substantially parallel outer walls or fanning-out outer walls. Further, in some embodiments, the branching waveguides form acute angles at the boundaries with the straight segment.

Abstract: An apparatus and method for high speed phase modulation of optical beam with reduced optical loss. In one embodiment, an apparatus includes a first region of an optical waveguide disposed in semiconductor material. The first region has a first conductivity type. The apparatus also includes a second region of the optical waveguide disposed in the semiconductor material. The second region has a second conductivity type opposite to the first conductivity type. A first contact is included in the apparatus and is coupled to the optical waveguide at a first location in the first region outside an optical path of an optical beam to be directed through the optical waveguide. The apparatus also includes a first higher doped region included in the first region and coupled to the first contact at the first location to improve an electrical coupling between the first contact and the optical waveguide. The first higher doped region has a higher doping concentration than a doping concentration within the optical path.

Abstract: An apparatus and method for high speed phase modulation of optical beam with reduced optical loss. In one embodiment, an apparatus includes a first region of an optical waveguide disposed in semiconductor material. The first region has a first conductivity type. The apparatus also includes a second region of the optical waveguide disposed in the semiconductor material. The second region has a second conductivity type opposite to the first conductivity type. A first contact is included in the apparatus and is coupled to the optical waveguide at a first location in the first region outside an optical path of an optical beam to be directed through the optical waveguide. The apparatus also includes a first higher doped region included in the first region and coupled to the first contact at the first location to improve an electrical coupling between the first contact and the optical waveguide. The first higher doped region has a higher doping concentration than a doping concentration within the optical path.

Abstract: An apparatus and method for splitting and combining optical beams with reduced contact loss and electrical isolation. In one embodiment, an apparatus according to embodiments of the present invention includes a first optical waveguide section disposed in semiconductor material. The apparatus further includes second and third optical waveguide sections symmetrically disposed in the semiconductor material proximate to an end of the first optical waveguide section. First and second insulating gap regions are disposed in the semiconductor material between the first and second optical waveguide sections and the first and third optical waveguide sections, respectively, such that there is a first evanescent coupling between first and second optical waveguide sections across the first insulating gap region and there is a second evanescent coupling between the first and third optical waveguide sections across the second insulating gap region. The first, second, and third waveguide sections are electrically isolated.

Abstract: A waveguide Bragg grating (WBG) is apodized by varying the duty cycle of selected grating periods while fixing the pitch of the grating periods. In one embodiment, the WBG is implemented in a silicon substrate using polysilicon filled trenches of varying width while keeping the grating periods' pitch constant. The polysilicon trenches are formed so that if the width of one trench is increased compared to an adjacent grating period, the trench width in the other adjacent grating period (if present) is decreased.

Abstract: A tunable Bragg grating method and apparatus. In one aspect of the present invention, a method according to an embodiment of the present invention includes directing an optical beam into a first end of an optical path having the first end and a second end disposed in a semiconductor substrate, reflecting a first portion of the optical beam having a first center wavelength back out from the first end of the optical path and tuning the optical path to reflect a second portion of the optical beam having a second center wavelength back out from the first end of the optical path. In one embodiment, the Bragg grating is tuned with a heater used to adjust a temperature of the semiconductor substrate. In another embodiment, charge in charge modulated regions along the optical path is modulated to tune the Bragg grating.

Abstract: An apparatus and method for reducing a mode size of an optical beam. In one embodiment, an apparatus according to embodiments of the present invention includes a first optical waveguide disposed in a first semiconductor material of a semiconductor layer. The first optical waveguide includes an inverted tapered inner core disposed in an untapered outer core of the first optical waveguide. The inverted tapered inner core includes a smaller end and a larger end. The apparatus further includes a second optical waveguide disposed in a second semiconductor material of the semiconductor layer. The second optical waveguide is a tapered optical waveguide having a larger end and a smaller end.

Abstract: An apparatus and method for modulating a phase of optical beam independent of polarization. In one embodiment, an apparatus according to embodiments of the present invention includes a first region of an optical waveguide disposed in semiconductor material, the first region having a first conductivity type, and a second region of the optical waveguide disposed in the semiconductor material, the second region having a second conductivity type opposite to the first conductivity type. The apparatus also includes a substantially V shaped insulating region disposed between the first and second regions of the optical waveguide, wherein a vertex of the substantially V shaped insulating region forms an intersecting line that is substantially parallel to an optical path of an optical beam to be directed through the optical waveguide.

Abstract: An apparatus and method for modulating a phase of optical beam. In one embodiment, an apparatus according to embodiments of the present invention includes a first region of semiconductor material having a first polarity. The apparatus further includes a second region of semiconductor material having a second polarity. The second region is disposed proximate to the first region such that an interface between the first and second regions defines interdigitated regions of the first and second regions of semiconductor material. The first and second regions are adapted to be reversed biased in response to a signal to modulate a depletion region in response to the signal at the interface between the first and second region. Accordingly, an optical beam directed through the interface between the first and second regions through the modulated depletion region is adapted to be phase shifted in response to the signal.

Abstract: An apparatus and method for modulating a phase of optical beam in an electrically isolated active region of an optical waveguide. In one embodiment, an apparatus according to embodiments of the present invention includes an active region of an optical waveguide disposed in a semiconductor layer. The active region includes a p doped region and an n doped region. The apparatus further includes an insulating region disposed in the semiconductor layer surrounding the active region in the semiconductor layer. The insulating region electrically isolates the active region of the optical waveguide from a passive region of the optical waveguide disposed in the semiconductor layer. An optical beam is to be directed through the optical waveguide and through the active region to be phase shifted in response to a modulated charge region in the active region in the optical waveguide.

Abstract: A semiconductor-based gain equalization device, method and apparatus. In one aspect of the present invention, an apparatus according to an embodiment of the present invention includes a semiconductor material. An optical path is included through the semiconductor material and is optically coupled to receive and transmit an optical beam. The gain equalization device is disposed in the semiconductor material. The optical gain equalization device includes a plurality of Bragg gratings disposed in the semiconductor material optically coupled to receive and transmit the optical beam. Each of the plurality of Bragg gratings have a different Bragg wavelength. The optical beam is to be directed from plurality of Bragg gratings with a non-uniform spectral response to compensate for the spectral non-uniformity of optical amplifiers.

Abstract: An apparatus and method for reducing a mode size of an optical beam with a dual taper waveguide device. In one embodiment, an apparatus according to embodiments of the present invention includes a buried tapered waveguide disposed in a semiconductor layer. The apparatus further includes a tapered rib waveguide disposed in the semiconductor layer proximate to the buried tapered waveguide. The tapered rib waveguide includes a rib portion adjoining a slab portion. The slab portion of the rib waveguide adjoins the buried tapered waveguide. An optical beam is directed into a larger end of the buried tapered waveguide and the tapered rib waveguide. The buried tapered waveguide is tapered to guide the optical beam therethrough into the slab portion of the rib waveguide.

Abstract: An optical steering method and apparatus. In one aspect of the present invention, the disclosed apparatus includes a multi-mode interference (MMI) device disposed in a semiconductor substrate. The MMI device includes an input and a plurality of outputs. Each one of the plurality of outputs of the MMI device is optically coupled to the input of the MMI device. A phase array is disposed in the semiconductor substrate. The phase array includes a plurality of inputs and a plurality of outputs. The plurality of inputs of the phase array optically are coupled to the plurality of outputs of the phase array. The phase array is coupled to control relative phase differences between optical beams output by each one of the plurality of outputs of the phase array.

Abstract: A semiconductor-based tunable optical dispersion compensation method and apparatus for multiple channels. In one aspect of the present invention, an apparatus according to an embodiment of the present invention includes a semiconductor material. An optical path through the semiconductor material is included. The optical path is optically coupled to receive an optical beam. A nonlinearly chirped Bragg grating is disposed in the semiconductor material. The optical path includes the nonlinearly chirped Bragg grating to substantially reduce chromatic dispersion in the optical beam.

Abstract: A semiconductor-based gain equalization device, method and apparatus. In one aspect of the present invention, an apparatus according to an embodiment of the present invention includes a semiconductor material. An optical path is included through the semiconductor material and is optically coupled to receive and transmit an optical beam. The gain equalization device is disposed in the semiconductor material. The optical gain equalization device includes a plurality of Bragg gratings disposed in the semiconductor material optically coupled to receive and transmit the optical beam. Each of the plurality of Bragg gratings have a different Bragg wavelength. The optical beam is to be directed from plurality of Bragg gratings with a non-uniform spectral response to compensate for the spectral non-uniformity of optical amplifiers.

Abstract: An apparatus and method for modulating an optical beam. In one embodiment, a method according to embodiments of the present invention includes splitting first and second optical beams having first wavelength and second wavelengths, respectively, into split first and second optical beams that co-propagate through first and second waveguides disposed in semiconductor material. The first optical beam having a signal encoded thereon. Free charge carriers are generated in response to the signal encoded on the first optical beam in first and second multiple quantum well (MQW) p-i-n structures disposed in the first and second waveguides, respectively. The split second optical beams are phase shifted in response to the generated free charge carriers in the first and second MQW p-i-n structures. The phase shifted split second optical beams are combined to modulate the second optical beam.

Abstract: An apparatus and method for modulating a phase of optical beam with reduced contact loss. In one embodiment, an apparatus according to embodiments of the present invention includes a first region of an optical waveguide disposed in semiconductor material. The first region has a first conductivity type. The apparatus also includes a second region of the optical waveguide disposed in the semiconductor material. The second region has a second conductivity type, which is opposite to the first conductivity type. The apparatus also includes an insulating region disposed between the first and second regions of the optical waveguide. A first contact is coupled to the optical waveguide at a first location outside an optical path of an optical beam, which is to be directed through the optical waveguide. A first buffer of insulating material is disposed along the optical waveguide between the first contact and the optical path of the optical beam.

Abstract: A semiconductor-based tunable add/drop method and apparatus. In one aspect of the present invention, a method according to an embodiment of the present invention includes splitting a first optical beam having multiple wavelengths into second and third optical beams with a first 3 dB optical coupler disposed in a semiconductor substrate. Portions of the second and third optical beams having a tunable wavelength are reflected back to the first 3 dB optical coupler with first and second pluralities of silicon and polysilicon interfaces, respectively, disposed along the semiconductor substrate. In another embodiment, the portions of the second and third optical beams having a tunable wavelength are reflected back to the first 3 dB optical coupler with first and second pluralities of modulated charged regions. Portions of the second and third optical beams not reflected are directed to a second 3 dB optical coupler disposed in the semiconductor substrate.

Abstract: A semiconductor-based laser tuning method and apparatus. In one aspect of the present invention, an apparatus according to an embodiment of the present invention includes a gain medium disposed in a semiconductor substrate. A laser cavity is disposed in the semiconductor substrate and is optically coupled to the gain medium. A first reflector defines one end of the laser cavity. The first reflector includes a first tunable Bragg grating disposed in the semiconductor substrate. The first tunable Bragg grating includes a first plurality of silicon and polysilicon interfaces along the semiconductor substrate such that there is a first plurality of perturbations of a refractive index along the Bragg grating. The first tunable Bragg grating selectively reflects light having a tunable center wavelength so as to emit light through stimulated emission having the tunable center wavelength in the laser cavity. A second reflector defines an other end of the laser cavity.

Abstract: An apparatus and method for high speed phase modulation of optical beam with reduced optical loss. In one embodiment, an apparatus includes a first region of an optical waveguide disposed in semiconductor material. The first region has a first conductivity type. The apparatus also includes a second region of the optical waveguide disposed in the semiconductor material. The second region has a second conductivity type opposite to the first conductivity type. A first contact is included in the apparatus and is coupled to the optical waveguide at a first location in the first region outside an optical path of an optical beam to be directed through the optical waveguide. The apparatus also includes a first higher doped region included in the first region and coupled to the first contact at the first location to improve an electrical coupling between the first contact and the optical waveguide. The first higher doped region has a higher doping concentration than a doping concentration within the optical path.