Abstract: The present invention, in one embodiment contemplates a polarization insensitive optical circuit constructed of an input/output signal separator, such as an optical circulator or a 1×2 or 2×2 coupler or N×M coupler, a polarization sensitive operator, and a polarization rotator reflector. In an alternate embodiment, the invention contemplates a polarization insensitive optical circuit comprising a polarization rotator reflector, and a polarization sensitive operator which may comprise for example a first polarization rotator, an operator/coupler, and a polarization beam combiner. Preferably at least one of the components in the optical circuit is constructed integrally from the substrate upon which the optical circuit is based. For example the polarization rotator and/or polarization sensitive operator of the present invention may be monolithic.

Abstract: The present invention includes a device and a method for fabricating a device that is an optical power mode transformer that accepts light in a mode transformation direction where the transformer is attached to or embedded in a semiconductor microchip and includes a first single or multimode optical input (SM) waveguide including a first core surrounded by a cladding, and, a second high contrast index grade (HC) waveguide including a second core having a tapered region and surrounded by said cladding, a portion of the tapered region of the core being embedded within the first optical input waveguide region with an embedded length sufficient for efficient light transfer from the first input waveguide to the said second waveguide wherein the embedded portion of the tapered region is fully surrounded by the first input waveguide along an axial and radial cross-section of the second waveguide in the mode transformation direction.

Abstract: An optical system is disclosed. The optical system includes first and second waveguides, a first dispersive element, and a coupler. The first waveguide is configured to support a first mode and a second mode of an optical input signal. The second mode being of a higher order than the first mode. The second waveguide has an input and an output and is configured to receive a portion of the optical input signal. The first dispersive element is disposed along a length of one of the first or second waveguides. The first dispersive element including a waveguide segment configured to induce a frequency-dependent phase shift in one of the portions of the optical input signal. The coupler is configured to couple the portion of the optical input signal in the second waveguide and the portion optical input signal in the first waveguide into the first waveguide. The coupling excites the second mode of the first waveguide to create a multimode optical signal.

Abstract: An optical coupler includes a first waveguide configured to supply a first optical signal having a wavelength and a second waveguide. The first optical signal having a first mode. The first waveguide has a tapered portion being spaced from the second waveguide by a distance sufficient to facilitate evanescent coupling of the first optical signal from the first waveguide to the second waveguide. A first effective refractive index of the first waveguide at a location in the tapered portion being equal to a second effective refractive index at a location in the second waveguide. The first effective refractive index being associated with the first mode and the second effective refractive index being associated with a second mode of a second optical signal having the wavelength. The second mode having a different order than the first mode, and the second waveguide being configured to supply the second optical signal.

Abstract: The present invention relates to a waveguide structure, and methods for making the same. The waveguide structure has a polarization rotator for rotating the polarization of the electromagnetic signal, preferably by about ninety-degrees. In one embodiment, the polarization rotator has a midsection with a first level and a second level. The first level of the midsection has a width that decreases along the length of the first level, while the second level has a substantially constant width along the length of the second level. Further, the waveguide structure can include an input conditioning section and the output conditioning section to facilitate matching between the polarization rotator and other waveguide elements.

Abstract: A polarization beam splitter-polarization rotator-polarization beam combiner optical structure comprising a pair of polarization rotators having a polarization beam splitter associated with the input ends of the two polarization rotators, and a polarization beam combiner associated with output ends of the two polarization rotators, and a method of purifying a light signal comprising TE and TM modes by disassociating the primary TE and TM modes from first order splitter and rotation error components.

Abstract: A polarization beam splitter-polarization rotator-polarization beam combiner optical structure comprising a pair of polarization rotators having a polarization beam splitter associated with the input ends of the two polarization rotators, and a polarization beam combiner associated with output ends of the two polarization rotators, and a method of purifying a light signal comprising TE and TM modes by disassociating the primary TE and TM modes from first order splitter and rotation error components.

Abstract: An optical device includes a first waveguide having an end portion configured to receive an optical signal, the optical signal having a fundamental mode; a second waveguide having an end portion spaced from the end portion of the first waveguide; and a cladding layer surrounding the first and second waveguides. The first waveguide is configured such that the optical signal undergoes multimode interference to focus the fundamental mode at the end portion of the second waveguide.

Abstract: Consistent with the present disclosure an optical filter is provided that preferably includes a plurality of looped or ring-shaped waveguides provided on a substrate which are coupled to one another by tunable couplers. Portions of each waveguide constitute part of each tunable coupler, which may include, for example, a Mach-Zehnder interferometer. A heater may be thermally coupled to one or both arms of the Mach-Zehnder interferometer, to thereby adjust an amount of optical coupling between adjacent looped waveguides. The filter bandwidth (i.e., the spectral width of the passband), which, as noted above, is related to such coupling, can thus also be tuned or varied. Additional heaters may be provided to tune the center wavelength of the passband so that a filter having both a variable passband spectral width and center wavelength can be obtained.

Abstract: Consistent with the present disclosure a compact, integrated tunable filter is provided that can adjust the power levels of optical signals output from an optical amplifier, for example, so that the amplifier has a uniform spectral gain. The tunable optical filter includes a planar lightwave circuit (PLC) having cascaded Mach-Zehnder interferometers, each of which having corresponding differential optical delays. At least one of the differential optical delays is different than the rest. Alternatively, the differential optical delays are different from one another. Each of the Mach-Zehnder interferometers is connected to one another by a tunable optical coupler. Such a filter has an improved frequency response in that the number of shapes that the transmission spectrum may have is increased. Accordingly, the optical filter may be more finely tuned to more effectively flatten, for example, the output of the optical amplifier.

Abstract: A geometrically shaped optical waveguide crossing with minimal transmission loss is described. A symmetrically tapered waveguide intersection is used to minimize loss in the intersecting region where at least two optical waveguides cross one another. The present invention embodies a waveguide crossing that includes tapering the width of the waveguides as they approach the intersecting region, forcing the field of light to contract, reducing asymmetric field distortions, and thus reducing transmission loss and effectively minimizing crosstalk. This is accomplished by focusing light through a perpendicular or near perpendicular intersection by simple linear tapering rather than by the use of a lens or other previously used devices.

Abstract: A planar lightwave circuit (PLC) includes a substrate, a tunable filter, a demultiplexer (DEMUX), and an optical processor each disposed on the substrate. The tunable filter is configured to filter at least one of a bandwidth or a wavelength of a Wavelength Division Multiplexed (WDM) optical input signal. The DEMUX is connected to the tunable filter and configured to receive a filtered WDM optical input signal at an input and to supply one of a plurality of channels of the filtered WDM input signal at a respective one of a plurality of outputs. Each of the plurality of channels corresponds to one of a plurality of wavelengths of the filtered WDM input signal. The optical processor includes a bit-delay interferometer communicating with a respective one of the plurality of outputs of the DEMUX. The optical processor is configured to receive one of the plurality of channels from the DEMUX and output a plurality of demodulated optical signal components.

Abstract: An optical receiver includes a first substrate including a demultiplexer and a first optical waveguide array. An input of the demultiplexer is configured to receive a wavelength division multiplexed optical input signal having a plurality of channels. Each of the plurality of channels corresponds to one of a plurality of wavelengths. Each of the plurality of outputs is configured to supply a corresponding one of the plurality of channels. The first optical waveguide array has a plurality of inputs. Each of the inputs of the first optical waveguide array is configured to receive a corresponding one of the plurality of channels. A second substrate is in signal communication with the first substrate and includes an optical detector array. The optical detector array has a plurality of inputs, each of which is configured to receive a corresponding one of the plurality of channels and generate an electrical signal in response thereto.

Abstract: A geometrically shaped optical waveguide crossing or intersection with minimal transmission loss is described. A symmetrically tapered waveguide intersection is used to minimize loss in the intersecting region where at least two optical waveguides cross one another at 90° or nearly 90°. The present invention embodies a waveguide crossing that includes tapering the width of the waveguides as they approach the intersecting region, forcing the propagating light to contract, thereby reducing asymmetric field distortions, and thus reducing transmission loss and effectively minimizing crosstalk. This is accomplished by focusing the propagating light through a perpendicular or near perpendicular in at least two waveguide intersection by simple linear tapering rather than by the use of a lens or other previously used devices.

Abstract: A method of fabricating a passive polarization sorter includes the steps of providing first and second waveguides. The first waveguide has an input and an output. The first waveguide supporting at least one guided TE polarized mode of mode ranking mode-i-TE and at least one guided TM polarized mode of mode ranking mode-j-TM. The second waveguide is positioned adjacent to the first waveguide, and the first and second waveguides are shaped to form an adiabatic region in which light having one of the TE and TM polarized modes remains within the first waveguide, and light having the other one of the TE and TM polarized modes evanescently couples into the second waveguide.

Abstract: The present invention is directed to an on-chip symmetric optical circuit having one or more integrally fabricated polarization rotators forming a monolithic, solid state polarization independent symmetric circuit. The symmetric optical circuit has at least one integrally fabricated rotator positioned in a plane of symmetry of at least one optical fiber, waveguide or circuit path of the symmetric optical circuit. The folded symmetric optical circuit may be for example a Mach-Zehnder type optical circuit or an arrayed waveguide grating optical circuit.

Abstract: A broadband optical via provides a low loss interconnection between waveguides in two vertically adjacent planar waveguiding layers. Two waveguides, one in each planar layer, evanescently interact over an interaction length, and substantially all of the power on one waveguide is transferred to the second waveguide. The relative detuning between waveguides is varied along the interaction region by tapering the width of one or both guides along the direction of propagation. The interaction strength is also varied by varying the physical separation between the two waveguides such that the interaction approaches zero near the two ends of the interaction length. The performance of the broadband optical via is fabrication tolerant, polarization tolerant, wavelength tolerant, and dimensionally tolerant.

Abstract: A multi-channel dispersion compensator comprising an optical signal waveguide that forms an input end for receiving an optical signal and an output end for providing a filtered optical signal. The multi-channel dispersion compensator also includes a series of closed-loop resonators providing frequency delay to at least one channel of the optical signal. The optical signal waveguide and each closed-loop resonator form a tunable coupler having a coupling value. The coupling value for each tunable coupler is selected to minimize constant dispersion and linear slope dispersion of the optical signal. Methods of fabrication and use are also described.

Abstract: The present invention is directed to an on-chip symmetric optical circuit having one or more integrally fabricated polarization rotators forming a monolithic, solid state polarization independent symmetric circuit. The symmetric optical circuit has at least one integrally fabricated rotator positioned in a plane of symmetry of at least one optical fiber, waveguide or circuit path of the symmetric optical circuit. The folded symmetric optical circuit may be for example a Mach-Zehnder type optical circuit or an arrayed waveguide grating optical circuit.

Abstract: An intermediate structure used to form an integrated optics device comprising a substrate, a cladding on the substrate, at least one real waveguide on the cladding, and at least one dummy waveguide optically coupled with the real waveguide. The real waveguide forms a part of a predetermined planar lightwave circuit. The dummy waveguide does not form a part of the predetermined planar lightwave circuit.