Abstract: Provided is a wavelength filter including: an optical waveguide core that includes n (n is an integer greater than or equal to 2) number of mode conversion parts and n?1 number of cavity parts that are alternately connected to each other in series; and cladding that surrounds the optical waveguide core. The mode conversion parts convert light having a specific wavelength of a p-order mode (p is an integer satisfying p?0) into light of a q-order mode (q is an integer satisfying q>p) and reflect the light. The cavity parts match phases of the light having the specific wavelength of the p-order mode propagating through the cavity part.

Abstract: The optical waveguide element has a first optical waveguide core; and a second optical waveguide core. In the optical waveguide element, the first optical waveguide core includes a first coupling portion configured to propagate any one polarized wave of a TE polarized wave and a TM polarized wave of a kth-order mode, the other polarized wave of an hth-order mode, and the other polarized wave of a pth-order mode, and a first Bragg reflector connected to the first coupling portion. The second optical waveguide core includes a second coupling portion.

Abstract: The optical waveguide element has a first optical waveguide core; and a second optical waveguide core. In the optical waveguide element, the first optical waveguide core includes a first coupling portion configured to propagate any one polarized wave of a TE polarized wave and a TM polarized wave of a kth-order mode, the other polarized wave of an hth-order mode, and the other polarized wave of a pth-order mode, and a first Bragg reflector connected to the first coupling portion. The second optical waveguide core includes a second coupling portion.

Abstract: Provided is a wavelength filter including: an optical waveguide core that includes n (n is an integer greater than or equal to 2) number of mode conversion parts and n?1 number of cavity parts that are alternately connected to each other in series; and cladding that surrounds the optical waveguide core. The mode conversion parts convert light having a specific wavelength of a p-order mode (p is an integer satisfying p?0) into light of a q-order mode (q is an integer satisfying q>p) and reflect the light. The cavity parts match phases of the light having the specific wavelength of the p-order mode propagating through the cavity part.

Abstract: Provided is a waveguide-type optical diffraction grating. A waveguide core includes a waveguide core that is asymmetric with respect to a thickness direction perpendicular to a light propagating direction. In the waveguide core, a phase adjustment portion is configured to adjust a phase difference between a forward wave traveling in an input direction and a reflected wave traveling in a direction reverse to the input direction in the waveguide-type optical diffraction grating, and the phase adjustment portion is provided in a manner that a sum of a phase of the forward wave and a phase of the reflected wave which are generated in the phase adjustment portion becomes a constant value irrespective of a polarization state of input light to the waveguide-type optical diffraction grating.

Abstract: There is provided an optical multiplexing and de-multiplexing element which is provided with a slab waveguide and a waveguide structure and can reduce radiation loss caused in a connection part between the slab waveguide and the waveguide structure. The waveguide structure includes a multimode interference (MMI) waveguide coupler and a narrow-width waveguide, the MMI waveguide coupler and the narrow-width waveguide are connected to each other in this order from a connection position with the slab waveguide along the waveguide direction, step portions are formed on both sides of the MMI waveguide coupler along the waveguide direction, and the thickness of the step portion is smaller than the thickness of the MMI waveguide coupler.

Abstract: An optical wavelength demultiplexer includes a wavelength demultiplexing device, a first wavelength filter and a first- and second-stage wavelength sub-filters. The wavelength demultiplexing device demultiplexes an input light into a first wavelength band including wavelengths ?1 and ?2 in the vicinity of 1310 nm and a second wavelength band including a wavelength ?3 of 1490 nm and a wavelength ?4 of 1550 nm to output. The first-stage wavelength sub-filter removes the wavelength ?2 longer than 1310 nm from the second wavelength band and transmits the wavelength ?3 of 1490 nm. The second-stage wavelength sub-filter removes the wavelength ?4 of 1550 nm and outputs the wavelength ?3 of 1490 nm, which is the remainder of the selected lights, with a sufficient wavelength spectral purity.

Abstract: There is provided an optical multiplexing and de-multiplexing element which is provided with a slab waveguide and a waveguide structure and can reduce radiation loss caused in a connection part between the slab waveguide and the waveguide structure. The waveguide structure includes a multimode interference (MMI) waveguide coupler and a narrow-width waveguide, the MMI waveguide coupler and the narrow-width waveguide are connected to each other in this order from a connection position with the slab waveguide along the waveguide direction, step portions are formed on both sides of the MMI waveguide coupler along the waveguide direction, and the thickness of the step portion is smaller than the thickness of the MMI waveguide coupler.

Abstract: Provided is a waveguide-type optical diffraction grating. A waveguide core includes a waveguide core that is asymmetric with respect to a thickness direction perpendicular to a light propagating direction. In the waveguide core, a phase adjustment portion is configured to adjust a phase difference between a forward wave traveling in an input direction and a reflected wave traveling in a direction reverse to the input direction in the waveguide-type optical diffraction grating, and the phase adjustment portion is provided in a manner that a sum of a phase of the forward wave and a phase of the reflected wave which are generated in the phase adjustment portion becomes a constant value irrespective of a polarization state of input light to the waveguide-type optical diffraction grating.

Abstract: An optical waveguide element includes a waveguide core formed of silicon, and a cladding layer formed of a material identical to the waveguide core for enveloping the waveguide core. The optical waveguide element comprising: a high-order propagation mode waveguide; a single input tapered waveguide that is provided on an input terminal of the high-order propagation mode waveguide; a plurality of output tapered waveguides that are provided on an output terminal of the high-order propagation mode waveguide; and an optical feedback elimination waveguide that is provided on the input terminal and disposed alongside the input tapered waveguide. In the optical waveguide element, the input tapered waveguide and the output tapered waveguides are tapered waveguides in which a waveguide width becomes gradually narrower the greater the separation from a terminal of connection to the high-order propagation mode waveguide, and the optical feedback elimination waveguide eliminates reflected light into the cladding layer.

Abstract: An optical waveguide element includes a waveguide core formed of silicon, and a cladding layer formed of a material identical to the waveguide core for enveloping the waveguide core. The optical waveguide element comprising: a high-order propagation mode waveguide; a single input tapered waveguide that is provided on an input terminal of the high-order propagation mode waveguide; a plurality of output tapered waveguides that are provided on an output terminal of the high-order propagation mode waveguide; and an optical feedback elimination waveguide that is provided on the input terminal and disposed alongside the input tapered waveguide. In the optical waveguide element, the input tapered waveguide and the output tapered waveguides are tapered waveguides in which a waveguide width becomes gradually narrower the greater the separation from a terminal of connection to the high-order propagation mode waveguide, and the optical feedback elimination waveguide eliminates reflected light into the cladding layer.

Abstract: An optical wavelength demultiplexer includes a wavelength demultiplexing device, a first wavelength filter and a first- and second-stage wavelength sub-filters. The wavelength demultiplexing device demultiplexes an input light into a first wavelength band including wavelengths ?1 and ?2 in the vicinity of 1310 nm and a second wavelength band including a wavelength ?3 of 1490 nm and a wavelength ?4 of 1550 nm to output. The first-stage wavelength sub-filter removes the wavelength ?2 longer than 1310 nm from the second wavelength band and transmits the wavelength ?3 of 1490 nm. The second-stage wavelength sub-filter removes the wavelength ?4 of 1550 nm and outputs the wavelength ?3 of 1490 nm, which is the remainder of the selected lights, with a sufficient wavelength spectral purity.

Abstract: An optical device includes an optical waveguide including a core and a cladding, and includes a wide optical waveguide. An input optical waveguide is connected with one side the wide waveguide and output optical waveguides are connected to an opposite side of the wide waveguide. Center intervals between adjacent ones of the output waveguides meet either a condition 1 that the center intervals are wider than or equal to 4ë?, where ë? is the optical wavelength in the wide waveguide, or they meet a condition 2 that the center intervals are narrower than 4ë? and adjacent output waveguides are disposed at intervals shorter than a length in which optical signals that propagate through each of the output waveguides interact with each other.

Abstract: A wavelength-selective path-switching element has a silicon substrate on which a pattern of optical waveguides including a first optical waveguide, a second optical waveguide and an intermediary optical waveguide is formed. The widths W1, W2, and W3 of these optical waveguides, lengths L1, L2, and spacing G1, G2 are so set that light of a first wavelength entered into the first optical waveguide propagates on the first, intermediary, and second optical waveguides, exits from the second waveguide, propagates on an output waveguide, and is outputted and that light of a second wavelength entered into the first waveguide after propagating on an input waveguide is outputted from this first waveguide. The wavelength-selective path-switching element can be easily fabricated at low cost and have no light leaking out.

Abstract: An optical waveguide includes a substrate, an upper clad layer arranged on the substrate; and an optical waveguide structure that is disposed in the upper clad layer so as to be parallel to a surface of the substrate. The optical waveguide structure includes a flat optical waveguide, channel optical waveguides that are each connected with a first edge face of the flat optical waveguide and extend radially therefrom, the channel optical waveguides each respectively have lateral sides parallel to the substrate surface that have a width therebetween which increases as the distance from the first edge face increases, and an input optical waveguide connected with a second edge face that is arranged at an side of the flat optical waveguide opposite to the first edge face.

Abstract: An optical wavelength filter has optical waveguides each of which includes a cladding layer and a core having a refractive index that is as high as that of the cladding layer by a factor of 1.4 or more. Each optical waveguide is partitioned into a reference section providing a reference and an adjustment section for adjusting phase differences. The reference section of each optical waveguide is so set that the optical waveguide in this section has a first equivalent refractive index and a first length. The adjustment section is so set that the waveguide in this adjustment section has a second equivalent refractive index and a second length. Two waves of light outputted from the output ends of adjacent two of the optical waveguides interfere with each other with a predetermined phase difference, thereby accomplishing independency of temperature and dimensional error.

Abstract: An optical path routing element includes first and second optical waveguide that are parallel to each other. The first and second waveguides have the same thickness and have the same width, the width being larger than the thickness. The width is within a range based upon coupling lengths of the first and second waveguides for a TE polarization and for a TM polarization such that the difference between the coupling length for TE polarization and the coupling length for TM polarization is no more than a predetermined percentage times the sum of the coupling length for TE polarization and the coupling length for TM polarization divided by 2.

Abstract: A polarization-independent optical multiplexer/demultiplexer with wide passbands has a core including an input optical waveguide, an input slab optical waveguide connected to the input optical waveguide, a waveguide array connected to the input slab optical waveguide, an output slab optical waveguide connected to the waveguide array, a pair of multimode couplers connected to the output slab optical waveguide, and a pair of output optical waveguides connected to the multimode couplers. The multimode couplers are dimensioned so that as both TE and TM polarized light propagates through them, the phase difference between the fundamental and second-order modes changes by an odd multiple of pi radians.

Abstract: An optical device includes an optical waveguide including a core and a cladding, and includes a wide optical waveguide. An input optical waveguide is connected with one side the wide waveguide and output optical waveguides are connected to an opposite side of the wide waveguide. Center intervals between adjacent ones of the output waveguides meet either a condition 1 that the center intervals are wider than or equal to 4??, where ?? is the optical wavelength in the wide waveguide, or they meet a condition 2 that the center intervals are narrower than 4?? and adjacent output waveguides are disposed at intervals shorter than a length in which optical signals that propagate through each of the output waveguides interact with each other.

Abstract: There is provided an optical device including a first optical waveguide of a directional coupler, a second optical waveguide connected to the first optical waveguide and which guides light, and a common cladding of the first and second optical waveguides, wherein: the common cladding of the first and second optical waveguides includes a first cladding and a second cladding, the second cladding being provided on the first cladding and having a higher refractive index than the first cladding; the first optical waveguide and the second optical waveguide are formed continuously on the first cladding with a constant width and a constant height and are integrated with each other, and a cross sectional shape of each of the first and second optical waveguides is a rectangular shape that is longest in a direction orthogonal to a surface of the first cladding.