Oki Electric Industry Co., Ltd.

Photonics Electronics Technology Research Association

Hideaki Okayama

Issei Asabayashi

Toshimasa Ishida

Masato Kawahara

Masao Kobayashi

Takashi Ushikubo

Chang Qing Xu

Yoshio Kawai

Hideki Ono

Nobuo Kobayashi

Hironori Sasaki

Keisuke Shinozaki

Haruo Mori

Yutaka Okabe

Kiyoshi Nagai

Saeko Oshiba

Hiroki Yaegashi

Chang-Qing Xu

Ryoko Shibuya

Akio Matoba

Yousuke Oonawa

Takayuki Kakinuma

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&#x2212;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&#x2265;0) into light of a q-order mode (q is an integer satisfying q&#x3e;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.

Wavelength filter

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 k-order mode, the other polarized wave of an h-order mode, and the other polarized wave of a p-order mode, and a first Bragg reflector connected to the first coupling portion. The second optical waveguide core includes a second coupling portion. The first Bragg reflector includes a rib waveguide including a grating configured to convert the one input polarized wave of the k-order mode into the other polarized wave of the h-order mode, reflect the converted polarized wave on the basis of Bragg reflection, and transmit the other input polarized wave of the p-order mode, and slab waveguides having thicknesses smaller than that of the rib waveguide and integrally formed with the rib waveguide on both side surfaces of the rib waveguide respectively, in the light propagation direction.

Optical waveguide element and receiving circuit

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.

Waveguide-type optical diffraction grating and optical wavelength filter

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.

Optical multiplexing and de-multiplexing element and arrayed-waveguide grating-type optical wavelength filter

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 &#x3bb;and &#x3bb;in the vicinity of 1310 nm and a second wavelength band including a wavelength &#x3bb;of 1490 nm and a wavelength &#x3bb;of 1550 nm to output. The first-stage wavelength sub-filter removes the wavelength &#x3bb;longer than 1310 nm from the second wavelength band and transmits the wavelength &#x3bb;of 1490 nm. The second-stage wavelength sub-filter removes the wavelength &#x3bb;of 1550 nm and outputs the wavelength &#x3bb;of 1490 nm, which is the remainder of the selected lights, with a sufficient wavelength spectral purity.

Optical wavelength demultiplexer having optical interference filters connected in cascade

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.

Optical waveguide element

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&#xeb;', where &#xeb;&#x2032; is the optical wavelength in the wide waveguide, or they meet a condition 2 that the center intervals are narrower than 4&#xeb;&#x2032; 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.

Optical device

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 W, W, and Wof these optical waveguides, lengths L, L, and spacing G, Gare 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.

Wavelength-selective path-switching element

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.

Flat optical waveguide with connections to channel and input optical waveguides

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.

Optical wavelength filter with wavelength characteristic variation minimized

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.

Optical multiplexer/demultiplexer

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.

Optical device and Mach-Zehnder interferometer

There is provided an optical resonator including: N individual optical waveguide paths of line segment shape disposed in a common flat-plane so as to intersect at a single intersection region, wherein N is an integer of 2 or more; curved optical waveguide paths connecting respective portions of the optical waveguide paths that extend towards the outside from the intersection region, wherein for a first to a 2Noptical waveguide path portions in a clockwise direction, connection is made between end portions at the opposite side to the intersection region of the (2i&#x2212;1)to 2ioptical waveguide path portions, wherein i is an integer of 1 to N; and an optical coupler that couples light input or output perpendicular to the flat-plane with the optical waveguide paths, the optical coupler being formed in a region containing the intersection region where the optical waveguide paths are connected.

Optical resonator, and fluid optical sensor employing an optical resonator

An optical device includes a core sandwiched between two clads. The core includes a planar waveguide layer with ridges protruding into one of the clads, forming a ridge waveguide structure that guides the propagation of light in the core. The core dimensions satisfy the following conditions: the ridge width is less than the total core height; the ridge height is less than the ridge width; the thickness of the planar waveguide layer is equal to or less than one-fourth of the total core height. Dimensions satisfying these conditions can be selected to provide polarization independent operation. The ridges may be arranged to define a pair of optical waveguides forming a Mach-Zehnder interferometer, an optical wavelength filter, or various other optical devices.

Polarization independent optical device

An optical device has two optical waveguides embedded in a clad. The optical waveguides are mutually parallel and are separated by a distance that allows optical coupling between them. The optical waveguides have identical square cross sectional shapes in a plane orthogonal to the direction of light propagation, so that light propagates through each optical waveguide without polarization dependence. The length of each side of the square cross section of the optical waveguides is determined from the refractive index of the clad and the distance between the longitudinal axes of the optical waveguides so that coupling between the two optical waveguides is also polarization independent for light with a wavelength of 1.49 micrometers, which is the longer of the two wavelengths used in optical subscriber networks.

Growing community of inventors

Tokyo, Japan

Hideaki Okayama