Nec Corporation

Photonics Electronics Technology Research Association

Masatoshi Tokushima

Jun Ushida

Kenichiro Yashiki

Masayuki Shirane

Shigeru Nakamura

Kazuhiko Kurata

Kazuhiro Iida

Tsuyoshi Shimoda

To provide an optical element that can be more easily aligned with an optical fiber, an optical element includes one grating coupler optically coupled to an optical fiber, a waveguide connected to the grating coupler, a multimode interferometer connected to the waveguide on the opposite side to the grating coupler, and a waveguide inserted between two input/output ports on the branched side of the multimode interferometer.

Optical element

Provided is a light receiving element with high light receiving sensitivity. The light receiving element comprises: a light absorbing layer that absorbs light to generate a carrier; and a diffraction element that converts the optical path of first polarized light, which is obliquely incident on a plane formed by the light absorbing layer, so that the first polarized light propagates in a first direction along the light absorbing layer, and that converts the optical path of second polarized light incident from the same direction as the first polarized light so that the second polarized light propagates in a second direction, opposite the first direction, along the light absorbing layer.

Photodetector having one-dimensional grating structure

An alignment optical measurement element includes a grating coupler, and a reflector coupled to the grating coupler. The alignment optical measurement element is arranged so that: the grating coupler diffracts an incident light in a first direction into a first diffracted light to propagate the first diffracted light as a first propagating light in a second direction, the reflector reflects the first propagating light into a second propagating light in a third direction opposite to the second direction; and the grating coupler diffracts the second propagating light into a second diffracted light to emit the second diffracted light as an emitted light in a fourth direction opposite to the first direction.

Optical measurement element for alignment in wafer-level testing and method for aligning an optical probe using the same

A grating structure for a grating coupler is provided which has a high efficiency resulting from the operating principle, is easily manufactured, and simultaneously has little reflection loss. This grating structure is provided with a core layer having periodic recesses and protrusions formed on the upper surface, a first upper cladding layer in contact with the upper surface of the core layer, a second upper cladding layer in contact with the upper surface of the first upper cladding layer, and a first lower cladding layer in contact with the lower surface of the core layer. The recessed portions of said recesses and protrusions are filled with the same material as the first upper cladding layer. The refractive index of the material forming the core layer is greater than the refractive index of the materials forming the first upper cladding layer, the second upper cladding layer and the first lower cladding layer. The refractive index of the material of the first upper cladding layer is greater than the refractive index of the material of the second upper cladding layer. The thickness from the upper surface of the protruding portions of the recesses and protrusions to the upper surface of the first upper cladding layer is within the range obtained by subtracting &#xbd; of the depth of the recesses and protrusions from ((2m&#x2212;1)/4&#xb1;&#x215b;) times (mbeing a positive integer) the wavelength, in the material forming the first upper cladding layer, of light inputted and outputted by the grating coupler.

Grating structure, and manufacturing method of grating coupler provided therewith

A grating coupler includes a grating including a core and an anti-phase reflection coating provided on at least one part of the grating. The anti-phase reflection coating includes a high refractive index layer and a buffer layer. The high refractive index layer has at least one selected from a plurality of attributes characterizing the high refractive index layer. The at least one selected attribute gradually deceases along a propagation direction of light in the core of the grating.

Grating coupler with high optical coupling efficiency for SMF

An optical circuit, wherein the effects of reflected light generated by an optical component are reduced. The optical circuit () is provided with an optical branching () for branching light, an optical coupler () for coupling a first portion of branched light to an optical waveguide () for transmission, and an optical reflecting unit () for reflecting a second portion of the branched light, the phase difference between the reflected light from the optical coupler () and the reflected light from the optical reflecting unit () being (2m&#x2212;1)&#x3c0; (where m is an integer) on an input side of the optical branching ().

Optical circuit

Disclosed is an optical conversion element capable of highly efficient optical coupling between a silicon waveguide and a general single-mode optical fiber only by butt-coupling without requiring anti-reflective coating. One embodiment is an optical conversion element that includes a waveguide structure and converts a mode field of guided light and is characterized in that at least a dual core is included, an innermost core of the dual core is a silicon inverse tapered thin wire core, a first outer core is a forward tapered ridge core having a ridge structure formed of an oxide film with only width of the ridge core changing. The first outer core is positioned on a narrow width side of the innermost core.

Optical conversion element and optical conversion element manufacturing method

A wavelength filter includes a first waveguide with a transmission band of a predetermined basic mode and a second waveguide, arranged in at least one location of the first waveguide, with a transmission band whose cutoff frequency corresponds to a finite value included in the transmission band of the basic mode. A pair of optical couplers constituting a Mach-Zehnder interferometer is connected to the opposite ends of a filter unit including the first waveguide and the second waveguide. When a plurality of wavelength filters is cascaded, the wavelength filters can be each varied in terms of the cutoff frequency of the second waveguide.

Wavelength filter

Disclosed is an optical delay element that makes use of a line-defect waveguide of a photonic crystal, in which long optical delay time and small group speed dispersion are rendered compatible with each other and in which waveform distortion that might otherwise be produced in processing an ultra-high speed signal is eliminated. Two line-defect waveguidesand, having different pillar diameters and group velocity dispersions of opposite signs, are interconnected by a line-defect waveguide, the pillar diameters of which are gradually varied from oneof the line-defect waveguides to the other line-defect waveguide, such as to compensate for group speed dispersion as well as to maintain an optical delay effect.

Optical control device

An optical switch is constituted of a wavelength filter and a control device. The wavelength filter includes a first waveguide exhibiting a transmission band of a predetermined basic mode and a second waveguide, arranged in at least one location of the first waveguide, exhibiting a transmission band with a cutoff frequency corresponding to a finite value included in the transmission band of the basic mode. A pair of optical couplers constituting a Mach-Zehnder interferometer is connected to opposite ends of a filter unit including the first waveguide and the second waveguide. When a plurality of wavelength filters is cascaded, these wavelength filters differ from each other in terms of the cutoff frequency of the second waveguide. The control device changes the cutoff frequency of the second waveguide within the transmission band of the first waveguide, thus adjusting the filtering band of the wavelength filter.

Optical switch

The object is to provide an optical switch capable of efficient operation and a manufacturing method thereof. The optical switch according to the present invention is a Mach-Zehnder interferometer type optical switch composed of a line defect waveguide of a photonic crystal. Further, the optical switch according to the present invention includes two directional couplersand, and two paths of waveguidesandtherebetween. Furthermore, between the two paths, group velocity of guided light differs in the first path waveguideand the second path waveguide

Optical switch and manufacturing method thereof

In an exemplary embodiment, an optical waveguide () includes a first dielectric medium (). In the first dielectric medium (), line-defect rods () are arranged in one row and non-line-defect rods () are arranged along the row of line-defect rods () and on both sides of the row of the line-defect rods (). The line-defect rods () and non-line-defect rods () form a two-dimensional square lattice. Of the rows of non-line-defect rods () arranged on the two sides of the row of line-defect rods (), the number of rows of non-line-defect rods () on at least one side is at least one and no greater than five.

Optical waveguide

A waveguide stub is connected to a pillar-type square-lattice photonic crystal waveguide. Within the waveguide stub, the diameter of a defect is made larger than that of the original photonic crystal waveguide thereby reducing the group velocity of a guided light. The original waveguide and the waveguide stub are smoothly connected via a taper waveguide. Because of low group velocity of light in the waveguide stub, free spectral range (FSR) decreases thereby allowing the size of the waveguide stub to be reduced.

Photonic crystal element

There is provided an optical control device including a plurality of line-defect waveguides provided in a photonic crystal; each line-defect waveguide including a multiplicity of dielectric pillars with a finite height arranged at lattice points of a two-dimensional Bravais lattice. The optical control device comprises: a first line-defect waveguide; a second line-defect waveguide provided with the dielectric pillars having a thickness different from that of the dielectric pillars of the first line-defect waveguide; and a third line-defect waveguide arranged between the first and second line-defect waveguides and provided with the dielectric pillars whose thicknesses are gradually varied from those of the dielectric pillars of the first line-defect waveguide to those of the dielectric pillars of the second line-defect waveguide along a wave guiding direction.

An optical converter comprises: a first waveguide, a second waveguide, and a tapered waveguide arranged between both the waveguides, wherein heights of a core of the first waveguide and a core of the second waveguide are different; both ends in a direction of wave guiding of a core of the tapered waveguide are respectively connected to the core of the first waveguide and the core of the second waveguide; cross-sectional shapes and refractive indexes of cores of two waveguides that are connected change continuously or in a stepwise manner at each connection part; and a cross-sectional shape and refractive index of the core of the tapered waveguide change continuously or in a stepwise manner along a direction of wave guiding.

Growing community of inventors

Tokyo, Japan

Masatoshi Tokushima