Abstract: An optical modulation element 100 includes a rib type optical waveguide that includes a rib portion 112 that has a P-N junction, a P-type slab area 114 that continuously extends from a P type area of the rib portion 112, and an N-type slab area 116 that continuously extends from an N type area of the rib portion 112. A first thin film 130 is formed on the P-type slab area 114 and is made of a material having an electron affinity that is different from that of the P-type slab area 114.

Abstract: An electro-optic waveguide device may include a slot waveguide including a lower high-refractive-index layer with a first refractive index and an upper high-refractive-index layer with a second refractive index, wherein the lower high-refractive-index layer and the upper high-refractive-index layer have conductivity and are disposed to face each other with a gap; and a slot part formed as a low-refractive-index layer, wherein the low-refractive-index layer is formed of a material producing an electro-optic effect and has a third refractive index lower than the first refractive index and the second refractive index, wherein the low-refractive-index layer is formed in the gap to come into contact with the lower high-refractive-index layer and the upper high-refractive-index layer, and wherein one of the lower high-refractive-index layer or the upper high-refractive-index layer includes a stretch stretching on both sides of a contact portion with the slot part in a width direction intersecting a transmission dir

Abstract: Provided is an optical waveguide element having a reduced optical loss, a lower driving voltage, and a reduced size. A rib waveguide core of an optical waveguide includes a first core region and a second core region which constitute a PN junction and which are provided so as to overlap each other in a horizontal direction. A depletion layer is formed between the first core region and the second core region. The depletion layer extends from a rib region to both of two slab regions. The depletion layer is located so as to be vertically lower in the slab regions than in the rib region.

Abstract: An electro-optic waveguide device may include a slot waveguide including a lower high-refractive-index layer with a first refractive index and an upper high-refractive-index layer with a second refractive index, wherein the lower high-refractive-index layer and the upper high-refractive-index layer have conductivity and are disposed to face each other with a gap; and a slot part formed as a low-refractive-index layer, wherein the low-refractive-index layer is formed of a material producing an electro-optic effect and has a third refractive index lower than the first refractive index and the second refractive index, wherein the low-refractive-index layer is formed in the gap to come into contact with the lower high-refractive-index layer and the upper high-refractive-index layer, and wherein one of the lower high-refractive-index layer or the upper high-refractive-index layer includes a stretch stretching on both sides of a contact portion with the slot part in a width direction intersecting a transmission dir

Abstract: Provided is an optical waveguide element having a reduced optical loss, a lower driving voltage, and a reduced size. A rib waveguide core of an optical waveguide includes a first core region and a second core region which constitute a PN junction and which are provided so as to overlap each other in a horizontal direction. A depletion layer is formed between the first core region and the second core region. The depletion layer extends from a rib region to both of two slab regions. The depletion layer is located so as to be vertically lower in the slab regions than in the rib region.

Abstract: An optical receiver circuit includes: a substrate; and an optical waveguide device that is formed on the substrate. The optical waveguide device includes: a first optical splitter section branching the signal light into a first signal light propagation waveguide and a second signal light propagation waveguide and; a second optical splitter section branching the local-oscillator light into a first local-oscillator light propagation waveguide and a second local-oscillator light propagation waveguide; a first optical coupler section that combines the signal light propagating through the first signal light propagation waveguide and the local-oscillator light propagating through the first local-oscillator light propagation waveguide with each other; a second optical coupler section that combines the signal light propagating through the second signal light propagation waveguide and the local-oscillator light propagating through the second local-oscillator light propagation waveguide with each other.

Abstract: To reduce the optical loss, lower the driving voltage, produce a smaller product, and simplify the production process, an embodiment of the present invention includes a rib waveguide core (101) having a rib region (101r) and two slab regions (101s), where a depletion layer (113) is so formed as to extend from the rib region (101r) to the two slab regions (101s).

Abstract: An optical waveguide device includes a substrate; a lower cladding disposed on the substrate; a rib waveguide including a slab disposed on the lower cladding and a single rib disposed on the slab contiguous to the slab; and an upper cladding disposed on the rib waveguide. The rib waveguide includes a first doped region having a first electric conductivity exhibiting a P-type electric conductivity across the rib and the slab and a second doped region being contiguous to the first doped region and having a second electric conductivity exhibiting an N-type electric conductivity across the rib and the slab.

Abstract: An optical waveguide element includes a core and a cladding that is made of SiO2. When ng_i_TE is a group refractive index of a TE0 polarized wave in the i-th waveguide counted from a light incidence plane of the core and ng_i_TM is a group refractive index of a TM0 polarized wave in the i-th waveguide, the length L—i[m] of the i-th waveguide satisfies a predetermined relation.

Abstract: An optical waveguide device includes: a mode splitter including a main waveguide in which lights can be propagated in at least two propagation modes with different propagation orders and a subsidiary waveguide which includes a coupling section disposed in parallel with the main waveguide at a certain distance away from the main waveguide so as to constitute a directional coupler and is capable of splitting at least one propagation mode out of the two or more propagation modes from the main waveguide. Also, ncore/ncladding which is a refractive index ratio between a core and a cladding which constitute the main waveguide and the subsidiary waveguide is in a range of 101% to 250%.

Abstract: An optical modulation device configured of a planar optical waveguide, includes: a light incidence unit which allows light to be incident on the planar optical waveguide; a Mach-Zehnder interferometer which includes a first optical splitter section branching the light incident on the light incidence unit, two arm portions guiding the light branched by the first optical splitter section, a phase modulation unit linearly disposed on each of the two arm portions, and a first optical coupler section combining the light guided from the two arm portions; a light launching unit which launches the light combined by the first optical coupler section from the planar optical waveguide; and a traveling-wave electrode which includes an input unit and an output unit, and applies a voltage to the phase modulation unit.

Abstract: An optical integrated circuit includes: a mode conversion and branching section that launches light from a first optical waveguide to a second optical waveguide, converts light from the first optical waveguide into converted light, and launches the converted light to a third optical waveguide; an optical multiplexing and branching section that multiplexes lights from the second and third optical waveguides into one multiplexed light component, and branches the multiplexed light component into a light component to be input to a fourth optical waveguide and a light component to be input to a fifth optical waveguide; a phase modulation section that is provided in at least one of the fourth and fifth optical waveguides and modulates a phase of guided light; and an optical multiplexing section that multiplexes light components from the fourth and fifth optical waveguides into one light component.

Abstract: An optical waveguide element includes a core and a cladding that is made of SiO2. When ng_i_TE is a group refractive index of a TE0 polarized wave in the i-th waveguide counted from a light incidence plane of the core and ng_i_TM is a group refractive index of a TM0 polarized wave in the i-th waveguide, the length L_i[m] of the i-th waveguide satisfies a predetermined relation.

Abstract: To reduce the optical loss, lower the driving voltage, produce a smaller product, and simplify the production process, an embodiment of the present invention includes a rib waveguide core (101) having a rib region (101r) and two slab regions (101s), where a depletion layer (113) is so formed as to extend from the rib region (101r) to the two slab regions (101s).

Abstract: An optical receiver circuit includes: a substrate; and an optical waveguide device that is formed on the substrate. The optical waveguide device includes: a first optical splitter section branching the signal light into a first signal light propagation waveguide and a second signal light propagation waveguide and; a second optical splitter section branching the local-oscillator light into a first local-oscillator light propagation waveguide and a second local-oscillator light propagation waveguide; a first optical coupler section that combines the signal light propagating through the first signal light propagation waveguide and the local-oscillator light propagating through the first local-oscillator light propagation waveguide with each other; a second optical coupler section that combines the signal light propagating through the second signal light propagation waveguide and the local-oscillator light propagating through the second local-oscillator light propagation waveguide with each other.

Abstract: A high-order polarization conversion device configured of a planar optical waveguide, includes: a substrate; a lower clad disposed on the substrate; a core including a lower core and an upper core, the lower core being disposed on the lower clad and having a fixed height in a rectangular sectional shape, the upper core being formed of the same material as the lower core and having a fixed height in a rectangular sectional shape that is disposed continuously on the lower core; and an upper clad that is disposed on the core and the lower clad and is formed of the same material as the lower clad. The high-order polarization conversion device performs high-order polarization conversion between TE1 of the start portion and TM0 of the end portion.

Abstract: An optical waveguide device includes a substrate; a lower cladding disposed on the substrate; a rib waveguide including a slab disposed on the lower cladding and a single rib disposed on the slab contiguous to the slab; and an upper cladding disposed on the rib waveguide. The rib waveguide includes a first doped region having a first electric conductivity exhibiting a P-type electric conductivity across the rib and the slab and a second doped region being contiguous to the first doped region and having a second electric conductivity exhibiting an N-type electric conductivity across the rib and the slab.

Abstract: A polarization conversion element is disclosed in which an optical waveguide formed on a substrate sequentially includes a first waveguide portion, a polarization rotation portion, and a second waveguide portion, an effective refractive index of a TE mode having the highest effective refractive index in an eigen mode of waveguide light on a sectional surface of the first waveguide portion is higher than an effective refractive index of a TM mode having the highest effective refractive index, an effective refractive index of the TM mode having the highest effective refractive index on a sectional surface of the second waveguide portion is higher than an effective refractive index of the TE mode having the highest effective refractive index, and heights of waveguide structures (for example, cores) of the first waveguide portion and the second waveguide portion are equal to each other.

Abstract: An optical waveguide element includes: a rib waveguide and a pair of slab portions including a first slab portion and a second slab portion connected to both sides of the rib portion so as to sandwich the rib portion. The rib portion has a cross-sectional dimension which allows the propagation of a fundamental mode and a higher order mode in a predetermined single polarization state, and has a first P-type semiconductor and a first N-type semiconductor forming a PN junction, the first slab portion has a second P-type semiconductor and a P-type conductor connected to each other, the second P-type semiconductor is connected to the first P-type semiconductor of the rib portion, the second slab portion has a second N-type semiconductor and an N-type conductor connected to each other, and the second N-type semiconductor is connected to the first N-type semiconductor of the rib portion.

Abstract: A polarization conversion element is disclosed in which an optical waveguide formed on a substrate sequentially includes a first waveguide portion, a polarization rotation portion, and a second waveguide portion, an effective refractive index of a TE mode having the highest effective refractive index in an eigen mode of waveguide light on a sectional surface of the first waveguide portion is higher than an effective refractive index of a TM mode having the highest effective refractive index, an effective refractive index of the TM mode having the highest effective refractive index on a sectional surface of the second waveguide portion is higher than an effective refractive index of the TE mode having the highest effective refractive index, and heights of waveguide structures (for example, cores) of the first waveguide portion and the second waveguide portion are equal to each other.