Abstract: An optical element has a quarter-wave plate formed on the X-Y plane and laminated in the Z-axis direction in three-dimensional space X, Y, Z. The groove in the wave plate is curved, and the angle relative to the Y-axis varies continuously in the range of 0° to 180°. The optical element separates and converts incoming circularly polarized light into light passing therethrough and circularly polarized light reversely rotating a given angle toward the X axis from the Z axis, and outputs the light.

Abstract: To provide a volume-type optical element in which a self-cloning photonic crystal is used. An optical element is provided with half-wave plates of photonic crystals formed on the xy plane and laminated in the z-axis direction in a three-dimensional space x, y, z. The groove direction of the photonic crystals is a curved line, and the angle in relation to the y-axis direction changes continuously in the range of 0°-180°. Light entering the optical element in the axial direction is emitted from the optical element upon being divided and converted into clockwise circularly polarized light in the direction facing the x-axis by a given angle from the z-axis and anticlockwise circularly polarized light in the direction facing the ?x-axis by a given angle from the z-axis. Laminating or placing a quarter-wave plate comprising a photonic crystal on one or both surfaces makes it possible to divide light entering from the z-axis direction of the optical element into two orthogonal linearly polarized lights.

Abstract: To provide an optical element and an optical circuit enabling easy integration. An optical element has a quarter-wave plate formed on the X-Y plane and laminated in the Z-axis direction in three-dimensional space X, Y, Z. The groove in the wave plate is curved, and the angle relative to the Y-axis varies continuously in the range of 0° to 180°. The optical element separates and converts incoming circularly polarized light into light passing therethrough and circularly polarized light reversely rotating a given angle toward the X axis from the Z axis, and outputs the light.

Abstract: To provide a volume-type optical element in which a self-cloning photonic crystal is used. An optical element is provided with half-wave plates of photonic crystals formed on the xy plane and laminated in the z-axis direction in a three-dimensional space x, y, z. The groove direction of the photonic crystals is a curved line, and the angle in relation to the y-axis direction changes continuously in the range of 0°-180°. Light entering the optical element in the axial direction is emitted from the optical element upon being divided and converted into clockwise circularly polarized light in the direction facing the x-axis by a given angle from the z-axis and anticlockwise circularly polarized light in the direction facing the ?x-axis by a given angle from the z-axis. Laminating or placing a quarter-wave plate comprising a photonic crystal on one or both surfaces makes it possible to divide light entering from the z-axis direction of the optical element into two orthogonal linearly polarized lights.

Abstract: A waveguide type variable optical attenuator has: a substrate; two optical circuits that are in parallel formed on the substrate, each of the optical circuits including two couplers that conduct the branching and coupling of light and are connected to the input port and output port of light and two waveguides through which the two couplers are connected; a polarization maintaining fiber one end of which is connected to the output port of one of the two optical circuits and the other end of which is connected to the input port of the other of the two optical circuits while being twisted 90°; and a heater that is provided around neighboring waveguides of the two optical circuits such that the neighboring waveguides share heat to be generated by the heater.

Abstract: A waveguide-type optical multiplexer/demultiplexer with low crosstalk characteristics and reduced wavelength dispersion is provided. A waveguide-type optical multiplexer/demultiplexer comprising, first, second and third optical multiplexer/demultiplexer circuits connected in multistage, each multiplexer/demultiplexer circuit has four input-output ports, third input-output port of first optical multiplexer/demultiplexer circuit is connected to third input-output port of second optical multiplexer/demultiplexer circuit, and fourth input-output port of first optical multiplexer/demultiplexer circuit is connected to fourth input-output port of third optical multiplexer/demultiplexer circuit, when wavelength division multiplex signals having wavelength ?1, ?2, ?3, ?4, ?5, ?6 . . . are input through first input-output port of first optical multiplexer/demultiplexer circuit, multiplex signals of odd wavelength ?1, ?3, ?5 . . .

Abstract: In an optical multiplexer/demultiplexer comprising optical multiplexer/demultiplexer circuits connected in multistage, the optical multiplexer/demultiplexer circuits each have two input ports and two output ports, an optical path, through which input optical signals with predetermined wavelengths are output after multiplexing and demultiplexing, varies depending upon the input port; the optical paths in each of the optical multiplexer/demultiplexer circuits have mutually opposite wavelength dispersion characteristics, and one of the optical paths in a first optical multiplexer/demultiplexer circuit is connected to one of the optical paths, in a second optical multiplexer/demultiplexer circuit, having wavelength dispersion characteristics opposite to the optical path in the first optical multiplexer/demultiplexer circuit.

Abstract: A waveguide type variable optical attenuator has: a substrate; two optical circuits that are in parallel formed on the substrate, each of the optical circuits including two couplers that conduct the branching and coupling of light and are connected to the input port and output port of light and two waveguides through which the two couplers are connected; a polarization maintaining fiber one end of which is connected to the output port of one of the two optical circuits and the other end of which is connected to the input port of the other of the two optical circuits while being twisted 90°; and a heater that is provided around neighboring waveguides of the two optical circuits such that the neighboring waveguides share heat to be generated by the heater.

Abstract: To provide a waveguide-arrayed optical wavelength multiplexer/demultiplexer in which a mode configuration of a waveguide slab output part is matched to a mode configuration of waveguide array input parts, to achieve a reduced loss irrespective of distances between arrayed waveguides, and a manufacturing method of the same, a wavelength multiplexer/demultiplexer (10) is formed on a substrate (11) with a plurality of input waveguides (12) for inputting wavelength division multiplexed optical signals, an output waveguide (13) for combining the wavelength division multiplexed optical signals to be output, a waveguide array (15) as a set of arrayed waveguides (15b) having predetermined waveguide length differences (&Dgr;L), an input waveguide slab (14) for interconnecting the plurality of input waveguides (12) and the waveguide array (15), and an output waveguide slab (17) for interconnecting the waveguide array (15) and the output waveguide (13), and the input waveguide slab (14) and the output waveguide slab (17

Abstract: In the optical multiplexer/demultiplexer according to the invention, an MMI (multi mode interference) coupler having a percentage coupling of about 50% is used as first and second optical couplers, and a directional coupler having a percentage coupling of less than 10% is used as third and fourth optical couplers. By virtue of this constitution, the optical multiplexer/demultiplexer according to the invention has a small dependency upon wavelength and can be used in a wide waveband, is less susceptible to a preparation error, and, at the same time, has good wavelength flatness in passband and a wide rejection band.

Abstract: A waveguide-type optical multiplexer/demultiplexer with low crosstalk characteristics and reduced wavelength dispersion is provided. A waveguide-type optical multiplexer/demultiplexer comprising, first, second and third optical multiplexer/demultiplexer circuits connected in multistage, each multiplexer/demultiplexer circuit has four input-outpu ports, third input-output port of first optical multiplexer/demultiplexer circuit is connected to third input-output port of second optical multiplexer/demultiplexer circuit, and fourth input-output port of first optical multiplexer/demultiplexer circuit is connected to fourth input-output port of third optical multiplexer/demultiplexer circuit, when wavelength division multiplex signals having wavelength &lgr;1, &lgr;2, &lgr;3, &lgr;4, &lgr;5, &lgr;6 . . . are input through first input-output port of first optical multiplexer/demultiplexer circuit, multiplex signals of odd wavelength &lgr;1, &lgr;3, &lgr;5 . . .

Abstract: The present invention relates to an array waveguide grating and a method of manufacture thereof, in which a substantially smooth wavelength-loss characteristics is obtained in a pass band, rather than increasing the loss. In an array waveguide grating (10), wavelength multiplex division signal light is demultiplexed by a channel waveguide array (15), reflected by a Fabry-Perot resonator array (16), and passed through the channel waveguide array (15) again, so that a substantially smooth wavelength-loss characteristic is obtained in the pass band, rather than increasing the loss.

Abstract: The present invention relates to an array waveguide grating and a method of manufacture thereof, in which a substantially smooth wavelength-loss characteristics is obtained in a pass band, rather than increasing the loss. In an array waveguide grating (10), wavelength multiplex division signal light is demultiplexed by a channel waveguide array (15), reflected by a Fabry-Perot resonator array (16), and passed through the channel waveguide array (15) again, so that a substantially smooth wavelength-loss characteristic is obtained in the pass band, rather than increasing the loss.

Abstract: To provide a waveguide-arrayed optical wavelength multiplexer/demultiplexer in which a mode configuration of a waveguide slab output part is matched to a mode configuration of waveguide array input parts, to achieve a reduced loss irrespective of distances between arrayed waveguides, and a manufacturing method of the same, a wavelength multiplexer/demultiplexer (10) is formed on a substrate (11) with a plurality of input waveguides (12) for inputting wavelength division multiplexed optical signals, an output waveguide (13) for combining the wagelength division multiplexed optical signals to be output, a waveguide array (15) as a set of arrayed waveguides (15b) having predetermined waveguide length differences (&Dgr;L), an input waveguide slab (14) for interconnecting the plurality of input waveguides (12) and the waveguide array (15), and an output waveguide slab (17) for interconnecting the waveguide array (15) and the output waveguide (13), and the input waveguide slab (14) and the output waveguide slab (17

Abstract: In the optical multiplexer/demultiplexer according to the invention, an MMI (multi mode interference) coupler having a percentage coupling of about 50% is used as first and second optical couplers, and a directional coupler having a percentage coupling of less than 10% is used as third and fourth optical couplers. By virtue of this constitution, the optical multiplexer/demultiplexer according to the invention has a small dependency upon wavelength and can be used in a wide waveband, is less susceptible to a preparation error, and, at the same time, has good wavelength flatness in passband and a wide rejection band.

Abstract: In an optical multiplexer/demultiplexer comprising optical multiplexer/demultiplexer circuits connected in multistage, the optical multiplexer/demultiplexer circuits each have two input ports and two output ports, an optical path, through which input optical signals with predetermined wavelengths are output after multiplexing and demultiplexing, varies depending upon the input port; the optical paths in each of the optical multiplexer/demultiplexer circuits have mutually opposite wavelength dispersion characteristics, and one of the optical paths in a first optical multiplexer/demultiplexer circuit is connected to one of the optical paths, in a second optical multiplexer/demultiplexer circuit, having wavelength dispersion characteristics opposite to the optical path in the first optical multiplexer/demultiplexer circuit.