Abstract: An electro-optic waveguide polarization modulator includes cladding layers, and a waveguide core sandwiched between the cladding layers, wherein the waveguide core has a higher refractive index than the cladding layers. The modulator further includes primary electrodes arranged on the opposite side of one cladding layer to the core and a secondary electrode arranged on the opposite side of another cladding layer to the core. The electrodes are arranged to provide an electric field having field components in perpendicular directions within the waveguide core so as to modulate the refractive index such that electromagnetic radiation propagating through the core is converted from a first polarization state to a second polarization state. The modulator further includes a grading layer sandwiched between the cladding layers and the core, the grading layer having an effective refractive index intermediate between that of the waveguide core and the cladding layer.

Abstract: An athermal ring optical modulator includes a first clad layer, a ring optical resonator, a second clad layer, an input-output optical waveguide, a first conduction type region, and a second conduction type region. The ring optical resonator has a rib optical waveguide with a convex portion formed on a semiconductor slab layer. The semiconductor slab layer is formed on the first clad layer. The second clad layer covers an upper side of the rib optical waveguide. The input-output optical waveguide couples optically with the ring optical resonator. The first and second conduction type regions are formed in the semiconductor slab layer inside and outside the ring optical resonator, respectively. In addition, the second clad layer includes a material having a negative thermo-optical coefficient. The semiconductor slab layer outside the convex portion is thinner than the semiconductor slab layer inside the convex portion.

Abstract: A multibeam deflector includes a plurality of optical deflection devices formed on a single substrate and an output optical system. Each of the optical deflection devices includes a slab optical waveguide formed by a material having an electro-optic effect. The output optical system is configured to separate beams output from the optical deflection devices from each other.

Abstract: Electro-optic (EO) modulator and related device structures which can be used in conjunction with high EO materials to lower switching voltage and improve related performance parameters.

Abstract: Consistent with the present disclosure, MZ drive signal electrodes may be provided relatively close to and parallel to one another, such that the underlying waveguide arms may also be provided close to and parallel to one another. As a result, common mode performance of an MZ modulator may be obtained. In one example, an electrode wiring configuration consistent with the present disclosure may permit a waveguide arm separation of 40 microns or less.

Abstract: A silicon optical waveguide for transmitting an optical signal input to the optical waveguide with a first frequency. The optical waveguide includes a plurality of modulator circuits configured along a silicon optical transmission channel. Each modulator circuit includes at least one resonant structure that resonates at the first frequency when the modulator circuit that includes the at least one resonant structure is at a resonant temperature. Each modulator circuit has a different resonant temperature.

Abstract: The wavelength control device comprises a first Mach-Zehnder filter which receives a first optical signal and outputs an optical signal having a predetermined wavelength, a second Mach-Zehnder filter which receives a second optical signal and outputs an optical signal having a predetermined wavelength, a heating unit heating respective parts of either one of the waveguides of the first and second Mach-Zehnder filters, a first wavelength detecting unit which receives an optical signal from the first Mach-Zehnder filter and detects a wavelength thereof, a second wavelength detecting unit which receives an optical signal from the second Mach-Zehnder filter and detects a wavelength thereof, a power control unit which controls power supplied to the heating unit based on the wavelength received from the first wavelength detecting unit, and an output unit which outputs a wavelength value based on the wavelength received from the second wavelength detecting unit.

Abstract: A two-dimensional array of linear wave guides includes a plurality of 2D planar wave guide assemblies, columns, sets or layers which each produce a respective depth plane to for a simulated 4D light field. Linear wave guides may have a rectangular cylindrical shape, and may stacked in rows and columns. Each linear wave guide is at least partially internally reflective, for example via at least one opposed pair of at least partially reflective planar side walls, to propagate light along a length of the wave guide. Curved micro-reflectors may reflect some modes of light while passing others. The side walls or a face may reflect some modes of light while passing others. The curved micro-reflectors of any given wave guide each contribute to spherical wave front at a defined radial distance, the various layers producing image planes at respective radial distances.

Abstract: An optical device includes a phase modulation element having an optical waveguide part and electrodes, the optical waveguide part being configured such that a laser light beam emitted by a laser light source is inputted to the optical waveguide part and having an optical waveguide layer formed of an electro-optic material, the electrodes being provided on respective sides of the optical waveguide part to apply a voltage to the optical waveguide layer, the phase modulation element being configured to modulate a phase of the laser light beam by using a refraction index modulation region formed in the optical waveguide layer when a voltage is applied to the optical waveguide layer through the electrodes, and a pump light source configured to irradiate at least the refraction index modulation region of the optical waveguide layer with a pump light beam.

Abstract: The present invention is a method and an apparatus for dynamic manipulation and dispersion in photonic crystal devices. In one embodiment, a photonic crystal structure comprises a substrate having a plurality of apertures formed therethrough, a waveguide formed by “removing” a row of apertures, and a plurality of pairs of lateral electrical contacts, the lateral electrical contact pairs extending along the length of the waveguide in a spaced-apart manner. The lateral electrical contact pairs facilitate local manipulation of the photonic crystal structure's refractive index. Thus, optical signals of different wavelengths that propagate through the photonic crystal structure can be dynamically manipulated.

Abstract: In a light control element comprising a thin plate having a thickness of 10 [mu]m or less and exhibiting electro optic effect, an optical waveguide formed on the thin plate, and a control electrode for controlling light passing through the optical waveguide, the control electrode includes a first electrode and a second electrode so arranged as to sandwich the thin plate, and the first electrode has a coplanar electrode consisting of a first signal electrode and a ground electrode, while the second electrode has a second signal electrode. Modulation signals having mutually inverted amplitudes are inputted to the first signal electrode of the first electrode and the second signal electrode of the second electrode such that the modulation signals cooperate to apply an electric field to the optical waveguide.

Abstract: A transmission line and method for implementing includes a plurality of segments forming an electrical path and a continuous optical path passing through the segments. Discrete inductors are formed between and connect adjacent segments. The inductors are formed in a plurality of metal layers of an integrated circuit to balance capacitance of an optical modulator which includes the transmission line to achieve a characteristic impedance for the transmission line.

Abstract: An electric field detection device. In one embodiment, the electric field detection device includes an interferometer having a reference arm and an active arm. The reference arm comprises a first electro-optic waveguide. The active arm comprises a first electrically conductive plate, a second electrically conductive plate spaced apart from the first electrically conductive plate defining a first gap therebetween, a third electrically conductive plate disposed in the first gap and vertically extending from the first electrically conductive plate to define a T-shape structure and a second gap between the third electrically conductive plate and the second electrically conductive plate, where the second gap is substantially smaller than the first gap; and a second electro-optic waveguide disposed in the second gap and being in electrical communication with the second and third electrically conductive plates.

Abstract: According to an embodiment, a light deflecting element includes a dielectric body, a first electrode, and a second electrode. The second electrode is configured to sandwich the dielectric body with the first electrode so as to apply a voltage to the dielectric body. The second electrode includes orthogonal portions that are substantially orthogonal to an incident direction of a light beam passing through the dielectric body, parallel portions that are substantially parallel to the incident direction of the light beam. The orthogonal portions and the parallel portions are formed in an alternate manner on the light beam incident side of the dielectric body. The second electrode includes a linear sloping portion that slopes in a direction toward intersection with the incident direction of the light beam. The orthogonal portions, the parallel portions, and the linear sloping portion are formed integrally.

Abstract: A transmission line and method for implementing includes a plurality of segments forming an electrical path and a continuous optical path passing through the segments. Discrete inductors are formed between and connect adjacent segments. The inductors are formed in a plurality of metal layers of an integrated circuit to balance capacitance of an optical modulator which includes the transmission line to achieve a characteristic impedance for the transmission line.

Abstract: In an electro-optic device, a stack structure including a first silicon layer of a first conductivity type and a second silicon layer of a second conductivity type has a rib waveguide shape so as to form an optical confinement area, and a slab portion of a rib waveguide includes an area to which a metal electrode is connected. The slab portion in the area to which the metal electrode is connected is thicker than a surrounding slab portion. The area to which the metal electrode is connected is set so that a range of a distance from the rib waveguide to the area to which the metal electrode is connected is such that when the distance is changed, an effective refractive index of the rib waveguide in a zeroth-order mode does not change.

Abstract: An optical switch includes electro-optic crystal, and electrode unit including a plurality of electrodes arranged on the same plane in electro-optic crystal to extend in parallel to one another. A refractive index of a part of electro-optic crystal is changed by an electric field generated at electrode unit, thereby switching transmission and reflection of light incident on electro-optic crystal. Electro-optic crystal has an entrance surface through which light enters and an exit surface from which light exits. Electrode unit is located between the entrance surface and the exit surface. An angle ?x formed between a longitudinal direction of electrodes and at least one surface from among the entrance surface and the exit surface is set near an angle that satisfies the expression ?x=90°?Sin?1[ cos(Tan?1(n))] in a wavelength of light to be modulated.

Abstract: An optical waveguide electro-optic device including: a support substrate; an optical waveguide which has a core layer formed of a ferroelectric material, and is formed on an upper side of the support substrate; a lower electrode layer formed on a lower side of the core layer and which is adhered to the support substrate through an adhesion layer; an upper electrode layer formed on an upper side of the core layer; and an external electrode part, wherein the optical waveguide has an incidence plane from where light enters and an outgoing plane from where the light exits, the core layer has a polarization inversion region and a polarization non-inversion region, the upper electrode layer has a plane in such a shape that a width of the plane expands from a side of the incidence plane toward a side of the outgoing plane, to cover the polarization inversion region of the core layer, and the lower electrode layer is connected electrically to the external electrode part on the side of the incidence plane.

Abstract: The invention relates to an optical modulator, comprising a first waveguide for a signal to be modulated, a second waveguide for a control signal, and an auxiliary waveguide, wherein the auxiliary waveguide is supported by a carrier which can be deflected to change a distance between the first waveguide and the auxiliary waveguide, wherein the carrier also comprises two layers with different coefficients of thermal expansion and the second waveguide is guided in such a way that a temperature of the carrier at least in a section can be manipulated by light transported by the second waveguide. The invention further relates to an integrated optical circuit comprising such an optical modulator, and to a modulation method which can be performed with such a modulator.

Abstract: A multifunctional integrated optical device includes an input collimator (101) with a pigtail, an input birefringent crystal wedge (110), a Faraday rotator (120), a Pockels cell (130), an output birefringent crystal wedge (140) and an output collimator (102) with a pigtail, arranged along an optical path in turn. The optical device also includes an electric driver (150) for a variable attenuator and an optical switch, and another electric driver (160) for a modulator. The device employs the Pockels cell for dynamically rotating the polarization state of incident light at nanosecond speed for attenuation and modulation. The device can be used as a polarization independent optical isolator, an optical switch, a variable attenuator and a modulator, without mechanical moving parts, for use in various laser systems and particularly in a fiber optic telecommunication system.

Abstract: Disclosed are a PLC-type delay demodulation circuit and a PLC-type optical interferometer capable of reducing the size of a PLC chip with respect to the arrangement of various kinds of light output waveguides. In a PLC-type delay demodulation circuit, arm waveguides of a first MZI and arm waveguides of a second MZI are formed so as to overlap each other in the same region of a planar lightwave circuit. The optical paths of the MZIs are arranged such that the propagation directions of two DQPSK signals branched by a Y-branch waveguide are opposite to each other.

Abstract: An optical device includes a light-transmitting medium positioned on a base. The light-transmitting medium defines a waveguide. The optical device also includes a light sensor. The light sensor includes a light-absorbing medium positioned on the base. A portion of the waveguide ends at a facet such that a first portion of a light signal being guided by the wavegide passes through the facet and a second portion of the light signal bypasses the facet and remains in the light-transmitting medium. The light-absorbing medium is positioned on the light-transmitting medium such that the light-transmitting medium is between the light-absorbing medium and the base. Additionally, the light-absorbing medium is positioned on the light-transmitting medium such that the light-absorbing medium receives the first portion of the light signal that passes through the facet.

Abstract: It is an object of the present invention to provide an apparatus that can obtain a multiplied harmonic signal fast and with ease, and the method using the apparatus. The object is attained by the method for obtaining a multiple harmonic signal comprises, suppressing a different parity optical signal having parity different from fundamental optical signals; suppressing residual optical signals using an optical filter after suppressing the different parity optical signal; and obtaining the frequency difference component using the fundamental optical signals, and the device realizing the method.

Abstract: An optical phase modulator having a reduced time drift of an electro-optical response is disclosed. An optical waveguide exhibiting the electro-optic effect includes two serially coupled portions having opposite time drifts of magnitudes of their respective electro-optical responses. As a result, a time drift of an overall electro-optical response of the optical phase modulator is lessened.

Abstract: An electrooptic element includes an optical waveguide layer made from a ferroelectric material and having a polarization inverted region of a predetermined shape having an optical incidence face and an optical exit face, and an upper electrode layer and a lower electrode layer formed on a top face and a bottom face of the optical waveguide layer, respectively, in which the ferroelectric material is magnesium-oxide-doped lithium niobate, and at least one of the optical incidence face and the optical exit face of the optical waveguide layer is formed in parallel with a crystal face of the ferroelectric material.

Abstract: Embodiments relate to a method and apparatus for producing polarized light, having a modulator crystal, where the modulator crystal incorporates a birefringent electro-optic material. The modulator crystal has an optic axis, a first polarization axis, and a second polarization axis, where the first polarization axis and second polarization axis are each perpendicular to the optic axis and perpendicular to each other. The apparatus can also include an electrode pair, where application of an electric field modulates light passing through the modulator crystal that is polarized along the first polarization axis. Embodiments pertain to a method and apparatus for modulating light. The apparatus incorporates a modulator crystal having an electro-optic material. The device also has at least two electrode pairs, where each electrode pair modulates light passing through the modulator crystal that has a direction of travel that has a component parallel to the optic axis.

Abstract: The PLC-type delay demodulation circuit includes a planar lightwave circuit that is provided on one PLC chip and demodulates a DQPSK signal. The planar lightwave circuit includes a Y-branch waveguide that branches a DQPSK-modulated optical signal into two optical signals and first and second MZIs that delay the branched optical signals by one bit. A wave plate is provided in central portions of first and second arm waveguides of the first MZI and first and second arm waveguides of the second MZI in such a manner that the wave plate intersects all of the four arm waveguides, the four arm waveguides being close to one another in a portion where the wave plate is provided.

Abstract: An optical modulator apparatus and linearization method are disclosed. The optical modulator may include a buffer layer disposed proximate the electro-optical material substrate. The optical modulator may also include physically asymmetric waveguide elements, which may have physically asymmetric waveguide arms or physically asymmetric hot electrodes. The waveguide arms may include first and second waveguide arms having different dimensions, and the hot electrodes may include first and second hot electrodes having different dimensions. Modulator linearization may be achieved by the above-described modulator structure. Modulator linearization may also be achieved by asymmetric external driving of electric fields applied to the waveguide elements, where the waveguide or electrode dimensions may or may not be symmetric.

Abstract: An optical switch includes: an input-output port with three or more ports arranged along a direction; a modulator that includes an incident layer, a reflective layer, and a modulation layer disposed between these layers, spatially modulates light entering the incident layer from any port of the input-output port, and outputs the light spatially-modulated toward any of other ports of the input-output port; and a condensing lens that optically couples the input-output port and the modulator, wherein x2?2x1+x0 holds where: a coordinate axis is along the direction of the input-output port and an optical axis of the lens is set as an origin of the coordinate axis; x0, x1, and x2 respectively are coordinates of a first port to/from which light is input/output, and a second port and a third port from/to which light input to or output from the first port is output/input; and x1,x2>0.

Abstract: Provided is a semiconductor integrated circuit. The semiconductor integrated circuit includes a semiconductor pattern disposed on a substrate and including an optical waveguide part and a pair of recessed portions. The optical waveguide part has a thickness ranging from about 0.05 ?m to about 0.5 ?m. The recessed portions are disposed on both sides of the optical waveguide part and have a thinner thickness than the optical waveguide part. A first doped region and a second doped region are disposed in the recessed portions, respectively. The first and second doped regions are doped with a first conductive type dopant and a second conductive type dopant, respectively. An intrinsic region is formed in at least the optical waveguide part to contact the first and second doped regions.

Abstract: A PLC-type delay demodulation circuit includes a planar lightwave circuit that is provided on one PLC chip and demodulates a DQPSK signal. The planar lightwave circuit includes a Y-branch waveguide that branches a DQPSK-modulated optical signal into two optical signals and first and second MZIs that delay the branched optical signals by one bit. The length of a short arm waveguide of the first MZI is different from the length of a short arm waveguide of the second MZI, and the length of an optical path from the Y-branch waveguide to output ports of the first MZI through the short arm waveguide of the first MZI is equal to that of an optical path from the Y-branch waveguide to output ports of the second MZI through the short arm waveguide of the second MZI.

Abstract: An optical modulator including: a substrate which has electro-optic effect; a Mach-Zehnder optical interferometer which is formed in the substrate and which includes a first waveguide and a second waveguide; a signal electrode which applies an electrical field to the Mach-Zehnder optical interferometer through being supplied with an electric signal corresponding to a signal for optical modulation; a ground electrode formed apart from the signal electrode; and a conductor section which is narrow in a middle thereof along the light propagating direction and which gradually becomes wider towards the starting end and the terminating ends thereof along the light propagating direction in an interacting portion at which the electric field applied by the signal electrode interacts with light propagating through the first waveguide and the second waveguide.

Abstract: A semiconductor optical modulator that includes a first semiconductor optical waveguide having a laminated structure including a core layer, a first clad layer, a second clad layer, and a barrier layer, the first clad layer and the second clad layer being disposed below and above the core layer, the barrier layer being inserted between the second clad layer and the core layer; a second semiconductor optical waveguide having a laminated structure in which the second clad layer has a p-type semiconductor penetrating locally through a n-type semiconductor in a laminated direction in the laminated structure of the first semiconductor optical waveguide; a first electrode connected to the first clad layer of the first semiconductor optical waveguide; and a second electrode electrically connecting the second clad layer of the first semiconductor optical waveguide and the p-type semiconductor of the second clad layer of the second semiconductor optical waveguide.

Abstract: A method is provided for visual inspection of an array of interferometric modulators in various driven states. This method may include driving multiple columns or rows of interferometric modulators via a single test pad or test lead, such as test pad, and then observing the array for discrepancies between the expected optical output and the actual optical output of the array. This method may particularly include, for example, driving a set of non-adjacent rows or columns to a state different from the intervening rows or columns and then observing the optical output of the array.

Abstract: The present invention relates to an optical control device capable of achieving an accurate match of modulation timing and modulation intensity between optical waves propagating through optical waveguides disposed between a plurality of signal electrodes in an optical control device using an anisotropic dielectric substrate.

Abstract: A method of processing data is provided that includes receiving a plurality of binary electronic signals and generating an optical signal by a number of lasers that is equal to or greater than the number of binary electronic signals. The optical signal is generated at one of a plurality of intensity levels, and each intensity level represents a particular combination of bit values for the plurality of binary electronic signals. The optical signal is converted into an electronic signal having the plurality of intensity levels. An apparatus for processing data is provided that includes a plurality of lasers configured to emit light at a plurality of frequencies, and a plurality of modulators configured to receive a plurality of binary electronic signals and to modulate the light emitted by the lasers. An apparatus for transmitting data is provided that includes a photo receiver and an electronic signal generator.

Abstract: Liquid crystal waveguides for dynamically controlling the refraction of light. Generally, liquid crystal materials may be disposed within a waveguide in a cladding proximate or adjacent to a core layer of the waveguide. In one example, portions of the liquid crystal material can be induced to form refractive or lens shapes in the cladding that interact with a portion (e.g. evanescent) of light in the waveguide so as to permit electronic control of the refraction/bending, focusing, or defocusing of light as it travels through the waveguide. In one example, a waveguide may be formed using one or more patterned or shaped electrodes that induce formation of such refractive or lens shapes of liquid crystal material, or alternatively, an alignment layer may have one or more regions that define such refractive or lens shapes to induce formation of refractive or lens shapes of the liquid crystal material.

Abstract: A waveguide-type optical circuit comprises an optical coupler being an optical branch coupler constructed from waveguide cores which are closely arranged to each other, and dummy patterns that lay along sides of the waveguide cores in the optical coupler for preventing optical major axes of the waveguide cores from inclining.

Abstract: A conductive polymer and a semiconducting carbon nanotube material are combined to form a highly conductive composite. The composite can be used for EMI shielding, optical sensing, optical switching, and other uses.

Abstract: Provided is a concept for variably guiding optical waves by using a layer-stack having an electro-optic core layer of electro-optic material for guiding light and an electrode arrangement with at least a first electrode layer in proximity to the electro-optic core layer, wherein the electrode arrangement is configured to activate an electro-optic effect in a region of the electro-optic core layer by an electric field generated by means of the electrode arrangement, such that a propagation of the light is manipulated in the region of the activated electro-optic effect.

Abstract: An electromagnetically responsive element includes sets of arrangements of self-resonant bodies, such as atoms or quantum dots that form an effective dielectric constant, typically at or near a resonance.

Abstract: An electromagnetically responsive element includes sets of arrangements of self-resonant bodies, such as atoms or quantum dots that form an effective dielectric constant, typically at or near a resonance.

Abstract: The optical device includes a waveguide on a base. The device also includes a modulator on the base. The modulator includes an electro-absorption medium configured to receive a light signal from the waveguide. The modulator also includes field sources for generating an electrical field in the electro-absorption medium. The electro-absorption medium is a medium in which the Franz-Keldysh effect occurs in response to the formation of the electrical field in the electro-absorption medium. The field sources are configured so the electrical field is substantially parallel to the base.

Abstract: Provided is an electro-optic device. The electro-optic device includes an input Y-branch comprising a first input branch and a second input branch, an output Y-branch comprising a first output branch and a second output branch, a first optical modulator and a second optical modulator connected in series between the first input branch and the first output branch, and a third optical modulator connecting the second input branch to the second output branch. The first optical modulator comprises a PIN diode, and each of the second optical modulator and the third optical modulator comprises a PN diode.

Abstract: There is provided an optical module including photonic devices set in array, prepared by integrating a plurality of photonic devices with each other in such a state as arranged in such a array as to enable light beams to output in the common direction. The plural photonic devices each include a first electrode, and a second electrode, arranged in the same direction as the plural photonic devices are arranged, and the first and second electrodes of the photonic devices adjacent to each other are disposed such that respective electrode layouts are a mirror image of each other.

Abstract: A photonic crystal type light modulator is provided. The photonic crystal type light modulator includes: a substrate; a first electrode disposed on the substrate; an active layer disposed on the first electrode, where an optical characteristic of the active layer changes according to application of an electric field; a second electrode disposed on the active layer; and a photonic crystal layer disposed on the second electrode and comprising a 2D grating.

Abstract: An electro-optic device is provided. The electro-optic device includes a junction layer disposed between a first conductivity type semiconductor layer and a second conductivity type semiconductor layer to which a reverse vias voltage is applied. The first conductivity type semiconductor layer and the second conductivity type semiconductor layer have an about 2 to 4-time doping concentration difference therebetween, thus making it possible to provide the electro-optic device optimized for high speed, low power consumption and high integration.

Abstract: Disclosed is an optical element which includes a support substrate and a thin plate of single crystal stacked on the support substrate through a thermoplastic adhesive, having the advantages of easily regulating the phase of light waves and restoring the regulated state to the original state. The optical element includes a support substrate 4 and a thin plate 1 of single crystal stacked on the support substrate 4 through a thermoplastic adhesive 3. The optical characteristics of the optical element are regulated by applying stress within an elastic limit to at least a part of the thin plate in a state where the thermoplastic adhesive is softened by heating the optical element, forming a concavo-convex part 10 in the thin plate, and then cooling the optical element to fix the concavo-convex part.

Abstract: Liquid crystal waveguides for dynamically controlling the refraction of light. Generally, liquid crystal materials may be disposed within a waveguide in a cladding proximate or adjacent to a core layer of the waveguide. In one example, portions of the liquid crystal material can be induced to form refractive or lens shapes in the cladding that interact with a portion (e.g. evanescent) of light in the waveguide so as to permit electronic control of the refraction/bending, focusing, or defocusing of light as it travels through the waveguide. In one example, a waveguide may be formed using one or more patterned or shaped electrodes that induce formation of such refractive or lens shapes of liquid crystal material, or alternatively, an alignment layer may have one or more regions that define such refractive or lens shapes to induce formation of refractive or lens shapes of the liquid crystal material.

Abstract: A first exemplary aspect of the present invention is a wavelength-tunable optical transmitter including: a semiconductor substrate (101); a wavelength-tunable light source that is formed on the semiconductor substrate (101) and includes at least a first reflector (102) of a wavelength-tunable type and a gain region (104); a semiconductor optical modulator formed on the semiconductor substrate (101); a first semiconductor optical waveguide (105c) that is formed on the semiconductor substrate (101) and smoothly connected to the wavelength-tunable light source; a second semiconductor optical waveguide (105d) that is formed on the semiconductor substrate and smoothly connected to the semiconductor optical modulator; a waveguide coupling region (108) in which the first and second semiconductor optical waveguides are collinearly coupled with a length LC that is not equal to m/2 (m: integer) times a complete coupling length LC0; and a second reflector (113) formed at an end of the waveguide coupling region (108).