Abstract: An object is to realize optical signal transmitter-receiver module with high transmitting power and high receiving sensitivity at a low cost. The optical signal transmitter-receiver module 60 includes a planar lightwave circuit (PLC) 61 and a transmitter-receiver circuit. The PLC 61 is made up with a Si substrate 62, a laser diode (LD) 6 generating the optical signal Pt, and a photodiode (PD)7 receiving the optical signal Pr. Both LD 6 and PD 7 are arranged on the Si substrate 62. The LD6 is arranged such that its front face is located in the vicinity of an optical fiber 64. The LD 6 has an optical waveguide layer that is composed of an active layer generating the optical signal Pt and a clad layer functioning as a transparent layer to the optical signal Pr. The PD 7 is arranged such that its front face is located in the vicinity of the backside face of the LD 6 and receives the optical signal Pr having passed through the optical waveguide layer of the LD 6.

Abstract: A method for fabricating a transformer of linearly polarized light to elliptically polarized light is presented. The method involves twisting a birefringent fiber through angles that depend on the polarization desired. This technique obviates the need to splice fibers, as in common approaches. In the final step of the method, the polarization can be fine tuned by heating the fiber to cause the core of the fiber to diffuse into the cladding. Using this transformer of polarized light, a current sensor is presented that exploits the Faraday Effect in a Sagnac interferometer.

Abstract: A Bragg grating device (10) is provided including a semiconductive optical waveguide (12) with a Bragg grating structure (14) formed along its length. A first plurality of electrodes (16) are disposed on a first surface (18) of the optical waveguide (12) and individually communicate with select members of the Bragg grating structure (14). A second plurality of electrodes (20) are disposed on a second surface (22) of the optical waveguide (12) and individually communicate with select members of the Bragg grating structure (14) such that individual electrodes of the second plurality of electrodes (20) are electrically coupled to individual electrodes of the first plurality of electrodes (16) via the Bragg grating structure (14). As such, a plurality of addressable portions (30) of the Bragg grating device (6) are defined.

Abstract: A Mach-Zehnder modulator intensity modulating signal light using a simple drive circuit for the modulating voltage. The modulator includes two waveguides with respective multiple quantum well (MQW) structures. Well layers of the MQW structures of the two optical waveguides have different thicknesses or are made from different materials so the phase of light propagating through one waveguide advances and through the other waveguide is delayed in response to the same applied voltage. The phase-changed light signals are combined as an output light signal that is intensity modulated.

Abstract: Broad wavelength tuning range are achieved in an effectively reset-free, optical, automatic polarization controller by providing a device and method for varying the polarization of an input beam of light. A block of electro-optic material has two pairs of electrodes for applying a voltage across the block. Light is launched into an input end of the block for receiving the input beam of light. A controller controls a quadrature voltage applied to the first and a second pair of electrodes; the quadrature voltage has the form of a magnitude and an angle. The quadrature voltage can be varied in such a manner as to orient a given electric field within the electro-optic material through a plurality of angles, for example between 0 and 2&pgr; radians; the magnitude of the quadrature voltage can be set to create an arbitrary retardance from 0 to 2&pgr;. Any output polarization state can be realized by appropriately varying the magnitude and angle of the voltage applied to the Vx and Vy electrodes.

Abstract: Micromachined grating modulators which exhibit achromatic behavior are described. One embodiment includes narrow and wide ribbons suspended above a substrate and alternatingly interleaved with each other. Narrow and wide reflective surfaces are formed on the narrow and wide ribbons. Compensating reflective surfaces are formed in the gaps between and beneath the ribbons. The width of the ribbons as well as the width of the gaps and the compensating reflecting surfaces are designed so that incident optical beam can be modulated or attenuated in an achromatic fashion.

Abstract: A method of scanning a plurality of display elements or pixels of a display and an apparatus capable of performing the method of scanning, allow energy propagating along a primary path to be diverted sequentially by a series of energy diverting devices to a plurality of secondary paths in a scanning direction depending upon the finite turn-on and turn-off times of the energy diverting devices.

Abstract: A switchable waveguide having first and second states. In the first state, the waveguide guides light of a signal wavelength along a predetermined path. In the second state, no guiding of the light occurs. The waveguide includes a guide layer of a guide material having a first index of refraction in the absence of an electric field and a second index of refraction in the presence of the electric field. The electric field is generated in a portion of the guide layer by applying an appropriate electrical signal to a plurality of electrodes that define a guide region in the guide layer. The guide region has an index of refraction that is greater than that of the guide layer in regions adjacent to the guide region. The electrodes are separated from the guide region by a distance of at least one-half times the wavelength of the light being guided. The separation is maintained by arranging the electrodes such that the guide region is created at a location separated from the electrodes.

Abstract: Disclosed is an electroabsorption-type optical modulator, which includes a semiconductor substrate; and a semiconductor buffer layer, a semiconductor optical absorption layer and a semiconductor cladding layer which are layered in order on the semiconductor substrate. The absorption of a light wave supplied to an end of the semiconductor optical absorption layer is controlled by changing the intensity of an electric field applied to the semiconductor optical absorption layer. The semiconductor optical absorption layer has a first region with an absorption-edge wave length shorter than that of a second region of the semiconductor optical absorption layer.

Abstract: Disclosed is a hybrid waveguide structure, wherein a core or cladding has a hybrid section or "button" of a different optical property such as refractive index from the major portion of the core or cladding, respectively. The hybrid section can be made of a passive material or an electro-optic material. Methods of making a hybrid waveguide structure are also disclosed. These methods include rib-based methods and trench-based methods, and in either of these methods, a temporary filler is used in many instances to incorporate the hybrid section into the hybrid waveguide structure.

Abstract: A flat panel display is based on a new switching technology for routing laser light among a set of optical waveguides and coupling that light toward the viewer. The switching technology is based on poled electro-optical structures. The display technology is versatile enough to cover application areas spanning the range from miniature high resolution computer displays to large screen displays for high definition television formats. The invention combines the high brightness and power efficiency inherent in visible semiconductor diode laser sources with a new waveguide electro-optical switching technology to form a dense two-dimensional addressable array of high brightness light emissive pixels.

Abstract: An optical fiber which modifies the optical signals propagated through the fiber and has refractive properties which change in response to electromagnetic energy. The outer surface of the fiber forms at least one groove extending along a selected length of the fiber for receiving an electrode, which would apply an electrical voltage to the fiber resulting in a change of the refractive properties of the fiber.

Abstract: An electro-optical phased array beam modulator is an apparatus for modulating a polarized coherent light source to produce a directionally controlled output beam which can be continuously steered in two separate dimensions by two independently controlled input control signals. It includes a waveguide bundle comprising a multiplicity of similar phase modulator elements with an input end into which polarized coherent light is received and an emitting end on which is located an emitting array from which phase shifted light emerges.

Abstract: A semiconductor Mach-Zehnder modulator comprises a pair of phase modulator arm waveguides and a single driver for a push-pull modulation. A first electrode connected to p-type cladding layer of first modulator arm is maintained at a negative potential V.sub..pi., a second electrode connected to n-type cladding layer of first modulator arm and p-type cladding layer of second modulator arm is driven by a drive voltage, and a third electrode connected to n-type cladding layer of second modulator arm is maintained at a ground potential. The drive voltage changes between V.sub..pi. and V.sub..pi./2 for push-pull modulation of both modulator arms.

Abstract: A semiconductor TE/TM mode converter comprises a semiconductor waveguide layer including a compressive-strained first region and a tensile-strained second region, and a diffraction grating formed on the first region. The first region and second region are reversed-biased and forward-biased, respectively. TE mode light incident on the facet of the first region generates TM mode light outgoing from the facet of the second region. The diffraction grating in the first region has selective reflectance against TM mode light and reflects the TM mode light toward the second region, to lower the lasing threshold of TM mode light and raise the conversion efficiency.

Abstract: A high-frequency circuit exhibiting favourable characteristics even in frequency domains in excess of 40 GHz is obtained by configuring a matching circuit 40 with open stubs 16 joined to a microstrip line 14.

Abstract: According to the present invention, damage to a photo-detector disposed in clock signal extractor by means of an optical pulse having an optical power exceeding a rated value is prevented. A ring resonator generates a repetitive, high-frequency optical pulse. Optical branching circuit branches a portion of the optical pulse circulating through ring resonator, while optical branching circuit further branches a portion thereof to protective device. Pumping source generates an excitation light for exciting a rare-earth doped optical fiber. Optical multiplexer couples the optical pulse branched by optical branching circuit, and the excitation light. Upon excitation by means of the excitation light, rare-earth doped optical fiber amplifies and emits the incoming optical pulse. The optical power of the excitation light is adjusted such that the output of rare-earth doped optical fiber reaches a saturation power.

Abstract: A flat panel display is based on a new switching technology for routing laser light among a set of optical waveguides and coupling that light toward the viewer. The switching technology is based on poled electro-optical structures. The display technology is versatile enough to cover application areas spanning the range from miniature high resolution computer displays to large screen displays for high definition television formats. The invention combines the high brightness and power efficiency inherent in visible semiconductor diode laser sources with a new waveguide electro-optical switching technology to form a dense two-dimensional addressable array of high brightness light emissive pixels.

Abstract: An electro-optic polymer waveguide device capable of decreasing a driving voltage and an optical loss is disclosed. A vertical tapered waveguide is formed between passive waveguides of input and output portions in a waveguide and an electro-optic modulating region, and an amplitude of a waveguide mode of the input and output portion waveguide is equal to that of a optical fiber, thereby minimizing a connection loss with the optical fiber.

Abstract: An optical isolator capable of simultaneously transmitting a plurality of light beams emitted from a plurality of optical fibers in one direction. It includes a plurality of optical fibers for transmitting light beams; a pair of collimating lenses for converting the light beams, emitted from or entered into the optical fibers, into parallel light beams; a pair of symmetric birefringent elements having at least one tapered surface for emitting by polarization the plurality of parallel light beams having passed the collimating lenses, and condensing all the light beams traveling in a forward direction onto the optical fibers, respectively; and a Faraday rotator interposed between the birefringent elements for rotating the light beams incident thereto by 45 degrees. A plurality of tapered faces having the same tapered angle are formed on one surface of the birefringent element so that a plurality of light beams can be simultaneously transmitted in one direction.

Abstract: An integrated optical intensity modulator and a method for fabricating it. The integrated optical intensity modulator includes a substrate having spontaneous polarization, cut in an axial direction; an optical waveguide on the substrate; domain-inversion areas having domains reverse from the direction of spontaneous polarization, arranged in a staggered pattern around the optical waveguide; a first electrode on the optical waveguide on a surface of the substrate, and second and third electrodes on the substrate on opposite sides of and on the same surface as the first electrode. When a voltage is applied to the first electrode, a light wave is deflected and scattered in a domain-inversion area in accordance with a change of the refractive index of the domain-inversion area in the optical waveguide and the refractive index of the spontaneous polarization area.

Abstract: An optical waveguide (5) for use in the in the visible range, the infrared range or the ultraviolet range. The waveguide has two cholesteric liquid crystal polymer layers (10) positioned parallel to each other, forming a gap between them. When electrically modulated to an `on` state, one or more of the cholesteric liquid crystal polymer layers become optically reflective, so that the waveguide becomes internally reflective, allowing a light beam (15) to be transmitted along the waveguide. The liquid crystal polymer is optically non-reflective when electrically modulated to an `off` state. The cholesteric liquid crystal polymer layers are each disposed on a substrate (30) having an electrically conductive layer (35) disposed between the substrate and the cholesteric liquid crystal polymer. A modulating means impresses an electrical signal upon the cholesteric liquid crystal polymer layers to convert them from the optically reflective state to the optically non-reflective state.

Abstract: An optical fibre is formed with longitudinal recesses (11, 12) which extend toward its core (3) through cladding region (2). The recesses receive electrode structures (20a, b) made of glass, which include tongues (23a, b) that fit into the recesses, on which metal electrode strips (a, b) are formed. A potential difference applied between the strips (a, b) can induce electro-optic effects in the core.

Abstract: An optical fiber which modifies the optical signals propagated through the fiber and has refractive properties which change in response to electromagnetic energy. The outer surface of the fiber forms at least one groove extending along a selected length of the fiber for receiving an electrode, which would apply an electrical voltage to the fiber resulting in a change of the refractive properties of the fiber.

Abstract: Optical plasmon-wave attenuator and modulator structures for controlling the amount of coupling between an guided optical signal and a surface plasmon wave. Optical power coupled to the plasmon wave mode is dissipated in varying amounts producing an intensity modulation effect on the optical signal. For electrical modulation, an additional dielectric (or polymer) layer with variable refractive index in optical contact with a metal layer supporting at least one plasmon wave mode is used to perturb or vary the propagation constant of plasmon wave. Propagation constant variation results in the power coupling variation between the surface plasmon wave and the optical wave. The refractive index variation of the dielectric (or polymer) layer can be accomplished via an electro-optic traveling-wave, a lump-element, or any other integrated optics modulator configuration situated to affect the layer, thereby permitting data rates into tens of GHz.

Abstract: A low-loss optically active device is provided by forming a lower clad layer using linear polymer on a substrate capable of transmitting ultraviolet (UV) light, forming a non-linear polymer core region of a waveguide region; forming a linear polymer core region on opposite sides of the non-linear core region, and forming an upper clad layer on the lower clad layer and linear and non-linear core regions of the waveguide region. The waveguide is formed using non-linear polymer only at the region where the non-linear effect such as optical modulation or optical switching occurs, and is formed using linear polymer at the remaining regions, thereby minimizing the overall waveguiding loss of the device.

Abstract: A WDM ring configuration having reduced adjacent channel cross-talk is disclosed. In the WDM ring, an add/drop element having a filter for selecting an optical signal at a desired wavelength is spaced from another add/drop element having a filter adding an optical signal at an adjacent wavelength within a channel plan by at least one add/drop element that adds/drops an optical signal at a wavelength which is not next to either the optical signal at the desired wavelength or the adjacent wavelength.

Abstract: A discrete electroabsorption modulator for optical signals has an electrical blocking region (12a, 12b) which is large as compared with the absorber region (13). The height of the blocking region (12a, 12b) is 3-20 .mu.m, e.g. 4-6 .mu.m and preferably about 5 .mu.m. In addition, the blocking region (12a, 12b) is 2-250 times, e.g. 15-25 times the height of the absorber region (13). The modulation depth is substantially increased, e.g. to values above 40 dB, by a thick electrical blocking region. It is believed that the thick blocking layer (12a, 12b) works because parasitic signals which escape into the blocking region are spatially removed from the vicinity of the absorber region; thus they are not acquired at the output.

Abstract: In an optical waveguide type device, an optical waveguide is formed in a crystal substrate having an electro-optical effect. A buffer layer is formed on the crystal substrate. Further, an signal electrode is formed on the buffer layer so that microwave signals are given to the signal electrode. In addition, a dielectric substrate is formed under the crystal substrate. With this structure, a groove is formed in the dielectric substrate and below at least the signal electrode. In this case, the groove functions as the air gap for reducing an attenuation of the microwave signals. According to this invention, the microwave attenuation is reduced and further the handling of the chip becomes easy. Alternatively, such a reduction can be accomplished by selecting a first width of an active portion of a signal electrode, a second width of a feeder portion of the signal electrode, and a third width of a connector. Specifically, the second width is wider than the first width and is narrower than the third width.

Abstract: A flat panel display is based on a new switching technology for routing laser light among a set of optical waveguides and coupling that light toward the viewer. The switching technology is based on poled electro-optical structures. The display technology is versatile enough to cover application areas spanning the range from miniature high resolution computer displays to large screen displays for high definition television formats. The invention combines the high brightness and power efficiency inherent in visible semiconductor diode laser sources with a new waveguide electro-optical switching technology to form a dense two-dimensional addressable array of high brightness light emissive pixels.

Abstract: An optical interferometer incorporating a signal strength modulated optical phase delay, such as a Kerr effect element in one of its arms is employed to improve the cross-talk isolation/extinction ratio of an optical switch, amplitude modulator, or amplitude modulated optical transmitter. The Kerr element is constructed so that its intensity dependent optical path length is such as to provide destructive interference at the interferometer output when the light input to the interferometer is low, and constructive interference when the input is high. The place of the Kerr effect element can alternatively be taken by an electro-optic modulator driven with an electrical version of the data modulation appearing on the optical signal.

Abstract: An optical modulator for modulating light emitted from a signal light source has a substrate having electrooptic effect, an optical waveguide of a Mach-Zehnder type formed on the substrate, an electrode formed on the substrate to control light propagated in the optical waveguide, a light guiding unit for guiding light radiated or leaking from the optical waveguide, an interference light generating means for making light emitted from the light guiding unit and signal light leaking from the optical waveguide interfere with each other to generate interference light, and for emitting the interference light from an end surface of the substrate, a photo-detector for monitoring the interference light obtained by the interference light generating means, and a signal controlling circuit for controlling an operating point of the optical modulator according to a change of the interference light monitored by the photo-detector, thereby stably controlling the operating point of the optical modulator while facilitating a d

Abstract: The modulator includes a TE.revreaction.TM converter (3) between two electro-optical modulators (1, 2). The coupler includes two directional couplers interconnected via branches each including a TE.revreaction.TM converter. Another electro-optical component includes a light guide that is folded and metallization that extends at least over two juxtaposed portions of light guide.

Abstract: An optical waveguide device comprises: a waveguide substrate with a waveguide created therein; optical fibers optically linked to the waveguide at both end surfaces of the waveguide; and a double-refraction means provided at the one end surface for splitting an incident light into normal and abnormal lights. A rutile plate stuck to an end surface of the waveguide is used as an actual double-refraction means for arbitrarily selecting an incident light hitting the waveguide and splitting the incident light into normal and abnormal components. By providing rutile plate having a double-refraction effect such as the rutile plate on the end surface of the waveguide, a difference in phase between optical paths is resulted in due to polarization of the incident light, making separation into TE and TM modes possible. By optically linking lights split and radiated in the rutile plate to the incident end surface of the waveguide, any arbitrary polarization light can be applied to the waveguide.

Abstract: A flat panel display is based on a new switching technology for routing laser light among a set of optical waveguides and coupling that light toward the viewer. The switching technology is based on poled electro-optical structures. The display technology is versatile enough to cover application areas spanning the range from miniature high resolution computer displays to large screen displays for high definition television formats. The invention combines the high brightness and power efficiency inherent in visible semiconductor diode laser sources with a new waveguide electro-optical switching technology to form a dense two-dimensional addressable array of high brightness light emissive pixels.

Abstract: A signal light incident onto a first splitter of a polarization scrambler is split into two and propagated through a first and second optical paths, whereby phases of the signal lights are varied in accordance with a voltage applied by first voltage supplier. Further, a polarization of the signal light propagated through at least one of the first and second optical paths is rotated for adjusting a relative polarization angle between the signal lights by first plane-of-polarization rotator. The signal lights having passed through the optical paths are combined by first coupler so that a polarization condition of the incident signal light is scrambled and output. Polarization dispersion is allowed to occur only after the signal light has passed through the plane-of-polarization rotator.

Abstract: An extremely low-loss optical switch element includes a first waveguide segment having first and second regions longitudinally-adjacent with each other and having an index of refraction difference which is greater when the switch element is in an "on" state than when it is in an "off" state. The two regions have a common boundary which is oriented at an angle in the first waveguide so as to redirect optical energy through total internal reflection when the switch element is in the "on" state. The switch element further includes a second waveguide segment spaced from the first waveguide segment and disposed and oriented to guide optical energy redirected from the first waveguide segment when the switch element is in the "on" state.

Abstract: An electro-optic modulator is disclosed in the form of a compound waveguide device having a channel waveguide in optical proximity to an elongate waveguide propagating an optical signal therein. The channel waveguide includes a coupling surface through which optical energy is evanescently coupled to or from the optical signal propagating in the elongate waveguide. The channel waveguide is shaped to confine distribution of the optical energy therein along axes transverse to the axis of propagation of the optical energy. Transverse diffraction of the optical energy within the channel waveguide is thereby limited. The channel waveguide is formed from an electro-optically active material, and modulation of the optical signal propagating in the elongate waveguide is effected using the evanescent coupling effect between the two waveguides. In one embodiment, the elongate waveguide is a side-polished fiber-optic waveguide.

Abstract: A commercially attractive arrangement for monolithic integration of a nonlinear optical polymer transverse electro-optic device for high data rate optical signals on an electronic integrated circuit chip. The invention provides for conductive polymer sheet layers immediately adjacent to an optical signal transmitting nonlinear optical polymer core layer. Electrically passive polymer cladding layers are also provided adjacent to the conductive polymer sheet layers to achieve lower optical signal losses. The combination provides a reduced nonlinear optical polymer core layer poling voltage, reduced device length, and 5 VDC or less controlling voltage, allowing inclusion into electronic integrated circuit chips of a size compatible with multichip module integration.

Abstract: Two optical waveguides comprising a light transmitting medium are disposed close to each other on a substrate, and electrodes are disposed parallel to each other so as to sandwich one optical waveguide. The light transmitting medium is formed by dispersing fine droplets of a liquid crystal in a light transmitting material, such as glass or polymer, the liquid crystal fine droplets having droplet diameters of about one digit smaller (that is, about an order of magnitude smaller) than the wavelength of light. Linearly polarized light having a plane of polarization in a direction parallel to the direction of application of voltage to the optical waveguide, i.e., in the direction of the substrate surface, is fed as input lights into the optical waveguides. Upon application of voltage, the refractive index of one optical waveguide changes, while the refractive index of the other optical waveguide remains unchanged. Hence, the coupling ratio changes, achieving an optical switch.

Abstract: A traveling-wave electro-optic modulator using reflected signals to achieve a one-time rephasing. For a given crystal length, the interaction length is effectively doubled and a 3-dB gain is automatically achieved compared to a conventional traveling-wave modulator.

Abstract: A commercially attractive arrangement for monolithic integration of a nonlinear optical polymer transverse electro-optic device on an electronic integrated circuit chip. The invention provides for conductive polymer cladding layers immediately adjacent to an optical signal transmitting nonlinear optical polymer core layer. The cladding layers result in a reduced core layer poling voltage, reduced device length, and 5 VDC or less controlling voltage, allowing inclusion into electronic integrated circuit chips of a size compatible with multichip module integration.

Abstract: A new class of energy interaction devices, particularly optical energy transfer devices and energy guiding devices, use an energy field, particularly an electric field, applied to a poled structure to control energy propagation in a solid material. The poled structures, which may form gratings in thin film or bulk configurations, may be combined with waveguide structures to guide energy beams such as optical or acoustic beams. Electric fields applied to the poled structures, such as electrically-activated gratings, control routing of optical energy. Optical devices include but are not limited to, frequency-selective switchable- and adjustably-tunable reflectors, splitters, directional couplers, frequency-tunable switches and efficient beam combiners, as well as polarized beam combiners, am and fm modulators, mode selectors, energy transfer devices, optical data readers, panel display devices, and waveguide/reflector switching arrays.

Abstract: An electro-optical waveguide element with reduced DC drift phenomena is presented. The waveguide element is made up of an optical waveguide formed on a substrate possessing electro-optical effects, at least a pair of electrodes closely attached to the optical waveguide with a buffer layer sandwiched between the substrate and the electrodes, and a driver circuit for applying a voltage between the electrodes. The buffer layer is made of a material having a dielectric constant in the range of 20-1000. The buffer layer is more preferably made of a material having a dielectric constant in the range of 20-200. The material of the buffer layer is selected from the group consisting of HfO.sub.2, TiO.sub.2, SrTiO.sub.3, BaTiO.sub.3, LiNbO.sub.3, LiTaO.sub.3, Pb(Zr, Ti)O.sub.3, and (Pb, La)(Zr, Ti)O.sub.3.

Abstract: The gain provided by an erbium amplifier is stabilised by spectrally selective optical feedback to make the amplifier lase. The resulting laser emission is extracted from the amplifier output using a Mach Zehnder with matched Bragg reflectors in its two interference arms. The extracted light may be used for supervisory purposes. Part of the laser cavity defining feedback may be provided by the Mach Zehnder by arranging one of its Bragg reflectors to be displaced with respect to the other.

Abstract: There is disclosed a harmonic modulation device of waveguide type including a semiconductor laser, a waveguide for generating a nonlinear optical harmonic of the semiconductor laser by keeping phase matching, means for leading an optical beam of the semiconductor laser to the waveguide, electrodes disposed on the waveguide, and means for modulating a refractive index of the waveguide electro-optically to modulate a phase matching condition and thereby modulate an intensity of the harmonic.

Abstract: An optical modulator includes a substrate having an electrooptic effect, an optical waveguide formed on a surface of the substrate, and a control electrode formed on the substrate, and a control electrode formed on the substrate to oppose the optical waveguide. In this optical modulator, the control electrode is formed by stacking a plurality of layers in a direction perpendicular to the substrate surface.

Abstract: An exemplary embodiment of an acousto-optic planar waveguide modulator includes a planar waveguide structure with an input section connected to a multimode section connected to an output section. The input and output sections have structures for propagating an optical signal in a first transmission mode. The multimode section has a structure in which an optical signal can propagate in the first transmission mode and a second transmission mode. A surface acoustic wave source is used to direct a surface acoustic wave at the multimode waveguide section to cause a periodic change in the refractive index for coupling optical signal energy between the even and odd transmission modes. As a consequence, power of an optical signal propagating in the even transmission mode is transferred to the odd transmission mode. This power transfer causes an attenuation of the optical signal propagating in the even transmission mode from the multimode section to the output section.

Abstract: An electro-optic modulator (300) comprises a multiple quantum well core layer (320) in which the band gap and refractive index are adjusted to make the core layer (320) transparent to light at a selected wavelength and a voltage tunable, multiple quantum well cladding layer (330) in which an exciton absorption provides the cladding layer (330) with a first refractive index that is less than the core refractive index when a first voltage is applied and a second refractive index that approaches or exceeds the core refractive index when a second voltage is applied. The exciton absorption also provides the voltage tunable cladding layer (330) with a substantially greater absorption coefficient at the selected wavelength than that of the core layer (320).

Abstract: An integrated tunable optical filter comprising a substrate made of a semiconducting material. The substrate includes first and second sections. The first section forms a tunable transmission filter, based on a codirectional coupler having a low selectivity. The second section forms a reflection filter with a reflection spectrum containing a number of peaks. A first injector, designed for current injection into said first section, is provided. Thus, the filter response of the first section is shifted in wavelength over a large wavelength range. There is also a second injector, designed for current injection into the second section. As a result, the reflective spectrum of the second section is slightly shifted in wavelength, in such a way that one reflection peak of the reflection spectrum corresponds to the coupling wavelength of the first section. Consequently, the total filter response has a very narrow bandwidth and wide tunability.