Abstract: A system and method for programmable phase compensation of optical signals is disclosed. The systems and methods include the use of a polarization-independent spatial light modulator (PI-SLM), so that the state of polarization (SOP) of the incoming optical signal need not be known. The system includes a first dispersive module that spatially separates the optical signal into its frequency components. The frequency components are spread over the active area of the PI-SLM. The active area of the PI-SLM includes an array of independently programmable addressable regions capable of altering the phase of the light incident thereon. An exemplary application of the invention is chromatic dispersion compensation. By knowing the amount of chromatic dispersion in the optical signal, or alternatively, by knowing the amount of chromatic dispersion to be introduced into the optical signal downstream, the appropriate phase adjustments can be made to each frequency component of the signal.

Abstract: A photonic crystal having reversibly tunable photonic properties. The photonic crystal includes a phase change material having a plurality of structural states that vary with respect to fractional crystallinity. Optical constants including refractive index, extinction coefficient and permittivity vary as the fractional crystallinity of the phase change material is varied thereby providing tunability of photonic crystal properties. Variations among the structural states of the phase change material are reversibly effected through the addition of energy in forms including optical or electrical energy. The photonic crystals may include defects that provide photonic states within the photonic band gap. The position of these states is tunable through the control of the fractional crystallinity of the phase change material included in the photonic crystal. Electromagnetic radiation resonators including photonic crystals having photonic states in the photonic band gap are further provided.

Abstract: The present invention provides a method and a system for generating a phase-modulated wave front. According to the present invention, the spatial phase-modulation is not performed on the different parts of the wave front individually as in known POSLMs. Rather, the spatial phase-modulation of the present invention is performed by generating an amplitude modulation in the wave front, Fourier or Fresnel transforming the amplitude modulated wave front, filtering Fourier or Fresnel components of the Fourier or Fresnel distribution with a spatial filter such as a phase contrast filter, and regenerating the wave front whereby the initial amplitude modulation has transformed into a phase-modulation.

Abstract: Improved Wavefront Coding Optics, which apply a phase profile to the wavefront of light from an object to be imaged, retain their insensitivity to focus related aberration, while increasing the heights of the resulting MTFs and reducing the noise in the final images. Such improved Wavefront Coding Optics have the characteristic that the central portion of the applied phase profile is essentially flat (or constant), while a peripheral region of the phase profile around the central region alternately has positive and negative phase regions relative to the central region.

Abstract: A quantum-confined Stark effect quantum-dot optical modulator includes an interferometer having a beam splitter, first and second parallel optical branches fed by the beam splitter and a beam combiner fed by the first and second parallel optical branches and a laser for feeding a laser beam to the beam splitter. First and second optical phase shifters are provided in respective ones of the first and second parallel optical branches. Each optical phase shifter includes an intrinsic semiconductor crystalline planar layer and p-type and n-type planar semiconductor layers on opposite faces of the intrinsic semiconductor crystalline planar layer, the intrinsic layer lying in a plane parallel to a direction of propagation of the laser beam in the respective optical branch. The intrinsic layer has plural layers of planar arrays of quantum dots therein. A reverse bias D.C. voltage source is connected across the p-type and n-type layers.

Abstract: In the invention, light incident onto an end surface of one-dimensional photonic crystal is phase-modulated in the same period and direction as those of the photonic crystal to thereby propagate only specific high-order band light in the photonic crystal. That is, a phase modulation unit for generating phase-modulated wave having the same period as that of the periodic structure is disposed adjacent or close to a light incident surface of the periodic structure.

Abstract: An electrically adjustable phase-shifting device is arranged on a substrate comprising at least a first waveguide designed for guiding optical signals and a thermoelectric element arranged adjacent to the first waveguide in order to shift the phase of an optical signal in the first waveguide by means of a thermo-optic effect according to a control voltage applied to the thermoelectric element. In one embodiment, the thermoelectric element is a Peitier element which comprises at least first and second electrically conducting segments which are serially connected, the first and second elements alternating consecutively.

Abstract: An optical system with mechanical adjustment provides for the rotation and/or translation of one or more optical phase filters to variably select an extended depth of field, aberration-tolerance, and/or anti-aliasing properties of an optical imaging system. By adjusting the amount of phase induced on the wavefront, a user may select image quality selectively. The system may further automatically counter change of focus and/or aperture to maintain substantially constant image properties. Typically, two phase filters are used and moved concurrently to achieve desired image properties.

Abstract: An image projection apparatus and method includes a light separating unit that separates white light into monochromatic lights of different wavelengths, and then forms a plurality of monochromatic color stripes. A galvanometer receives the separated monochromatic lights and deflects the lights by a predetermined angle. The holographic optical element such as a hologram element can be used as the light separating unit, obtaining an advantageous reduction in light loss. Further, when the separated RGB monochromatic lights are scanned on the DMD panel by the use of galvanometer, only one color stripe is projected to be incident on the DMD panel in the initial scanning, thereby increasing light utilization efficiency. As a result, the quantity of light increases, the light efficiency improves, and the brightness of the realized image is enhanced.

Abstract: The present invention aims at providing a control technique for an optical modulator, which can accurately detect a phase shift between signals of a drive system of an optical modulator, to feedback control. To this end, a control apparatus of the present invention comprises, for example, in an optical modulator which generates a signal light corresponding to the CS-RZ modulation method by two LN modulators connected in series: a monitor section that extracts a specific frequency component from a spectrum of the CS-RZ signal light output from a latter LN modulator to detect the optical intensity thereof, and a control CPU that determines a phase shift between first and second drive signals corresponding to a clock signal supplied to the latter LN modulator based on the optical intensity detected by the monitor section, and controls a phase difference between the drive signals so that the phase shift is minimized.

Abstract: An apparatus and method for modulating a phase of optical beam with reduced contact loss. In one embodiment, an apparatus according to embodiments of the present invention includes a first region of an optical waveguide disposed in semiconductor material. The first region has a first conductivity type. The apparatus further includes a second region of the optical waveguide disposed in the semiconductor material. The second region has a second conductivity type, which is opposite to the first conductivity type. A first contact is coupled to the optical waveguide at a first location, which is outside an optical path of an optical beam that is to be directed through the optical waveguide. A first buffer of insulating material is disposed along the optical waveguide between the first contact and the optical path of the optical beam. A buffer plug of insulating material disposed in the optical waveguide on a same side as the first location.

Abstract: A light-controlled light modulator can achieve high-speed, low-loss wavelength conversion. Continuous light with a wavelength &lgr;j is launched into an MMI coupler via a port, and is split into two parts by the MMI coupler, which are led to a loop-type interferometer. In the loop-type interferometer, the two parts travel separately around the loop as clockwise traveling light and counterclockwise traveling light, are combined by the MMI coupler again via a filter-equipped phase modulator, thereby being emitted to the port. In this state, signal light &lgr;i(s) with a wavelength &lgr;i is launched into the filter-equipped phase modulator via a port. Even when the wavelength &lgr;i of the signal light &lgr;i(s) is equal to the wavelength &lgr;j of the wavelength converted output light, the wavelength conversion can be achieved with preventing noise from being mixed into the output light emitted from a port.

Abstract: A unique optical encoder is employed that utilizes an optical phase modulator, in which an arbitrary phase shift can be realized. The phase modulator is driven by an electrical signal, where the voltage amplitude is proportional to a desired arbitrary phase shift. However, any amplitude noise or poor rise and fall times of the driving voltage translates directly into phase errors. These problems are eliminated by employing a digital phase switch. One encoder, in accordance with the invention, employs an optical phase modulator that can switch the optical phase in a binary manner, wherein the two phase states of the modulator can be chosen to differ by any desired arbitrary angle depending on the splitting ratio of the optical signal to be modulated.

Abstract: An optical clock multiplier comprises a phase modulator (12) to shift a phase in pulse duration of an input optical clock pulse by &pgr;, a polarization mode dispersion device (16) having a predetermined time difference between first and second polarizations orthogonal to each other to divide an output light from the phase modulator into the first and second polarization components, and a polarization device (20) to extract one of polarization components in a third polarization practically inclined at an angle of 45° against the first polarization and a fourth polarization orthogonal to the third polarization out of the output light from the polarization mode dispersion device.

Abstract: A method and apparatus for information modulation for impulse radios are presented in both single-tone and pulse stream configurations. The modulation techniques include combinations of amplitude and phase modulation. The modulation techniques include both digital and analog schemes, including baseband on/off keying modulation, wavelet on/off keying modulation, pulse-position modulation, and FM modulation. Techniques for varying the modulation rate are also provided. Additionally, harmonics impulse ratio configurations are presented to take advantage of the modulation techniques.

Abstract: A method of reducing the appearance of speckle resulting from a coherent light beam, includes the steps of: providing an electro-optic device having, an electro-optic substrate, an electrode array arranged on the surface of the electro-optic substrate, at least one electrode located on the opposite surface of the electro-optic substrate, and means for applying voltage to the electrodes to generate a variation in a refractive index profile within the substrate; and directing the light beam through the electro-optic device while applying voltage to the device, whereby the temporal and spatial phase of a light beam passing through the substrate is altered, thereby reducing the appearance of speckle.

Abstract: An optical modulation apparatus includes an optical signal input section, an optical signal propagation path, an optical modulator that modulates the phase of optical signals in at least two of a plurality of optical paths, and a wavelength selective filter that selectively reflects and transmits. Optical signals input via the input section are divided into a plurality of optical paths at a branching point and phase modulated by the phase modulator, that divides the optical path into a plurality of optical paths. Light transmitted by the filter is output via the output section, while light reflected by the filter travels back along the optical path and is again phase modulated by the phase modulator combined at the branching point and output from the input section as an intensity modulated optical signal.

Abstract: An optical pickup device which includes (A) a light source, and (B) an objective lens and an aberration correcting optical system which are located in a light path from the light source to an optical recording medium is so arranged that the aberration correcting optical system imparts a phase distribution to luminous flux which transmits the aberration correcting optical system, so as to correct a predetermined aberration; and an amount of phase of the aberration correcting optical system when correcting the aberration is set in such a manner that the aberration correcting optical system imparts a larger amount of phase at a position farther from a point where the aberration correcting optical system crosses an optical axis of light emitted from the light source. With this, it is possible to increase a tolerance for the center misalignment of the objective lens so as to reduce aberration caused by the center misalignment.

Abstract: A Mach-Zehnder optical modulator that can attain a higher transmission speed than the driver signal speed but also attains, by setting multi-value amplitudes, an information transmission volume corresponding to an integer multiple of a single driver while allowing the transmission speed to remain as it is, wherein plural optical waveguide branches and plural Mach-Zehnder modulator portions are used, and by utilizing a propagation delay of a modulation signal for driving each of the modulator portions there is attained a transmission speed proportional to the delay time. This leads to a transmission signal having a frequency higher than the cut-off frequency of, for example, an IC or a transmission line substrate having an electrical characteristic of generating and propagating a modulation signal in such a form as an optical MUX (multiplexer).

Abstract: The present invention relates to an achromatic phase shift device (1) for introducing a wavelength independent optical phase shift in a first optical beam (40) during operation, comprising at least one dispersive element (55k) formed by first refractive means (2k) and second refractive means (4k), the first refractive means (2k) having a first refractive means input plane (6) for receiving the first optical beam (40) and a first refractive means output plane (8) being at a predetermined angle (&bgr;) to each other, the second refractive means (4k) having a second refractive means input plane (10) and a second refractive means output plane (12) being positioned parallel to the first refractive means input plane (6). The device may comprise further pairs (55k) of respective first and second refractive means (2k, 4k). The present invention also relates to an interferometer comprising at least one achromatic phase shift device.

Abstract: An apparatus and method for modulating a phase of optical beam. In one embodiment, an apparatus according to embodiments of the present invention includes a first region of semiconductor material having a first polarity. The apparatus further includes a second region of semiconductor material having a second polarity. The second region is disposed proximate to the first region such that an interface between the first and second regions defines interdigitated regions of the first and second regions of semiconductor material. The first and second regions are adapted to be reversed biased in response to a signal to modulate a depletion region in response to the signal at the interface between the first and second region. Accordingly, an optical beam directed through the interface between the first and second regions through the modulated depletion region is adapted to be phase shifted in response to the signal.

Abstract: In an optical phase modulator, a substrate has electro-optical effect. An optical waveguide is formed in a surface portion of the substrate. A phase modulation section is provided on an input side to change a refractive index of the optical waveguide for phase modulation to input light. An adjustment section is provided on an output side to change a refractive index of the optical waveguide for elimination of polarization dependency of the phase-modulated light. In this case, the refractive index change rate in the phase modulation section and the refractive index change rate in the adjustment section may have different signs each other.

Abstract: In case of the high-speed operation, it is difficult to ignore the time required for the voltage to rise to the level of voltage to be applied and the time to fall to 0V when the voltage is applied to the phase modulator. The first phase modulator 71 and the second phase modulator 73 are connected in parallel, and the optical path is switched by the switching unit 55 of the control unit 51 between the first optical switch 33 and the second optical switch 35. The switching unit 55 of the control unit 51 supplies the phase modulation data 31 stored in the phase modulation data memory 53 to the first voltage generating unit 57 or the second voltage generating unit 59 to generate the voltage necessary for the phase modulation.

Abstract: A semiconductor optical device includes a substrate, an optical waveguide layer on the substrate and having well and barrier layers. The semiconductor optical device also includes an optical absorbing layer on the substrate and adjacent to the optical waveguide layer so that incident light having an incident wavelength &lgr;LD is guided into the optical absorbing layer. Each of the well layers has a wavelength &lgr;g corresponding to the band gap of the well layers and that is larger than the incident wavelength &lgr;LD. Also, the band gap energy between base levels of a conduction band and a valence band of the optical waveguide layer is larger than the energy of the incident light having the incident wavelength &lgr;LD.

Abstract: A reconfigurable and stationary element for the engineering of the wavefront of electromagnetic radiation. The element includes a phase change material that may be reversibly transformed between its crystalline and amorphous states. By forming a gradient in crystallinity, a phase taper may be stored in the phase change material of the instant element. The phase taper provides control of the phase angle of reflected or reradiated electromagnetic radiation. An incident wavefront of electromagnetic radiation interacts with the instant element and is reradiated with controlled propagation characteristics imposed by the stored phase taper. The instant element may provide non-specular reflection, beam steering, focusing, defocusing, symmetrical and asymmetrical cross section effects, and wavefront correction. In a preferred embodiment, a pattern of amorphous marks is formed within a crystalline matrix of phase change material.

Abstract: In accordance with the invention, a train of RZ or CSRZ pulses is produced by passing phase modulated laser light through a delay interferometer. The parameters of the phase modulation and the delay interferometer are calculated from the desired pulse train characteristics (e.g. repetition rate, RZ or CSRZ, duty cycle). A directly modulated CW laser, or a CW laser followed by a phase modulator, produces the constant amplitude, phase modulated light. The phase modulated signal is split into two paths. One signal path is delayed with respect to the other by the calculated delay. The signals are recombined in an optical coupler to produce an RZ pulse train and/or a CSRZ pulse train.

Abstract: A light-controlled light modulator can achieve high-speed, low-loss wavelength conversion. Continuous light with a wavelength &lgr;j is launched into an MMI coupler via a port, and is split into two parts by the MMI coupler, which are led to a loop-type interferometer. In the loop-type interferometer, the two parts travel separately around the loop as clockwise traveling light and counterclockwise traveling light, are combined by the MMI coupler again via a filter-equipped phase modulator, thereby being emitted to the port. In this state, signal light &lgr;i(s) with a wavelength &lgr;i is launched into the filter-equipped phase modulator via a port. Even when the wavelength &lgr;i of the signal light &lgr;i(s) is equal to the wavelength &lgr;j of the wavelength converted output light, the wavelength conversion can be achieved with preventing noise from being mixed into the output light emitted from a port.

Abstract: A method for suppressing distortion in a multi-wavelengths system which uses a Mach Zehnder optical modulator includes adjusting an internal path length mismatch of the modulator and changing an applied voltage, Vb, such that the combination biases the modulator to the required &pgr;/2 phase bias.

Abstract: A quasi-optical system is provided. More specifically, a quasi-optical system is provided comprising various embodiments of quasi-optical grids (such as arrays or layers and the like) with reconfigurable quasi-optical unit cells. The quasi-optical system, grids and unit cells are configured to control an incident beam in a variety of ways.

Abstract: The present invention provides an electro-optic ceramic material including lead, zinc and niobium having a propagation loss of less than about 3 dB/cm and a quadratic electro-optic coefficient of greater than about 1×10−6 m2/V2 at 20° C. at a wavelength of 1550 nm. The present invention also provides electro-optic devices including an electro-optic ceramic material including lead, zinc and niobium having a propagation loss of less than about 3 dB/cm and a quadratic electro-optic coefficient of greater than about 1×10−16 m2 V at 20° C. at a wavelength of 1550 nm. The materials and devices of the present invention are useful in optical communications applications such as intensity and phase modulation, switching, and polarization control.

Abstract: A method of reducing speckle includes dividing a laser illuminated area into phase cells, subdividing the phase cells into cell partitions, and applying a temporal phase variation to the cell partitions within an integration time of an intensity detector viewing the laser illuminated area. An apparatus for reducing speckle includes illumination optics, a diffuser, and projection optics. The illumination optics couple a laser illumination to the diffuser, which is located in a first image plane. The diffuser divides the laser illumination into the phase cells and subdivides the phase cells into the cell partitions. The diffuser also applies the temporal phase variation to the cell partitions. The projection optics project an image of the first image plane onto a diffuse surface. A display apparatus adds a light modulator to the apparatus for reducing speckle and places the light modulator in a third image plane located between a laser source and the diffuser.

Abstract: A lens system for use with a phase plate in a transmission electron microscope comprises a phase plate placed after the back-focal plane of the objective lens in an imaging system mounted downstream of the objective lens. Phase lenses image the back-focal plane of the objective lens onto the phase plate such that the position and tilt of the electron beam relative to the optical axis are made conjugate. An alignment coil may direct the electron beam going out of the phase lenses toward the phase plate. A second alignment coil may direct the electron beam going out of the phase plate toward the imaging lenses located after the phase plate.

Abstract: The optical module has an element mounted thereupon for shifting an optical phase by the electro-optic effect, and includes an element for shifting an optical phase by an electro-optic effect having a signal electrode and a ground electrode formed thereupon; a connector for supplying a control signal of a microwave region to the signal electrode of the element, having a center conductor and an outer conductor; and a repeating board formed on a dielectric wafer having a coplanar line connecting the signal electrode and the ground electrode with the center conductor and the outer conductor of the connector respectively on the dielectric wafer, wherein an air layer is formed on the lower portion of the repeating board on which the center conductor of the connector is disposed.

Abstract: In a system for transmitting intensity modulated light waves (20) over an optical fiber (18), an optical data transmission apparatus (10) includes a cw laser (12) conformed to emit light at substantially a single frequency. A phase modulator (14) is connected in series with the cw laser (12), wherein the phase modulator (14) is conformed to cause the light from the cw laser (12) to vary in substantially a quadratic manner as a function of time during a time interval T. An intensity modulator (16) is connected in series with the phase modulator (14), wherein the intensity modulator (16) is conformed to transmit or block the light from the phase modulator (14) in accordance with an intensity modulation scheme for transmitting binary data, such that the transmitted light consists of pulses (22) of temporal width T during which the phase of the light varies in substantially a quadratic manner as a function of time.

Abstract: The invention discloses phase-shifters, modulators, and method that produces a smaller &pgr; by means of a field excitation using multiple electrodes. A negative signal is introduced that travels with the positive signal, which enhances the electric field significantly. The field enhancement is provided by the superposition of the fields accumulated from each electrode. A base or substrate material can be made from any compound having linear electro-optic properties, such as lithium niobate, lithium tantalite, potassium lithium niobate, potassium titanyl phosphate or gallium-arsenide. For lithium niobate, there are two possible orientations of electric field, z-cut orientation or x-cut orientation.

Abstract: A display device or a receiver device for use with coherent light. A controller applies phase shift values to a multi-region phase array at a frequency sufficiently higher than the flicker fusion rate of the human eye or other intended receiver in order to remove the perception of speckling artifacts which would otherwise appear due to the coherency of the light.

Abstract: An active optical system and method for phase-shifting desired portions of an incoming optical wavefront. A control optics assembly receives an incoming optical wavefront and adjusts that incoming optical wavefront in accordance with first desired wavelength and beam propagation parameters. Spatial light modulator (SLM) addressing optics receives the control optics output wavefront and produces a desired beam size therefrom. An SLM receives the output from the SLM addressing optics and provides localized phased shifting of the resulting wavefront. The SLM comprises a microscopic array of pixelated silicon nanocluster elements and a voltage source for applying independently controlled voltages on desired nanocluster elements. SLM egressing optics receives the output of the SLM and returns the beam size of the wavefront to the initial beam size. The output of the SLM egressing element has desired portions of its phase shifted relative to the incoming optical wavefront.

Abstract: A quantum-confined Stark effect quantum-dot optical modulator includes an interferometer having a beam splitter, first and second parallel optical branches fed by the beam splitter and a beam combiner fed by the first and second parallel optical branches and a laser for feeding a laser beam to the beam splitter. First and second optical phase shifters are provided in respective ones of the first and second parallel optical branches. Each optical phase shifter includes an intrinsic semiconductor crystalline planar layer and p-type and n-type planar semiconductor layers on opposite faces of the intrinsic semiconductor crystalline planar layer, the intrinsic layer lying in a plane parallel to a direction of propagation of the laser beam in the respective optical branch. The intrinsic layer has plural layers of planar arrays of quantum dots therein. A reverse bias D.C. voltage source is connected across the p-type and n-type layers.

Abstract: The invention relates to an optical signal transmission system with phase modulation and the implementation method. The system adds a phase modulator in the optical signal-emitting module. The optical pulses after intensity modulation and a high-speed data stream are input to the phase modulator synchronously, where the optical pulses are modulated in phase according to the high-speed data stream into high-speed optical signals with chattering. According to the invention, the phase modulator added in the optical signal-emitting module modulates optical signals in phase, which has been modulated in intensity. Appropriate chattering modulation can depress effectively the non-linear effect in the transmission of optical pulses through the interaction between chromatic dispersion and non-linear effects. Thus, the power input of individual channels is increased effectively, and the passive relay regeneration distance is extended.

Abstract: A device (16) in a system (10) modulates an optical signal (13) and tunes the duty cycle of the optical signal (13) for optimizing system performance as a response of the duty cycle. The device (16) includes a tunable duty-cycle Mach-Zehnder interferometer (MZI) acting as a pulse-width shaper (160) for modulating the optical signal (13) and tuning the duty cycle of the optical signal (13). The MZI (160) has a transmittance transfer function of the interferometer (160). At least one electrode structure (163) generates a DC voltage and an AC voltage for biasing and controlling the swing of the Mach-Zehnder interferometer (160) with the respective amplitudes of the DC and AC voltages such that the maximum power transmittance point on the transfer function is less than 100% for tuning the duty cycle of the optical signal (13) such that system performance is optimized.

Abstract: A device (16) in a system (10) modulates an optical signal (13) and tunes the duty cycle of the optical signal (13) for optimizing system performance as a response of the duty cycle. The device (16) includes a tunable duty-cycle Mach-Zehnder interferometer (MZI) acting as a pulse-width shaper (160) for modulating the optical signal (13) and tuning the duty cycle of the optical signal (13). The MZI (160) has a transmittance transfer function of the interferometer (160). At least one electrode structure (163) generates a DC voltage and an AC voltage for biasing and controlling the swing of the Mach-Zehnder interferometer (160) with the respective amplitudes of the DC and AC voltages such that the maximum power transmittance point on the transfer function is less than 100% for tuning the duty cycle of the optical signal (13) such that system performance is optimized.

Abstract: An optical communications system comprises, among other things, a laser source; an optical waveguide interconnected to the laser source to carry an optical signal from the source to an optical receiver; an optical receiver interconnected to the optical waveguide for decoding the signal; and a mechanical modulator adapted to substantially continuously mechanically perturb a portion of the optical waveguide so as to reduce Rayleigh backscattering from the optical waveguide.

Abstract: The present invention relates to an interferometer useful in the interleaving and de-interleaving of optical wavelength channels. Typically the invention comprises a beamsplitter and two resonators, e.g. GT etalons or ring resonators. The beamsplitter splits an input beam of light into a first sub-beam directed to follow a first path and a second sub-beam directed to follow a second path. The first resonator has a first effective cavity length and receives the first sub-beam. The second resonator has a second effective cavity length and receives the second sub-beam. The first path and the second path have an effective optical path difference approximately equal to one-half the first effective cavity length. In one embodiment, the front plates of the GT etalons each have a different reflectivity, and are selected to provide a desired spectral response.

Abstract: A method of reducing speckle includes dividing a laser illuminated area into phase cells, subdividing the phase cells into cell partitions, and applying a temporal phase variation to the cell partitions within an integration time of an intensity detector viewing the laser illuminated area. An apparatus for reducing speckle includes illumination optics, a diffuser, and projection optics. The illumination optics couple a laser illumination to the diffuser, which is located in a first image plane. The diffuser divides the laser illumination into the phase cells and subdivides the phase cells into the cell partitions. The diffuser also applies the temporal phase variation to the cell partitions. The projection optics project an image of the first image plane onto a diffuse surface. A display apparatus adds a light modulator to the apparatus for reducing speckle and places the light modulator in a third image plane located between a laser source and the diffuser.

Abstract: An optical clock multiplier comprises a phase modulator (12) to shift a phase in pulse duration of an input optical clock pulse by &pgr;, a polarization mode dispersion device (16) having a predetermined time difference between first and second polarizations orthogonal to each other to divide an output light from the phase modulator into the first and second polarization components, and a polarization device (20) to extract one of polarization components in a third polarization practically inclined at an angle of 45° against the first polarization and a fourth polarization orthogonal to the third polarization out of the output light from the polarization mode dispersion device.

Abstract: The invention relates to a modulation controlling circuit for supplying a modulating signal to an external modulator that outputs a modulated optical signal, while setting a proper operating point in the external modulator. The external modulator that operates in cooperation with the modulation controlling circuit of the invention enables high-quality modulation at a wide bit rate range. Therefore, in an optical transmission system or a measuring instrument to which the invention is applied, the characteristics and the performance are improved and the operation is made stable without loss of advantages of the external modulator.

Abstract: A low voltage optical phase modulator includes a splitter having an input, a first output, and a second output. The input receives an optical signal and is split between the first and second outputs. A phase adjustment element is coupled to the second output and produces a predetermined optical shift in the optical signal to produce a phase-shifted optical signal. A first electroabsorptive element is coupled to the first output and blocks transmission of the optical signal when the first electroabsorptive element is activated with a low voltage. A second electroabsorptive element is coupled to the phase adjustment element and blocks transmission of the phase-shifted optical signal when the second electroabsorptive element is activated using the low voltage. An optical combiner having a first combiner input, a second combiner input, and a combiner output is coupled to the first and second electroabsorptive elements and receives the optical signal and the phase-shifted optical signal.

Abstract: For the purpose of optical transmission, narrow pulses are generated with the aid of at least two modulators (M1, M2), in which use is made of drive signals (TS1, TS2) of the same frequency with different amplitudes, the modulators having different working points.

Abstract: The invention relates to an interleaver circuit (10, 10′) for interleaving optical signals, comprising a first and a second input port (12, 14), an output port (16), a first optical filter (18; 18′) that has a first filter function with periodic passbands (32, 34, 36) and is connected to the first input port (12), a second optical filter (20; 20′) that has a second filter function with periodic passbands (38, 40) and is connected to the second input port (14), and an optical interleaver (22). The latter comprises a multiplexing port (23) connected to the output port (16) and two de-multiplexing ports (24, 26) connected to the first input port (12) via the first optical filter (18; 18′) and the second optical filter (20; 20′), respectively. At least one optical filter (18, 20; 18′, 20′) is tunable such that the passband frequencies are collectively shiftable without altering the periodicity of the filter function.

Abstract: An optical switch for an optical network, which can switch a light beam from and input fiber to an output fiber quickly and without expensive intermediate conversions to electrical form. The optical switch changes the relative phase of the individual portions of a cross section of a wave front of a beam using wave front interference and can be used in packet switching with switching speeds of about 10 nanoseconds. These optical switches use a phase spatial light modulators (PSLM) that include an array of phase shifting elements preferably of Gires-Tournois interferometers. Each of the phase shifting elements has either a stationary reflective surface with a movable reflective surface or an electro-refractive medium sandwiched between two stationary surfaces. In the first embodiment, the stationary reflective surface with a movable reflective surface is kept a known distance apart by applied potential.