Showing papers on "Optical modulator published in 1975"

Electro-optic light modulator with branched ridge waveguide

Abstract: A light modulator based on an electro‐optic phase modulation and an optical interference of Mach‐Zehnder type has been demonstrated. The modulator is constructed monolithically with a branching ridged optical waveguide on TiO2‐diffused LiNbO3. The half‐wave voltage is 19 V and the extinction ratio is 34%.

Optical Waveguide Modulators

Abstract: A tutorial survey of recent work on optical waveguide modulators in electrooptic, acoustooptic, and magnetooptic materials is presented. Methods for realizing waveguiding layers in modulating materials and various modulator configurations are considered.

Integrated optical circuits

Abstract: An integrated optical circuit transmitter fabricated on a single semiconductor substrate, which includes a source of optical pulses of variable wavelengths at a predetermined repetition rate. This source may take the form of a surface laser of III-V semiconductor compound material or a mixed ternary III-V semiconductor composition which includes a portion of the substrate and a semiconductor mesa of III-V semiconductor compound material or mixed ternary III-V semiconductor composition mounted on the substrate and having an active surface laser region along the top thereof in which laser radiation is generated in response to the admission of laser radiation through the substrate and the mesa in a direction extending thereto. An optical waveguide is disposed in juxtaposition to the active surface laser region and is coupled thereto to form an evanescent field-coupling therebetween matching the phase velocity of the laser radiation generated in the active surface laser region to that of the optical waveguide for transmitting laser radiation to the optical waveguide. In a more specific aspect, an integrated optical circuit transmitter is disclosed utilizing a laser source to obtain optical pulses of variable wavelengths at a predetermined repetition rate, an optical waveguide transmission path configuration including branch waveguide transmission paths, an optical modulator mounted on the primary waveguide transmission path to impart pulse code modulation to the optical pulse train as provided by the laser source, wherein the optical pulse train in the primary waveguide transmission path may be directed into one or the other of branch waveguide transmission paths in response to activation of the optical modulator, and an acousto-optic switch to enable transfer of the optical pulses from one branch waveguide transmission path to another separate optical waveguide portion upon activation thereof.

Optical-fibre phase modulator

Abstract: A clip-on piezoelectric transducer is described which may be easily attached to a plastics-coated optical fibre and used to phase modulate signals within the glass fibre. The technique is applicable to a 1-way optical telemetry highway.

Broad bandwidth optical modulator and switch

Abstract: A modulator and switch for optical energy includes an optical waveguide dning a path for the propagation of optical energy, a source of microwave energy, and at least one strip transmission line disposed in co-directional proximity relative to the optical waveguide and connected to the source of microwave energy. The strip transmission line is designed to have dimensions and dielectric constants for producing a propagation velocity of the microwave energy substantially equal to the propagation velocity of the optical energy in the optical waveguide. A suitable microwave load is connected to the transmission line for completing an electrical circuit with the source of microwave energy.

High-speed electrooptic waveguide grating modulator using epitaxial ZnO

Abstract: The results of a detailed study of electrooptic waveguide grating modulators are presented. Using low-loss epitaxial ZnO on sapphire waveguides with deposited interdigital electrodes diffraction percentages up to 80 percent at 80 V with rise times below 3 ns are observed. Capacitive power requirements on the order of 4 mW/MHz are predicted. A theoretical description which includes carrier and piezoelectric effects is given and is shown to be adequate for designing this type of modulator. The grating waveguide modulator spatially separates the diffracted from the main beam and thus can be used for switching. In addition, the spatial separation allows a number of these to be cascaded on a common waveguide. These features make it probable that grating modulators will find a variety of uses in integrated optics.

Coupled mode analysis of light modulation in dielectric waveguides

Abstract: A detailed analysis of electrooptic light modulation in optical waveguides is presented. Several important problems of a waveguide modulator, such as the difference of waveguide axes from crystalline electrooptic ones, the distribution of transverse and longitudinal field components of light modes, and the traveling-wave property of the modulating field, are discussed. The analysis is based on the coupled mode theory, regarding the modulation as the coupling among sidebands of unperturbed waveguide modes. The coupled mode equation is derived for the modulation in optical waveguides. It can be solved if the normal modes of the waveguide are given. Actually the equation is solved for the modulation in dielectric slab waveguides and the mechanism of modulation is discussed. The results of the analysis are applied to designing two types of waveguide modulators. In an example (10.6 μm modulator with a GaAs slab waveguide) a new efficient crystal orientation is found. The calculated phase retardation with this orientation is 0.13 rad/(V·cm) with a 1 μm thick slab. Another example of a 0.633 μm modulator using a LiTaO3 crystal as a substrate is also described.

Optical intensity modulator with three−dimensional waveguide

Abstract: A LiTaO3 optical waveguide modulator, in which a laser beam is confined in both transverse dimensions, has been fabricated. The three−dimensional waveguiding operation was achieved by using an ion−etched thin core slab and a slit metal cladding. Waveguide porperties for 0.633− and 1.15−μm laser beams and dc and rf modulation performance for a 1.15−μm beam are described.

Push−pull thin−film optical modulator

Abstract: An electro−optic amplitude modulator was made by placing two channel−defined waveguide phase modulators in the legs of a Jamin interferometer. Using a novel detection method, modulation was observed up to 1.8 GHz, although the roll−off in the modulator response started at about 750 MHz. Full amplitude modulation was produced by 17 V, giving a power band width characteristic for the separate phase modulators of 200 μW/MHz for a modulation index of 1 rad.

Elastomer wave guide optical modulators

Abstract: Optical modulators and methods of modulating light include introducing light to an optical wave guide from a light source. The wave guide is formed of an elastomer film which is deformable by a mechanical or electrostatic force acting to change the cross section of the film and thereby modulate the light passing through the wave guide.

High speed optical matrix multiplier system

Abstract: Matrix-vector multiplication is accomplished by continuous wave polarized ght energy transmitted along a plurality of optical waveguides through modulation by a first optical modulator in response to a column vector type input signal and additional modulation by a second optical modulator in response to a row vector type input signal. The resultant modulated light energy outputs are received by a polarization analyzer for transforming modulations in polarization and phase to commensurate amplitude modulations. A photo-responsive storage and integrating means receives the light energy associated with each of the optical waveguides and develops a cumulative signal representative of the matrix-vector multiplication.

Image information handling device

Abstract: A device for handling output information from an electronic computer or the like at high speed utilizing a light beam, said device including a modulator for modulating a light beam in accordance with an image information signal such as a character, design or other output from a computer or the like, a medium for receiving the modulated light beam, means such as a galvanometer mirror for causing the modulated beam to scan the medium and optical means between the modulator and the scanning means for directing the modulated beam along any one of a plurality of light paths extending to the medium, the optical means being effective to vary the image forming characteristics such as image magnification of the beam incident on the medium.

Device for producing a signal indicating the directional movement required to achieve focus

Abstract: A light focus sensor having first and second grids comprised of interlaced light transmissive and light reflective portions and a rotating optical modulator comprised of a plurality of alternate light transparent and light opaque portions. The modulator portions are half the size of the reflective portions of the grids and the modulator is positioned in relation to the grids such that the phase relationship between the portions of one grid and the portions of the modulator is 180° different than the phase relationship between the portions of the other grid and the portions of the modulator such that the composite signal passing through the modulator is indicative of the directional movement required to achieve focus.

Waveguide Type Optical Modulator Using Kerr Magnetooptic Effects in Ni–Fe Thin Films: Theoretical Study

Abstract: A fundamental analysis of modes in a dielectric guide fabricated on a lossy gyromagnetic substrate has been developed for a thin film waveguide type optical modulator application experimentally discussed in the preceding paper. It is shown that when the substrate is of gyromagnetic material, the propagating modes become hybrid in character. Phase and attenuation curves as well as wave function profiles for such type of modes are computed. Power flow characteristics for the HE0 mode are also discussed. A comparison with the experimental results reported earlier has been made.

Method and apparatus for acousto-optical interactions

Abstract: Method and apparatus for causing light to interact with surface acoustic waves so that the light is either scattered out of or coupled into an optical wave guide. In the case of scattering when the light is propagating in an optical wave guide and chirped surface acoustic waves interact with the light, the light is scattered out of the optical wave guide into a focused beam. The focused beam of light travels in a path parallel to the surface acoustic waves and at the same velocity as the acoustic waves. The focused beam can scan objects to obtain electrical signals corresponding to the optical image of the objects and also the beam can be focused on a plurality of photodetectors to multiplex the light. In the case of coupling when the light is incident on an optical wave guide and the frequency of the chirped surface acoustic waves is selectively varied, the light is selectively coupled into the optical wave guide in a corresponding manner. The selective coupling of the light permits the frequency spectrum and the angular distribution of the light to be analyzed.

Modulation-sensitivity enhancement in electro-optic slab waveguides

Abstract: Analysis of the phase modulation characteristics of electro-optic or acousto-optic waveguide modulators reveals that a significant increase of modulation sensitivity, per unit of applied field, above that of conventional, bulk devices can occur in multimode waveguides with tight confinement. In the limit, an enhancement of as much as a factor of 3 is theoretically attainable. Explicit formulas for relative modulation sensitivity are given for both TE- and TM-mode polarizations, and illustrative curves are presented for a wide variety of structural parameters. Semiquantitative experimental verification of the effect is presented, using results of a GaAs electro-optic thin-film modulator at 10.6 μm.

Optical detector of remote movement including cyclic scanning of target

Abstract: A detector of remote movement in which light from a laser is directed at a target and, on reflection from the target, is mixed with reference light from the laser to produce a Doppler signal denoting the movement of the target The beam of light from the laser is directed through an optical system which brings the light to a focus and thereafter projects the light from the focus at the target The optical system includes a lens which is mounted in a ferromagnetic carrier which can be vibrated in two orthogonal directions each normal to the axis of the light beam and the axis of the lens Coils disposed to produce these orthogonal movements are energized in quadrature so as to produce conical scanning of the beam of light on the target Signals which denote the modulation of the amplitude of the Doppler signal produced by the conical scanning are compared with the driving signals for the coils processed to produce bias signals which are used to bias the mean direction of the beam in a sense to increase the amplitude of the Doppler signal and thereby to control the beam automatically to seek a point on the target which produces a maximum amplitude in the derived Doppler signal

Contribution of thermoelastic stresses to dn/dT of hexagonal and trigonal crystals heated by laser radiation

Abstract: Analytic expressions are obtained for thermoelastic stresses. A calculation is given of the contribution of these stresses to the refractive index of hexagonal and trigonal crystals heated locally by a laser beam traveling along the optic axis. Numerical estimates are given for z-cut LiNbO3 crystals, which are frequently used as optical modulators. It is shown that the thermoelastic stresses in LiNbO3 increase the temperature coefficient of the refractive index dn/dT by 47% compared with the homogeneous heating case.

Efficient modulation and coupling of CW junction laser light using electrooptic waveguides

Abstract: The use of an electrooptical-waveguide modulator to achieve over 80-percent modulation of 7980-A light from a room temperature laser diode operating at 10 mW CW is reported. The insertion loss of the modulator including couplers is 8.5 dB, and the output beam has high coherence.

Integrated optical data bus coupler

Abstract: A data bus coupler having a fiber optic bundle input, a separate optical ulator or detector (described in a concurrent disclosure by the same inventors) attached to each fiber of the bundle for adding information to, extracting information from, or detecting the information conducted by the fiber, and an output wherein the fibers are rejoined into a fiber optic bundle. The optical modulator/detectors are double heterojunction semiconductors that are switched "on" by reverse biasing and with large voltages they may act as photoavalanche diodes when detecting incident radiation.

Epitaxially grown single crystal KTN for thin film optical modulators

Abstract: We report here on the growth, by liquid phase epitaxy, of single crystal thin films of potassium tantalate niobate (KTN), and the preliminary evaluation of these films as light guides and modulators. The material KTN exists over the complete solid solution range 0 < x < 1 in the formula KTa, -,Nb,O,, and exhibits a ferroelectric state for all compositions except those close to x = 0. By suitable choice of x the cubicto-tetragonal ferroelectric transition can be made to occur near room temperature. Advantage of the enhanced electrooptic coefficients' accompanying the transition has been taken in designing room temperature bulk electrooptic devices3 characterized by a particularly low half-wave voltage. Typically, this voltage is a factor ten smaller than for comparable devices using LiNbO, or LiTaO, .3,4

Modulation of laser radiation in liquid thin-film waveguides

Abstract: An investigation was made of liquid waveguide modulators utilizing liquid crystals and nitrobenzene. A 50% depth of amplitude modulation was achieved for He-Ne laser radiation (0.63 μ) by applying a modulation voltage of about 100 V at a frequency of 50 kHz to liquid-crystal thin-film waveguides based on the orientation modulation of absorption. Polarization modulation of the radiation emitted by an injection laser was achieved in a nitrobenzene thin-film waveguide; in this case the depth of modulation was 90% when the modulation voltage was 60 V and its frequency was of the order of 1–2 MHz.

Electro-optic modulators for lasers

Abstract: This paper presents a comparison between internal and external amplitude modulation of a laser using electro-optic modulators. For a high ratio of laser gain to modulator loss, internal phase modulation can give a higher signal output power and a better signal-to-noise ratio, with greater efficiency.

Self-drive of a resonant-piezoelectrooptic light modulator

Abstract: It is demonstrated experimentally that a resonant-piezoelectrooptic light modulator can be self-driven because the active crystal can simultaneously be used as the light modulator and the controlling element of an oscillating circuit.

Resonant piezo-electrooptic modulation

Abstract: ing a 1.06 pm Nd:YAG laser beam onto the cleaved edge of the waveguide. To observe the electrooptic channeling effect, a magnified image of the near field intensity pattern at the waveguide output is focused on an infrared vidicon and displayed on a T.V. monitor. When the input laser beam is focused directly underneath the Schottky barrier at zero bias, little light emerges from the waveguide because of the high attenuation associated with the Pt-Au contact. When 40 V reverse bias is applied to the Schottky barrier, the output intensity increases by a factor of 18. A loss coefficient of 3-8 cm-’ has been determined for these waveguides by measuring the transmission of several lengths of the same sample. The time response of an electrooptic channel waveguide operating as a modulator is determined by focusing the output on an RCA 7102 photomultiplier and driving the device with a delay line pulser having a 2 nsec rise time. A phototube limited rise time of 5 nsec has been measured for a 21 pm wide device implying a minimum bandwidth of 150 MHz. The combined capacitance of this modulator and the transistor header to which it is attached is 7 pF. This gives an RC time constant across 50 R of 0.35 nsec and a projected bandwidth of 900 MHz. The actual device capacitance is estimated to be 5 pF, yielding an ultimate bandwidth limitation of 1.2 GHz. With a reverse bias of 40 V, the modulator current is less than 1 mA. For the measured bandwidth of > 150 MHz, the required modulator power per unit bandwidth is < 300 pW/MHz.