Showing papers on "Optical modulator published in 1979"

Guided-wave acoustooptic Bragg modulators for wide-band integrated optic communications and signal processing (Invited Paper)

Abstract: This paper presents a selective review of planar guided-wave acoustooptics, including some of the most recent results. The emphasis is on those aspects which relate to wide-band multichannel optical communications and real-time signal processing. First to be discussed are the analytical and numerical techniques required for the treatment of a Bragg modulator which uses a single aperture SAW transducer. The frequency responses generated for Y -cut LiNbO_3 waveguides using a digital computer serve as the basic data for the design of such a basic modulator. Next the key device parameters relevant to modulation and signal processing are discussed. The design parameters and procedures for wide-band Bragg modulators and deflectors are then established. Finally, some potential applications of such wide-band modulators and deflectors in optical communications and RF signal processing together with the best measured performance figures are described.

Effects of external perturbations on LiNdP 4 O 12 lasers

Abstract: Resonance-like behaviors and spiking oscillations were observed in the LiNdP 4 O 12 (LNP) laser by placing a moving light scattering object across the output beam. Intensity fluctuations, corresponding to relaxation oscillations, were observed when the LNP laser light beam was coupled to an optical modulator as well as to an optical fiber. Classical rate equations, including a loss modulation term, were given to explain the observed phenomena. All the intensity fluctuations due to external perturbations were found to be completely suppressed by using a YIG Faraday rotation optical isolator.

Fiber optical measurement apparatus

Abstract: The invention relates to an optical measuring device for measuring physical magnitudes such as position, speed, acceleration, force, pressure, elongation, temperature, etc., comprising at least one optical fiber for conducting light between an electronic unit and a transducer forming an optical modulator which is directly or indirectly influenced by the quantity being measured and, in dependence thereon, modulates the light emitted to the transducer. The transducer contains at least one optical filter having spectrally varying absorbing and/or transmitting and/or reflecting characteristics within the spectra of the emitted light. The light filter generates one or more stabilizing signals for the fiber optic and optoelectronics, and possibly one or more measurement signals within one or more wavelength ranges.

Interferometer with a single-mode waveguide coil

Abstract: An interferometer with a single-mode optical waveguide wound in a coil which waveguide has a surface at each end for the acceptance of the light into the waveguide ends and for the display of light in the waveguide characterized by an improvement comprising at least one optical directional coupler having four input/output ends being provided. One of the four input/output ends is coupled into one of the pair of ends of the waveguide forming the coil and a second of the input/output ends is coupled to the other end of the pair of ends of the waveguide forming the coil. Preferably, the coupling of light from a light source utilizes a second additional directional coupler, which has an input/output end coupled to a third input/output end of the first mentioned coupler and the device preferably has a pair of light sensitive elements with one of said elements receiving a superimposed image from the fourth input/output end of the first mentioned coupler and the other receiving light from one of the input/output ends of the second or additional coupler.

Impedance characteristics of double-hetero structure laser diodes

Abstract: The effects of the onset of lasing on the I-V characteristics, the impedance characteristics and the light modulation characteristics of laser diodes have been discussed by introducing the rate equations which involve carrier diffusion process in the active layer interacting with the radiation field intensity The static I-V characteristics exhibit a kink at lasing threshold current, reflecting the decrease of effective lifetime of carriers Effective carrier lifetimes decrease with increasing light intensity, which results in a steep attenuation of injected carrier density in the active region The impedance and light modulation characteristics are obtained in the small signal approximation The small signal light modulation characteristics depend strongly on whether the laser diode is excited by the constant current modulation or the constant voltage modulation The impedance is changed drastically by the onset of lasing and exhibits a resonance which coincides exactly with the optical modulation resonance frequency

Apparatus for measuring pressure by absorption spectrum change

Abstract: A fiber optical measuring device for measuring physical magnitudes comprises a transducer having a body constituting an optical modulator. The optical properties of the modulator are dependent on the mechanical forces acting on the modulator. The optical property utilized is the pressure dependency of at least one light-absorption edge of the absorption spectrum of the modulator material. Optical fibers are used for leading light into the modulator and for leading out light that has passed through the modulator.

Device for receiving and transmitting coded light signals and IFF system incorporating this device

Abstract: A device to receive coded light signals and to transmit modulated light signals in the direction of the incident signals, comprising an omnidirectional detection device composed of a plurality of radiation sensors, an optical device for reflecting the light signal in its own direction, a recognition and encoding circuit connected to the sensors and an optical modulator operable to prevent the reflection of the light signal, the modulator being controlled by the recognition and encoding circuit, the modulator comprising a shutter rotatable about the axis of the detection device, a member for driving the shutter controlled by the recognition and encoding circuit and a second circuit connected to the outputs of the sensors to determine which one of the sensors receives the incident beam, the second circuit delivering to the drive member a control signal for setting the initial angular position of the shutter.

Optical apparatus for the reproduction of images using a liquid crystal cell

Abstract: This invention relates to an optical apparatus for the reproduction of images, comprising an optical modulator formed by a nematic liquid crystal cell the length of which is at least equal to the width of the paper to be printed, comprising on an inner surface N electrodes corresponding to the N points forming a line and a counter electrode on the other surface, this cell being placed between two polarizers. The modulator produces or does not produce extinction of the radiation for each point, depending on whether a voltage is not or is applied between the counter electrode and the electrode corresponding to the point which is to be reproduced. The light-sensitive paper travels against the second polariser and is printed by a line of light modulated spatially along the N points. To ensure that the optical modulator thus produced functions satisfactorily, the light source should flash on when the liquid crystal has reached a stable state, i.e., just before the fluctuation in the control voltage applied between the counter electrode and the electrodes.

A 1 Gbit/s integrated optical modulator

Abstract: A waveguide directional coupler modulator is demonstrated with a bandwidth of 1 GHz and a rise time of 590 ps. An analysis of the electrical parasitics is presented and the device response is found to be transit-time limited. The scaling of the frequency response is shown to be characterized by a bandwidth-length product of 1.1 GHz - cm.

Electro-optical light modulators, light wavelength multiplex signal transmitting apparatus and light wavelength separating switches utilizing the same

Abstract: In a light wavelength separating modulator there is provided a crystal manifesting an electro-optical effect which rotates the principal axes of the refractive index ellipsoid of the crystal, a plurality of juxtaposed electrodes formed on the crystal in the direction of transmission of light and having different periods, and means for applying modulation signals to respective electrodes. When light generated by a light source, having a light spectrum where half value bandwidth exceeds 100A, is transmitted through the modulator, a light wavelength multiplex signal transmitting apparatus is obtained; whereas when a birefringence body is located on the output side of the modulator, a light wavelength separating switch is obtained.

High speed ambiguity function evaluation by optical processing

Abstract: An optical system which computes the ambiguity integral using one-dimensional spatial light modulators rather than the two-dimensional data masks or spatial light modulators used in the prior art is revealed. The coding is accomplished by compressing the light beam along one dimension, passing it through a one-dimensional spatial light modulator, and re-expanding the beam along the compressed dimension. The signal may be rotated to produce a linear dependence. In the preferred embodiment an acousto-optic cell commonly known as a Bragg cell is the one-dimensional spatial light modulator chosen.

Optical modulator with ringing suppression

Abstract: Ringing caused by acoustic resonances in an electro-optical crystal modulator and commencing at the trailing edge of a pulse may be suppressed by the combination of a second electro-optical crystal and a polarizer. The polarization of the ringing passing through the second crystal is rotated 90° by applying an appropriate voltage to the second crystal at the trailing edge of the pulse. The polarizer, properly oriented, then blocks the ringing. The crystals may comprise such materials as Cadmium Telluride or Gallium Arsenide.

Light modulator or light switch with variable transmission and method of making the same

Abstract: This variable transmission light modulator or light switch includes two mirrors (3, 5) consisting of dielectric layers with at least two different refractive indices and, between the two of them, an active substance (4), two current-conducting layers (2, 6) - one for each mirror - being provided, and it being possible for the transmission of the device to be varied by low voltage The light modulator or light switch is produced at least partially using vacuum technology

Electro optical modulation system

Abstract: An electro optical modulation system utilizes electro optical effect of a crystal. The electro optical modulation system comprises a voltage comparator for comparing a modulated light intensity signal with a reference voltage; and a bias controlling device which feeds a differential signal between mean value signal of the output of the voltage comparator and mean value signal of the inverted output of the voltage comparator, to an optical modulator as a bias voltage.

Scophony light valve

Abstract: The optical modulator in a flying spot scanner converts the electronic video signal into a corresponding temporal modulation of a light beam. An alternative configuration, which directly exploits the spatial modulation of an acoustooptic cell, is the Scophony scanner, first developed by the Scophony Laboratories of London during the 1930s. The Scophony scanner responds like a coherent imaging system, whereas the flying spot scanner performs like an incoherent imaging system, when the light source is spatially coherent. The Scophony response is intimately linked to the concepts of FM blur and the deflector as video spectrum bandpass filter.

Optical apparatus and process for recording information and record carrier formed by this apparatus; optical apparatus for retrieving the recorded information

Abstract: Apparatus and process for writing video information in the form of a frequency-modulated signal upon a disc member and for retrieving the recorded information. The disc member (10) formed by the writing apparatus is also described. The apparatus includes a laser (30) as a source of write light beam (29) and a write optical system for directing the focused beam to a moving disc member. The member comprises a substrate carrying a light responsive coating (26) at least on one surface. The write optical system includes an optical modulator (44) that charges the intensity of the write laser beam with respect to a predetermined threshold intensity sufficient to form a first type of indicia in the coating and a feedback apparatus that stabilises the operating level of said modulator. The read optical system includes a light sensing circuit (158) for changing the intensity-modulated reflected-light beam to a corresponding electrical signal. A triangular frequency modulator (Figure 14C) for driving a Pockels cell (68), for obtaining a sinusoidal-shaped light-modulation output signal from the linear polariser (70) and a bias circuit (264) employed for removing the second harmonic intermodulation distortion of the modulated write beam, are described.

Transmissive surface layer effect electro-optic device for use in optical modulators and the like

Abstract: An electro-optic device for use in optical modulating systems and the like comprises a pair of optically transparent, multi-element interdigital electrodes which are sandwiched between a pair of electro-optic crystals, whereby symmetrical fringing fields having a predetermined periodicity widthwise of the device are coupled into the crystals when a voltage is applied to the electrodes, thereby creating substantially identical phase diffraction gratings in the crystals for sequentially diffracting an incident optical beam.

Interferometer with a coil composed of a single mode waveguide

Abstract: An interferometer with a single mode optical waveguide wound in a coil, which waveguide has an end surface at each end for the acceptance of light into the waveguide and for the emitting of light that is in the waveguide, a beam dividing element for superimposing a portion of light from each of the end surfaces of the waveguide into two separate superimposed beams of light characterized by a polarizer arranged in the path of each of the superimposed beams of light for filtering the light as it is received by a beam receiver, which may be a screen or a light sensitive element such as a photo diode. The beam splitting element may be a beam splitting element having a reflective surface such as a partially reflective mirror or a beam splitting cube or may be optical directional couplers.

Magneto-optical light modulator

Abstract: The light source produces two colors and is combined with an optical dispersive element for the wavelength-dependent rotation of the plane of polarization of a light beam transmitted by the dispersive element, the layer having a modulation characteristic to enable each modulation element in combination with the polarizer to transmit or to block one color or the other color of the two colors produced by the light source.

Optical modulation device

Abstract: The disclosed device comprises two duty ratio detectors for detecting respective duty ratios of an input modulation signal modulating an incoming light beam and a modulated intensity-of-light signal proportional to an intensity of an outgoing light beam, a differential amplifier for producing a difference between both duty ratios, and a bias control for supplying this difference to an optical modulator through a bias amplifier.

Preliminary experiment for stabilizing unmodulated He‐Ne laser to an iodine hyperfine component

Abstract: First‐ and third‐derivative signals of saturated absorption in iodine 127 molecular vapor are detected by using a frequency‐modulated 190‐cm‐long 633‐nm He‐Ne laser with a Fox‐Smith–type resonator and an iodine absorption cell which is set outside of the resonator. Aiming to stabilize the laser with unmodulated output, a retroreflector‐type optical modulator is added to the above system, and the first‐derivative signal is obtained by external modulation. Comparing the obtained signal with those obtained by the frequency‐modulated laser, possibilities to detect the third‐derivative signal by using the optical modulator and to stabilize the unmodulated laser are found.

Controlling Light with Light: Optical Bistability and Optical Modulation

Abstract: A simple GaAs etalon has been used to observe optical bistability, pulse shaping, and modulation of one light beam by another. Such devices may lead to all-optical, high-speed computation and communication; all-optical signal processing may be appropriate with the advent of low-loss, high bit-rate optical transmission systems. The etalon consists of a sandwich of 4 µm of GaAs between 0.2 µm layers of Al0.42Ga0.58As grown by molecular beam epitaxy. Nonlinear laser spectroscopy was used to identify appropriate non-linearities essential to the operation of this device.

Response of a Bi12SiO20 Pockels readout optical modulator to x rays

Abstract: Response of a Pockels readout optical modulator to x rays has been measured. Sensitivity data and results of cursory imaging experiments suggest novel applications such as on‐line radiography.

Resolution of an electron-beam spatial light modulator using a DKDP crystal

Abstract: An investigation was made of a spatial light modulator based on an electro-optic DKDP crystal. A theoretical and experimental study was made of the frequency-contrast characteristic and resolution of the modulator.

Optical device for and method of amplitude modulation of light beam

Abstract: An optical modulator suitable for use with a collimated light beam having a moderate cross section and a fast response time and operational at relatively low voltage includes a glass prism 12 and a smooth metal surface 14 that are separated by an adjustable gap 18. The gap is filled with air, having an index of refraction lower than the prism. A beam 22 of monochromatic light is passed into the prism at a specific angle of incidence 0 to undergo total internal reflection at the glass prismgap interface. A change of approximately 1 micron in the thickness of the gap is sufficient to change the reflectivity from greater than 95% to essentially zero. The size of the gap is mechanically adjusted and this mechanical device 20 determines the frequency response of the light modulation.

Stereoscopic image display device

Abstract: PURPOSE:To make it possible to display a stereoscopic image by reproducing necessary picture elements with the use of plural holograms which are constituted such that the three-dimensional optical elements or the picture elements are arranged and reproduced. CONSTITUTION:The beam, which has its intensity modulated in intensity by an optical modulator 2 and which comes from a laser beam source 1, is deflected through two optical deflectors 3 and 5 in a preset direction and then is condensed by a condensing lens 6 thereby to reproduce a hologram recording medium 8, in which a plurality of holograms 10 corresponding to plural optical stops 11 are recorded independently three-dimensionally while using the light beam having passed through the lens 6 as a reproduced light. The intensity pattern of the stereoscopic image is produced by modulating the reproduced light, which corresponding to the hologram 10 for reproducing any optical spot 11, at the respective optical spots acting as the picture elements by means of the modulator 2. The stereoscopic image thus reproduced is observed as the enlarged stereoscopic image through a lens 9.

Microchannel Spatial Light Modulator As A Storage Medium

Abstract: The Microchannel spatial light modulator is an optically-addressed spatial light modulator that is being developed for low-light-level, real-time, optical signal processing. In addition to its framed or continuous real-time mode of operation, it can also be used for short-time (hours), low resolution (less than 20 cycles/mm) optical information storage. In this Paper we describe the structure of the device, its principles of operation, some of its preliminary characteristics, and the first attempts at optical information storage.

Theory and Experiment on Coupled-Waveguide Optical Modulators with Schottky Contacts

Abstract: Coupled-waveguide optical modulators with Schottky contacts are analysed in two waveguide configurations, namely, in embedded-waveguide configuration and in rib-waveguide configuration. It is shown that the heterostructured embedded-waveguide device is suitable for efficient modulation and that the homostructured rib-waveguide device has fairly small modulating power per bandwidth P/Δf in spite of its simpler structure. GaAs homostructured rib-waveguide devices including those with two sections of alternating Δβ were fabricated, and optical modulation was carried out at the light wavelength of 1.06 µm.