Showing papers on "Optical modulator published in 1980"

Traveling wave optical modulator using a directional coupler LiNbO 3 waveguide

Abstract: Fabrication methods for low drive voltage and broad-band LiNbO 3 waveguide directional coupler optical modulator are described. Optical waveguides were prepared by conventionaly Ti in-diffusion into LiNbO 3 c -cut plate. To obtain wide-band frequency response, traveling wave electrodes were used. Electrode characteristic impedance measured by time domain reflectometry method coincided well with the calculated value by conformal mapping. Measured electrode conductor losses followed square root of frequency. To reduce electrode conductor losses, asymmetric and 3-μm thick Al electrodes were used. Directional coupler optical modulator frequency response was analyzed, using the phase difference average value along the propagation directions. Calculated value by this method coincided well with measured value obtained by a swept frequency technique. The characteristics of this modulator at the 1.317-μm wavelength are as follows: 100 percent modulation voltage is 4 V, extinction ratio is 17 dB, optical insertion loss is 5.4 dB, 3-dB bandwidth is 3.6 GHz, and rise time is about 400ps.

Multi-channel optical sensing system

Abstract: A multi-channel optical sensing system for measuring temperature at a number of measuring points includes optical sensors, each of which modulates the incident light beam by light intensity modulation according to the temperature at each measuring point and returns the modulated light beam back to the same optical path. The individual optical sensors are coupled to optical fibers which transmit respective light beams of different wavelengths. These optical fibers are coupled to a wavelength multiplexer/demultiplexer unit, which receives modulated light beams and supplies non-modulated light beams. This unit spectroscopically multiplexes the modulated light beams and spectroscopically demultiplexes the non-modulated light beams. It is optically coupled to another spacially spaced-apart wavelength multiplexer/demultiplexer via an optical system for transmitting light. This other wavelength multiplexer/demultiplexer unit spectroscopically demultiplexes the modulated multiplexed light beam into component light beams supplied to respective other optical fibers and also spectroscopically multiplexes light beams of different wavelengths supplied from the respective other optical fibers. To each of these other optical fibers are coupled a light source unit and modulated light and non-modulated light detecting units.

High-speed operation of LiNbO 3 electro-optic interferometric waveguide modulators

Abstract: High-speed optical intensity modulation is reported for the first time using single-mode electro-optic interferometric waveguide modulators formed from Ti-diffused waveguides in LiNbO3. For cw 0.633-μm optical inputs, modulation at rates up to 1.4 GHz has been achieved by driving the interferometer through multiple-π phase shifts. Envelope modulation of a 275-MHz optical pulse train from a cw mode-locked frequency-doubled Nd:YAG laser with a 68.9-MHz drive signal has also been demonstrated.

Single component transceiver device for linear fiber optical network

Abstract: A single component transceiver device for a linear single fiber optical network which allows both reception and transmission of light information onto a linear data line. One embodiment discloses a light source 10 which would apply modulated light signals, or an unmodulated light carrier, onto an optical medium at the end 12 thereof. This light would reach point 14 along the optical fiber and be detected and/or further modulated by diode 16 and this light information is introduced unidirectionally onto the optical fiber. A second embodiment would include a diode 52 along an optical fiber which would detect and/or radiate light signals bidirectionally along an optical fiber. A proposed light transceiver 90 which could be utilized with the above two embodiments is also disclosed.

Method for measuring the rf modulation characteristics of Mach-Zehnder-type modulators

Abstract: We derive the frequency spectrum of the light output from Mach‐Zehnder‐type waveguide modulators and demonstrate the excellent agreement of the experimental results with theory. From the measurement of the frequency spectrum the rf modulation characteristics can be deduced. This method is advantageous as it permits the evaluation of the modulator performance up to frequencies above 1 GHz without requiring high optical power, thus eliminating the risk of optical damage in the waveguides. The tested modulator shows a 3‐dB cutoff frequency of 1.1 GHz; the figure of merit is Q≈130 μW/MHz.

Some implications of the cutoff-rate criterion for coded direct-detection optical communication systems

Abstract: The cutoff rate is derived for a digital communication system employing an optical carrier and direct detection. The coordinated design of the encoder, optical modulator, and demodulator is then studied using the cutoff rate as a performance measure rather than the more commonly employed error probability. Modulator design is studied when transmitted optical signals are subject simultaneously to average-energy and peak-value constraints. Pulse-position modulation is shown to maximize the cutoff rate when the average-energy constraint predominates, and the best signals when the peak-value constraint predominates are identified in terms of Hadamard matrices. A time-sharing of these signals maximizes the cutoff rate when neither constraint dominates the other. Problems of efficient energy utilization, choice of input and output alphabet dimension, and the effect of random detector gain are addressed.

4-Bits digitally driven integrated amplitude modulator for data processing

Abstract: A digitally driven integrated-optical amplitude modulator, acting as a digital-analogue convenor, has been fabricated on a LiNbO3 substrate. It can be driven by 4-bits digital circuitry with a command voltage of 2.6 V.

Light intensity modulator in an integrated optical circuit with feedback means

Abstract: The invention relates to a light intensity modulator, in integrated optics and an integrated optical circuit comprising such a modulator. The modulator comprises a two-arm interferometer in which there is created by electro-optical effect, a phase shift controlled by a modulating voltage between the light waves propagated in the two arms. It is characterized by a feedback loop comprising a light separator placed on the output guide of the interferometer, and a photodiode collecting the fraction of output intensity from the separator and supplying an electric voltage which is superimposed in the interferometer on the modulating voltage. Thus linearization of the output intensity-modulating voltage response curve is obtained.

Dual-frequency optical pumping for spin-polarizing a lithium atomic beam

Abstract: A lithium-6 atomic beam is spin-polarized by means of optical pumping with a single-mode dye laser operating on the resonance transition. Simultaneous pumping of both hyperfine substates is achieved by frequency-splitting the laser light with an acousto-optic modulator. A polarization dependent signal, obtained by probing the optical activity of the beam with linearly polarized light, is utilized in a microprocessor-controlled laser stabilization scheme. The polarization is analyzed with a sextupole magnet and its overall value is 0.70 for an intensity of 1×1014 atms s−1. By reversing the sense of circular polarization of the pumping light the atomic beam polarization is easily reversed in direction.

Apparatus for measuring electrical or magnetic fields by absorption spectrum change

Abstract: A fiber optical measuring device for measuring a magnetic or electric field comprises an optical modulator influenced by the field. The optical properties of the modulator are dependent on the magnetic or electric field acting on the modulator. The optical property which is made use of is the field dependence of at least one absorption edge of the radiation absorption spectrum of the modulator material. Optical fibers may be used for feeding light into the modulator and for leading away light that has passed through the modulator.

Optical modulators and apparatus including such modulators

Abstract: An optical modulator which is capable of passing the greatest intensity of light incident upon it when the light incident upon it is either unpolarized or has a partial or variable state of polarization, comprises a beam splitter (1) to resolve the light beam incident upon it into two plane polarized components having mutually perpendicular polarization states, one or more electro-optic cell or cells (2,18,19,22,23) which is or are arranged to receive both components of the light beam and, in use change the state of polarization of both of the components to a corresponding extent in dependence upon an electrical modulation signal applied to it or them. The optical modulator also includes analyzer means (1,17) arranged to receive the output from the electro-optic cell or cells (2,18,19,22,23) the arrangement being such that the intensity of the light output from the analyzer means (1,17) is a function of the change of the state of polarization generated in both components during their passage through the electro-optic cell or cells (2,18,19,22,23). The beam splitter and the analyzer means may be formed by the same piece of apparatus (1) and in this case the modulator preferably includes a half wave plate in the light path of both components to change their polarization states.

Optical surface wave mode converters and modulators utilizing static strain-optic effects

Abstract: Periodic perturbations of dielectric waveguides can be obtained by an evaporated SiO 2 thin film grating through the static strain-optic effect. These waveguides are applied to TE-TM mode converters and modulators in Ti-diffused LiNbO 3 waveguides. Using a coupling length of 3 mm in an optical surface waveguide, we have demonstrated a TE-TM mode conversion efficiency of 80 percent and a TE-TM mode modulator with 100 percent modulation with an applied field of 2 V/μm. A theoretical analysis of a reflector for a semiconductor laser waveguide is also described.

Electro-optical modulator for randomly polarized light

Abstract: Electro-optical apparatus for modulating a randomly polarized light beam is disclosed. The apparatus includes an electro-optical cell and a plurality of optical elements configured to polarize the randomly polarized light beam into two light beam components and to guide the light beam components along two respectively corresponding sets of optical paths, a portion of each set of optical paths passing colinearly through a predetermined axis of the electro-optical cell. Each set of paths are combined to reform an associated portion of the randomly polarized light beam which is exited at a corresponding exit surface of the apparatus, the reformed exited portion, in each case, being a function of the energization of the electro-optical cell. In one application, the electro-optical apparatus is disposed in the optical cavity of a laser system and operative therein as a Q modulator wherein the Q of the laser cavity is dependent on the energization level of the electro-optical cell.

Spatial light modulator and process of modulation

Abstract: Coherent light such as a laser beam is spatially modulated by causing it to interact at a photosensitive material such as a crystal with a focussed image of non-coherent light An electric potential is applied to the crystal either transversely to the direction of the light or in line with the direction of the light according to either the Kerr effect or the Pockels effect Typical crystals include Bismuth-silicon-oxide and strontium-barium-niobate

LiNbO 3 and LiTaO 3 Microchannel Spatial Light Modulators

Abstract: The Microchannel Spatial Light Modulator (MSLM) is a relatively new, highly sensitive, optically-addressed light modulator that is being developed for low-level-light, real-time, optical information processing. This Paper presents an update of recent progress on the development of the MSLM. Vacuum-sealed and demountable devices employing electro-optic crystals of LiTaO3 and LiNbO3 respectively, are evaluated. These devices are found to have similar characteristics. A halfwave exposure sensitivity of 8.4 nJ/cm2 and a long-term optical information storage time of more than two weeks have been demonstrated with the vacuum-sealed LiTaO3 device; the demountable LiNbO3 MSLM has been cycled at 10 frames per second.© (1980) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Ccd driven integrated optical modulator array

Abstract: A CCD driven integrated optical modulator array including an array of chirp grating optical lenses implemented on the surface of an electro-optical crystal such as LiNbO3 or LiTaO3, a plurality of channel waveguides and a thin metal film pattern on the surface of the waveguides for modulating the optical waveform in each channel. The thin metal film form planar capacitors, each of the capacitors being electrically connected to the output circuit of a corresponding semiconductor device, such as a CCD array. The CCD array is implemented on a semiconductor wafer bonded to the electro-optical crystal. Signals in each optical channel in the electro-optical crystal are thereby modulated by corresponding circuit elements associated with corresponding CCD channels implemented on the major surface of the semiconductor wafer.

Optical method for current measurement - uses magneto=optical interaction between field around wire and laser light passing through coiled optical fibre

Abstract: The system uses a laser (3) producing a beam of light (21) which is linearly polarised The light passes through a half-wave plate (4) before entering an optical cube (5) The cube splits the beam into two parts (22,23) One part of the beam is sent via further optical components (6,8) to one end of an optical fibre (2) The fibre is coiled around a former (1a) on the current carrying wire The light passes through a fibre around the coil and emerges at the other end (2b) to be reintroduced into the optical system Two signals are derived and compared by a differential amplifier (17) to determine the differential modulation between them As a result of the magneto-optical effect between the current and the beam this provides a signal indicating the magnitude of the current

Opto-mechanical device to control the direction of beams of visible light

Abstract: A rotating optical element can be used to produce a rotating beam of light from a fixed incident light beam. This rotating beam of light is directed into a suitable optical element which focuses the beam in only one direction. By use of the device disclosed herein, a beam of light can be reoriented according to the requirements of the user while preserving resolution ability, deflection frequency, and general applicability of the invention to special-purpose applications.

Optical signal processing device

Abstract: An optical system including a radio frequency signal input; a chirp signal input; a source for emitting a beam of radiation; a first acousto-optical modulator disposed in the path of the beam and functioning to modulate the beam with the radio frequency signal to produce a first modulated beam; a second acousto-optical modulator disposed in the path of the first modulated beam to modulate the beam with the chirp signal to produce a third modulated beam; and a single detector disposed in the path of the third modulated beam.

Exposure-Induced Charge Distribution Effects On The Modulation Transfer Function (MTF) Of Electrooptic Spatial Light Modulators

Abstract: The theoretical resolution of an electrooptic spatial light modulator [such as the Pockels Readout Optical Modulator (PROM)] is a function of the electrostatic field distribution arising from stored point charges located within the active electrooptic crystal layer. The Fourier transform of the voltage distribution (which can be directly related to the modulation transfer function) is expressed as a function of the charge location within the electrooptic crystal. In addition, the resultant analytic expression contains the dielectric constants of the blocking layers and electrooptic crystal, and the thicknesses of the three layers. This formulation allows the effects of charge trapping within the bulk of the electrooptic crystal to be modeled. In particular, the low spatial frequency response decreases linearly and the high spatial frequency response decreases exponentially with the distance of the point charge from the dielectric blocking layer/electrooptic crystal interface. Thus the overall sensitivity and resolution are degraded strongly by charge storage in the bulk away from the interface. Utilizing superposition, this formulation can be readily extended to accommodate arbitrary charge distributions arising from different exposure parameters. The spatial frequency response of the PROM is calculated for both analytic (exponential hole/gaussian electron) and iterative (exposure-induced charge transport) continuous charge distributions. The limiting form of the high spatial frequency response is shown to be independent of the particular distribution of volume charge. The implications of these results for device design and operation are discussed.© (1980) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Light intensity correcting device of acoustic optical light deflector

Abstract: PURPOSE:To make the intensity of an emitted beam uniform to obtain accurate read and beautiful recording, by processing intensity difference between the incident beam and the emitted beam of an acoustic optical light deflector electrically and by feeding back it to a driving circuit of a light modulator or a laser light source, or a polarizer. CONSTITUTION:The light beam from laser light source 1 is modulated by acoustic optical modulator (AOM) 2 and is deflected by acoustic optical light deflector (AOD) 5, and a part of the emission light is incident to photosensor 9 by semipermeable mirror 7. Meanwhile, a part of the light emitted from AOM2 is sent to photosensor 8 by semipermeable mirror 4. Output signals of photosensors 8 and 9 are input to differential amplifying circuit 10, and the difference signal between them has the gain adjusted by feedback circuit 11, and the modulating signal is added by adding circuit 12, and the output is sent to driving circuit 3 of AOM2. Otherwise, the output of adding circuit 12 is applied to the driving circuit of laser 1 or driving circuit 6 of AOD5. As a result, accurate signal read and beautiful recording are possible.

New Birefringence Theory And Uses Of The Photo-DKDP Spatial Light Modulator In Optical Data Processing

Abstract: The photo-DKDP spatial light modulator is found to be an excellent candidate real-time and reusable 2-D optically-addressed spatial light modulator. Extensive sensitometry, MTF, and other device data are reported with emphasis on a new field dependent photo-sensitivity and the importance of linear MTF data. A new spatial birefringent modulation transfer function is described and its use in obtaining more linear device response, bias level suppression, phase modulation and 1 msec erase time are noted. New real-time image processing, optical pattern recognition, and optical signal processing applications of this SLM are described with emphasis on the accuracy of the photo-DKDP based real-time experiments.

Method and device for stabilizing the light power carried by an optical fibre

Abstract: 1. Method of stabilizing the light power carried by an optical fiber in which the output power of the light source is controlled by means of a control signal derived from the light beam radiated by a light source, characterized in that as a control signal is used the Rayleigh scattered radiation emanating in a reverse direction from a section of the optical fiber which can be determined according to location and length, in which the Rayleigh scattered radiation is directly proportional to the light power guided in the optical fiber itself.

Effects Of Charge Dynamics And Device Parameters On The Resolution Of Electrooptic Spatial Light Modulators

Abstract: The theoretical resolution of an electrooptic spatial light modulator [such as the Pockels Readout Optical Modulator (PROM)] is a function of the electrostatic field distribution arising from stored point charges located within the active electrooptic crystal layer. The Fourier transform of the voltage distribution (which can be directly related to the modulation transfer function) is derived as a function of the charge location within the electrooptic crystal. In addition, the resultant analytic expression contains the dielectric constants of the blocking layers and electrooptic crystal, and the thicknesses of the three layers. This formulation allows the effects of charge trapping within the bulk of the electrooptic crystal to be modeled. In particular, the low spatial frequency response decreases linearly and the high spatial frequency response decreases exponentially with the distance of the point charge from the dielectric blocking layer/electrooptic crystal interface. Thus the overall sensitivity and resolution are degraded strongly by charge storage in the bulk away from the interface. Utilizing superposition, this formulation can be readily extended to accommodate arbitrary charge distributions arising from different exposure parameters. The implications of these results for device design and operation are discussed.

Optical recording device

Abstract: PURPOSE:To obtain the accurate reproduction data by giving the correction to both the rise and fall timing of the record signal and thus eliminating the extension component of the spot which is caused by the thickness of the light beam CONSTITUTION:Record signal 25 is supplied to rise and fall phase correction circuits 7 and 8 within correction circuit 11 Mixer circuit 9 mixes up the output of circuits 7 and 8, and then gives the phase delay and the phase gain to the rise and the fall respectively to deliver record signal 24 Optical modulator 2 keeps output beam 21 at a high level for the high-level period of correcting record signal 24 and also keeps the output beam at a low level for the low-level period of signal 24 respectively

PLZT modulators for optical communications

Abstract: Techniqus for efficient modulation of multimode unpolariezed light are important for optical communications. Integrated optic and micro-optic modulators were constructed using the electric field induced scattering effects in 9/65/35 PLZT and modulation bandwidths of up to 1MHz were obtained. With proper de bias, a modulation effieciency of 30mW/MHz for 50% modulation indices was achieved in anintegrated optic modulator. The micro-optic modulator was constructed to allow for efficient coupling into optical fiber. The design and performance of these modulators were presented.

Timing signal generating system

Abstract: PURPOSE:To realize the output of high-accuracy timing signals by generating previously the plural number of pulse signals featuring the same frequency and different phases and then delivering selectively the pulse signal which turns first to the phase mode in the form of the timing signal after generating the input pulse. CONSTITUTION:The laser beam is modulated based on the print information and by optical modulator 4 provided at the path of laser beam 3 from beam source 2, and the image is formed on recording medium 6 through reflection via rotary polyhedral mirror 9. Photo detector 12 is installed to drum 5 of medium 6 to detect the scanning timing of scanning beam 11, and thus beam 11 is detected through detector 12 to deliver pulse P1 in the form of the scanning timing information of beam 11. Pulse P1 is then applied to timing signal generator 13, and timing signal S1 is applied to character generation control circuit 14 driving modulator 4 from generator 13. At the same time, reset pulse P2 is generated through circuit 14 with every scanning of beam 11, and generator 13 is reset to generate the high-accuracy timing signal through circuit 13.

Twooway light transmitter

Abstract: PURPOSE:To obtain a two-way optical communication device featuring the small loss and wide band with use of the optical modulator in which the electrode possessing the cycle in the light transmitting direction is formed on the crystal which shows the electrical engineering effect to cause the rotation of the main shaft for the refractive index oval substance of the crystal. CONSTITUTION:The light given from light source 13 is led to optical modulator 11 via polarizing isolator 16 and then transmitted to optical fiber 9 via polarizer 15 and lens 17 after modulation by the signal given from signal generator 12. At the same time, the reception optical signal sent from fiber 9 is led to optical detector 14 via the opposite route to that mentioned above. Modulation 11 is formed by providing the inter-digital electrode onto the crystal plate 1 of lithium tantalate possessing earthed electrode 3, and the maximum conversion efficiency is obtained when the cycle lambda features the specified relation with the wavelength of the incident light.