Showing papers on "Optical modulator published in 1983"

Cancer diagnosis device utilizing laser beam pulses

Abstract: Cancer diagnosis device contains an endoscope comprising a light pipe used to transmit light beams from respective light sources and an image guide used to observe the flesh of the organism during both diagnosis and treatment. The tip of the endoscope faces toward the focuses where a photosensitive material having an affinity to the focuses of cancer has been absorbed so that a treatment for cancer can be performed by exposing the organism affected by cancer to the laser beam. The attainable the laser beam within a focus is thus increased by the use of the laser beam pulse from a first laser beam pulse source. In addition to the above, the cancer diagnosis device contains a second laser beam pulse source used to transmit a light beam to the focuses through the light pipe for making a diagnosis, a selector used to selectively pick up the light beam from the first laser beam pulse source or the second laser beam pulse source, a spectroscope used to obtain the spectral response from emission of light led through the image guide used for observation from the flesh of the organism where fluorescence occurs, an imaging device used to pick up the spectral response, a graphic display used to graphically display the processed spectra picked up by the imaging device, and a controller used to control emission of light from the second laser beam pulse source and also to make the operation of the imaging device synchronize with the second laser beam pulse source.

Electroabsorption by Stark effect on room‐temperature excitons in GaAs/GaAlAs multiple quantum well structures

Abstract: We report the first observation of electroabsorption in GaAs/GaAlAs multiple quantum well structures. We have been able to induce Stark shifts for room‐temperature exciton resonances of ∼10 meV for applied field ∼1.6×104 V/cm in a sample with 96‐A GaAs layers, giving large changes in optical absorption (e.g., a factor of 5 or ∼4×103 cm−1 increase). This should permit optical modulators with micron path lengths and potentially very fast operation.

17‐GHz bandwidth electro‐optic modulator

Abstract: A high‐speed integrated‐optic Ti:LiNbO3 Mach–Zehnder interferometric modulator for 0.83‐μm wavelength operation has been fabricated and characterized. The modulator exhibits smooth, resonance‐free frequency response with a 17‐GHz 3‐dB bandwidth. The modulator has a built‐in phase bias of π/2 for maximum linearity. Complete intensity modulation can be achieved with 120‐mW drive power. Optical modulation was measured up to 18 GHz directly by using a very high‐speed photodiode and indirectly using the swept frequency technique.

High-speed traveling-wave directional coupler switch/modulator for λ = 1.32 µm

Abstract: We have designed and fabricated a Ti:LiNbO 3 waveguide traveling-wave directional coupler switch/modulator operating at \lambda = 1.32 \mu m that exhibits a 3 dB modulation bandwidth of 7.2 GHz, a switching voltage of 4.5 V, and power per unit bandwidth of 7.6 mw/ GHz. Using short drive pulses, optical pulsewidths as short as 58 ps have been generated and directly measured with a high-speed InGaAs/InP p-i-n photodiode. Thick ( \sim 2.8 \mu m) electroplated gold has been used to produce a small gap (5 μm) and low-loss coplanar strip electrode. The 1.5 cm long, 15 μm wide electrode has a dc resistance of 7 Ω and a total microwave power loss of ∼4dB at 5 GHz.

Time- and frequency-domain response of directional-coupler traveling-wave optical modulators

Abstract: We analyze the time- and frequency-domain response of directional-coupler traveling-wave optical modulators (DCTWOM) in which the optical and electrical velocities are not matched. We demonstrate for traveling-wave modulators that a directional-coupler device is intrinsically faster, by nearly a factor of \sqrt{3} for the same drive, than an interferometric device of the same length. We also show, that because of nonlinearities in the directional-coupler response, the switching speed inferred through a numerical analysis in the frequency domain underestimates the impulse response derived directly in the time domain. For a directional-coupler traveling-wave modulator based in LiNbO 3 , the Fourier transformation of the impulse response (33 ps/cm FWHM) indicates a characteristic length-bandwidth product of 15 GHz. cm when microwave loss is neglected. When realistic frequency-dependent losses are included in the frequency-domain calculations, we conclude that a 1-cm-long directional coupler in LiNbO 3 has a large signal 3-dB bandwidth in excess of 10 GHz. We determine the optical response to closely spaced electrical pulses, in order to evaluate the signal encoding bit rate capabilities of the device and its relation to the frequency bandwidth.

Printer head and electrophotographic printer utilizing the same

Abstract: A printer head comprising a light source device, and an optical modulator element for switching the light projected from the light source device, a device for splitting the light projected from the light source device into two polarized light components to form respectively a first light path and a second light path, a device for converting the polarized light of the second light path into light having the same polarization as the light component of the first light path, and a device for directing light of the first light path and/or the second light path to the optical modulator element.

Method for measuring an optical length of light path and a laser interferometer for carrying same into effect

Abstract: A method for measuring an optical length of light path based on use of multiple-beam interference of light and carried into effect by forming an original light beam with two collinear components having mutually independent polarizations and different frequencies in such a manner that when forming each of the following interfering light beams from the preceding one, polarizations of the light components having different frequencies are mutually converted, whereupon the interfered light is converted into an electric signal and its phase is measured, by which the light path optical length is determined. A laser interferometer carrying said method into effect comprises: a laser and arranged consecutively along the direction of run of the light beam: a device for offsetting the frequency of one of the light components, reflecting elements, a polarizing element for separating the light of the interfering beams according to polarization, and a photoelectric converter of the interfered light into an electric signal, as well as a unit for measuring the phase of an electric signal, connected to the photoelectric converter and also a birefringent plate located between the reflecting elements and adapted for mutual conversion of polarizations of the two light components.

Characteristics Of The Linear Array Total Internal Reflection (TIR) Electrooptic Spatial Light Modulator For Optical Information Processing

Abstract: A first order analytical model which describes the imaging performance of the total internal reflection (TIR) linear array spatial light modulator is presented. Two modulator configurations are identified, each with a distinct imaging response. The modulator crystal orientation defines which image response model applies. Several optical readout techniques for converting the optical phase modulation into an intensity modulation are described.© (1983) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

High-speed optical modulation with GaAs/GaAlAs quantum wells in a p-i-n diode structure

Abstract: A new type of high speed optical modulator is proposed and demonstrated. An electric field is applied perpendicular to GaAs/GaAlAs multiple quantum well layers using a "p-i-n" diode doping structure of 4/µm total thickness. The optical absorption edge, which is particularly abrupt because of exciton resonances, shifts to longer wavelengths with increasing field giving almost a factor of 2 reduction in transmission at 857 nm with 8V reverse bias. The shifts are ascribed to changes in carrier confinement energies in the wells. The observed switching time of 2.8 ns is attributed to RC time constant and instrumental limitations only, and fundamental limits may be much faster.

Mach-Zehnder interferometer tuning with Ta 2 O 5 film loading

Abstract: Unwanted path length variations cause integrated optical Mach-Zehnder modulators to have random intrinsic phase and directional couplers to have uncertain coupling lengths. The feasibility of tuning these devices by modifying the propagation constant with Ta2O5 loading of Ti:LiNbO3 waveguides was studied. The intrinsic phase of a Mach-Zehnder modulator was adjusted by this method.

Fourier transformation using an electroabsorptive CCD spatial light modulator

Abstract: The use of a GaAs CCD as a spatial light modulator is described and its application to coherent optical Fourier transformation is analyzed. In this device, the transmission through the two-dimensional buried-channel CCD may be electroabsorption modulated near the GaAs cutoff wavelength since the electric field in each storage well is controlled by the transferred charge. One of the primary advantages of this modulator is the ability to electrically address the device at high speed. Analysis of the two-dimensional modulator with a silicon CCD detector array yields a projected dynamic range approximately equal to the number of modulator array elements. For arrays containing greater than 1000 elements, detector performance and nonuniformities can limit the maximum range to 30-40 dB. The device can also be optically addressed, and in this mode of operation it has a comparable dynamic range to the electrically addressed structure with an optical write energy an order of magnitude lower than liquid crystal or photorefractive light valves. An alternative mode of device operation is a waveguide mode in which the light propagates along an epitaxial layer and is modulated as it passes under a one-dimensional CCD. The detection is done by a second linear CCD. The higher modulation efficiency results in a dynamic range approximately one hundred times the number of elements but is again limited to 30-40 dB because of detector response and nonuniformities.

Picosecond pulse response of broad-band guided-wave interferometric light modulators

Abstract: Picosecond pulse operation of the guided-wave light modulator is reported in this paper. First, we analyze the time responses of phase and intensity modulators of the traveling-wave type, and the modulated output waveforms related to the modulating pulses are discussed. It is shown that there is an optimum interaction (or electrode) length of the modulator whereby the drive voltage is minimized for a desired output pulse width. The traveling-wave push-pull light intensity modulator of Ti-diffused LiNbO 3 waveguides was modulated by a pulse train of 1 GHz repetition frequency, and the modulated output was observed by the image tube streak camera modified for sinusoidal scan at the same frequency. The duration of the modulated light pulses was less than 45 ps, which shows good agreement with the predicted one.

Optical scanning device

Abstract: PURPOSE:To correct position distortion of a scanning light beam to turning fluctuation of a rotary polygon mirror with high accuracy by obtaining an estimated split scanning time by an optical scanning start and end point detector and plural intermediate photodetectors to change a scanning light modulation clock frequency. CONSTITUTION:The light from a laser light source 2 is modulated by an optical modulator 3, polarized in the main scanning direction by the rotary polygon mirror 4, reflected on a plane mirror 6 via an image forming optical system 5 and the image is formed on a moving table 9. Ahead the scanning of a photodetecting region 12, scanning time Ti from an optical scanning start point detector 7 on a mirror surface (i) of the polygon mirror 4 to the optical scanning end point detector 8, split scanning time Tij of the intermediate photodetector adjacent to plural intermediate photodetectors 11, and the scanning time between the detectors 7 and 8 at each mirror surface of the polygon mirror 4 at the scanning of the region 12 are measured. The scanning time between the detectors 7 and 8 of the mirror surface (i) is measured while the scanning of the region 4, the estimated split scanning time of the detector 11 adjacent to the mirror surface (i) of this scanning is obtained based on a difference deltaTi between the obtained result and Ti, and the Tij, then the frequency of the scanning optical modulation clock is changed at each detector 11 based thereupon.

GaAlAs p-i-n junction waveguide modulator

Abstract: Optical communications systems often require modulating elements which change the intensity, phase, or polarization of the light. A waveguide modulator has been fabricated in the form of a GaAlAs p-i-n heterostrueture grown on the

Self-heating effects in electro-optic light modulators

Abstract: The performance of an electro-optic light modulator under high average laser power is studied theoretically and experimentally. Absorption of laser radiation produces a thermal gradient in the electro-optic crystal which degrades the performance of the modulator. Measurements on modulators using KDP and KD*P crystals support the analytical results.

Optical sensing devices

Abstract: Optical sensing devices comprising dual chamber apparatii which use signal and reference light beams together with interferometric methods for detection of physical quantities of interest. The signal part of the chamber experiences the effects of a particular physical quantity to be measured which produces variations in the optical length of the light beam by movement of a mirror, thereby modulating that beam in proportion thereto. Concurrently, the reference beam, of equal pathlength, is passed through an adjacent chamber, isolated from such effects. The modulated signal beam and unmodulated reference beam are then combined to form a fringe pattern, the zero and first order fringes which are superimposed on apertures of an optical fibers, which carry the resultant light beams to a photodetectors for converting the optical signals to proportional electrical signals.

Video disc type recording and reproducing system

Abstract: A video disc recording/reproducing system is improved by preventing secondary or higher order sidebands of the FM modulated video signal from affecting an audio signal multiplexed with the video signal. This is achieved by incorporating a filter means 8a which is connected between a first frequency modulator 1 for modulating a video signal and an adder circuit 3 in which the modulated video signal is combined with a modulated audio signal from the audio modulator 2. The output from the adder circuit 3 is fed via a limiter 4 to an electrical/optical modulator 5.

Multi-channel test system using optical waveguide modulators

Abstract: A test system utilizing modulators responsive to signals to be tested positioned between a source of electromagnetic radiation and a sensor with the signal to be tested coupled to the input of the modulators. Preferably the modulators are positioned in optical wave guides with the modulators being electric-field operated devices to prevent any significant loading of the signals to be tested. Disclosed embodiments utilize light as the electromagnetic energy with lithium niobate substrates having titanium diffused therein forming the optical wave guides. Modulators are provided by planar electrodes affixed to the surface of the lithium niobate substrate to change the electric field across the optical waveguide. Coupling is conveniently provided to the wave guides through fiber optic bundles.

Space optical modulating and demodulating device

Abstract: PURPOSE:To attain the miniaturization as well as a simultaneous optical communication with just a single light source by unifying a corner cube, an optical demodulator and an optical modulator. CONSTITUTION:An optical modulator 1 modulates the light beams of a laser 2 with an information signal 3 and irradiates these modulated beams to a corner cube 4. A semi-transparent reflecting plate is provided to the cube 4 together with a photoelectric transducer attached to the rear side of the cube 4. Thus an optical demodulator 5 is obtained. In such a way, a part of the incident light is supplied to a signal processing circuit 6 after photoelectric conversion and demodulation. While the reflected light sent from the reflecting plate is reflected again by a reflecting plate set at the same cube 4. A modulator element made of a material having an electro-optical effect and containing an optical switch function is provided at the front of the reflecting plate. Thus an optical modulator 8 is formed. Thus the reflected light is modulated with an information signal 7 and reflected in parallel to the incident light. This reflected light is sent to an optical demodulator 9 to receive photoelectric conversion and then supplied to a signal processing circuit 10 after demodulation.

Optical fiber bidirectional transmission system

Abstract: PURPOSE:To extent the distance of transmission, by optically amplifying an optical signal which is transmitted to the opposite direction taking an optical signal transmitted unidirectionally as a stimulating light, with an optical fiber stimulated scattering amplification in an optical fiber. CONSTITUTION:A binary signal of, 100Mb/s from an input terminal 5 of the 1st optical transmitter/receiver 1 is given to an optical modulator 8 via a driver 7, where an output light of an Nd:YAG laser 9 having 1.32mum wavelength and +35dBm of output light level is modulated and the result is transmitted to an optical receiver 13 via a branching filter 4, an optical fiber 10, and a branching filter 12 of the 2nd optical transmitter/receiver 11. Further, a binary signal, 97Mb/s from a terminal 15 is converted into an optical signal having 0dBm of output light level at an InGaAsP semiconductor laser having 1.55mum wavelength and transmitted to the fiber 10 via the branching filter 12. This optical signal, 1.55mum of wavelength is amplified with fiber stimulated scattering by taking the optical signal of 1.32mum wavelength as a stimulated light by 30dB and given to an optical receiver 3.

Disk recording or reproducing system

Abstract: PURPOSE:To improve the use rate of a disk while allowing signal recording and reproduction even in a deficient band area by making recording density lower than that of a main recording part, and recording a coded signal on an internal circumferential surface. CONSTITUTION:A head 4 is moved to an internal circumferential surface and a rotation driver 3 is rotated at a specified speed; and a bar code signal is supplied from a condition signal supplying circuit 11 to an optical modulator 8. Consequently, a radiation beam from a light source 6 is modulated by a bar code signal to obtain a modulated light beam 2, which is projected upon a disk 1 to form a recording area corresponding to the bar code signal. During reproduction, light radiated from a light emitting element 16 is reflected by the disk 1 to reach a photodetecting element 17, and a bar code reader 18 reads the bar code signal. Then, a main recording signal is recorded and reproduced. Consequently, a condition signal in the form of a bar code is recorded by the same recording device with the main recording signal, improving the use rate of the disk.

Electromagnetic Sensor Using Integrated Optic Channel Waveguide Modulator And Polarization Preserving Fibers

Abstract: Guidedwave optical modulators have been designed and tested for applications as electro-optic data link for electromagnetic sensing. The ruggedized data link consists of an injection laser diode pigtailed to a stress induced birefringent fiber, an electro-optic coupled channel waveguide modulator, a graded index multimode fiber for return signal, and a laser driver optical receiver electronics box. The electronics box can be physically separated from the laser diode-fiber-modulator-fiber assembly for ease in field installation. This link has demonstrated a frequency range between 10 kHz to 200 MHz, and a dynamic range of 40 dB at 200 MHz bandwidth operation.© (1983) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Light guide type sensor

Abstract: PURPOSE:To measure voltage, temperature or the like with high resolution without influenced by the variation of laser light source power by providing the titled device with a light guide element projecting two kinds of light, two photodetectors and an arithmetic circuit. CONSTITUTION:Light from a laser light source 1 is made incident to the light guide element 2. The incident light is branched into three components and light rays passed through optical pathes 21a, 21b, 22a, 22b are projected from optical pathes 21, 22 respectively. These light rays pH1, pH2 are changed like sine waves while keeping the phase difference of 90 deg. each other in accordance with the voltage applied between the electrodes 23, 24 and 25, 26. Light PH3 projected from a light path 20 is used as monitor to the light source 1 to remove bias components from respective light PH1, PH2. A signal e3 from a photodetector 33 corresponds to the intensity of the laser light source or the change of the transmission efficiency of an optical transmission line and influence due to the change of the laser light source or the like is removed by reducing the signal e3 by subtracting circuits 41, 42 on the basis of respective signals e1, e2 obtained from photodetectors 31, 32. The arithmetic circuit 50 calculates voltage.

Magnetic transferring recorder

Abstract: PURPOSE:To record a signal with its unevennesses whose dimensions in both directions of the width of the track and the wavelength coincide with a magnetized pattern in a magnetic recording and reproducing device, by irradiating a laser beam upon a magnetic layer through a special optical system. CONSTITUTION:A laser beam from a laser oscillator 11 is irradiated, after the laser beam is modulated by an optical modulator 12 in accordance with a signal 13 to be recorded, upon a magnetic layer 3 or a non-magnetic layer, on which the magnetic layer is to be formed, of a magnetic recording medium 1 through an optical system containing a cylindrical lens 15 and an optical filter 14 which evens the strength distribution of the laser beam at least in the direction of the width of the track on the magnetic layer 3 or the non-magnetic layer within the width of the track, and an unevenness is formed according to the signal 13. The magnetic recording medium 1, on which the signal 13 is recorded by the unevenness, is used as a medium for transferring the recorded information to other magnetic recording media by impressing the magnetic field upon the other media while the medium 1 is in contacted with the other media.

X-ray picture reader and recorder

Abstract: PURPOSE:To obtain an inexpensive device, by allowing the single device to read and register data. CONSTITUTION:A reading and writing means 10 and a picture processing means 20 are constituted in one device. The reading and writing means 10 is equipped with a light source 13 and a photodetector 14. Reading operation is carried out by shunting a modulator 16 off a light beam 19 by a driving mechanism 17. Light decreased in intensity according to the density of an image on a film 15 is made incident to the photodetector 14. For recording, the photodetector is shunted by a driving means 18. Then, a latent image having density corresponding to the modulation of the optical modulator 16 is formed on the film 15.

Optical Sensor With Fibre Optic Links: A Shutter Modulator

Abstract: Results are reported for a series of gratings of different pitch.IntroductionThere is a need in the process industries for intrinsically safe, passive methods of measurement which arereliable, robust, corrosive resistant and free from electrical interference; typical qualities to be measuredare pressure, temperature and flow. Optical fibres seem well suited to provide the necessary data links but tomake effective use of these links, optical sensors are required which modify the light intensity, phase,spectrum or polarization. Mechanical transducers are readily available which translate common processvariables into displacement with ranges varying, for example, from a few millimetres for bellows and Bourdontubes to micrometre movement for diaphragms and temperature- sensing elements. It was decided, therefore todevelop initially, optical sensors, which used the displacement output from an established mechanical sensingelement as its input. Two simple systems of modulating the intensity of incoherent light in an optical sensorby displacement were examined in a feasibility study2: (1) a modulator using a neutral- density photographic

Polarization-independent integrated optical modulator

Abstract: 1. An integrated optical phase modulator device comprising, on the surface of a flat substrate (13) possessing electro-optical properties, at least one waveguide produced by the creation of a zone (7) in which the refractive index is greater than that of the substrate, a first TE guided mode and a second TM guided mode being transmitted in this waveguide (7) at depths of h and h' with respect to the surface of the substrate (13), and a set of electrodes disposed on either side of that waveguide (7) in order to generate electric fields perpendicular to the direction of the waveguide (7), these electrodes being able to partially cover this waveguide (7), this set of electrodes making it possible to adjust the phase shift of the TE and TM guided modes in such a manner that the phase shifts of these two modes are equal, these TE and TM modes having radii W'y and Wy, and W'z and Wz along two perpendicular axes in a plane orthogonal to the direction of the waveguide (7), one of these axes being parallel to the surface of the substrate (13), characterized in that this set of electrodes comprises a single pair of two rectangular electrodes (E8 , E9 ) of a width b, these electrodes being parallel to each other and disposed at the surface of the substrate symmetrically with respect to an axis DELTA' of a direction parallel to that of the waveguide (7), and a distance 2a apart from each other, the two transmitted TE and TM modes having their axes of symmetry DELTA1 and DELTA2 whose projections of the surface of the substrate (13) are respectively at distances c' and c from the axis DELTA', and that the quantities a, b, c, c', h, h', Wy, W'y, Wz and W'z are such that the relationship DELTA nTE = DELTA nTM is true, DELTA nTE and DELTA nTM being the transversal index variations in the substrate corresponding to the two guided TE and TM modes.

Photothermomagnetic track moving method

Abstract: PURPOSE:To perform diverse operation such as information rewriting by moving a track, having an array of pieces of bit information recorded photothermomagnetically, over light irradiation, and erasing and selectively reading the pieces of bit information. CONSTITUTION:A nonreflective coating layer 1c, a reflective film 1d, and a protective 1e are adhered to the thin film obtained by growing a magnetic thin film 1a of garnet on a crystal substrate 1b. This constituted thermomagnetic record reader 1 is fixed to a bias magnetic field generator 2 and applied with a bias magnetic field. Laser light from a light generator 5 is introduced into an optical modulator 6 to form bits on the device 1 through the constitution shown in the figure. Then, the repetitive frequency is set to 100Hz and while the bias magnetic field is unchanged, light irradiation is carried out in the opposite direction to writing. As a result, the bits move to the opposite side to form a new track. For the reading of the bit information, reflected light is introduced into a detector 15 and observed.

Applications Of Multi-Beam Acousto-Optical Modulators In Laser-Electrophotographic Printing And Drawing Machines

Abstract: Application examples of multi-beam acusto-optical modulators in laser-electrophotographic printer and film plotter are given. A family of laser-graphic equipments has been built with a unique acousto-optic modulator: - high quality laser printers - high speed, high resolution film drawing machine Main advantages of multi-beam modulation: it facilitates high speed and high resolution writing and reduced mechanical complexity at the same time, the deflection system is simpler than in single-beam equipments, lower modulation frequency is required at the same writing speed. Printouts and drawings made by the equipments demonstrate our results.© (1983) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.