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Showing papers on "Optical modulator published in 1968"


Patent
Jakes William C1
29 Nov 1968
TL;DR: In this paper, a television system that utilizes wave front reconstruction techniques to provide a real-time three-dimensional image at the receiving end of the system, with the image changing in perspective as the object and/or observer moves.
Abstract: This disclosure relates to a television system that utilizes wave front reconstruction techniques to provide a real time three-dimensional image at the receiving end of the system, with the image changing in perspective as the object and/or observer moves. The coherent light from a laser is first modulated at a frequency in the microwave range and one sideband of the coherent light is filtered out and used to illuminate an object scene. The light reflected from the object scene impinges on a photodetector while a narrow reference beam of coherent light raster scans the photodetector to thereby generate a signal which is modulated in phase and amplitude in accordance with the interference pattern formed on the photodetector. The signal carrying the modulated phase and amplitude information is then transmitted to a remote receiver. At the received end, the phase and amplitude modulated information is recovered and stored, a frame at a time, in respective storage devices. At the end of a complete frame the stored information is read out and respectively applied to an array of phase and amplitude optical modulators. Also, at the end of a complete frame received information, a second laser at the receiver is pulsed with the light therefrom directed toward said array. In this manner, an image of the original object is obtained at the receiver. The described operation is continued a frame at a time.

35 citations


Journal ArticleDOI
01 Jan 1968
TL;DR: In this article, the spectrum change of diode laser output light by millimeter-wave amplitude modulation was observed and the spectrum consisting of the sideband by modulation showed apparent dependence on the resonance condition of the diode dimensions.
Abstract: Spectrum change of diode laser output light by millimeter-wave amplitude modulation is observed. The spectrum consisting of the sideband by modulation showed apparent dependence on the resonance condition of the diode dimensions. A spectrum of less than 50 GHz modulation is observed when the diode dimensions are well designed.

26 citations


Patent
28 Aug 1968
TL;DR: An ellipsometric device and method for applying a phase modulation and a polarization direction modulation to a beam of light at two different frequencies and using a polarized parallel monochromatic light beam, a polarization modulator, a phase modulator and means to angularly displace with respect to each other is described in this article.
Abstract: An ellipsometric device and method for applying a phase modulation and a polarization direction modulation to a beam of light at two different frequencies and using a polarized parallel monochromatic light beam, a polarization modulator, a phase modulator, and means to angularly displace with respect to each other, an assembly having on one hand a beam polarizer phase and azimuth modulator and on the other hand the sample, an equalizer, analyzer and photoreceiver.

16 citations


Patent
06 Mar 1968
TL;DR: An improved optical modulator having means for dissipating the various, extraneous internal energies within the optical crystal, to thus improve the frequency response of the modulator, the means including impedance matching acoustic boundaries and refractive index matching optical boundaries disposed along selected sides and ends of the optical crystalline, as well as acoustic and light dissipative or absorbing materials selectively disposed about the sides of the crystal.
Abstract: An improved optical modulator having means for dissipating the various, extraneous internal energies within the optical crystal, to thus improve the frequency response of the modulator, the means including impedance matching acoustic boundaries and refractive index matching optical boundaries disposed along selected sides and ends of the optical crystal, as well as acoustic and light dissipative or absorbing materials selectively disposed about the sides of the crystal. The acoustic matching on the surfaces of the crystal may be quarter-wave plates which provide an impedance match to the surrounding material to dissipate internal energy due to piezoelectric effects and the like. The refractive index matching on the surfaces of the crystal may also be quarter-wave transparent films of appropriate indices of refraction between the various mediums of the modulator through which the light beam passes. The dissipative materials absorb acoustic energies released to the surround, and extraneous light scattered or internally reflected within the crystal as the beam passes therethrough.

10 citations


Patent
21 Oct 1968
TL;DR: In this paper, the first ultrasonic light modulator is sandwiched between crossed polarizers that block the passage of light under quiescent conditions, and acoustic pulses are propagated through the second ultrasonic modulator.
Abstract: An optical pulse expansion device includes first and second ultrasonic light modulators and a coded mask positioned so that a collimated light beam can be passed serially through these elements and focused on a photodetector. The first ultrasonic light modulator is sandwiched between crossed polarizers that block the passage of light under quiescent conditions. First acoustic pulses are propagated through the first ultrasonic light modulator in synchronism with second acoustical pulses that are propagated through the second ultrasonic light modulator. These pulses limit the light to the acoustically stressed regions of the second ultrasonic light modulator when scanning the coded mask.

8 citations


Journal ArticleDOI

8 citations


Journal ArticleDOI
J.L. Putz1
TL;DR: In this article, an experimental KDP light modulator with a 10 percent (half-m) bandwidth at 6 GHz was described, where the crystals were used in the longitudinal mode, i.e., with the light beam along the optic axis.
Abstract: An experimental potassium dihydrogen phosphate (KDP) light modulator with a 10 percent (half-m) bandwidth at 6 GHz is described. When arranged for amplitude modulation, a modulation depth of 40 percent was obtained with 10 watts of input power at band center. With a different optical arrangement, phase modulation is also possible. The modulator uses a ring-plane traveling-wave circuit with cylindrical KDP crystals filling the space inside the rings. The crystals are used in the longitudinal mode, i.e., with the light beam along the optic axis, thus avoiding some of the thermal problems associated with transverse node operation. The circuit provides adequate cooling for the crystals and CW or pulsed operation at average RF levels of 10 watts is possible. Measurements indicate that the limitation in bandwidth is due mainly to the dispersion of the circuit and that with suitable modifications bandwidths of 20 percent are quite feasible.

6 citations


Patent
25 Mar 1968
TL;DR: In this article, a beam of coherent monochromatic light from a laser interacts with an acoustic wave signal in a Debye-Sears interaction cell, thereby to phase modulate the beam with the acoustic wave signals and with intelligence information carried thereby.
Abstract: A beam of coherent monochromatic light from a laser interacts with an acoustic wave signal in a Debye-Sears interaction cell, thereby to phase modulate the beam with the acoustic wave signal and with intelligence information carried thereby. At a fixed distance along the beam path from the interaction cell the modulation of the light beam shall have been converted from phase to amplitude modulation and a slit positioned at such location admits both the undiffracted and the first-order diffracted components of the modulated beam to a detector where the beam is demodulated and the intelligence recovered. Increased efficiency is obtained by using a series of slits, rather than a single slit, disposed across the light beam at the aforesaid particular location. Where Bragg angle diffraction is achieved in an interaction cell, as distinguished from Debye-Sears diffraction, the emerging light beam exhibits both amplitude and phase modulation. If the system employs two acoustic wave signals interacting with a single light beam in the cell, with the pair of acoustic wave signals having the proper angular relation, the output of the interaction cell may be demodulated as to its phase modulation content by the same technique employed in demodulating the output of the Debye-Sears diffraction cell. This increases the efficiency of the system over what is otherwise obtained if demodulation is confined to the initial amplitude modulation of the modulated light beam.

6 citations


Journal ArticleDOI
TL;DR: In this paper, the synchronization bandwidth of center-fed and end-fed, capacitive electrooptic modulators that employ a modulation field transverse to the direction of optical beam propagation is calculated.
Abstract: Expressions are given that can be used to calculate the synchronization bandwidth of center-fed and end-fed, capacitive electrooptic modulators that employ a modulation field transverse to the direction of optical beam propagation.

6 citations


Patent
02 Dec 1968
TL;DR: In this paper, a lithium tantalate electrooptical modulator crystal is mounted between massive, acoustically absorbent, support members which also provide an electric circuit interface for applying electric signals to the modulator.
Abstract: Acoustical ringing which results from piezoelectric effects in an electrooptical modulator is suppressed by mounting the modulator crystal between massive, acoustically absorbent, support members which also provide an electric circuit interface for applying electric signals to the modulator. Solder provides such an absorbent mounting for a lithium tantalate electrooptical modulator crystal. Both solder support members are flowed into place during the same heating interval and permitted to cool simultaneously.

6 citations


Patent
Herbert Ing Grad Meyer1
26 Feb 1968
TL;DR: A DIGITAL OPTICAL MODULATOR where the intensity of RADIATION may be varied in STEPS by means of passing the beam THROUGH two separate MODULATORS, each switchable between two operating points as discussed by the authors.
Abstract: A DIGITAL OPTICAL MODULATOR WHEREIN INTENSITY OF RADIATION MAY BE VARIED IN STEPS BY MEANS OF PASSING THE BEAM THROUGH TWO SEPARATE MODULATORS, EACH SWITCHABLE BETWEEN TWO OPERATING POINTS, THEREBY SUBJECTING EACH MODULATOR TO TWO DIFFERENT FIELD STRENGTHS.

Journal ArticleDOI
TL;DR: In this article, the three-terminal GaAs device was used as a light emitter-modulator and the effect of light emission can occur during all the r.f.w. cycle or during only part of it.
Abstract: The three-terminal GaAs device which previously showed c.w. microwave oscillations has now been used as a light emitter-modulator. Depending on the external circuit, light emission can occur during all the r.f. cycle or during only part of it. At present, the amplitude modulation of the emitted light has been limited to a frequency of 100MHz; at 1GHz, the effect has been indirectly observed.

Journal ArticleDOI
A. R. Tynes1
TL;DR: By reinterpreting the transverse spatial dimensions as distances parallel to the light beam, theory shows that this technique should result in a very sensitive optical ranging device.
Abstract: A sensitive method for measuring small displacements of a light beam is described which does not require the use of light probes or multielement detectors. Instead, the light beam whose displacement is to be measured, as well as a comparison light beam, is passed alternately through a rotating light chopper and then both beams are made to overlap on the surface of a photodetector. If the intensity of the two beams is made equal and if the phase (relative to the light chopping sequence) is properly adjusted, the photodetector output will be constant. Any beam displacement perpendicular to the edge of the rotating light chopper will disrupt the established phase relationship and produce a signal component in quadrature (i.e., 90° out of phase) with that which would be produced if only the intensity of one beam were changed. Theory shows the relationship between the amplitude of the quadrature component and the beam displacement. Measurements as small as 5 × 10−6 cm have been made and another more sensitive configuration is suggested. By reinterpreting the transverse spatial dimensions as distances parallel to the light beam, theory shows that this technique should result in a very sensitive optical ranging device.

Journal ArticleDOI
TL;DR: In this paper, a travelling-wave light-intensity modulator was described which uses two natural crystals of ZnS. This prototype needs a peak microwave pulse of 2 kW for 45% modulation, and has an overall bandwidth of 15% at 9.75 GHz.
Abstract: A travelling-wave light-intensity modulator is described which uses two natural crystals of ZnS. This prototype needs a peak microwave pulse of 2 kW for 45% modulation, and has an overall bandwidth of 15% at 9.75 GHz.

Patent
02 Dec 1968
TL;DR: In this article, a Gunn effect device is used to provide pulses of the high amplitude and frequency needed to drive an optical modulator, such as a lithium tantalate crystal for efficiently utilizing the bandwidth of light transmitted through the modulator.
Abstract: A Gunn effect device is utilized to provide pulses of the high amplitude and frequency needed to drive an optical modulator, such as a lithium tantalate crystal for efficiently utilizing the bandwidth of light transmitted through the modulator. An acoustically absorbent mounting is provided for the modulator to suppress acoustical ringing resulting from piezoelectric effects in the modulator. The modulation system is initially aligned by simulating at a comparatively low frequency the drive amplitudes in order to establish a maximum condition of modulation in the optical part of the system. Thereafter, signals at the Gunn effect device output rate are supplied for controlling the modulator. Information-representative signals coupled to the modulator through the Gunn effect device are synchronized with the optical system utilizing the modulator.

Journal ArticleDOI
TL;DR: In this article, a general solution for the resulting light diffraction patterns is obtained, from which the conditions are determined for which the diffracted light intensity distribution will be a valid representation of the power spectral density of the input electrical noise signal.
Abstract: Excitation of an ultrasonic light modulator by random electrical signals will cause a random modulation to be imposed on the emerging light wavefront. A general solution for the resulting light diffraction patterns is obtained, from which the conditions are determined for which the diffracted light‐intensity distribution will be a valid representation of the power spectral density of the input electrical noise signal. The necessary experimental conditions for which the variance of the spectral measurements will be small are determined. The percentage of the light‐modulator bandwidth over which measurements will be valid is found to be dependent on the product of the spatial‐frequency bandwidth of the light modulator and the length of the optical aperture; this effect is evaluated and numerical results are presented. The case in which the input to the ultrasonic light modulator consists of a deterministic signal and noise is also considered. Using these results, the diffracted light levels due to signal an...

Journal ArticleDOI
TL;DR: In this paper, the effect of the length of the light path on the operation of a light modulator is considered for a range of values for which Raman and Nath's simplified approach is no longer valid.
Abstract: The operation of fused‐silica Debye‐Sears light modulators is investigated for normal light incidence over a range of conditions such that the effect of amplitude modulation of the light beam by the acoustic wave, as well as phase modulation, must be taken into account. Using the approximations of Raman and Nath, for which the ultrasonic wave can be treated as a phase grating, the relationships between input electrical excitation and the resulting spatial modulation are determined for shear and compression waves. The effect of the length of the light path on the operation of the light modulator is then considered for a range of values for which Raman and Nath's simplified approach is no longer valid. From the results of Bhatia and Noble it is shown theoretically and verified experimentally that, for single frequency excitation, a value of this dimension can be specified such that the effective spatial modulation of the light beam can be maximized. The case of electrical excitation over a finite frequency ...

Journal ArticleDOI
TL;DR: In this paper, the Schlieren method was used to obtain the light diffracted by the ultrasonic waves traveling through the water and the presence or absence of these waves will be transformed into transparency variations.
Abstract: placed in a tank filled with water that control in each instant the locations of the ultrasonic waves traveling through the water. Using the Schlieren method, only the light diffracted by the ultrasonic waves can be obtained. So, the presence or absence of these waves will be transformed into transparency variations. As an application, a reference pattern was generated with a pattern recognition device. When the reference character matches with the unknown one, the light caught by a photomultiplier

01 Jun 1968
TL;DR: In this paper, the second laser beam affects the transmission characteristics of the free carrier source to light from the signal carrier laser, thus modulating it, and the second beam is optically modulated by a second beam of different frequency acting on a free source to which the first beam is directed.
Abstract: Signal carrier laser beam is optically modulated by a second laser beam of different frequency acting on a free carrier source to which the signal carrier laser is directed. The second laser beam affects the transmission characteristics of the free carrier source to light from the signal carrier laser, thus modulating it.