Showing papers on "Signal beam published in 1986"

Optical digital logic operations by two-beam coupling in photorefractive material.

Abstract: The nonlinear phenomena of signal beam saturation, pump beam depletion, and optically controlled coupling coefficient of two-beam interaction in photorefractive materials are analyzed. Applications of these phenomena to digital logic operations is discussed and supported by experimental results obtained in photorefractive BaTiO3.

Polarization controlling device comprising a beam splitter for controllably bifurcating an input polarized beam to two polarization controlling elements

Abstract: For first and second polarization controlling elements (181, 182) driven by first and second driving voltages in a polarization controlling device, a beam splitter (15) has a dividing ratio controllable between 1:0 and 0:1 and divides an input polarized beam having an input polarization state. An output polarized beam is derived from first and second polarization controlled beams to have an output polarization state. While the dividing ratio is kept at 1:0 so that the second polarization controlled beam is null, the first driving voltage may approach either of a positive and a negative limit. In this event, a control unit (25) changes the dividing ratio to 0:1. Even while the second polarization controlled beam is null, the control unit controls the second driving voltage so that the both driving voltages are congruent modulo a unit voltage difference which makes each element carry out equivalent polarization control. The first driving voltage is likewise controlled. When the input polarization state optionally varies, the output polarization state can be defined by a mode filter, a laser diode, or two parameters descriptive of a coherent polarized beam. Irrespective of the input polarization state, the output polarization state can be defined by a signal beam which reaches the device with an optionally varying polarization state.

System and method for automatically fabricating multi-hologram optical elements

Abstract: A system and method for automatically fabricating multi-hologram optical elements. Signal and reference beams are formed and directed along separate paths that intersect at a recording medium; and a gate is moved through a first sequence to expose a plurality of views, one at a time, to the signal beam to spatially modulate that beam. A matrix of beams, each of which converges toward a different area of the recording medium, is generated from the spatially modulated signal beam, and a mask is moved through a second sequence to pass the matrix beams onto the recording medium to record a plurality of diffraction patterns thereon.

Optical system including device for optically processing electromagnetic radiation at a repetition rate greater than about 1.25×104 Hz

Abstract: An optical system is disclosed which includes at least a first source of electromagnetic radiation (signal beam radiation), a device for processing the signal beam radiation, and a detector for detecting the processed signal beam radiation. The processing device functions, for example, as an amplitude modulator, a demultiplexer, or a switch, and includes a material region exhibiting a nonlinear optical response at one or more resonant wavelengths of electromagnetic radiation, as well as at least a second source of electromagnetic radiation (control beam radiation) for selectively inducing the nonlinear optical response. Significantly, the wavelength, duration and intensity of the control beam radiation are chosen to induce a resonant, nonlinear optical response, essentially free of any relatively slow component, in said material region at repetition rates higher than about 1.25×10 4 Hz, or higher than about 3.3×10 10 Hz, or even as high, or higher, than about 2.5×10 11 Hz.

Systems and methods for processing optical correlator memory devices

Abstract: An optical correlator memory processing system. By operating the system within preselected maximum and minium wavelengths, by preselecting certain parameters of the system, and by operating the system within certain additional constraints, the system can be used to always cause interference between the Fourier transform of a spatially modulated signal beam and a reference beam at a recording medium at a multitude of wavelengths. This allows a matched filter to be fabricated and played back at these multitudes of wavelengths without changing the sensitivity of the system. The system may be used to fabricate matched filters, and as a correlation system to detect the presence or absence of a particular target in a selected view or scene.

Nonlinear optical doppler imaging amplifier

Abstract: A nonlinear optical receiver includes a source of coherent light of frequency ω for illuminating a spatial region. The portion of the source light which is reflected from objects within the spatial region constitutes a signal beam. A reference beam of coherent light of frequency ω is also provided. A photorefractive element receives the signal and reference beams and amplifies the signal beam by two-wave mixing. The receiver may include a first polarizer, having a first polarization direction, placed between a cubic photorefractive element and the signal and reference beams, and a second polarizer, having a second polarization direction perpendicular to the first polarization direction, placed so that the amplified signal beam must pass therethrough. A frequency shifting element, such as a Bragg cell modulator, is used to change the frequency of the reference beam. pa A first laser may provide both the source of coherent light and the reference beam of coherent light, or a first laser may provide the source of coherent light while a second laser provides the reference beam of coherent light. The photorefractive element may be a cubic photorefractive crystal or a nonlinear optic material. A two dimensional focal plane array may be added for detecting the amplified signal beam.

Apparatus for measuring wavelength dispersion of optical fiber

Abstract: PURPOSE:To achieve the reduction in the cost of a measuring apparatus and the enhancement in measuring accuracy, by transmitting measuring signal beam and reference signal beam by the same optical fiber. CONSTITUTION:The output of the laser 121 in (n) modulated lasers 121-12n difference in the wavelength of output beams is set as reference signal beam and one laser 12i (i=2-n) selected from the lasers 122-12n by a change-over circuit 13 is set as measuring signal beam. The reference signal beam and the measuring signal beam are synthesized by a synthesizer 14 to be incident to an optical fiber 15 to be tested and divided by a wave divider 16 after propagated through the optical fiber 15. The divided reference and measuring signal beams are respectively converted by photoelectric converters 17, 18 and amplified by amplifiers 19, 20 to be inputted to a phase difference measuring instrument 21. The relative phase difference of the signal beams of the laser 12i at the output and input terminals of the fiber 15 on the basis of the laser 121 is measured by the measuring instrument 21. By using a specific formula, relative delay time difference due to the propagation of both signal beams through the optical fiber 15 is calculated on the basis of the measuring signal beam of the laser 12i based on the reference signal beam of the laser 121.

Method and apparatus for optical communication by frequency modulation

Abstract: Laser optical communication according to this invention is carried out by producing multi-frequency laser beams having different frequencies, splitting one or more of these constituent beams into reference and signal beams, encoding information on the signal beams by frequency modulation and detecting the encoded information by heterodyne techniques. Much more information can be transmitted over optical paths according to the present invention than with the use of only one path as done previously.

Ultrasonic-wave flow speed and flow rate meter utilizing doppler shift

Abstract: PURPOSE:To measure the accurate flow speed and flow rate all the time, by the constitution, wherein the axis of an ultrasonic wave beam from a transmitting transducer is approximately common to the axis of a receiving transducer having the receiving directivity. CONSTITUTION:A transmitted signal from a signal oscillator 1 is converted into an ultrasonic wave signal. The signal is transmitted by a transmitting transducer 2 as an ultrasonic signal beam into a fluid to be measured 5 in a pipe 4. The transmitting transducer 2 is arranged on the wall of the pipe 4. Meanwhile, solid state particles 8 in the fluid to be measured 5 reflect said ultrasonic wave beam. A receiving transducer 11 receives the reflected wave and converts the wave into an electric signal. The receiving transducer 11 is arranged at the neighboring position to the transmitting transducer 2 so that an axis 7 of the ultrasonic wave signal beam is made common to an axis 7a of the reflected wave having the receiving directivity. Thus the accurate flow speed and flow rate can be always measured regardles of the pollution concentration of the fluid to be measured.

Method for measuring connection length of polarization surface preservation fiber

Abstract: PURPOSE:To enable highly accurate and simple measurement, by allowing linear polarized modulated light to be incident to two inherent polarization modes of a polarization surface preserving fiber and calculating a connection length from the phase difference of emitted lights. CONSTITUTION:The sine wave modulated beam of a laser diode 2 is transmitted through a polarization plate 4 to be converted to linear polarized beam which is, in turn, further transmitted through an 1/2 wavelength plate 5 to rotate a vibration surface but the plate 5 is adjusted so as to allow the vibration surface of the linear polarized beam to coincide with the short axis of two inherent polarization axes of SPF 3. A part of the linear polarized beam transmitted through the plate 5 is passed through a half mirror 6 to be incident to SPF 3 in a short axis mode as signal beam and the remainder is reflected by the mirror 6 to be converted as reference beam by a photoelectric converter 8 while the signal beam incident to SPF 3 is converted by a photoelectric converter 7 after transmission and both of them are respectively incident to a phase meter 9 to measure the phase difference $phis of the signal beam of the short axis mode and the reference beam. In the same way, the phase difference phiL of signal beam of a long axis mode and the reference beam is measured and the connection length of SPF 3 is calculated from the differences phiS, phiL, a beam wave length, modulated frequency and optical velocity.

Optical logic circuit

Abstract: PURPOSE:To enable integration of an optical ligic circuit, by forming a plurality of phototransistors on a semiconductor laser in an integrated manner, and electrically isolating the phototransistors from each other. CONSTITUTION:Two phototransistors Tr 2 are formed on a semiconductor laser 1 in series in the direction of the resonator axis. Thereafter, a groove 116 is provided in such a manner as to cut the resonator axis for the purpose of increasing the electrical resistance between the two phototransistors Tr 2. Thus, the phototransistors Tr 2 can be substantially isolated electrically from each other. When signal beam 200 are simultaneously injected into the phototransistors Tr 2, the laser 1 is allowed to oscillate. When either one of the beam 200 is absent, no oscillation occurs. In this way, it is possible to form an optical integrated AND circuit which operates at low power consumption. An OR circuit can also be formed by changing the size of the beam 200 in this optical logic circuit. When the width of the groove 116 is enlarged, the optical output-electric current characteristics or the like of the laser 1 have hysteresis. Therefore, the optical logic circuit can operate as a memory circuit.

Experimental investigation of a CO2 amplifier with a mirror utilizing a degenerate four-wave interaction

Abstract: A description is given of the construction of a two-pass CO2 amplifier system with a mirror utilizing a degenerate four-wave interaction in SF6 gas and having an output energy of about 30J with an angular divergence of 4.4×10−4 rad at 50% of the maximum energy. A partial compensation of simulated inhomogeneities introduced into the signal beam was observed.

Fourier planar repetition type optical filter mechanism

Abstract: An optical filtering system (50) in which a signal beam (54) of optical radiation is passed through the optical filtering means a multiplicity of times. The filtering system has an optical Fourier transformer means (14), a spatial filter (18), optical inverse Fourier transform means (20) and a pair of reflectors (38, 40) in the Fourier plane of the spatial filter. An input signal beam to be filtered is optically Fourier transformed by the transform means (14) and is passed through the spatial filter (18) where unwanted frequencies of the signal beam are attenuated. The filtered beam is reflected by one of the reflectors back through the filter and the second mirror reflects it back through the filter a third time. Subsequent reflections back through the filter with a consequent further filtering of the signal beam can be accomplished by appropriately positioning the reflectors. After multiple filtering passes, the filtered beam is extracted for utilization. By maintaining the recursions of the beam in the Fourier plane of the filter, which preferably is of a programmable type, the optical throw of the filter system can be significantly reduced and a flexible imaging system without the restraints of external recursion is realizable in a robust structure with fewer components. An embodiment of the system being used in a heterodyning RF optical filtering system is described.