Hughes Aircraft Company

Hughes Electronics Corporation

Cleveland Crystals, Inc.

Melvin E Pedinoff

Yuri Owechko

Jan Grinberg

Thomas R O'Meara

Bernard H Soffer

Gregory L Tangonan

Oscar Magnus Stafsudd

Christopher N Pannell

Jonathan David Ward

Thomas E Stenger

Morris Braunstein

Ramesh K Shori

An acousto-optic modulator includes a (100), (010) or (001) single crystal silicon acousto-optic interaction medium, and at least one transducer for emitting an acoustic wave attached to the single crystal. The transducer has a first electrode layer disposed on one side and a second electrode layer disposed on its other side. The transducer is aligned to the single crystal so that the direction of acoustic propagation in the silicon crystal is substantially along the (100), (010) or (001) direction. A q-switched laser includes a modulator according to the invention.

Silicon acousto-optic modulator

Methods and apparatus are disclosed for an intrusion detection system for secure fiber optic communication systems. A guard signal is transmitted over the optical fiber communication link and both the modal power and modal phase delay of this signal are monitored. Intrusions into the link for the purpose of intercepting information being transmitted, cause changes in the modal phase delay and power of the guard signal. These changes, when detected by the monitoring system, indicate the presence of an intruder. A fiber profile which is optimal for both transmission and intrusion detection purposes is described.

Intrusion detection system for secure fiber optics

An optical beam scanner incorporating an array of beam deflection elements commonly controlled to steer an optical beam impingent on the array is described. The beam steering elements are arranged in the array as individually controlled elements and the deflection of the beam is accomplished by setting the phase tilt and the phase offset of each element according to a calculation which removes modulo 2.pi. phase shift from the required position relative to a flat plane. Thus, the array elements can be thin and need only supply about 2 radians of phase shift. These elements may be incorporated in a planar array using beam deflection elements such as liquid crystal beam deflectors by choosing a drive scheme representing either a blazed array or a flat piston array. Operation may be designed for a large range of light wavelengths and the system may efficiently accommodate a combination of the blazed and flat piston techniques to obtain beam deflection characteristics otherwise unavailable by the exclusive use of each individual technique. By use of the liquid crystal phased array approach, rapid, high accuracy, large area beam deflection is possible without the necessity of any moving parts and with low power drive requirements. Phased arrays of the type described above may be arranged in successive parallel planes with a common beam axis to provide two-dimensional beam deflection.

Phased array for optical beam control

There is disclosed a polarizer particularly suited for use in the infrared wavelengths which comprises a wire grid polarizer in optically cascaded relationship with a Brewster's Angle Polarizer. Not only do the extinction ratios of the optically cascaded polarizers multiply to provide higher extinction ratios at these wavelengths, but also the reflective mirror properties of the wire grid polarizers can be used in combination with the known optical properties of Brewster Polarizers to provide a combined device which optimizes both the extinction ratios achieved and the balance between the reflection and recombination problem of the system on the one hand and the offset or beam walking problem on the other hand in a manner to provide optical characteristics which are not achievable from any simple combinations of either type of polarizer alone.

Hybrid Brewster's angle wire grid infrared polarizer

There is disclosed a pulse processing method and apparatus for compressing or changing the time scale of signal information represented by the modulation of a pulse of carrier energy which method and apparatus utilizes a crystal through which both a pulse of radio frequency acoustic energy and a pulse of polarized optical energy are simultaneously and colinearly transmitted to scatter energy in the optical pulse from one polarization state into the orthogonal polarization state. The crystal output is thus comprised of two optical pulses. One is the pulse having the original state of polarization and the other is the pulse resulting from the energy scattered to the orthogonal polarization state. The optical energy of rotated polarization is modulated in a fashion reproducing the modulation of the ultrasonic wave by which it is scattered. Furthermore, a short optical pulse can pass through the ultrasonic wave in a time short compared to the duration or length of the ultrasonic wave in the crystalline device. In so doing it reads the modulation of the acoustic pulse and transfers it to a time compressed pulse scale on the scattered optical output pulse. It is shown that the compression ratio is equal to the ratio of the velocity of light divided by the product of the velocity of sound in the crystal times the absolute value of birefringence of the crystal. If both the optical and acoustic pulses are passed through the crystal colinearly and in the same direction, the device takes a time function represented by the acoustic pulse, reverses it in time and compresses it by the ratio of light velocity to sound velocity thus producing a compressed inverse function. If the acoustic pulse and the light pulses are transmitted through the crystal colinearly but in opposite directions, the device takes a time function and without reversing it, compresses it in substantially the same ratio. The device may be applied, for example as a means of improving the signal-to-noise ratio, detection ratio and range resolution in radar systems or the like.

Method and apparatus for acousto-optic pulse compression

There is disclosed a method and apparatus for radio frequency signal spectrum analysis wherein an acoustic wave having frequency components representative of those which exist in the radio frequency signal to be analyzed is derived from the signal and transmitted through an optically anisotropic crystal simultaneously and colinearly with a beam of polarized wide-band white light. The acoustic wave produces changes in the index of refraction of the crystalline material which result in diffraction of the plane of polarization of those frequency components of the light beam which bear a unique predetermined relationship to the frequency components present in the acoustic wave. The output of the crystal is then passed through a polarization analyzer to transmit only those frequency components which have been polarization diffracted. The light output of the polarization analyzer is applied to a grating or other means for dispersing the light output so that its various frequency components are deflected by varying amounts indicative of the frequency. The rays deflected from the grating or other dispersing means are then displayed in any suitable manner to provide a visually readable spectrum analysis of the original signal.

Growing community of inventors

Thousand Oaks, CA, United States of America

Melvin E Pedinoff