Showing papers on "Waveplate published in 1970"

Polarization independent light modulation means using birefringent crystals

Abstract: A first optically birefringent crystal divides an incident randomly polarized light beam into two linearly polarized orthogonal components, namely, an ordinary ray and an extraordinary ray. The incident light beam is so related to the optic axis of the birefringent crystal that ordinary ray is undeviated but the exgraordinary ray is deviated by a selected amount, both of the rays emerging from the birefringent crystal parallel to each other. The amount of deviation is a function of the index of refraction and the length of the path through the crystal. The spaced rays are then directed through an electro-optical polarization modulator which electronically converts the linearly polarized components to elliptically polarized beams with the eccentricity dependent upon the magnitude of an applied electric field. For a particular magnitude of applied electric field, the polarization modulator will cause a 90 DEG rotation of the orthogonal components. The two emerging rays are then passed through a second birefringent crystal which recombines the two rays with the intensity along the emerging axis proportional to the magnitude of the electric field applied to the polarization modulator. In the unenergized state of the polarization modulator maximum transmittance is obtained. In the energized state the transmittance varies according to T = sin2 KE where E is the magnitude of the applied electric field and K is a proportionality constant. Thus, the light modulation system can be controlled electronically to make it selectively transmissive for incident light of all polarizations. The system is also described as applied to a resonant optical cavity such as a Q-switching device for randomly polarized stimulated emission of radiation devices (lasers).

Light beam polarization modulator

Abstract: A parallel cell electro-optical phase modulator is used in combination with two birefringent crystals and a half wave plate to produce polarization modulation of an incident light beam. A first birefringent crystal provides a lateral relative displacement between the two orthogonal components of the incident light beam to form two spaced light paths, one through each of the respective electro-optical crystals. The half wave plate rotates the linear polarization of the orthogonal components to allow a second birefringent crystal to recombine the orthogonal components into a single light beam.

High order wave plate correction of polariscopic effects in windows having infrared filtering

Abstract: A light-transmitting window apparatus including a system which impedes the transmission of infrared radiation and comprises a light-polarizing element and a high order wave plate.

A ferroelectric-ferroelastic electrically operated optical shutter device

Abstract: An optical shutter or an optical pattern generator, such as a page composer in a laser holographic memory, as an application thereof, comprising a pair of polarizers, and a quarter wave plate (2n + 1/4 wave plate) and optical shutter crystal both disposed between said pair of polarizers. This optical shutter crystal is made of a ferroelectric-ferroelastic crystal having zcut end faces the distance between which is arranged to be (2n + 1/4 lambda , one z-plane being provided with a plurality of mutually parallel transparent electrodes, the other Z-plane being provided with a uniform transparent electrode, so as to apply an electric field at least equal to the coercive electric field of the crystal.

Light deflection by external conical refraction

Abstract: A system for producing continuously variable displacement either spacially or angularly of a beam of linearly polarized light of appropriate collimation as specified comprising a source of linearly polarized light, a polarization rotater and an appropriately oriented optically biaxial crystal. A novel electro-optic continuous polarization rotater is provided.

Apparatus for converting linearly polarized radiation into linearly polarized radiation having a plane of polarization varying linearly with time

Abstract: An improved apparatus for converting linearly polarized radiation having an arbitrary plane of polarization into linearly polarized radiation in which the orientation of the plane of polarization changes linearly as a function of time from the initial arbitrary orientation is discussed, in which apparatus the radiation passes at least thrice through a birefringement element, at least one of the elements traversed being an electrooptical crystal. It is shown that by using a retrodirective element the number of birefringement elements can be reduced and also the voltage to be applied to the electro-optical crystals can be considerably lower.

On a Method of Generating Ultrasonic Circularly Polarized Waves

Abstract: In the present paper, we suggest a device that is able to produce circularly polarized ultrasonic waves by transposing the optical arrangement known as Fresnel's parallelepiped into the acoustic domain. A plane elastic transverse wave is propagated in an isotropic solid medium and then reflected at a plane air‐solid interface. This wave is linearly polarized at 45° to the plane of incidence and so results in two components of equal amplitude, which are in phase. After reflection at an appropriate angle, the two transverse waves are in phase quadrature and the reflected wave is circularly polarized. This result is essentially independent of frequency.

Apparatus for measuring the linear displacement of a moving object

Abstract: 1285277 Polarizing apparatus V DEMIDENKOV V K PROSVETOV S G SKROTSKY B V RYBOKOV and A M KHROMYKH 20 Nov 1970 55192/70 Heading G2J [Also in Divisions H1 H4 and G1] Linear displacements of an object having a mirror attached thereto, are measured by apparatus including: a laser producing radiation at two slightly differing frequencies, the difference frequency being in the r.f. range; a first photodetector receiving the radiation from the laser to produce a phase reference waveform at the difference frequency; a second photo-detector, receiving radiation from the laser which both has and has not been reflected from the mirror, to produce a waveform whose phase is compared with the reference to indicate the displacement. Ring laser as source. In the arrangement of Fig. 1, a ring laser 1 is used with the aid of Faraday effect device 2, to produce two pairs of beams of the two different frequencies. One pair is mixed by mirror 3 and semi-transparent plate 4 for detection by first detector 9. The beams of the other pair are directed to mirror 5 and to mirror 8 on the object 4 (via semi reflecting plate 6), the reflected beams being combined at semi reflector 7 for detection by the second detector 10. The phase comparison is performed by meter 13 after amplification at 11, 12. Linear laser as source. The axial magnetic field applied to laser 14 produces from either end of the device radiation circularly polarized in clockwise and anti-clockwise directions, the radiation from each end containing both frequencies. At one end, the radiation is passed through a polarizer 17 which converts the beam to linearly polarized radiation and detector 18 develops the reference difference frequency signal. At the other end, radiation passes through quarter wave plate 19 providing radiation linearly polarized in two directions at right angles, these beams being separated by Wollaston prism 20 and subsequently combined at detector 26 by optical mixer elements 21-24 after reflection from mirror 24 fixed to the object. Polarizer 25 ensures that all the radiation reaches the detection polarized in the same direction.

Improvements in or relating to Light Modulators

Abstract: 1,192,394 Light modulators MULLARD Ltd 22 June, 1967, No 28909/67 Heading H4F A light modulator comprises a multi-cavity microwave slow-wave structure having electrooptical material, eg ADP, disposed in a plurality of the cavities, the structure being arranged to impart to microwaves of a given frequency coupled into end of said structure, a phase velocity which is the same as the phase velocity of light directed along a path which successively passes through the material in each cavity As shown, Fig 1, the structure may comprise a circular waveguide closed for microwaves by terminating discs 2 and 3 and provided internally with spaced apertured transverse discs 4-8 and 26 which form ends of cavities 9-14 and 27 The electro-optical material may be in the form of a rod 15, or as an alternative it may be in the form of discrete portions provided within each cavity, the portions being optically matched to one another by a second transparent material, eg Canada Bolsam, which interconnects the electrooptical material in each adjacent pair of cavities and passes through the apertures in the intervening discs A standing wave may be set up with its electric vector extending longitudinally along the structure and hence along the ADP rod, and laser light polarized parallel to x 1 or y 1 passing along path P will be phase-modulated at the microwave frequency The structure need not be resonant at the input modulation frequency, in which case the structure is terminated at its output end by a matched load 25 (shown dotted) The structure may be made up from a series of identical silver-plated brass sections each containing one transverse disc, the sections being brazed together To provide amplitude modulated light a quarter wave plate and an analyser are provided at the output of the slowwave structure Fig 2 (not shown)