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Field Induced Light Beam Deflector

IP.com Disclosure Number: IPCOM000076989D
Original Publication Date: 1972-May-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 31K

Publishing Venue

IBM

Related People

Ludeke, R: AUTHOR

Abstract

A structure for the deflection of a light beam, either free or guided, by a field induced change in the refractive index of the dielectric medium is shown in Fig. 1. When light beams propagate in a thin-film medium, it is often desirable to change the direction of their propagation. The use of the electrooptical effect in a film made of a material which exhibits such effect is the most obvious way of achieving light deflections, but such material may not be compatible with monolithic technology to incorporate sources and detectors. It is, however, possible to achieve field induced changes of optical constants by the Franz-Keldysh effect, which is most pronounced near the fundamental edge of a semiconductor. Changes in the retractive index, n, of 0.1 are achievable with fields of the order of 10/4/ v/cm.

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Field Induced Light Beam Deflector

A structure for the deflection of a light beam, either free or guided, by a field induced change in the refractive index of the dielectric medium is shown in Fig. 1. When light beams propagate in a thin-film medium, it is often desirable to change the direction of their propagation. The use of the electrooptical effect in a film made of a material which exhibits such effect is the most obvious way of achieving light deflections, but such material may not be compatible with monolithic technology to incorporate sources and detectors. It is, however, possible to achieve field induced changes of optical constants by the Franz- Keldysh effect, which is most pronounced near the fundamental edge of a semiconductor. Changes in the retractive index, n, of 0.1 are achievable with fields of the order of 10/4/ v/cm. Such change is sufficient to produce appreciable deflections in a light beam at large angles of incidence with respect to a field plate or prism. The structure in Fig. 1 is capable of producing rather large deflections.

The field plate can be manufactured by the sequential evaporation through a mask of an insulator (oxide) and a conductor (metal) onto the semiconducting thin film wave guide. An alternate method would be simply to evaporate a metal- field electrode; the internal field necessary for deflection is then generated by the Schottky effect.

The material of the wave guide shown in Fig. 1 should be chosen to have a band g...