RADIATION DEFLECTOR ASSEMBLY

Abstract: A radiation deflector assembly, primarily for deflecting optical radiation, comprises three waveguides mounted in V-­ shaped grooves (2,3,4) of a substrate (1) which are substanti­ ally coplanar. A cantilevered beam (6) integral with the sub­ strate (1) is positioned in a cavity (5) of the substrate such that when the beam (6) is in a first position radiation passes be­ tween optical waveguides in two of the grooves (2,3) and when the beam is in a second position optical radiation passes between optical waveguides in another two of the grooves (2,4). Control means including electrodes (8,9) is responsive to control signals to generate a suitable electrostatic field for moving the beam (6) between the two positions.

Description: The invention relates to radiation deflector assemblies of the kind comprising at least three radiation waveguides; a controllable radiation deflector positioned such that when the deflector is in a first position radiation passes between one combination of two of the waveguides, and when the deflector is in a second position radiation passes between another combination of two of the waveguides; and control means responsive to control signals for controlling the position of the deflector. Such assemblies are hereinafter referred to as of the kind described. Radiation deflector assemblies of the kind described find particular application as switches in optical transmission systems. IBM Technical Disclosure Bulletin Vol 27, No 2 of July 1984 (pages 1119-1120) describes a solid-state array of mirrors positioned beneath three groups of optical fibres. In a relaxed position, optical radiation impinging on the mirrors from one group of fibres is deflected towards another group. When the mirrors are in a deflected position, optical radiation is instead deflected towards the third group of fibres. The major problem with this arrangement is that it is difficult accurately to align the optical fibres with the mirrors. Alignment is important when large arrays of mirrors are concerned so as to maximise the number of mirrors per unit area. In accordance with the present invention, a radiation deflector assembly of the kind described is characterised in that the deflector is integrally formed with a substrate; the waveguides are mounted in or formed in the substrate; and radiation passing between a combination of two of the waveguides, exits one waveguide prior to being deflected to enter another waveguide. The invention deals with the alignment problem by having both the waveguides and the deflector in the same substrate. Preferably, the waveguides are substantially coplanar, and conveniently the direction of movement of the deflector is in substantially the same plane as the plane of the waveguides. In alternative arrangements, however, the waveguides may extend in different planes. The invention is particularly suitable where the substrate comprises a single crystal of for example silicon, since anisotropic etching techniques may be used to define grooves of the same or different depths into which the waveguides are mounted. The invention is particularly suitable for deflecting radiation in the optical waveband and typically a large number of radiation deflector assemblies according to the invention will be assembled together to constitute an optical switch array. Preferably, the deflector comprises a cantilevered arm which is controlled to pivot between the first and second positions. The integral formation of the deflector with the susbstrate can be achieved by using conventional etching techniques or laser etching technology. Preferably, the deflector is adapted to deflect the radiation in both the first and second positions although in some examples, radiation could pass directly from one waveguide to another when the deflector is in the first position and be deflected towards another waveguide when the deflector is in the second position. In some examples, the waveguides could be formed by diffusing a suitable material into the substrate but conveniently each waveguide is mounted in a groove formed in a surface of the substrate, typically a V-shaped groove. As has previously been mentioned, the substrate may comprise silicon but other substrate materials are possible such as silica or lithium niobate or III-V compounds such as gallium arsenide. The position of the deflector can be controlled using conventional electrostatic techniques or by thermal methods similar to those described in our copending British Patent Application of even date entitled "Movable Member Mounting" (our case ref: 23332/GB). An example of an optical deflection assembly according to the invention for use in an optical switch array will now be described with reference to the accompanying drawing which is a schematic perspective view of the assembly. The optical element or assembly shown in the drawing includes a substrate comprising a single crystal silicon slice 1 in the upper surface of which three V-shaped grooves 2-4 have been etched using an anisotropic masking and etching technique. The grooves 2-4 all have substantially the same depth and are effectively coplanar. Each groove 2-4 terminates in a cavity 5 formed in the substrate 1. Monomode optical fibres (not shown) are positioned in each of the grooves 2-4 with their ends facing into the cavity 5. A cantilevered, vertically hinged silicon beam 6 is positioned in the cavity 5 and is integrally formed with the remainder of the substrate 1. The beam 6 acts as an optical reflector. The beam can pivot about its end 7 between first and second positions in response to an electrostatic field generated by a pair of electrodes, one of which 8 is mounted to the substrate and the other of which is mouned to the facing surface of the beam 6. If the beam is at ground potential, the second electrode is not required. The electrodes are connected to electrical control apparatus including a power source (not shown). In its first position, the reflector 6 reflects optical radiation passing along the optical fibre in the groove 2 into the optical fibre in the groove 3. In its second position, optical radiation impinging on the reflector 6 from the fibre in the groove 2 is reflected into the fibre in the groove 4. The element shown in the drawing can thus be used as an optical switch to switch incoming radiation in the optical fibre in the groove 2 into either the optical fibre in the groove 3 or the optical fibre in the groove 4.

Claims: 1. A waveguide deflector assembly comprising at least three radiation waveguides, a controllable radiation deflector (6) positioned such that when the deflector (6) is in a first position radiation passes between one combination of two of the waveguides and when the deflector (6) is in a second position radiation passes between another combination of two of the waveguides; and control means (8) responsive to control signals for controlling the position of the deflector (6) characterised in that: the deflector (6) is integrally formed with a substrate (1); the waveguides are mounted in or formed in the substrate (1); and radiation passing between a combination of two of the waveguides exits one waveguide prior to being reflected to enter another waveguide. 2. An assembly according to claim 1, wherein the radiation waveguides are substantially coplanar. 3. An assembly according to claim 1 or claim 2, wherein each waveguide comprises a waveguide member mounted in a respective groove (2, 3, 4) formed in the substrate (1). 4. An assembly according to any of the preceding claims, wherein the deflector (6) comprises a cantilevered arm. 5. An assembly according to any of the preceding claims, wherein the deflector (6) is adapted to reflect radiation in both the first and second positions. 6. An assembly according to any of the preceding claims, wherein the waveguides and deflector (6) are adapted to guide and deflect optical radiation respectively. 7. An assembly according to any of the preceding claims, wherein the substrate (1) is a single crystal.

Inventors: STANLEY, IAN WILLIAM, DR.
Applicants: BRITISH TELECOMMUNICATIONS PUBLIC LIMITED COMPANY
Application year: 1986
Main classification: G02B26
IPC codes: G02B6, G02B7, H01S3, G01J3, H01S5, G01D5, G02B26