Note: Descriptions are shown in the official language in which they were submitted.
~ 23334/GB
RADIATION DEFLECTOR ASSEMBLY
The invention re1ates 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 assembliess are hereinafter referred to
as of the kind described.
Radiation deflector assemblies of the kind described
find particular application as switches in optical
1' transmission systems. IBM Technical Disclosure Bulletin
Vol 27, No 2 of July 1984 ~pages 11-12) 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
2~ fibres is reflected towards another group. When the
mirrors are in a deflected position, optical radiation is
instead reflected 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
i radiation deflector assembly of the kind described is
characterised in that the waveguides and the deflector
are mounted in a common substrate.
The invention deals with the alignment problem by
mounting both the waveguides and the deflector in the
same substrate.
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Preferably, the waveguides are substantially
coplanar, and conveniently the direction of movement of
the deflector is in substantially the sa~le plane as the
plane of the waveguides. In alternative arrangements,
S 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
1~ which the waveguides are mounted.
The invention is particularly suitable for
deflecting radiation in the optical waveband and
;typically a large number o~ radiation deflector
assemblies according to the invention will be assembled
together to cons~itute an optical switch array.
In some arrangements, the deflector may comprise a
piston member which moves to and fxo between the 'irst
and second positions. Preferably, however, the deflector
comprises a cantilevered arm which is controlled to pivot
betweer. the first and secon2 position~.
It is particularly convenient i' the deflector is
integrally formed with the substrate. This can be
achieved using conventional etching techniques or laser
etching technology.
25Preferably, the deflector is adapted to deflect the
radiation in both the first and secona positions although
in some examples, radiation could pass directly fro~ 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.
` The deflector will typically comprise a radiation
reflector but other deflectors are possible such as a
- re'ractor or diffractor.
In some examples, the waveguides could be formed by
diffusing a suitable material into the substrate but
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convenien-tly 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 cr 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
Canadian Patent Application, serial number 520,799
entitled "Movable Member Mounting".
An example of an optical reflection 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.
~S Each groove 2-4 termina-tes 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 cavi-ty 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
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; mounted 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
l~ 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 eithex the optical fibre in the groove 3 or the
optical fibre in the groove 4.
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