Positioning optical components and waveguides

DETAILED DESCRIPTION Recent developments in the field of optical communication have lead to the more widespread use of monomode waveguides such as monomode optical fibres.
It is particularly important in this case to devise a method for accurately positioning an optical component such as a laser chip or photosensor in alignment with an optical waveguide.
In accordance with one aspect of the present invention we provide a method of positioning an optical component and at least one optical waveguide in alignment with one another, the method comprising (a) forming at least one elongate waveguide and a locating formation in a common substrate; and, (b) mounting an optical component in the locating formation, the relative positions of the locating formation and the or each waveguide being such that in use an optical beam may be coupled between the optical component and the or each waveguide.
By using such a locating groove, we have discovered that it is possible accurately to align a component with an optical waveguide since the component is located by the groove which is in the same single crystal as the waveguide.
For example, a single crystal of silicon is a particularly suitable substrate for a number of reasons.
These include the fact that silicon is readily available in large sizes to the most exacting standards of purity and perfection; photolithographic and etching techniques for defining surface and sub-surface geometries are highly developed; and most importantly large anisotropic etching rates exist between different crystallographic axes in the crystal.
Furthermore, silicon has particularly useful electrical, mechanical and optical properties which enable the crystal to be used for opto-electronic sub-assemblies such as electro-optical modulators.
The invention also enables an optical component to be mounted in the same substrate as other optical devices.
The invention is particularly suitable for use with laser chips which have a line emission from an edge of the chip or with optical sensing chips