Patent
1985-10-10
1987-08-25
LaRoche, Eugene R.
350 9612, G02B 610, G02B 612
Patent
active
046888810
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to an optical, integrated waveguide component including a single crystal body, which has a flat upper surface provided with waveguides and flat, parallel end surfaces, the crystal having cleavage planes along which the crystalline bonds are weaker than the other bonds in the crystal so that cleavage of the crystal is facilitated along these cleavage planes, and the crystal has a greatest and a least refractive index in two mutually right-angular directions so that an optical axis can be determined, in the direction of which the refractive index of the crystal has a given value independent of the polarization direction of an incident light ray, and the cleavage planes have given inclination in relation to the optical axis.
BACKGROUND
In optical information transmission, it is essential that the transmission losses are small, both in the different parts of the transmission system and in the coupling between these parts. Waveguide components of the kind mentioned for such systems are known, and in them the orientation of the single crystal body in relation to the crystalline structure is such that the attenuation and dispersion of the light in the waveguides are small. In order that the components will also have small coupling losses, the end surfaces of the body are carefully polished, and this makes the production of the components complicated. Waveguide components are also known where the end surfaces of the body are cleavage surfaces, which gives small coupling losses. The latter components are produced in a simple way, but the orientation of the single crystal body in relation to the crystalline structure is such that large losses are obtained in the waveguides. These components are therefore not usable in many applications.
SUMMARY OF THE INVENTION
The problems mentioned are solved by the orientation of the single crystal body in relation to the crystalline structure being selected so that coupling of light into the waveguides takes place via a cleavage surface and the flat upper surface of the component is oriented in a special way in relation to the optical axis, so that optimum optical properties are obtained. The invention is characterized in the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
An embodiment of the invention will now be described in conjunction with the accompanying drawings, where
FIG. 1 is a perspective view of an optical, integrated waveguide component,
FIG. 2 schematically illustrates the crystalline structure for lithium niobate,
FIG. 3 illustrates how single crystal bodies in known components are oriented in relation to the crystalline structure,
FIG. 4 illustrates how a single crystal body in accordance with the invention is oriented in relation to the crystalline structure,
FIG. 5 is a perspective view of a crystal body for a waveguide component in accordance with the invention and
FIG. 6 is a cross section of an end portion of a component in accordance with the invention.
BEST MODE FOR CARRYING OUT THE INVENTION
As an example there is illustrated in FIG. 1 an optical, integrated waveguide component, which is a so-called directional coupler. A more detailed description of it will be found in IEEE Journal of Qantum Electronics, Vol. QE 17, No. 6, June 1981, Rod C. Alferness, "Guided-Wave Devices for Optical Communication". A single crystal body 1 made of material such as lithium niobate LiNbO.sub.3 or lithium tantalate LiTaO.sub.3 conventionally carries light waveguides 3 and 4 on its upper flat surface 2. These waveguides have a higher refractive index than the crystalline material and can be provided, for example, by diffusing titanium into the crystal to a suitable depth in a desired pattern. Light is introduced into one waveguide 3 e.g. by a lens system or, as is illustrated in the Figure, an optical fiber 5. The fiber is directed towards the mouth of the waveguide at the end surface 7 of the body, at a small distance from the end surface. The light is spread to a small part in the crystal and may be led over to the other
REFERENCES:
patent: 4198115 (1980-04-01), Kaminow
patent: 4433895 (1984-02-01), Puech et al.
LaRoche Eugene R.
Mottola Steven J.
Telefonaktiebolaget LM Ericsson
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