Optical waveguides – Planar optical waveguide
Patent
1996-05-06
1998-01-13
Palmer, Phan T. H.
Optical waveguides
Planar optical waveguide
385130, 385131, 385 14, 372 45, G02B 612
Patent
active
057087504
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a manufacturing process for an integrated optic device comprising a glass substrate and at least one optic wave guide, said wave guide having at least one first portion arranged in the substrate at a first depth with respect to a face of the substrate, at least one second portion arranged in the substrate at a second depth, greater than the first, with respect to said face and a transition portion between the first and second portions.
BACKGROUND OF THE INVENTION
Integrated optics techniques enable the form of a wave guide to be easily varied in one dimension, i.e. in a horizontal plane, that is to say in a plane parallel to a face of the substrate. For certain applications, it is desirable to form wave guides whose form also varies in depth.
Currently, two types of techniques enable wave guides of variable depth to be formed. According to a first technique, a predetermined part of the surface of the substrate is etched, by physical or chemical methods, to make the wave guide flush. With this first technique the surface of the substrate obtained after treatment is not flat, such that subsequent manufacturing stages are detrimentally effected. Moreover, it is difficult to control precisely the ablation depth of the substrate, which limits the manufacturing reproducibility. Losses or reflections occur at the transition zones which are not gradual and may present thermal withstand problems.
According to a second technique, a non-homogeneous electrical field is applied between a first face, or front face, of the substrate and an electrode arranged on a part of a second face, or rear face, of the substrate, opposite the first face. Applying an electrical field results in the wave guide being buried under the partial electrode and a transition zone of variable depth being formed in the rest of the substrate. The form of the transition zone is linked to the form of the field lines. This technique is only usable in a technology using mobile ions. In addition, the transition zone is always long, about several times the thickness of the substrate. As an example, for a substrate 3 mm thick, the transition zone is about 10 mm or more. Furthermore, alignment of the electrode situated on the rear face with respect to the guide situated on the front face requires a complex adaptation of existing machines.
SUMMARY OF THE INVENTION
The object of the invention is to achieve a process which does not present these various shortcomings. This object is achieved by the fact that the process according to the invention comprises placing a mask on said face of the substrate, said mask comprising at least one edge cutting the wave guide obliquely at a predetermined, preferably very small, angle so as to define at least one totally masked axial portion of the wave guide designed to form the first portion, an unmasked axial portion of the wave guide designed to form the second portion and a partially masked axial portion of the wave guide to form said transition portion, the process comprising a burying stage of the wave guide in the substrate, in the presence of said mask, to place the second portion of the wave guide at said second depth and form the transition portion, followed by a removal, stage of the mask.
The process according to the invention is notably perfectly suited to mass production, has excellent compatibility with other manufacturing stages of several integrated optics technologies and enables optimum control of the dimensions of the transition zone.
According to a first development, the process comprises a prior formation stage of an initial guide before said mask is placed on the face of the substrate. The prior formation stage of the initial guide and the wave guide burying stage are then performed, for example, by ion exchange technology, the mask being made of a material not permeable to ions, and the burying stage being performed by application of an electrical field.
According to a second development, formation of the wave guide is performed in a single stage, in the presence of t
REFERENCES:
patent: 4711514 (1987-12-01), Tangonan et al.
patent: 5237639 (1993-08-01), Kato et al.
Electronics Letters, vol. 28, No. 14, Jul. 2, 1992, "Novel Vertical Directional Coupler Made by Field-Assisted Ion-Exchanged Slab Waveguides In Glass", pp. 1340-1342.
Patent Abstracts of Japan, vol. 7, No. 198 (P-220).
Kevorkian Antoine
Persegol Dominique
Palmer Phan T. H.
Schneider Electric S.A.
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