DE3630479A1 - Process for the production of a planar, polarising, monomodal optical waveguide - Google Patents

Abstract

In a process for the production of a planar, polarising, monomodal optical waveguide (optical fibre) having light-conducting regions, thin, glass-like coatings are deposited from the gas phase in a heterogeneous reaction onto a substrate by first applying to the substrate a coating containing a dopant (boron, fluorine) which reduces the refractive index and then, on top of this coating, a top coat of B2O3-doped SiO2 as diffusion barrier for this dopant, structured by conventional mask technology in accordance with a desired stripe pattern, and subsequently allowing the dopant to substantially diffuse out of the uncovered areas by heating, thus forming part of the core region of the light-conducting regions; through mask technology and etching, two narrow bridges adjacent to the core region are worked out, the etched-out part of the top coat is replaced by an SiO2 coating and completed by a further coating system with a suitable refractive index profile of the core region, and the cladding region is formed.

Description

Subject of the main patent (patent application P 35 36 781.4) is a process for producing a planar light waveguide with light-guiding areas, by deposition thin glassy layers from the gas phase after one Scheme that enables a predetermined refractive index curve, on a substrate, so that a light-guiding core area and cladding layers adjacent to this core area are formed, this separation from the gas phase by means of a heterogeneous reaction (CVD method) leads to a layer on this substrate a dopant which lowers the refractive index is brought, then on this layer a cover layer as Diffusion barrier applied for this dopant is, this cover layer in the usual mask technique structured according to the desired stripe pattern then the one with these layers The substrate is heated so strongly that this dopant largely diffuse out of the uncovered areas dated and so the core area or part of the core area the light-guiding areas is formed, and afterwards additional layers are applied, the refractive indices of which are controlled so that they complete the optical fiber standing.

It has now been found that a planar single-mode light waveguide, which is able to light with defined To transmit polarization direction, according to which in the Patent application P 35 36 781.4 described method can be manufactured.

For this purpose, in the process of the main patent, the covering layer being built up from SiO ₂ and B ₂ O ₃ , after the dopant has evaporated, the covering layer is etched away to two narrow, narrow webs immediately adjacent to the uncovered areas, and then a thin layer is etched out SiO _{2 is} deposited from the gas phase, in a next step this SiO _{2 is} etched away in the core area and on the narrow webs and in a last procedural step further layers of fluorine-doped SiO _{2 are} applied, the course of the refractive index being chosen so that the core area is completed and the Mantelbe is richly trained.

Light whose polarization plane is parallel to the substrate can leave the core area by "tunneling" through the narrow webs of SiO ₂ and B ₂ O ₃ ; this polarization plane is therefore decoupled and a planar, polarizing optical waveguide is obtained. The light emerging from this optical waveguide is polarized in a plane perpendicular to the substrate.

This polarization is maintained by voltage birefringence, which is caused by the two narrow webs consisting of B ₂ O ₃ doped SiO ₂ .

The present invention will be explained with reference to the drawing tert.

After the evaporation of the fluorine from the core region 1 , the remaining SiO ₂ doped with B ₂ O _{3 is} etched away except for two narrow webs 2 and 2 ' directly adjacent to the core region 1 ' . Then a thin layer 3 of SiO _{2 is} deposited from the gas phase, which replaces the cover layer. In the next step, this SiO _{2 is} etched away in the core region 1 and on the narrow webs 2 and 2 ' and finally another layer system 4 is applied, the course of the refractive index being chosen such that the core region 1 is completed and the cladding region is formed.

Claims (1)

Method for producing a planar optical waveguide with light-guiding areas, by depositing thin glass-like layers from the gas phase according to a scheme that enables a predetermined refractive index curve, on a substrate, so that a light-guiding core area and cladding layers adjacent to this core area are formed, this deposition is carried out from the gas phase by means of a heterogeneous reaction (CVD method), a layer with a dopant which lowers the refractive index is first applied to this substrate, then a cover layer is applied to this layer as a diffusion barrier for this dopant, this cover layer is structured in the usual masking technique in accordance with a desired stripe pattern, then the substrate provided with these layers is heated to such an extent that this dopant largely diffuses out of the uncovered areas and thus the core area or a part of the core area of the light-guiding areas is formed, and then further layers are applied, the refractive indices of which are controlled so that they complete the optical waveguide, according to P 35 36 781, characterized in that a layer doped with boron is applied as this covering layer is that after the evaporation of the dopant the cover layer is etched away to two narrow, directly adjacent to the uncovered narrow webs, then a thin layer of SiO _{2 is} deposited from the gas phase, that in a next step this SiO ₂ in the core area and is etched away on the narrow webs and in a last process step further layers of fluorine-doped SiO _{2 are} applied, the course of the refractive index being chosen such that the core area is completed and the cladding area is formed.