EP1356323A1 - Optics-integrated structure comprising in a substrate at least a non-buried guide portion and method for making same - Google Patents

Optics-integrated structure comprising in a substrate at least a non-buried guide portion and method for making same

Info

Publication number
EP1356323A1
EP1356323A1 EP02701339A EP02701339A EP1356323A1 EP 1356323 A1 EP1356323 A1 EP 1356323A1 EP 02701339 A EP02701339 A EP 02701339A EP 02701339 A EP02701339 A EP 02701339A EP 1356323 A1 EP1356323 A1 EP 1356323A1
Authority
EP
European Patent Office
Prior art keywords
guide
buried
substrate
covering element
structure according
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP02701339A
Other languages
German (de)
French (fr)
Inventor
Gilles Clauss
Serge Valette
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Teem Photonics SA
Original Assignee
Teem Photonics SA
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Teem Photonics SA filed Critical Teem Photonics SA
Publication of EP1356323A1 publication Critical patent/EP1356323A1/en
Withdrawn legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
    • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
    • G02B6/122—Basic optical elements, e.g. light-guiding paths
    • G02B6/125—Bends, branchings or intersections
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
    • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
    • G02B2006/12083—Constructional arrangements
    • G02B2006/12097—Ridge, rib or the like
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
    • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
    • G02B2006/12083—Constructional arrangements
    • G02B2006/12119—Bend
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
    • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
    • G02B2006/12166—Manufacturing methods
    • G02B2006/12183—Ion-exchange

Definitions

  • the present invention relates to a structure in integrated optics comprising in a substrate at least one portion of guide which is not buried as well as its production method. It applies to numerous components produced in integrated optics such as in particular optical amplifiers, optical multiplexers, optical dividers, optical couplers, and, in general to any component using at least one portion of an unground buried optical guide.
  • An optical guide is made up of a central part generally called the heart and surrounding media located all around the heart and which may be identical to each other or different.
  • the refractive index of the medium making up the heart must be different and in most cases higher than that of the surrounding media.
  • the guide will be likened to its central part.
  • all or part of the surrounding media will be called a substrate, it being understood that when the guide is not or only slightly buried, one of the surrounding media may be outside the substrate and be, for example, air.
  • the substrate can be monolayer or multilayer.
  • an optical guide in a substrate can be more or less buried in this substrate and in particular comprise guide portions buried at variable depths.
  • the optical guides of an integrated optical structure produced in a substrate in particular by ion exchange technology, must be at the input and at the output of the structure connected to optical fibers.
  • the waveguides at least at the input and at the output must have a mode of propagation of the light close respectively to that of the fiber which must be associated with it.
  • this mode of propagation is often relatively unconfined.
  • Low confinement does not allow, moreover, to produce curved optical guides, with radii of curvature typically less than 20 mm, which can be detrimental in terms of the size of the component.
  • portions of guides at least at entry and exit at low confinement these portions have a width adapted to that of the fibers and are therefore buried in the technology for producing guides by ion exchange, - and on the other hand portions of guides with high confinement suitable for producing a small radius of curvature and which are therefore in this technology in the vicinity of the surface of the substrate .
  • the guides located in the vicinity of the surface are poorly protected from the environment and have optical losses which can be high and which can change over time due to pollution on the surface of the substrate.
  • the invention relates to a structure in integrated optics comprising in a substrate at least one portion of a non-buried guide which is isolated from the environment by means which cause little or no mechanical stress on the structure.
  • a guide located in the vicinity of the surface of the substrate, that is to say that the thickness of material separating the core from the surface of the substrate is either zero or insufficient to avoid losses optical, for example by evanescent wave associated with a mode of propagation of the light wave in the guide.
  • the invention relates to an integrated optical structure comprising in an substrate an optical guide having at least one portion of guide which is not buried; it is characterized in that it further comprises on the surface of the substrate at least one covering element above the non-buried guide portion capable of isolating in said guide portion, a light wave propagating in it .
  • the structure of the invention comprises several portions of non-buried guides, each portion is associated with a covering element.
  • the guide comprises at least one non-buried guide portion and at least one buried guide portion, the covering element being located above the buried and non-buried guide portions. Also in this mode, the overlap is limited since it is not carried out on the entire substrate.
  • the covering element has a thickness
  • Wp at least equal to the minimum thickness Wm necessary so that an evanescent wave associated with the light wave guided in said portion cannot leave the structure.
  • the covering element is mono or multilayer; the refractive index or indices are such that an evanescent wave associated with the light wave guided in said portion cannot leave the structure. More precisely, the refractive indices are respectively less than the smallest of the effective indices of the propagation modes which can be guided in said non-buried portion and preferably less than the maximum refractive index of the substrate.
  • the covering element is chosen, for example, from silica, or a glass with an appropriate index.
  • the covering element has a width
  • the width Lp can be either constant or variable. In particular, when covering elements cover both the buried and non-buried portions of the guide, then the width of these elements may follow the width of the modes guided in the corresponding guide portions or be greater than the width of the mode in the guide less confined.
  • the invention also relates to a method for producing an integrated optical structure comprising in an substrate an optical guide having at least one portion of guide which is not buried and on the surface of the substrate at least one covering element above the guide portion not buried; this process comprising the following steps:
  • Step B) comprises the deposition on the substrate of a covering layer and then the production on this layer of a mask protecting the guide portion or portions to be covered, the etching of the covering layer through the mask. so as to obtain the covering element (s).
  • the mask is usually removed but it can of course be kept in some cases.
  • step A) comprises the formation in a glass substrate of a waveguide by ion exchange, the localized re-diffusion of this guide so as to bury at least one portion of the guide, the portion of non-buried guide having greater confinement than the buried portion.
  • This replay can be conventionally obtained by metal masking and application of an electric field on either side of the portion to be buried.
  • This re-diffusion in the substrate is carried out so as to ensure the desired functionality of the component in the portion or portions considered. For example, it is implemented to optimize the coupling with input and ⁇ or output optical fibers.
  • FIGS. 1a, 1b represent it schematically, different stages of an embodiment of a structure of the invention
  • FIG. 2 shows schematically and in perspective, a first variant of the structure of the invention.
  • FIG. 3 shows schematically and in perspective, a second variant of the structure of
  • FIG. 1a schematically represents a first step in producing a structure in integrated optics according to the invention.
  • a waveguide is produced through a mask (not shown) by the known technique of ion exchange.
  • the waveguide 1 shown in this figure is not buried, it is parallel to the plane defined by the surface of the substrate and includes straight parts la and curved parts lb.
  • this non-buried waveguide preferably has significant confinement.
  • the method of the invention consists in causing portions of the guide to be diffused locally under an electric field in order to bury them.
  • FIG. 1b represents the structure at the end of this operation.
  • the mask (not shown) used to carry out the diffusion is preferably eliminated at the end of this operation. It can however, in certain cases, be removed later or even kept above the guides to form part of the covering elements.
  • FIG. 1b we therefore see zones Ze of the structure comprising the straight guide portions 1a which are buried in the substrate and a zone Zne of the structure comprising the non-buried guide portion, this portion comprising the curved guides 1b.
  • transition zones Zt Between the buried and non-buried guide portions, there are transition zones Zt; the part of these zones in which the thickness of material separating the core of the guide from the surface of the substrate is either zero or insufficient to avoid optical losses, is considered to be part of the portion of guide which is not buried; and the part of these zones in which said thickness is sufficient to avoid optical losses is considered to be buried.
  • non-buried guide In this exemplary embodiment, a single portion of non-buried guide has been shown, but of course we could have had a guide with several portions of non-buried guide separating for example two parts of curved guides respectively.
  • the figure illustrates the realization of a covering layer 3 on the structure.
  • This layer is monolayer or multilayer and for example made of silica or glass of refractive index adapted as we have seen previously so that an evanescent wave associated with the light wave guided in said portion cannot leave the structure; this layer is deposited by sputtering or vacuum evaporation. Furthermore, the thickness Wp of this layer is chosen so that the evanescent wave associated with the guided mode in the non-buried portion cannot see the medium located above the layer. This thickness will generally be comprised, typically between 0.3 and 5 ⁇ m.
  • the covering element or elements are then produced.
  • Several methods of implementation are possible. According to a first mode shown in the figure
  • the covering layer 3 is etched so as to leave only a covering element 5 situated above the assembly of the guide both in its non-buried portion and in its buried portion.
  • the width Lp of the covering element must be greater than or equal to a determined minimum width so that the evanescent wave associated with the guided mode in the non-buried portion of the structure cannot see the medium located above said element. This width can be constant as shown or variable.
  • the covering layer 3 is etched so as to leave only a covering element 7 situated only above the non-buried guide portion.
  • a mask of resin is produced on the covering layer, for example, which is exposed and developed. according to conventional techniques of microelectronics so as to obtain a pattern corresponding to the covering element that one wants to obtain. Then the covering layer is etched through this mask, for example by an etching of the ion machining type or chemical etching for a layer of silica. The mask is then generally removed unless it does not interfere with the structure.
  • the covering element is of the type of that shown in FIG. 2, that is to say that it is above the guide and follows the same path.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Optical Integrated Circuits (AREA)

Abstract

The invention concerns an optics-integrated structure comprising in a substrate an optical guide having at least a non-buried guide portion and on the substrate surface at least an overlapping element (5) located above the non-buried guide portion and designed to isolate said guide portion, a light wave propagating therein. The invention is applicable to optics-integrated components such as in particular optical amplifiers, optical multiplexers, optical divider, optical couplers and the like.

Description

STRUCTURE EN OPTIQUE INTEGREE COMPORTANT DANS UN INTEGRATED OPTICAL STRUCTURE COMPRISING IN A
SUBSTRAT AU MOINS UNE PORTION DE GUIDE NON ENTERREESUBSTRATE AT LEAST ONE UNDERGROUND GUIDE PORTION
AINSI QUE SON PROCEDE DE REALISATIONAS WELL AS ITS PRODUCTION PROCESS
Domaine techniqueTechnical area
La présente invention concerne une structure en optique intégrée comportant dans un substrat au moins une portion de guide non enterrée ainsi que son procédé de réalisation. Elle s'applique à de nombreux composants réalisés en optique intégrée tels que notamment des amplificateurs optiques, des multiplexeurs optiques, des diviseurs optiques, des coupleurs optiques , et, de façon générale à tout composant utilisant au moins une portion de guide optique non enterrée.The present invention relates to a structure in integrated optics comprising in a substrate at least one portion of guide which is not buried as well as its production method. It applies to numerous components produced in integrated optics such as in particular optical amplifiers, optical multiplexers, optical dividers, optical couplers, and, in general to any component using at least one portion of an unground buried optical guide.
Etat de la techniqueState of the art
Un guide optique se compose d'une partie centrale appelée généralement cœur et de milieux environnants situés tout autour du cœur et qui peuvent être identiques entre eux ou différents.An optical guide is made up of a central part generally called the heart and surrounding media located all around the heart and which may be identical to each other or different.
Pour permettre le confinement de la lumière dans le cœur, l'indice de réfraction du milieu composant le cœur doit être différent et dans la plupart des cas supérieure à ceux des milieux environnants.To allow the confinement of light in the heart, the refractive index of the medium making up the heart must be different and in most cases higher than that of the surrounding media.
Pour simplifier la description on assimilera le guide à sa partie centrale. Par ailleurs, on appellera tout ou partie des milieux environnants, substrat, étant bien entendu que lorsque le guide est pas ou peu enterré, un des milieux environnants peut être extérieur au substrat et être par exemple de l'air. Suivant le type de technique utilisé, le substrat peut être monocouche ou multicouches .To simplify the description, the guide will be likened to its central part. Furthermore, all or part of the surrounding media will be called a substrate, it being understood that when the guide is not or only slightly buried, one of the surrounding media may be outside the substrate and be, for example, air. Depending on the type of technique used, the substrate can be monolayer or multilayer.
En outre, suivant les applications, un guide optique dans un substrat peut être plus ou moins enterré dans ce substrat et en particulier comporter des portions de guide enterrées à des profondeurs variables .In addition, depending on the applications, an optical guide in a substrate can be more or less buried in this substrate and in particular comprise guide portions buried at variable depths.
Ainsi par exemple dans certaines applications, les guides optiques d'une structure en optique intégrée, réalisés dans un substrat notamment par la technologie d'échange d'ions, doivent être en entrée et en sortie de la structure connectés à des fibres optiques. De ce fait, les guides d'onde au moins en entrée et en sortie doivent présenter un mode de propagation de la lumière proche respectivement de celui de la fibre qui doit lui être associée. Or ce mode de propagation est souvent, relativement peu confiné .Thus, for example, in certain applications, the optical guides of an integrated optical structure, produced in a substrate in particular by ion exchange technology, must be at the input and at the output of the structure connected to optical fibers. As a result, the waveguides at least at the input and at the output must have a mode of propagation of the light close respectively to that of the fiber which must be associated with it. However, this mode of propagation is often relatively unconfined.
Un faible confinement ne permet pas, par ailleurs, de réaliser des guides optiques courbes, avec des rayons de courbure typiquement inférieurs à 20 mm, ce qui peut être pénalisant sur le plan de 1 ' encombrement du composant .Low confinement does not allow, moreover, to produce curved optical guides, with radii of curvature typically less than 20 mm, which can be detrimental in terms of the size of the component.
Pour obtenir de faibles rayons de courbure, il faut donc augmenter le confinement latéral des guides.To obtain small radii of curvature, it is therefore necessary to increase the lateral confinement of the guides.
Pour concilier ces contraintes, il est connu de réaliser des guides présentant :To reconcile these constraints, it is known to produce guides presenting:
- d'une part des portions de guides au moins en entrée et en sortie à faible confinement, ces portions ont une largeur adaptée à celle des fibres et sont donc enterrées dans la technologie de réalisation de guides par échange d'ions, - et d'autre part des portions de guides à fort confinement adapté à la réalisation de faible rayon de courbure et qui sont donc dans cette technologie au voisinage de la surface du substrat.on the one hand, portions of guides at least at entry and exit at low confinement, these portions have a width adapted to that of the fibers and are therefore buried in the technology for producing guides by ion exchange, - and on the other hand portions of guides with high confinement suitable for producing a small radius of curvature and which are therefore in this technology in the vicinity of the surface of the substrate .
Les guides situés au voisinage de la surface sont mal protégés de l'environnement et présentent des pertes optiques qui peuvent être élevées et qui peuvent évoluer dans le temps à cause de pollution sur la sur ace du substrat .The guides located in the vicinity of the surface are poorly protected from the environment and have optical losses which can be high and which can change over time due to pollution on the surface of the substrate.
Par ailleurs, l'utilisation d'une couche de protection sur le substrat pour protéger la structure de l'environnement induirait des contraintes mécaniques sur celle-ci (à cause en particulier de problèmes de coefficients de dilatation thermique différents) et nuire à sa fonctionnalité. Ces contraintes pourraient notamment créer des effets de biréfringence qui sont préjudiciables pour certaines applications.Furthermore, the use of a protective layer on the substrate to protect the structure of the environment would induce mechanical stresses on it (due in particular to problems of different coefficients of thermal expansion) and impair its functionality. . These constraints could in particular create birefringence effects which are detrimental for certain applications.
Exposé de l'invention et brève description des figuresStatement of the invention and brief description of the figures
L'invention concerne une structure en optique intégrée comportant dans un substrat au moins une portion de guide non enterrée qui est isolée de l'environnement par des moyens qui n'induisent pas ou peu de contraintes mécaniques sur la structure.The invention relates to a structure in integrated optics comprising in a substrate at least one portion of a non-buried guide which is isolated from the environment by means which cause little or no mechanical stress on the structure.
On entend dans la présente invention par "non enterré" un guide situé au voisinage de la surface du substrat, c'est-à-dire que l'épaisseur de matériau séparant le cœur, de la surface du substrat est soit nulle, soit insuffisante pour éviter les pertes optiques, par exemple par onde évanescente associée à un mode de propagation de l'onde lumineuse dans le guide .In the present invention is meant by "not buried" a guide located in the vicinity of the surface of the substrate, that is to say that the thickness of material separating the core from the surface of the substrate is either zero or insufficient to avoid losses optical, for example by evanescent wave associated with a mode of propagation of the light wave in the guide.
De façon plus précise, l'invention a pour objet une structure en optique intégrée comportant dans un substrat un guide optique présentant au moins une portion de guide non enterrée ; elle est caractérisée en ce qu'elle comprend en outre sur la surface du substrat au moins un élément de recouvrement au-dessus de la portion de guide non enterrée apte à isoler dans ladite portion de guide, une onde lumineuse se propageant dans celui-ci.More specifically, the invention relates to an integrated optical structure comprising in an substrate an optical guide having at least one portion of guide which is not buried; it is characterized in that it further comprises on the surface of the substrate at least one covering element above the non-buried guide portion capable of isolating in said guide portion, a light wave propagating in it .
La structure de l'invention comporte plusieurs portions de guides non enterrées, chaque portion est associée à un élément de recouvrement.The structure of the invention comprises several portions of non-buried guides, each portion is associated with a covering element.
L'utilisation d'éléments de recouvrement au moins sur les portions non enterrées des guides permet d'isoler celles-ci de l'extérieure et d'éviter des pertes optiques. Ces éléments de recouvrement permettent donc d'avoir des structures présentant des guides à fort confinement puisque ce type de guide ne peut être enterré et de ce fait permettent d'avoir des guides courbes et notamment à faibles rayons de courbure . Par ailleurs, le fait de limiter le recouvrement par des éléments disposés sur les portions non enterrées des guides permet par ailleurs de minimiser l'apparition d'effets parasites tels que des contraintes mécaniques qui pourraient nuire notamment à la fonctionnalité de la structure. Selon un mode de réalisation, le guide comporte au moins une portion de guide non enterrée et au moins une portion de guide enterrée, l'élément de recouvrement étant situé au-dessus des portions de guide enterrée et non enterrée. Dans ce mode également, le recouvrement est limité puisqu'il n'est pas réalisé sur l'ensemble du substrat.The use of covering elements at least on the non-buried portions of the guides makes it possible to isolate them from the exterior and to avoid optical losses. These covering elements therefore make it possible to have structures having guides with high confinement since this type of guide cannot be buried and therefore make it possible to have curved guides and in particular with small radii of curvature. Furthermore, the fact of limiting the overlap by elements disposed on the non-buried portions of the guides also makes it possible to minimize the appearance of parasitic effects such as mechanical stresses which could in particular harm the functionality of the structure. According to one embodiment, the guide comprises at least one non-buried guide portion and at least one buried guide portion, the covering element being located above the buried and non-buried guide portions. Also in this mode, the overlap is limited since it is not carried out on the entire substrate.
L'élément de recouvrement présente une épaisseurThe covering element has a thickness
Wp au moins égale à l'épaisseur minimum Wm nécessaire pour qu'une onde évanescente associée à l'onde lumineuse guidée dans ladite portion ne puisse sortir de la structure .Wp at least equal to the minimum thickness Wm necessary so that an evanescent wave associated with the light wave guided in said portion cannot leave the structure.
L'élément de recouvrement est mono ou multicouches ; le ou les indices de réfraction sont tels qu'une onde évanescente associée à l'onde lumineuse guidée dans ladite portion ne puisse sortir de la structure. De façon plus précise, les indices de réfraction sont respectivement inférieurs au plus petit des indices effectifs des modes de propagation pouvant être guidés dans ladite portion non enterrée et de préférence inférieurs à l'indice de réfraction maximum du substrat .The covering element is mono or multilayer; the refractive index or indices are such that an evanescent wave associated with the light wave guided in said portion cannot leave the structure. More precisely, the refractive indices are respectively less than the smallest of the effective indices of the propagation modes which can be guided in said non-buried portion and preferably less than the maximum refractive index of the substrate.
L'élément de recouvrement est choisi par exemple parmi de la silice, ou un verre d'indice approprié. L'élément de recouvrement présente une largeurThe covering element is chosen, for example, from silica, or a glass with an appropriate index. The covering element has a width
Lp telle qu'une onde évanescente associée à l'onde lumineuse guidée dans ladite portion ne puisse sortir de la structure. De façon plus précise, elle est supérieure ou égale à la largeur du mode de propagation le plus large des modes pouvant se propager dans ladite portion de guide non enterrée. La largeur Lp peut être soit constante soit variable. Notamment, lorsque des éléments de recouvrement recouvrent aussi bien les portions enterrées et non enterrées du guide, alors la largeur de ces éléments peut suivre la largeur des modes guidés dans les portions de guide correspondantes ou être supérieure à la largeur du mode dans le guide le moins confiné .Lp such that an evanescent wave associated with the light wave guided in said portion cannot leave the structure. More precisely, it is greater than or equal to the width of the widest propagation mode of the modes that can propagate in said portion of guide which is not buried. The width Lp can be either constant or variable. In particular, when covering elements cover both the buried and non-buried portions of the guide, then the width of these elements may follow the width of the modes guided in the corresponding guide portions or be greater than the width of the mode in the guide less confined.
L'invention a également pour objet un procédé de réalisation d'une structure en optique intégrée comportant dans un substrat un guide optique présentant au moins une portion de guide non enterrée et sur la surface du substrat au moins un élément de recouvrement au-dessus de la portion de guide non enterrée ; ce procédé comportant les étapes suivantes :The invention also relates to a method for producing an integrated optical structure comprising in an substrate an optical guide having at least one portion of guide which is not buried and on the surface of the substrate at least one covering element above the guide portion not buried; this process comprising the following steps:
A) réalisation dans un substrat d'au moins un guide d'onde avec au moins une portion de guide non enterrée,A) production in a substrate of at least one waveguide with at least one portion of guide which is not buried,
B) formation au-dessus de la portion non enterrée de l'élément de recouvrementB) formation above the non-buried portion of the covering element
L'étape B) comporte le dépôt sur le substrat d'une couche de recouvrement puis la réalisation sur cette couche, d'un masque protégeant la ou les portions de guide à recouvrir, la gravure de la couche de recouvrement à travers le masque de façon à obtenir le ou les éléments de recouvrement.Step B) comprises the deposition on the substrate of a covering layer and then the production on this layer of a mask protecting the guide portion or portions to be covered, the etching of the covering layer through the mask. so as to obtain the covering element (s).
Le masque est généralement enlevé mais il peut bien entendu être conservé dans certains cas.The mask is usually removed but it can of course be kept in some cases.
Selon un mode de réalisation, le dépôt de la couche de recouvrement est réalisé par pulvérisation cathodique ou évaporation sous vide. Selon un exemple de réalisation, l'étape A) comporte la formation dans un substrat de verre d'un guide d'onde par échange ionique, la rediffusion localisée de ce guide de façon à enterrer au moins une portion de guide, la portion de guide non enterrée étant à plus fort confinement que la portion enterrée .According to one embodiment, the deposition of the covering layer is carried out by sputtering or vacuum evaporation. According to an exemplary embodiment, step A) comprises the formation in a glass substrate of a waveguide by ion exchange, the localized re-diffusion of this guide so as to bury at least one portion of the guide, the portion of non-buried guide having greater confinement than the buried portion.
Cette rediffusion peut être obtenue classiquement par un masquage métallique et application d'un champ électrique de part et d'autre de la portion à enterrer.This replay can be conventionally obtained by metal masking and application of an electric field on either side of the portion to be buried.
Cette rediffusion dans le substrat est réalisée de façon à assurer la fonctionnalité désirée du composant dans la ou les portions considérées. Par exemple, elle est mise en œuvre pour optimiser le couplage avec des fibres optiques d'entrée et\ou de sortie .This re-diffusion in the substrate is carried out so as to ensure the desired functionality of the component in the portion or portions considered. For example, it is implemented to optimize the coupling with input and \ or output optical fibers.
Les caractéristiques et avantages de l'invention apparaîtront mieux à la lumière la description qui va suivre. Cette description porte sur des exemples de réalisation, donnés à titre explicatif et non limitatif. Elle se réfère par ailleurs à des dessins annexés sur lesquels :The characteristics and advantages of the invention will appear more clearly in the light of the description which follows. This description relates to exemplary embodiments, given by way of explanation and without limitation. It also refers to attached drawings in which:
- les figures la, lb, le représentent de façon schématique, différentes étapes d'un mode de réalisation d'une structure de l'invention,FIGS. 1a, 1b, represent it schematically, different stages of an embodiment of a structure of the invention,
- la figure 2 représente de façon schématique et en perspective, une première variante de la structure de l'invention .- Figure 2 shows schematically and in perspective, a first variant of the structure of the invention.
- la figure 3 représente de façon schématique et en perspective, une seconde variante de la structure de- Figure 3 shows schematically and in perspective, a second variant of the structure of
1 ' invention. Exposé détaillé de modes de réalisation1 invention. Detailed description of embodiments
La figure la représente de façon schématique une première étape de réalisation d'une structure en optique intégrée selon l'invention.FIG. 1a schematically represents a first step in producing a structure in integrated optics according to the invention.
Dans un substrat par exemple en verre, on réalise à travers un masque (non représenté) par la technique connue d'échange d'ions un guide d'onde. Le guide d'onde 1 représenté sur cette figure est non enterré, il est parallèle au plan défini par la surface du substrat et comprend des parties droites la et des parties courbes lb .In a substrate, for example made of glass, a waveguide is produced through a mask (not shown) by the known technique of ion exchange. The waveguide 1 shown in this figure is not buried, it is parallel to the plane defined by the surface of the substrate and includes straight parts la and curved parts lb.
Pour permettre la réalisation de guide à faibles rayons de courbure et obtenir notamment des composants à faible encombrement, ce guide d'onde non enterré, présente de préférence un confinement important .To allow the production of a guide with small radii of curvature and in particular to obtain components with a small footprint, this non-buried waveguide preferably has significant confinement.
Après réalisation de ce guide, le procédé de l'invention consiste à faire diffuser localement sous champ électrique des portions du guide afin d'enterrer celles-ci.After this guide has been produced, the method of the invention consists in causing portions of the guide to be diffused locally under an electric field in order to bury them.
Un exemple de réalisation d'enterrage partiel d'un guide est illustré notamment dans le brevet US-5 708 750.An exemplary embodiment of partial burial of a guide is illustrated in particular in US Pat. No. 5,708,750.
La figure lb représente la structure à l'issu de cette opération. Le masque (non représenté) utilisé pour réaliser la diffusion est de préférence éliminé à la fin de cette opération. Il peut être cependant dans certain cas de figures, enlevé ultérieurement ou même conservé au-dessus des guides pour faire partie des éléments de recouvrement. Sur la figure lb, on voit donc des zones Ze de la structure comportant les portions de guides droits la qui sont enterrées dans le substrat et une zone Zne de la structure comportant la portion de guide non enterrée, cette portion comportant les guides courbes lb.FIG. 1b represents the structure at the end of this operation. The mask (not shown) used to carry out the diffusion is preferably eliminated at the end of this operation. It can however, in certain cases, be removed later or even kept above the guides to form part of the covering elements. In FIG. 1b, we therefore see zones Ze of the structure comprising the straight guide portions 1a which are buried in the substrate and a zone Zne of the structure comprising the non-buried guide portion, this portion comprising the curved guides 1b.
Entre les portions de guides enterrées et non enterrées, il existe des zones de transition Zt ; la partie de ces zones dans laquelle l'épaisseur de matériau séparant le cœur du guide, de la surface du substrat est soit nulle, soit insuffisante pour éviter les pertes optiques, est considérée faisant partie de la portion de guide non enterrée ; et la partie de ces zones dans laquelle ladite épaisseur est suffisante pour éviter les pertes optiques est considérée comme enterrée .Between the buried and non-buried guide portions, there are transition zones Zt; the part of these zones in which the thickness of material separating the core of the guide from the surface of the substrate is either zero or insufficient to avoid optical losses, is considered to be part of the portion of guide which is not buried; and the part of these zones in which said thickness is sufficient to avoid optical losses is considered to be buried.
Dans cet exemple de réalisation, on a représenté une seule portion de guide non enterrée, mais bien entendu on aurait pu avoir un guide avec plusieurs portions de guide non-enterrées séparant par exemple respectivement deux parties de guides courbes.In this exemplary embodiment, a single portion of non-buried guide has been shown, but of course we could have had a guide with several portions of non-buried guide separating for example two parts of curved guides respectively.
La figure le illustre la réalisation d'une couche de recouvrement 3 sur la structure.The figure illustrates the realization of a covering layer 3 on the structure.
Cette couche est mono ou multicouches et par exemple en silice ou en verre d'indice de réfraction adapté comme on l'a vu précédemment pour qu'une onde évanescente associée à l'onde lumineuse guidée dans ladite portion ne puisse sortir de la structure ; cette couche est déposée par pulvérisation cathodique ou évaporâtion sous vide. Par ailleurs, l'épaisseur Wp de cette couche est choisie de façon que l'onde évanescente associée au mode guidé dans la portion non enterrée ne puisse voir le milieu situé au-dessus de la couche. Cette épaisseur sera comprise généralement, typiquement entre 0,3 et 5 μm.This layer is monolayer or multilayer and for example made of silica or glass of refractive index adapted as we have seen previously so that an evanescent wave associated with the light wave guided in said portion cannot leave the structure; this layer is deposited by sputtering or vacuum evaporation. Furthermore, the thickness Wp of this layer is chosen so that the evanescent wave associated with the guided mode in the non-buried portion cannot see the medium located above the layer. This thickness will generally be comprised, typically between 0.3 and 5 μm.
Après réalisation de la couche de recouvrement, le ou les éléments de recouvrement sont alors réalisés. Plusieurs modes de mise en œuvre sont envisageables. Selon un premier mode représenté sur la figureAfter completion of the covering layer, the covering element or elements are then produced. Several methods of implementation are possible. According to a first mode shown in the figure
2, la couche de recouvrement 3 est gravée de façon à ne laisser subsister qu'un élément de recouvrement 5 situé au-dessus de l'ensemble du guide aussi bien dans sa portion non enterrée que dans sa portion enterrée . La largeur Lp de l'élément de recouvrement doit être supérieure ou égale à une largeur minimum déterminée pour que l'onde évanescente associée au mode guidé dans la portion non enterrée de la structure ne puisse voir le milieu situé au-dessus dudit élément. Cette largeur peut être constante comme représentée ou variable.2, the covering layer 3 is etched so as to leave only a covering element 5 situated above the assembly of the guide both in its non-buried portion and in its buried portion. The width Lp of the covering element must be greater than or equal to a determined minimum width so that the evanescent wave associated with the guided mode in the non-buried portion of the structure cannot see the medium located above said element. This width can be constant as shown or variable.
Selon un deuxième mode de réalisation représenté sur la figure 3 , la couche de recouvrement 3 est gravée de façon à ne laisser subsister qu'un élément de recouvrement 7 situé uniquement au-dessus de la portion de guide non enterrée.According to a second embodiment shown in FIG. 3, the covering layer 3 is etched so as to leave only a covering element 7 situated only above the non-buried guide portion.
Les caractéristiques de cet élément sont les mêmes que pour celui de la figure 2.The characteristics of this element are the same as for that of Figure 2.
Pour graver l'élément de recouvrement aussi bien dans l'exemple de la figure 2 que celui de la figure 3, on réalise sur la couche de recouvrement par exemple un masque de résine que l'on insole et que l'on développe selon les techniques classiques de la microélectronique de façon à obtenir un motif correspondant à l'élément de recouvrement que l'on veut obtenir. Puis on grave, la couche de recouvrement à travers ce masque par exemple par une gravure du type usinage ionique ou gravure chimique pour une couche en silice. Le masque est ensuite généralement éliminé à moins qu'il ne gêne pas la structure.In order to etch the covering element both in the example of FIG. 2 and that of FIG. 3, a mask of resin is produced on the covering layer, for example, which is exposed and developed. according to conventional techniques of microelectronics so as to obtain a pattern corresponding to the covering element that one wants to obtain. Then the covering layer is etched through this mask, for example by an etching of the ion machining type or chemical etching for a layer of silica. The mask is then generally removed unless it does not interfere with the structure.
Selon un autre exemple de réalisation, si le guide de la structure est complètement non enterré, alors l'élément de recouvrement est du type de celui représenté figure 2, c'est-à-dire qu'il est au-dessus du guide et suit le même cheminement. According to another exemplary embodiment, if the guide of the structure is completely not buried, then the covering element is of the type of that shown in FIG. 2, that is to say that it is above the guide and follows the same path.

Claims

REVENDICATIONS
1. Structure en optique intégrée comportant dans un substrat un guide optique (1) présentant au moins une portion de guide non enterrée (lb) , caractérisée en ce qu'elle comprend en outre sur la surface du substrat au moins un élément de recouvrement (5, 7) situé au- dessus de la portion de guide non enterrée et apte à isoler dans ladite portion de guide, une onde lumineuse se propageant dans celui-ci.1. Integrated optics structure comprising in an substrate an optical guide (1) having at least one portion of non-buried guide (lb), characterized in that it further comprises on the surface of the substrate at least one covering element ( 5, 7) located above the non-buried guide portion and able to isolate in said guide portion, a light wave propagating in it.
2. Structure selon la revendication 1, caractérisée en ce que le guide comporte plusieurs portions de guide non enterrées, chaque portion étant associée à un élément de recouvrement.2. Structure according to claim 1, characterized in that the guide comprises several non-buried guide portions, each portion being associated with a covering element.
3. Structure selon l'une quelconque des revendications 1 et 2 , caractérisée en ce que le guide comporte au moins une portion guide non enterrée (lb) et au moins une portion de guide enterrée (la) , l'élément de recouvrement étant situé au-dessus des portions de guide enterrée et non-enterrée .3. Structure according to any one of claims 1 and 2, characterized in that the guide comprises at least one non-buried guide portion (lb) and at least one buried guide portion (la), the covering element being located above the buried and non-buried guide portions.
4. Structure selon l'une quelconque des revendications 1 à 3, caractérisée en ce que l'élément de recouvrement présente une épaisseur Wp au moins égale à l'épaisseur minimum Wm nécessaire pour qu'une onde évanescente associée à l'onde lumineuse guidée dans ladite portion de guide non enterrée ne puisse sortir de la structure. 4. Structure according to any one of claims 1 to 3, characterized in that the covering element has a thickness Wp at least equal to the minimum thickness Wm necessary for an evanescent wave associated with the guided light wave in said portion of guide not buried can not leave the structure.
5. Structure selon l'une quelconque des revendications 1 à 4, caractérisée en ce que l'élément5. Structure according to any one of claims 1 to 4, characterized in that the element
• de recouvrement est mono ou multicouches et le ou les indices de réfraction sont respectivement inférieurs au plus petit des indices effectifs des modes de propagation pouvant être guidés dans ladite portion non enterrée . • overlap is mono or multilayer and the refractive index or indices are respectively less than the smallest of the effective indices of the propagation modes that can be guided in said non-buried portion.
6. Structure selon la revendications 5, caractérisée en ce que l'indice de réfraction de l'élément de recouvrement est inférieur à l'indice de réfraction maximum du substrat .6. Structure according to claim 5, characterized in that the refractive index of the covering element is lower than the maximum refractive index of the substrate.
7. Structure selon l'une quelconque des revendications 1 à 6, caractérisée en ce que l'élément de recouvrement présente une largeur Lp supérieure ou égale à la largeur du mode de propagation le plus large pouvant se propager dans ladite portion de guide non enterrée .7. Structure according to any one of claims 1 to 6, characterized in that the covering element has a width Lp greater than or equal to the width of the widest propagation mode which can propagate in said portion of guide which is not buried .
8. Structure selon l'une quelconque des revendications 1 à 7, caractérisée en ce que l'élément de recouvrement est choisi parmi de la silice, un verre d'indice approprié.8. Structure according to any one of claims 1 to 7, characterized in that the covering element is chosen from silica, a glass with an appropriate index.
9. Procédé de réalisation d'une structure en optique intégrée comportant dans un substrat un guide optique (1) présentant au moins une portion de guide non enterrée (lb) et sur la surface du substrat au moins un élément de recouvrement (5, 7) au-dessus de la portion de guide non enterrée ; ce procédé comportant les étapes suivantes :9. Method for producing an integrated optical structure comprising in an substrate an optical guide (1) having at least one portion of guide which is not buried (lb) and on the surface of the substrate at least one covering element (5, 7 ) above the guide portion not buried; this process comprising the following steps:
A) réalisation dans un substrat d'au moins un guide d'onde avec au moins une portion de guide non enterrée,A) production in a substrate of at least one waveguide with at least one portion of guide which is not buried,
B) formation au-dessus de la portion non enterrée de l'élément de recouvrementB) formation above the non-buried portion of the covering element
10. Procédé selon la revendication 9, caractérisé en ce que l'étape B) comporte le dépôt sur le substrat d'une couche de recouvrement (3) puis la réalisation sur cette couche, d'un masque protégeant la ou les portions de guide à recouvrir, la gravure de la couche de recouvrement à travers le masque de façon à obtenir le ou les éléments de recouvrement.10. Method according to claim 9, characterized in that step B) comprises the deposition on the substrate of a covering layer (3) then the production on this layer, of a mask protecting the guide portion or portions to be covered, the etching of the covering layer through the mask so as to obtain the covering element or elements.
11. Procédé selon l'une quelconque des revendications 9 et 10, caractérisé en ce que le dépôt de la couche de recouvrement est réalisé par pulvérisation cathodique ou évaporation sous vide.11. Method according to any one of claims 9 and 10, characterized in that the deposition of the covering layer is carried out by sputtering or evaporation under vacuum.
12. Procédé selon l'une quelconque des revendications 9 et 11, caractérisé en ce l'étape A) comporte la formation dans un substrat de verre d'un guide d'onde par échange ionique, la rediffusion localisée de ce guide de façon à enterrer au moins une portion de guide. 12. Method according to any one of claims 9 and 11, characterized in that step A) comprises the formation in a glass substrate of a waveguide by ion exchange, the localized re-diffusion of this guide so as to bury at least a guide portion.
EP02701339A 2001-01-31 2002-01-29 Optics-integrated structure comprising in a substrate at least a non-buried guide portion and method for making same Withdrawn EP1356323A1 (en)

Applications Claiming Priority (3)

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FR0101300A FR2820217B1 (en) 2001-01-31 2001-01-31 INTEGRATED OPTICAL STRUCTURE HAVING AT LEAST ONE UNDERGROUND GUIDE PORTION AND ITS MANUFACTURING METHOD
FR0101300 2001-01-31
PCT/FR2002/000343 WO2002061474A1 (en) 2001-01-31 2002-01-29 Optics-integrated structure comprising in a substrate at least a non-buried guide portion and method for making same

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KR920005445B1 (en) * 1989-08-10 1992-07-04 한국과학기술원 Optical waveguide
FR2712396B1 (en) * 1993-11-12 1995-12-22 Merlin Gerin Method for manufacturing an integrated optical device and device thus manufactured.
US6270604B1 (en) * 1998-07-23 2001-08-07 Molecular Optoelectronics Corporation Method for fabricating an optical waveguide
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US5479552A (en) * 1993-08-27 1995-12-26 Nec Corporation Waveguide-type optical device
FR2776784A1 (en) * 1998-03-30 1999-10-01 France Telecom Electro-optical modulator, forming a Pockels cell

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CA2435456A1 (en) 2002-08-08
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US20040057690A1 (en) 2004-03-25
WO2002061474A1 (en) 2002-08-08

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