WO2006090028A1

WO2006090028A1 - Optimized transition of a guide in a cladding

Info

Publication number: WO2006090028A1
Application number: PCT/FR2005/050487
Authority: WO
Inventors: Christophe Martinez; Cyril Guidoux; Olivier Jacquin
Original assignee: Teem Photonics
Priority date: 2004-06-24
Filing date: 2005-06-23
Publication date: 2006-08-31
Also published as: FR2872298A1

Abstract

The invention concerns an optical device comprising in a substrate of refractive index n1, an optical guide of index n2, an optical cladding of index n3 independent of the guide and enclosing a portion of said guide in a zone of the substrate called interaction zone, said guide and said cladding being obtained by treating parts of the substrate through ion exchange technique. It further comprises a zone, called transition zone, located at the interface of the substrate and the cladding on the guide path, said zone accompanying the penetration of the guide into the substrate or into the cladding as the case may be, said zone having a refractive index which is gradually adapted over a determined minimum length so as to reduce the difference of index when the guide passes from the substrate to the cladding and/or from the cladding to the substrate. The invention also concerns a method for making said device including the following steps: a) providing a substrate wherein the device will be produced, b) introducing a first ionic species into the substrate to enable the optical cladding to be produced after step e), c) introducing a second ionic species into the substrate to enable the transition zone to be produced after step e), d) introducing a third ionic species into the substrate to enable the guide to be produced after step e), e) burying the ions introduced at steps b, c, and d) to produce the cladding, the transition zone and the guide.

Description

OPTIMIZED TRANSITION OF A GUIDE IN A SHEATH

DESCRIPTION

TECHNICAL AREA

The field of the invention relates to optical components composed of a guide associated with an artificial sheath, said sheath surrounding the guide on a given portion. Examples of these optical components include ACG ("artificial cladding grating") components which are artificial cladding networks. The invention will make it possible in particular to reduce the optical losses caused in the guide during the burting of said guide in the sheath.

The invention can be used in all components comprising an artificial sheath and a guide. The invention will be very useful in areas requiring spectral filtering. For example, the invention may be used in ACG components to achieve gain flatteners for optical amplifiers widely used in the telecommunications field.

STATE OF THE PRIOR ART

Artificial cladding components consist of a substrate, an optical guide and an optical cladding. The optical guide is buried in the substrate and the optical cladding, which is independent of the guide, surrounds at least a portion of the guide in a zone of the substrate called interaction zone. The refractive index of the sheath is different from the index of refraction of the substrate and less than the index of refraction of the guide at least in the portion of the cladding adjacent to the guide in the interaction zone. For the artificial sheath to effectively surround the guide, it is generally necessary that the guide enters the sheath and eventually.

Figures la, Ib and Ic show three configurations of components with artificial sheath.

In Fig. La, a guide 2a is made in a glass substrate 1, over the entire length of the substrate, and a sheath 3a surrounds the guide along its entire length. In this example, a network 4a makes it possible to produce an ACG type component. This network, made in the interaction zone of the guide, is able to couple at least one guide mode of the guide to at least one duct mode or vice versa. The disadvantage of this configuration lies in the fact that it allows the mode of the fiber to couple in the sheath (and vice versa). Indeed, if the input mode is not perfectly adapted to the mode of the input guide, there can be a significant part of the input mode that leaks into the sheath and can thus be guided throughout of the sheath. In this particular case, the output of the component is recovered a superposition of the mode of the guide and one or more modes of weak sheath. These modes, by interfering, can disrupt the functioning of the component and make delicate its characterization and its connection. It is therefore generally preferable to return the guide in the sheath after a portion of propagation in the substrate over a few millimeters, thus allowing the filtering of the ray modes in the substrate at the entrance. This case is shown in FIG. 1b: the sheath 3b is shorter than the zone 3a and the guide 2b enters through a zone A and eventually leaves it by an identical zone A or not.

Other alternatives can be considered. The guide 2c can indeed come out or enter through the edge of the sheath 3c as shown in Figure Ic (zone B). This can be useful if you want to have access to the sheath at the end of the component.

Note that we have taken the example of an ACG component in Figures Ic (a network 4a, 4b, 4c is placed in the guide), but it goes without saying that the problem is generalizable to all components to artificial sheath.

To achieve these components with an artificial sheath, the technique of ion exchange is generally used. We observed experimentally during the field burial of the guide that this technique has the disadvantage that high losses occur at the transitions of the substrate guide to the sheath or sheath to the substrate. Figures 2a to 2c show the main cause responsible for the losses observed. When burying the guide and the sheath, the guide is buried faster at the sheath than at the substrate, because of the presence of the ions of the sheath. FIGS. 2a and 2b show two views of a component comprising a 2c and a sheath 3 made in a substrate 1. Figure 2c shows a magnification of the penetration area of the guide 2 in the sheath 3. It is seen in this Figure 2c that the guide has a deviation or differential of bury dh on a distance dz. Under the effect of this gap of burial, the guide bends

(see Figure 3). By making the approximation that the curvature of the guide corresponds to two arcs of circles, it is shown that the radius of curvature R1 induced of the guide is given by the relation:

Knowing that the separation gap dh of the guide is generally of the order of a few micrometers to about ten micrometers and that its dz bursting area is of the order of 10 microns, it is deduced that the radius of curvature Rl is close to ten micrometers. However, generally used guides admit a minimum radius of curvature of between mm and ten mm depending on the manufacturing method used. By using the ion exchange technique, one thus obtains a radius of curvature too small, which results in many losses.

PRESENTATION OF I / INVENTION To avoid that the radius of curvature is too low, it is proposed to control these parameters. We can limit dh, which is difficult for a given manufacturing process, but we can also find a solution to extend the transition range dz. This second solution was chosen.

The invention solves the problems of the prior art with an optical device comprising in a refractive index substrate ni, an optical guide of index n ₂ , an optical cladding of index n ₃ independent of the guide and surrounding a portion. of said guide in an area of the so-called interaction zone substrate, said guide and said sheath being obtained by treatment of parts of the substrate by the ion exchange technique, said device being characterized in that it further comprises a zone , said transition zone, placed at the interface of the substrate and the sheath on the path of the guide, said zone accompanying the penetration of the guide in the substrate or in the sheath as appropriate, this zone having a refractive index which is progressively adapted to a minimum length determined so as to reduce the difference in index occurring during the passage of the guide from the substrate to the sheath and / or the sheath to the substrate.

Advantageously, when the guide passes from the sheath to the substrate, the adaptation of the refractive index of the transition zone is a decrease of the index.

Similarly, when the guide passes from the substrate to the sheath, the adaptation of the refractive index of the transition zone is advantageously an increase in the index. According to a first embodiment, the transition zone is an integral part of the guide. In in other words, this transition zone is a constituent part of the guide.

In this case, the guide advantageously has its cross section which varies in the transition zone, this section being smaller in the sheath than in the substrate and this difference coming from a progressive narrowing of the section of the guide. Indeed, knowing that the differential of burial comes from a difference of velocity between zones more or less concentrated in ions exchanged, one can, to correct this effect, to cause a difference of concentration in the guide which will allow to compensate this differential. Note that the transition from the broad guide to the narrow guide must be done by an adiabatic transition.

According to a second embodiment, the transition zone projects from the sheath into the substrate. Here, the transition zone is an integral part of the sheath. According to a third embodiment, the transition zone protrudes from the substrate in the sheath. Here, the transition zone is an integral part of the substrate.

For these last two embodiments, one can have the case where the transition zone is placed at the end of the sheath. In this case, if for example dh = 5 μm, it is necessary that the transition zone has a length ranging from one hundred microns to the order of mm to obtain a radius of curvature of the mm to the tens of mm. It is also shown that the base of the zone of transition (that is to say the portion contiguous to the end of the sheath) is of the order of tens of microns. As the transition zone has the particular function of accompanying penetration of the guide into the substrate or into the sheath, the base of the transition zone can be extended to about fifteen microns in order to avoid misalignment defects of the guide on the zone.

One can also have the case where the transition zone is placed laterally with respect to the sheath. For some applications, it is indeed interesting to make out the guide of the sheath by one of its sides to allow extended guidance in the sheath, regardless of the guide. But in this case, two loss effects must be taken into account. The first concerns the losses caused by the curvature of the guide required for its lateral exit, the second, the curvature losses due to the interception differential. From Figure 9, we see that to allow a sufficient radius of curvature, the transition length Lt must be sufficiently large and the angle α sufficiently small. For this, the guide must leave the sheath by following a sinusoidal type function ensuring the continuity of the radius of curvature. In this case, the minimum radius of curvature is given by the relation:

And the angle OC is given by the relation: d \ + d2 tana = 2x-

Lt

The distance dl depends on the size of the sheath, the distance d2 depends on the chosen design. By taking for example dl = 40 μm and d2 = 40 μm and to have a minimum radius of curvature of 10 mm, it is necessary to have a transition length Lt of about 2.5 mm. In this case, the angle of passage of the guide through the sheath is about 4 °. But to overcome the burst differential, the angular condition is stricter. We must indeed consider the diagram of Figure 3 for which we replace dz by dz / sinα. If we have dz = 10 μm and dh = 5 μm, we must have α = 1, 2 ° to avoid the differential. At this angle, the sinusoidal curvature length of the guide Lt becomes of the order of 7.6 mm. If the bursting differential is too great or if we want to reduce this transition length (curvature length), we can move the guide laterally by a transition zone ("tap"). This transition zone should have dimensions that allow a radius of curvature sufficient to avoid causing propagation losses in the sheath.

Advantageously, all these embodiments, that is to say the case where the transition zone is part of the guide, the sheath or the substrate, can be combined. The optical device according to the invention can thus advantageously have several transition zones. In the case where the transition zone is part of the substrate or sheath, the transition zone may have a triangular shape. Note that other shapes can be used provided that the extent of the burst transition is sufficiently long. In this case, the guide will or advantageously enter the transition zone by the top of the triangle-shaped zone.

Advantageously, the guide may also enter or leave the transition zone by an inclined edge of the triangle-shaped zone. The transition zone may for example have the shape of a right triangle. In this case, the inclined edge of said zone advantageously makes an angle of the order of 1 ° with the guide penetrating or leaving the sheath. Ideally, this angle will be less than 1 °.

In a particular case, the transition zone projecting from the sheath or the substrate may be formed of a series of elementary zones arranged one after the other, each elementary zone having a constant refractive index and different from its neighbors. . By arranging these elementary zones one after the other in order of increasing or decreasing indices, a transition zone is thus obtained having a refractive index which is progressively adapted to a minimum determined length, which makes it possible to reduce the difference of index occurring during the passage of the guide from the substrate to the sheath and / or the sheath to the substrate. To recapitulate, to limit the losses due to the differential of burial that undergoes the guide during its passage from the substrate to the artificial sheath or vice versa, a transition zone is produced, which is placed on the path of the guide between the substrate and the sheath, and in which the refractive index is modified. Knowing that the implantation of the sheath and the guide in the substrate is performed by the ion exchange technique, two solutions are presented to us to vary the refractive index of this zone along the guide. On the one hand, one can shrink the sheath or the substrate during their manufacturing process but by introducing that same same amount of ions. This has the effect of reducing the concentration of ions in the narrowed zone and therefore of reducing its refractive index. This transition zone is here a narrowing zone which is in the form of a protrusion that is called "typing" in English terminology. On the other hand, it is also possible to cause a difference in concentration in this transition zone to compensate for the differential. It is for this purpose that we have refraction index zones

(or concentrations) decreasing or increasing one after the other which forms a "taper", says

"Typing" fragmented. It is this sequence of zones that will make it possible to extend the transition distance. Depending on the filling rate function of these zones, the fragmented "typing" will be more or less long. The typical length of this "type" is of the order of a few mm. According to a particular case, if the optical guide leaves the sheath of index n ₂ to penetrate into another sheath index ₄ , a transition zone joining the two sheaths can be placed on the passage of the guide to avoid the problem of interception differential. We can then use all kinds of transition zones (or "tapers") previously seen to perform this junction. If the two sheaths have the same refractive index, the transition zone will be a transition band composed of the same material as the sheaths. If the two sheaths have different refractive indices, the transition zone will join the two sheaths in the form of a tip whose cross section decreases or segments whose concentration decreases.

According to a particular embodiment, the device according to the invention further comprises a network located in the interaction zone.

Another object of the invention consists in a method of manufacturing the optical device according to the invention, said method comprising the following steps: a) providing a substrate in which the device will be made, b) introducing a first ionic species in the substrate so as to obtain after step e) the optical cladding, c) introducing a second ionic species into the substrate so as to obtain after step e) the transition zone, d) introduction of a third ionic species into the substrate so as to obtain after step e) of the guide, e) burying the ions introduced in steps b), c) and d) so as to obtain the sheath , the transition zone and the guide.

The embodiment of the device according to the invention is not limited to the ion exchange technique. The sheath and / or the guide and / or the transition zone can indeed be made by any type of technique for modifying the refractive index of the substrate. In addition to the ion exchange techniques, it is possible, for example, to use ion implantation and / or radiation implantation techniques, for example by laser irradiation or laser photo-inscription (the radiation producing local heating), or by the deposition of ions. layers.

The ion exchange technology in glass is particularly interesting, but of course other substrates can be used. Advantageously, the substrate will be chosen from the group comprising glass, crystalline substrates of KTP or LiNbO _{3 type} , and LiTaO ₃ .

Advantageously, the introduction of the first and / or the third and / or the second ionic species will be carried out by ion exchange, or by ion implantation.

The first, second and third ionic species may be the same or they may be different. The introduction of the first and / or second and / or third ionic species can be achieved with the application of an electric field. Note that if the sheath and / or the guide and / or the transition zone are made by ion exchange, the substrate must contain ionic species that can be exchanged.

According to a preferred embodiment, the substrate will be glass and contain Na ⁺ ions previously introduced. The first, second and third ionic species will be Ag ⁺ and / or K ⁺ ions.

According to one embodiment, step b) comprises the production of a first mask comprising a pattern suitable for obtaining the sheath, the introduction of the first ionic species being carried out through this first mask, the step c) comprises the elimination of the first mask and the production of a second mask comprising a pattern suitable for obtaining the transition zone, the introduction of the second ionic species being carried out through this second mask and the step d) comprises the elimination of this second mask and the production of a third mask comprising a pattern suitable for obtaining the guide, the introduction of the third ionic species being produced through said mask. According to a particular embodiment, steps b) and c) are performed at the same time, the first and second masks being replaced by a single mask whose pattern allows the realization of the sheath and the transition zone. By performing steps b) and c) at the same time, it is possible to obtain a "tap" entering the sheath.

According to another particular embodiment, steps c) and d) are performed at the same time, the first and second masks being replaced by a single mask whose pattern allows the realization of the guide and the transition zone, the an integral part of the guide. The masks used in the invention are for example aluminum, chromium, alumina or dielectric material.

According to a first embodiment of step e), the burying of the first ionic species is carried out at least partially before step c), the burying of the second ionic species is carried out at least partially before the step d), the burying of the third ionic species is carried out at least partially after step d). According to a second embodiment of step e), the first, second and third ionic species are buried simultaneously after step d).

Advantageously, at least part of the burial is performed with the application of an electric field.

According to a particular embodiment, the manufacturing method further comprises a step of making a network in the interaction zone of the device according to the invention. BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood and other advantages and particularities will appear on reading the following description, given by way of non-limiting example, accompanied by the appended drawings among which:

FIGS. 1a-1c, already described, show different configurations of ACG components according to the prior art; FIGS. 2a, 2b, already described, respectively show an artificial sheath component according to the prior art seen from the side and seen from face,

FIG. 2c, already described, is an enlargement of FIG. 2a and presents the principle of the differential bursting problem,

FIG. 3, already described, represents the guide of FIG. 2c curved under the effect of the separation gap, the curvature being approximated to two arcs of circle,

FIG. 4 is a diagram of a transition by size change of the guide according to the invention,

FIGS. 5, 6 and 7 are exemplary diagrams of end "tapers" projecting from the sheath towards the substrate according to the invention,

FIG. 8 is a diagram of an end "taper" protruding from the substrate towards the sheath according to

The invention,

FIG. 9 is a schematic diagram of the lateral outlet of a guide in a sheath according to the invention,

FIG. 10 is a diagram of a lateral "tap" according to the invention, - Figure 11 is a diagram of a transition between two sheaths according to the invention.

- Figures 12a to 12d illustrate the steps of the method of producing an optical device according to the invention, from the ion exchange technology.

DETAILED PRESENTATION OF PARTICULAR EMBODIMENTS

FIG. 4 illustrates the case where the guide is narrowed: one passes from a guide 2f of a certain diameter at the level of the substrate to a 2nd guide of smaller diameter at the level of the sheath, the transition from a guide to the the other is through a transition zone 5 whose cross section varies. The burial is thus reduced in the sheath and the differential is corrected.

Figures 5, 6 and 7 give three possible solutions of transition zones or "tapers" to perform the sheath end transition by decreasing the losses.

In FIG. 5, a "taper" 6 of triangular shape is disposed at the end of the sheath 3 to accompany the penetration of the guide 2. In FIG. 6, another solution is presented for which the guide enters the sheath with a " tap "7 inclined edge whose edge angle to" tap "relative to the guide is ideally less than 1 °. For example, the "typing" can be a right base triangle 15 μm and length 2 mm.

Figure 7 shows a fragmented "taper". This "tap" 8, disposed at the end of the sheath, consists of a series of elementary zones or segments making it possible to extend the transition distance. Depending on the filling rate function of these segments, the "type" will be more or less long.

In the cases discussed above, the "tap" protrudes from the sheath to the substrate, but "tapers" protruding from the substrate to the sheath can obviously also be used. Figure 8 gives an example: we see a "tap" 9 entering the sheath 3.

The guide can also leave the sheath, not by one end, but by a side wall of the sheath. As for the end tapers, we can have sharp lateral tapers or fragmented tapers. Figure 10 shows for example a "tap" 10 in the form of a tip. The disadvantage of these lateral "tapers" is that they can cause propagation losses in the sheath. The sizing of these "tapers" must therefore allow a radius of curvature sufficient to avoid losses. This is why the "tap" of Figure 10 has a bent tip shape to follow the curvature of the guide.

FIG. 11 illustrates the case where the guide 2 leaves the sheath 3d to penetrate into another sheath 3e, the guide passing through a transition zone 11 to avoid the problem of bursting differential.

We will make an ACG component, that is to say an artificial sheath network, with an "end tap". FIGS. 12a to 12d are sections made in a plane perpendicular to the surface of the substrate and perpendicular to the z direction of propagation of the guide, said plane containing an interaction zone, ie an area in which the guide is surrounded by the sheath.

In FIG. 12a, the substrate 1 containing B ions is seen. A first mask 61 is produced, for example by photolithography, on one of the faces of the substrate. This mask has an opening determined according to the shape and dimensions (width, length) of the sheath 3 and the "tap" that is desired. A first ion exchange is then carried out between the A ions and the B ions contained in the substrate, in an area of the substrate situated in the vicinity of the opening of the mask 61. This exchange is obtained for example by dipping the substrate provided with the mask in a bath containing A ions and optionally applying an electric field between the face of the substrate on which the mask is disposed and the opposite face. The zone of the substrate in which this ion exchange has been carried out forms the sheath and the "tap". Once the ion exchange is done, we must bury the sheath and "bang" it. For this, the mask 61 is removed and a step of rediffusion of the A ions is carried out by applying an electric field as previously. Figure 12b shows the sheath 3 and the "tap" after they have undergone a partial burial step.

The next step shown in FIG. 12c is to form a new mask 65 on the face

(previously cleaned) of the substrate using, for example, photolithography. This mask has patterns capable of allowing the realization of a guide 2 and a network. Note that the pattern of the network can be defined on the mask allowing the realization of the sheath and / or on the mask allowing the realization of the guide or on a specific mask for the realization only of the network). A second ion exchange is then carried out between the B ions of the substrate and C ions of the guide, these C ions may be the same or different than the A ions. This ion exchange can be carried out as previously by soaking the substrate in a bath containing C ions and possibly applying an electric field. Finally, FIG. 12d illustrates the component obtained after burying the guide 2 obtained by rediffusion of the C ions and final burial of the sheath and the "tapping", with the assistance or not of an electric field. The mask 65 is generally removed before this burial step.

It is noted that the conditions of the first and second ion exchanges are defined so as to obtain the differences in desired refractive indices between the substrate, the sheath, the "tap", and the guide. The adjustment parameters of these differences are notably the exchange time, the bath temperature, the ion concentration of the bath and the presence or absence of an electric field.

As an exemplary embodiment, the substrate 1 is glass containing Na ⁺ ions, the masks 61 and 65 are made of aluminum.

The first ion exchange is carried out by quenching the substrate in a bath comprising Ag ⁺ ions (about 20% concentration), at a temperature of about 33O ⁰ C and for an exchange time of about 5 minutes. A re-diffusion of the ions is first carried out in the open air at a temperature of approximately 33O ⁰ C and for 30 s, then a partial burial of the sheath and the "taper" thus formed in the glass. This burial is carried out by rediffusion in a sodium bath at a temperature of approximately 26O ⁰ C. The duration of this step depends on the desired depth of burial for the final component. Thus, for a surface component, a duration of about 3 minutes is sufficient, whereas for a buried component, a duration of about 20 minutes will be chosen. In this second case, it is also necessary to do a burial under the sheath and the "type" before proceeding to the second exchange. A current of 20 mA is thus applied between two sodium baths on either side of the substrate at a temperature of 26O ⁰ C and for 10 minutes.

The second ion exchange is carried out with a bath comprising Ag ⁺ ions (approximately 20% concentration), at a temperature of about 33O ⁰ C and for an exchange time of about 5 minutes. A rediffusion of the ions is first carried out in the open air at a temperature of about 33O ⁰ C and for 30s. Then, a partial burial of the guide thus formed in the glass is carried out by rediffusion in a sodium bath at a temperature of about 260 ^° C. and for 3 minutes. For a buried component, this step is not necessary.

The final burying of the sheath, of the "tapping" and of the guide is done under an electric field, the two opposite faces of the substrate being in contact with two baths (in this example of sodium) able to allow a potential difference to be applied. between these two baths. To obtain a surface component, a duration of less than one minute is sufficient; in the case of a buried component, a duration of the order of 30 minutes is used, the burping being done with a current of 20 mA at 24O ⁰ C.

Claims

An optical device comprising in a refractive index substrate (1) and an optical guide (2, 2a, 2b, 2c) of index n ₂ , an optical cladding (3, 3a, 3b, 3c) of index n ₃ independent of the guide and surrounding a portion of said guide in an area of the so-called interaction zone substrate, said guide and said sheath being obtained by treatment of parts of the substrate by the ion exchange technique, said device being characterized in that it further comprises a zone, referred to as the transition zone (5, 6, 7, 8, 9, 10, 11), placed at the interface of the substrate and of the cladding on the path of the guide, said zone accompanying the penetration of the guide into the substrate or into the sheath as the case may be, this zone having a refractive index which is progressively adapted to a minimum length determined so as to reduce the difference in index occurring during the passage of the guide from the substrate to the sheath and / or the sheath to the substrate.

2. Optical device according to the preceding claim, characterized in that the adaptation of the refractive index of the transition zone (5,6,7,8,9,10,11) is a decrease of the index when the guide passes from the sheath to the substrate.

Optical device according to claim 1, characterized in that the adaptation of the refractive index of the transition zone (5,6,7,8,9,10,11) is an increase in the index as the guide passes from the substrate to the sheath.

4. Optical device according to any one of the preceding claims, said device being characterized in that the transition zone (5) is an integral part of the guide.

5. Optical device according to the preceding claim, characterized in that the guide has its cross section which varies in the transition zone (5), this section being smaller in the sheath than in the substrate and this difference from a narrowing progressive section of the guide.

6. Optical device according to any one of claims 1, 2, 3, characterized in that the transition zone (6,7,8,10) protrudes from the sheath in the substrate.

7. Optical device according to any one of claims 1, 2, 3, characterized in that the transition zone (9) protrudes from the substrate in the sheath.

8. Optical device according to any one of claims 6, 7, characterized in that said transition zone is placed at the end of the sheath.

9. Optical device according to any one of claims 6, 7, characterized in that the transition zone is placed laterally with respect to the sheath.

10. An optical device according to one or more of claims 4, 6, 7, characterized in that it has several transition zones.

Optical device according to one of Claims 6, 7, characterized in that the transition zone has a triangular shape

12. Optical device according to the preceding claim, characterized in that the guide enters or leaves the transition zone by the top of the triangle-shaped zone.

13. An optical device according to claim 11, characterized in that the guide enters or leaves the transition zone by an inclined edge of the triangle-shaped zone.

14. Optical device according to the preceding claim, characterized in that the inclined edge of said zone makes an angle of the order of 1 ° with the guide penetrating or leaving the sheath.

Optical device according to one of claims 6, 7, characterized in that that the transition zone (8) is formed of a succession of elementary zones arranged one after the other, each elementary zone having a constant refractive index and different from its neighbors.

16. Optical device according to any one of claims 1 to 3 and 6 to 15, characterized in that, if the guide leaves the cladding of index n ₂ to penetrate into another sheath of index n ₄ , a zone of transition (10) joining the two sheaths is placed on the passage of the guide 2.

17. Optical device according to any one of the preceding claims, characterized in that it further comprises a network (4a, 4b, 4c) located in the interaction zone.

18. A method of manufacturing an optical device according to any one of claims 1 to 16, characterized in that it comprises the following steps: a) providing a substrate (1) in which the device will be realized, b) introducing a first ionic species into the substrate so as to obtain, after step e), the optical cladding (3), c) introducing a second ionic species into the substrate so as to allow obtaining after step e) of the transition zone, d) introducing a third ionic species into the substrate so as to obtain after step e) of the guide (2), e) burying the ions introduced in steps b), c) and d) so as to obtain the sheath (3), the transition zone and the guide (2).

19. A method of manufacturing an optical device according to the preceding claim, characterized in that step b) comprises the production of a first mask comprising a pattern suitable for obtaining the sheath, the introduction of the first ionic species being produced through this first mask, step c) comprises the elimination of the first mask and the production of a second mask comprising a pattern suitable for obtaining the transition zone, the introduction of the second ionic species being produced through this second mask and step d) comprises the elimination of this second mask and the production of a third mask comprising a pattern suitable for obtaining the guide, the introduction of the third ionic species being performed through said mask.

20. A method of manufacturing an optical device according to the preceding claim, characterized in that steps b) and c) are performed at the same time, the first and second masks being replaced by a single mask whose pattern allows the realization of the sheath and the transition zone.

21. A method of manufacturing an optical device according to claim 19, characterized in that steps c) and d) are performed at the same time, the first and second masks being replaced by a single mask whose pattern allows the realization of the guide and the transition zone, the zone forming an integral part of the guide.

22. A method of manufacturing an optical device according to claim 18, characterized in that the burying of the first ionic species is carried out at least partially before step c), the burying of the second ionic species is carried out at least partially before step d), the burying of the third ionic species is carried out at least partially after step d).

23. A method of manufacturing an optical device according to claim 18, characterized in that the buries of the first, second and third ionic species are carried out simultaneously after step d).

24. A method of manufacturing an optical device according to claim 18, characterized in that it further comprises a step of making a network (4a, 4b, 4c) in the interaction zone of the device according to the invention. .