WO2006003313A1

WO2006003313A1 - Method for making an optical block with an integrated optical circuit by spot photopolymerisation of an organic matrix via two-photon absorption and optical block thus obtained

Info

Publication number: WO2006003313A1
Application number: PCT/FR2005/001441
Authority: WO
Inventors: Kokou Dodzi Dorkenoo; Olivier Cregut; Alberto Barsella; Alain Fort; Chantal Andraud
Original assignee: Universite Louis Pasteur, U.L.P.; Centre National De La Recherche Scientifique, Cnrs
Priority date: 2004-06-11
Filing date: 2005-06-10
Publication date: 2006-01-12
Also published as: FR2871582A1; FR2871582B1

Abstract

The method according to the invention, which is used for making an optical block with an integrated optical circuit (1), consisting of a block (2) made of a matrix (4) in which an integrated optical circuit (3) is inserted, comprises the following steps: preparing an at least partially organic matrix that can be polymerised by two-photon absorption and shaping same in the form of a block; inserting at least two integrated connexions (10) at the edge of said block; providing an optical circuit in the volume of the block by spot photopolymerisation of the matrix via two-photon absorption; polymerising the entire remaining volume of the block by exposing same to white light. The invention also relates to an optical block with an integrated optical circuit obtained via this method, and, in particular, to a block containing one or more Mach-Zehnder interferometers (17).

Description

A method of manufacturing an integrated optical circuit optical block by localized photopolymerization of an organic matrix by two-photon absorption and optical block thus obtained.

The present invention relates to an optical integrated circuit optical block with integrated connections to the ends of optical fiber connection and its manufacturing process by photopolymerization by two-photon absorption.

More particularly, it relates to an optical integrated circuit optical unit connected to at least one optical fiber and comprising one or more electro-optical modulators, preferably one or more Mach-Zehnder interferometers.

With the development of new technologies, fiber optic transmissions are increasingly being used for their considerable bandwidth capacity. They are particularly used in the telecommunications field, for example to transmit long-distance or high-speed communications.

These recent applications of optical fibers give rise to new needs, for example that of optical components capable of carrying out operations, such as modulation, multiplexing or the like, directly on the optical signals without having to convert them into electrical signals.

To this end, components have been developed called optical integrated circuits or "CIOs" which include one or more optical elements, such as waveguides, modulators, interferometers, networks, etc., realized and associated with each other. ) on a single substrate, these elements having a refractive index different from that of the substrate.

To date, optical integrated circuits are generally made from inorganic materials, such as lithium niobate (LiNbO ₃ ), doped glasses or semiconductors. These materials have the disadvantage of being expensive, to impose multi-step manufacturing processes, complicated and expensive for the realization of optical integrated circuits.

In addition, once the integrated optical circuit realized, it must be connected to its input and output to optical fibers transmitting the light signal. With this type of integrated optical circuit, the connection is established after the manufacture of the CIO which is then in the solid state. This connection is delicate and particularly difficult in the case where several fibers must be connected.

To overcome these drawbacks, efforts are currently being made to develop organic materials that can replace inorganic materials.

It is then necessary to create in these materials a localized and permanent variation of the refractive index and to give them the appropriate electro-optical properties, in order to trace the circuit and its various optical elements.

Components prepared by masking and chemical etching of an organic matrix are thus known. Such a method, similar to those used in microelectronics, comprises many successive steps. It is long and complex, especially during the final stage of development. In addition, it requires the use of many solvents, acids and other treatment chemicals, toxic and harmful to the environment. Also known is patent FR 2.817.049 in the name of the CNRS which relates to a photocrosslinkable material by visible light formed of a matrix of a monomer with three crosslinkable functions containing a chromophore and a photosensitizer which has an absorption peak. in the visible distinct from that of the chromophore. This document also describes an optical integrated circuit obtained from this material after crosslinking and the process for preparing this circuit.

To achieve the circuit according to this prior method, the photocurable material must be in the form of a layer, apply an electric field so as to align the chromophores, have a mask leaving free an area corresponding to the pattern of the desired optical circuit and illuminate the layer by visible light through this mask to perform photocrosslinking in the area left free by the mask, remove the electric field and illuminate the entire layer to crosslink the rest of the layer.

This process, based on the photon photon absorption photonticulation principle, has certain advantages over the other techniques previously described. It is simpler and does not require the use of ecotoxic chemicals. In addition, it facilitates the optical connection of the circuit, because it is possible to embed an optical fiber in the material during the first step of the process and start the circuit from this fiber.

However, it still requires the use of a mask and only provides a plane optical circuit in the form of a layer.

Indeed, in this process by absorption to a photon, the wavelength of the light illumination is chosen so that the absorption of a single photon is sufficient to trigger the crosslinking of the material in the illuminated area. As a result, the photon density being of the same order over the entire depth of material traversed by the ray, the crosslinking takes place in the illuminated zone over the entire depth of the material.

With such a method according to the prior art, it is limited to a flat integrated circuit, made in the form of a layer, because it is impossible to control the depth of realization of the circuit.

The object of the invention is to provide an integrated optical circuit made from organic materials, much less expensive than the inorganic materials used in the prior art and which can easily be implemented.

Another object of the invention is to provide an integrated optical circuit optical unit in which the optical circuit can be made in three dimensions at any depth of the matrix.

The invention also aims to provide an integrated optical circuit optical unit already connected to one or more optical fibers.

Finally, the invention aims to teach a method of manufacturing such an integrated optical circuit that is simple, fast and uses neither mask nor chemical treatment.

To solve this technical problem, the invention teaches a method of manufacturing an integrated optical circuit optical block formed of a matrix block in which is inscribed an integrated optical circuit comprising waveguides capable of channeling and transmitting light, which involves the following steps:

. preparation of an organic or hybrid matrix organic-inorganic polymerizable by two-photon absorption and shaping thereof in the form of a block; . inserting at least two integrated connections at the edge of the matrix block;

. forming within the volume of the matrix block of the waveguides of the optical integrated circuit, leaving and resulting in these integrated connections, by photopolymerization. localized by two-photon absorption, non-solitonic photopolymerization induced by a laser beam focused within the matrix block and whose focal point moves relative to the matrix block, according to the waveguide pattern to be made;

. polymerization of the entire remaining volume of the block by exposure to white light.

The invention also teaches an integrated optical circuit optical block formed of a matrix block in which is inscribed an integrated optical circuit comprising at least one optical element formed of waveguides capable of channeling and transmitting the light, which is characterized in that the matrix is composed at least partially of organic materials and in that the optical circuit is the result of localized photopolymerization of the matrix by two-photon absorption.

The use of functionalised photopolymers makes it possible very easily to structure the linear and non-linear optical properties, without having to resort to numerous steps based on sophisticated and expensive technologies.

The method for producing optical guides according to the invention makes it possible to inscribe guides with electro-optical properties in a single step, in the volume of the matrix, at any depth. desired, which can be variable, thus making it possible to trace optical circuits in three dimensions. These can be provided with electro¬ optical properties addressable by electrodes applied to the sample.

The miniaturization of the circuit is obtained thanks to the reduced size of the polymerization, of the order of one cubic micrometer because of the same process of absorption with two photons, and which is moreover controllable in three dimensions inside a matrix may have a significant thickness of several hundred microns.

The optical blocks with integrated optical circuits obtained have many advantages, such as for example allowing the integration on the same block of numerous functions (optical switches, modulators, tunable filters, etc.). These characteristics make them very attractive, especially as broadband modulators requiring only a low control voltage.

In addition, the optical connection of the circuit is particularly easy and generates much less losses than optical circuits of the prior art. Indeed, the end of one or more optical fibers can be previously embedded in the organic matrix and the optical circuit can be traced from this end. Advantageously, the input and output optical fibers can be positioned at any point in the matrix and are not necessarily aligned or at the same height.

Finally, the process according to the invention is environmentally friendly because it does not require the use of solvents or other chemicals.

Other features and advantages of the invention will appear on reading the the

detailed description which follows, description made with reference to the accompanying drawings, in which:

. Figure 1 is a schematic perspective view of an integrated optical circuit optical unit according to the invention containing a Y-divider for connecting an input optical fiber and two output optical fibers;

. FIG. 2 is a schematic perspective view of an integrated optical circuit optical unit according to the invention containing a Mach-Zehnder modulator connected to an input optical fiber and an output optical fiber;

. FIG. 3 is a schematic perspective view of an integrated optical circuit optical unit according to the invention, connected to three input optical fibers and three output optical fibers and containing three Mach-Zehnder modulators in parallel;

. FIG. 4 is a simplified block diagram of an assembly making it possible to implement the method according to the invention and to produce an optical block with an integrated optical circuit according to the invention.

The integrated optical circuit optical block according to the present invention and its method of manufacture will now be described in detail with reference to Figures 1 to 4. The equivalent elements shown in the different figures will bear the same reference numerals.

FIGS. 1 to 3 show an integrated optical circuit optical block 1 according to the present invention formed of a block 2 in which an integrated optical circuit 3 is inscribed. Block 2 is preferably substantially parallelepipedic in shape. and made from a matrix 4 of organic materials. Block 2 may adopt any other suitable form and for example that of a disk.

The matrix 4 is in the form of a resin which at room temperature is in a state of viscous liquid, paste or gel, or which can be temporarily placed in a similar state so that it can be easily shaped and allow the insertion of the end 5 of one or more optical fiber sections 6.

This matrix 4 is composed in the majority of molecules of a monomer or a mixture of monomers capable of being polymerized by two-photon absorption. It may also contain other constituents useful for the photopolymerization or imparting to the material the optical properties necessary for the desired application.

Matrix means that the monomers form a homogeneous structure in which the other elements are distributed in a substantially uniform and homogeneous manner.

In addition to the monomer, the matrix 4 contains a photoinitiator compound whose role is to absorb radiation by two-photon absorption, which creates free radicals and initiates the polymerization. For greater efficiency, a photoinitiator is preferably used which has a large two-photon absorption cross section.

By way of example, mention may be made of a resin formed of 70% by weight of an isocyanurate triacrylate monomer which exhibits a radical inhibition level of 100 ppm, of 29.5% by weight of poly (styrene). co-acrylonitrile) as binder and 0.5% by weight of (E, E, E, E, E, E) -I, 13-bis- [4- (diethylamino) phenyl] tri-deca 1, 3,5,6,8,10,12-hexaen-7-one as a photoinitiator.

The invention is however not limited to organic matrices alone but also matrices made from organic / inorganic hybrid materials called "sol-gel" which are also polymerizable by two-photon absorption.

When it is desired to use this photopolymerizable matrix to produce an integrated optical circuit 3 according to the invention, it may be necessary to add other components to give it additional properties.

In the preferred embodiment of the invention which aims at producing an integrated electro-optical modulator 7 of the Mach-Zehnder type, it is essential to provide the material with macroscopic electro-optical properties. For this purpose, the matrix may also contain molecules with nonlinear optical properties called chromophores.

Chromophores are molecules with a dipole moment that causes their orientation when placed in an electric field. The chromophores also have a significant linear polarizability anisotropy that can be likened to birefringence at the molecular level. They possess, in addition, a quadratic hyperpolarizability, at the base of the electro-optical effect.

The chromophore family groups together very different molecules. However, in the applications targeted by the invention, use is preferably made of intramolecular charge transfer chromophores also known as "push-pull" molecules. These molecules have both an electron accepting group and an electron donor group, these groups being linked by a conjugation path allowing the delocalization of the electrons on the whole of the molecule.

The chromophore molecules are dispersed within the matrix, where they are preferentially distributed homogeneously. This distribution is carried out by any suitable means. It can thus be performed for example by simple mixing of the various elements making up the matrix, the latter then being doped with the chromophores. The matrix can also be provided with chromophores grafted onto the polymer chains, by main or lateral chain grafting.

According to the invention, an optical circuit 3 is inscribed inside the block 2 formed by the matrix 4 of organic materials.

The optical circuit 3 is composed of waveguides 8, capable of channeling and transmitting light, produced by localized photopolymerization of the organic matrix 4 by means of the method described below of two-photon absorption.

These waveguides 8 extend in the heart of the constituent material of the block 2. They are not necessarily planar and can follow any curved path as long as they remain able to guide the light. They thus realize the three-dimensional plot of the various optical elements 9 constituting the integrated optical circuit 3.

These waveguides 8 are connected to the input and the output of the optical integrated circuit optical unit 1 according to the invention to integrated connections 10 which make it possible to connect the optical unit 1 to the optical fibers of connection transmitting the light signal. .

The integrated connections 10 are preferably in the form of optical fiber sections 6, one of the ends 5 of which is integrated in the block 2. The end 5 of the fiber section 6 is integral part of the block 2 and can for this be embedded in the matrix 4 during the formation of the block 2.

The waveguides 8 of the integrated optical circuit 3 originate and lead to these integrated connections 10. According to the method of the invention, the waveguides 8 are produced after the introduction of the optical fiber sections 6 and are drawn from the sunken ends of these sections 6. The losses at the interface are thus particularly low.

The sections of optical fiber 6 can then be easily connected to the optical fiber connection carrying the light signal. This connection, not shown, can be carried out by any appropriate known means for connecting two optical fibers and presents no difficulty for the skilled person.

The integrated optical circuit optical unit 1 according to the invention comprises at least two integrated connections 10, an input connection 11 and an output connection 12, located at any location on the edges of the block 2 and to any depth which is not necessarily the same for both connections.

The number of integrated connections 10 is not limited to two. Any higher number may be freely chosen depending on the nature of the optical circuit 3 and the application for which it is intended. Advantageously, the distribution and the disposition at the edge of the block of these connections are unspecified, which offers many possibilities of connection.

For example, the optical block 1 shown in FIG. 2 comprises only two integrated connections 10, an input connection 11 and the

an output connection 12, while the embodiment of Figure 1 has three, an input connection 11 and two output connections 12, and that of Figure 3 has six, including three inputs 11 and three outputs 12.

The integrated optical circuit 3 according to the invention comprises one or more optical elements 9, which may be identical or different and of variable nature depending on the desired application.

In FIG. 1 for example, the optical circuit 3 is composed of a Y-divider 13. This comprises an input waveguide 14, which starts from the integrated input connection 11 and is divided at the level from a nodal point 15 to two output waveguides 16 terminating at the two integrated output connections 12. Such a circuit makes it possible to divide the incoming light beam into two outgoing light beams.

The invention makes it possible to produce many other integrated optical circuits 3 that can be much more complex. An example of a circuit comprising a Mach-Zehnder type interferometer 17 has been represented in FIG.

In this variant, an input waveguide 18 starts from the integrated input connection 11 and divides at a first node 19 into two waveguides forming the two arms 20 and 21 of the interferometer 17. These two branches 20 and 21 meet again at a second node 22 to form a single output waveguide 23 leading to the integrated output connection 12.

Thanks to the particularly advantageous method of the invention, the integrated circuit 3 is not necessarily flat or limited to a single depth as with the prior methods of production in layers. The circuit can thus, for example and as shown in FIG. 2, be inclined so as to the

connect two integrated connections 10 of different depth.

In order to produce interference at the output, the two branches 20 and 21 must constitute a different optical path for the light signal. The chromophores incorporated in the matrix make it possible to obtain such an effect. For this, it causes the orientation of the chromophore molecules located at one of the so-called active branches, for example, the interferometer 17 by placing it in an electric field. The remainder of the optical block 1 and in particular the other branch 21, so-called passive, of the interferometer are excluded from the electric field. The chromophore molecules of these zones therefore do not have a preferential orientation of their dipole moment, which results in isotropy at the macroscopic level.

The difference in orientation of the molecules between the active branch 20 and the passive branch 21 generates a phase shift between the two light beams and causes the creation of interference during the recomposition of the signal at the second nodal point 22 and the guide of output wave 23.

The electric field is applied via electrodes 24 deposited on the optical block 1. These electrodes 24 are arranged around the active branch 20 of the interferometer 17 so as to place the modulation zone of this waveguide 20 in FIG. an electric field capable of orienting the chromophore molecules that it contains.

Several arrangements can be envisaged, on the surface or in volume, for the electrodes 24 as long as the electric field generated is appropriate to fulfill the expected function. In the embodiment shown, they are on the surface, one 24a on the lower face 25 and the

the other 24b on the upper face 26 of the block 2.

It is also conceivable to place the electrodes in the volume of the matrix 4 on either side of the active branch 20, using, for example, electrodes in the form of wires embedded in the block 2.

According to other variants, the electrodes 24 are not always limited to two. It is thus possible to imagine an embodiment comprising two pairs of crossed electrodes, which advantageously makes it possible to obtain a device that is insensitive to the polarization state of the light beam, such a configuration that can be sought in certain optical applications.

For example, it is possible to use for this purpose a first pair of electrodes placed on the surface and a little further along the branch 20 a second pair of electrodes at depth or vice versa. According to a preferred embodiment, the electrodes of the first pair are disposed one on the upper face 26 and the other on the lower face 25 of the block 2 and establish a substantially vertical electric field, while the electrodes of the second pair pair are substantially vertical and placed in the volume of the block 2 on each side of the active branch 20 so as to create a substantially horizontal field.

The electric field generated by the electrodes 24 may be static. In this case, the orientation of the chromophores of the branch 20 remains fixed once established. We then obtain a so-called passive Mach-Zehnder interferometer, always producing the same interference.

Such a configuration can also be obtained during the manufacture of interferometer by blocking the chromophores of the active branch 20 in a selected oriented position. the

For this purpose, the zone of the matrix intended to contain the active interferometer branch 20 is placed, before the optical circuit is made, in a static electric field suitable for inducing the desired orientation of the chromophores of this zone. During the production of the waveguide 20, the monomers of this zone of the matrix polymerize by two-photon absorption and trap the chromophores by fixing their orientation. The electric field can then be removed.

A passive Mach-Zehnder interferometer is thus obtained which no longer needs an electric field to function, the electrodes 24 being omitted. However, its properties are determined and fixed to the design and can not be changed thereafter, unlike the previous embodiment in which it is sufficient to modify the parameters of the applied electric field by means of the electrodes 24.

In this case, the chromophores used to be completely frozen during the polymerization are generally larger than those to remain free. They are also preferably grafted and no longer simply doped. This blocking in the manufacture of the orientation of the chromophores advantageously makes it possible to control the nonlinear optical properties of the guides produced, which makes possible other applications, for example the doubling of optical frequencies realized in integrated guides.

According to another preferred variant, the electric field created at the level of the electrodes 24 is variable, which results in a variation of the orientation of the chromophores and thus by a modification of the interferences produced at the output of the the

1'interféromètre. The electrical modulation applied at the electrodes is thus transformed into optical modulation of the light signal passing through the Mach-Zehnder interferometer 17 according to the invention. The latter then becomes an interferometer said active, that is to say a true electro-optical modulator 7.

One can finally consider another variant in which the two branches 20 and 21 of the interferometer 17 are both active and each subjected to the influence of a different pair of electrodes 24. In this case, it is advantageous to apply an electric field of opposite sign on each of the interferometer branches in order to orient the chromophores in the opposite direction in the two branches. Such a configuration is very interesting, because it allows to use a much less powerful electric field to obtain the same difference between the two branches in the case where interferometer has only one active branch.

The Mach-Zehnder interferometer 17 according to the invention can function as a two-state switch, whether or not to let the light pass. It is then possible to carry out and transmit via it an optical signal coded in binary.

Advantageously, it can also be used as an opto-electronic modulator which makes it possible to transform an electrical modulation into optical modulation and which outputs a modulated optical signal.

Thanks to the precision and the miniaturization of the polymerization that can be accomplished at any point in the volume of the matrix 4, the integrated optical circuit optical unit 1 according to the invention can contain several optical elements 9 grouped on the same block 2. These optical elements 9 may be identical or different, independent or interconnected, connected in series or in parallel ... They are arranged in space in any suitable manner with respect to each other.

By way of example, FIG. 3 shows an optical block 1 containing three Mach-Zehnder interferometers, respectively lower 27, intermediate 28 and higher 29, arranged parallel to one another above each other.

Each of these interferometers 27, 28 and 29 conventionally comprises an active branch, respectively 30, 31 and 32, and a passive branch, respectively 33, 34 and 35, and is connected on the one hand with an integrated input connection 36 , 37 or 38 via an input waveguide 29, 40 or 41, and on the other hand with an integrated output connection 42, 43 or 44 via a control guide. output wave 45, 46 or 47.

The lower interferometer 27 is independent of the other two interferometers 28 and 29. On the contrary, the intermediate interferometer 28 and upper 29 are connected at their output waveguide, 46 and 47, respectively, by means of a guide. transverse link wave 48.

To allow a selective orientation of the chromophores of the active branches 30, 31 and 32 of each of the interferometers, a distinct pair, respectively 49, 50 and 51, of electrodes 24 surrounds each of these branches. Each of these pairs 49, 50 and 51 of electrodes here comprises a lower electrode, respectively 49a, 50a and 51a, placed on the lower face of the block 2 and an upper electrode, respectively 49b, 50b and 51b, placed on the upper face. from block 2.

Active branches of different Interferometers are, in this case, shifted relative to each other so that the electric field produced by each pair of electrodes 24 affects only one active branch. However, it can be envisaged that, in other applications, a pair of electrodes 24 act simultaneously on several interferometers.

It should be understood that the integrated optical circuit optical unit 1 according to the invention may comprise, depending on the intended application, one or more optical elements or components 9 which are not limited to those previously described and shown. An additional example is a directional coupling module, a multimode interferometer (MMI) or any other optical component that can be produced by the two-photon absorption photopolymerization process which will now be described.

In order to realize an integrated optical circuit optical block 1 according to the invention, the first step of the manufacturing process consists in preparing and shaping the organic or hybrid organic-inorganic matrix 4 which constitutes the polymerizable material by two-photon absorption.

This preparation step consists in mixing the various constituents of this matrix, namely the monomer (s), the photoinitiator compound, the possible chromophores and / or any other compound that is useful for producing the optical block according to the invention. A so-called "functionalized" resin is then obtained.

This mixture can be made directly or in any solvent that can be removed later.

As already indicated above, the chromophores can be incorporated into the matrix by grafting instead of simple doping by mixing.

The matrix 4 is also shaped, that is to say that it is placed under conditions allowing the further process and in particular the insertion of the integrated connections 10. For this, the matrix must be sufficiently fluid or flexible . It can be naturally or treated to achieve this result for example by heating, dissolution, or other more appropriate treatment.

The layout of the matrix also consists of making it take the shape and dimensions chosen for block 2.

It is thus preferentially deposited homogeneously on a first glass plate, then covered by a second glass plate so as to form a block of thickness generally between 50 and 500 microns.

With the resin mentioned above, the inventors have for example proceeded as follows. The monomer, which was in the solid state at room temperature, was dissolved in chloroform and the other components were added. The solution was then deposited on a glass plate and then heated at 65 ⁰ C to evaporate the chloroform. A homogeneous layer was obtained, on which a second glass plate was applied parallel to the first, at a distance of about 150 microns.

The second step of the method according to the invention consists in inserting the integrated connections 10 at the edge of the matrix block 2. For this, the ends 5 of the optical fiber sections 6 forming these connections 10 are simply introduced at the desired position in the block 2 whose texture allows the insertion of these optical fibers.

This insertion can also take place during the shaping of the matrix and therefore simultaneously with the first step of the process. This is for example the case when positioning the integrated connections 10 prior to depositing the matrix layer which then drown them.

Before making the inscription in the volume of the matrix 4 of the optical waveguides 8 by localized photopolymerization, it is advantageous to carry out an additional and optional step of controlled prepolymerization of the matrix by volume.

This prepolymerization, which is preferably carried out by controlled exposure of the matrix to white light, makes it possible to increase the very low viscosity of the initial mixture so that the waveguides 8 remain at their original location after their training.

It also has the effect of allowing a control of the values of the refractive index of the different zones of the sample, so that the difference in refractive index between the guides 8 subsequently made by photopolymerization at two photons and the rest of the block 2 is suitable for these guides 8 can guide the light satisfactorily.

The method according to the invention then comprises the essential step of producing the structures or guides 8 of the optical integrated circuit 3 within the volume of the matrix block 2 by photopolymerization by two-photon absorption. This step is preferably carried out by means of a modified confocal microscope optical assembly such as that illustrated by way of example in FIG. 4.

The sample or block 2 is positioned on a support plate 52 located under the objective 53 of a modified confocal microscope 54. The support plate 52 is movable in the three directions x, y and z and its movements are very precisely controlled by a computer 55.

Before initiating the polymerization, the absolute position of the end 5 of the integrated connections 10, and in particular the core of the optical fibers 6 which constitute them, is preferably marked by optical means and in particular by means of a laser pointing not shown.

A precise identification of the position of the core of the optical fibers 6, constituting the starting and finishing points of the waveguides 8 to be produced, is particularly important because it makes it possible to ensure the alignment of the waveguides 8 inscribed during the method according to the invention with the integrated connections 10 of arrival and output of the block. The coupling losses at the junction between the optical fibers and the waveguides can thus be minimized.

This can be done by using the following preferred automated tracking method.

For each of the optical fibers 6 to be characterized, a two-dimensional scanning of two orthogonal planes is carried out successively, by means of the photopolymerization laser, on the axis of the optical fiber 6 serving as an integrated connection 10, these planes being both located. a little before the end of it.

When the laser beam is focused in the matrix, the photoinitiator molecules present in the matrix re-emit a portion of the received energy and thereby generate a detectable fluorescence. On the contrary, when the beam is focused on the end of the optical fiber 6 in silica, no fluorescence occurs.

Simultaneously with the scanning, the fluorescence emitted at each point. It is thus possible to produce a fluorescence image of these two planes in which the optical fiber is materialized by a zone of zero fluorescence which is, after corrections due to the differences in indices, in the form of a disk.

In each of these measurement planes, the core of the optical fiber lies precisely in the center of these disks. A simple computer processing makes it possible to determine the spatial coordinates of these centers and by a linear extrapolation to determine the equation describing the core of the fiber in its end portion.

These equations, defining the beginning and the end of the guides 8 to be produced, are used by the computer 55 to calculate the displacements that it must impose on the support plate 52 as a function of the path of the optical circuit 3 chosen by the user.

In order to obtain the most perfect connection possible, the path of the waveguide begins and ends inside the corresponding optical fiber 6 and follows the core of the fiber to beyond its end according to the previously calculated equation , even if the laser beam does not have effect as long as it is focused in the optical fiber.

The photopolymerization is carried out by means of a femtosecond laser 56, whose characteristics correspond for example to 910 nm, 100 fs and 80 MHz. After having passed through a series of lenses 57 and having been reflected against a dichroic mirror 58, the light beam 59 coming from the laser 56 is focused by the objective 53 of the microscope at any point in the volume of the block 2.

Due to the nature of the two-photon absorption phenomenon, the polymerization is limited to a very small volume of material, of the order of a few cubic micrometers, located around the focal point 60. By moving the support plate 52 in a sequence programmed in advance, a polymerization figure corresponding to the drawing of the desired optical circuit 3 is produced.

It is thus possible to produce, within the volume of the matrix block 2, the waveguides 8 of the desired optical integrated circuit 3, starting and ending at the integrated connections 10, by means of a localized photopolymerization by two-photon absorption. This non-solitonic photopolymerization is induced by the laser beam 59 focused inside the matrix block 2 and whose focal point 60 moves relative to the matrix block 2, according to the waveguides 8 to be produced. .

The relative displacement of the focal point 60 is preferably obtained by a displacement of the support 52 carrying the block 2. However, a displacement of the laser beam, although more difficult to implement, is also conceivable.

Advantageously, this arrangement also makes it possible to observe and characterize the optical circuit 3 produced with the same optical microscopy system.

For this purpose, the light 61 diffused by the optical circuit 3 produced, coming from a conventional backlighting or from a fluorescence can be detected by a photomultiplier 62 and / or a CDD camera 63, after passing through the objective 53 and the dichroic mirror 58. The characterization of the beam is preferably completed by one or more spectrographs 64 analyzing the wavelengths.

In the case where these two detection means are present, the beam is preferentially divided by means of a splitter plate 65. A number of other conventional optical elements, such as filters 66, lenses 67 or a hole 68, appear in FIG. 4. Their function will be easily understood by those skilled in the art.

The collected data can be viewed and / or recorded using computer 55 or any other independent data acquisition system.

In the case where it is desired to make a passive Mach-Zehnder interferometer, it may be advantageous to orient the chromophores of one of its branches as soon as it is manufactured. For this, the corresponding part of the matrix 4 is immersed in a suitable electric field by means of a generator 69 and electrodes of any suitable type, arranged on either side of the block 2 prior to the production of the optical guides 8.

Advantageously, the glass plates used during the forming step of the matrix 4 may be conductive plates, for example of the "ITO" (indium tin oxide) type, on which the appropriate electrodes have been drawn.

In the case where it is desired to obtain an active Mach-Zehnder modulator, the method according to the invention also comprises a step of placing electrodes 24 which may take place at any time before or after the polymerization step. optical waveguides 8 by two-photon absorption.

Here again, the electrodes may be of any suitable type, but are preferably made from conductive glass plates, in particular of the ITO type, placed for example during the shaping step of the matrix 4.

The last step of the process consists of allowing the entire volume of the optical block 1 to be cured by exposing it to white light. Under the influence of this radiation, a less complete polymerization than that obtained by two-photon absorption will be accomplished in the areas left free of the block 2.

The integrated optical circuit optical block 1 obtained is thus stabilized and rigid enough to be then easily used in all kinds of applications. However, thanks to this difference in nature of the polymerization, it retains a suitable difference in refractive index between the polymerized matrix and the optical circuit 3.

Obviously, the invention is not limited to the preferred embodiments described above and shown in the various figures, the skilled person can make many modifications and imagine other variants without departing from the scope and scope of the invention.

Claims

1. A method of producing an integrated optical circuit optical block (1) formed of a matrix block (2) in which is inscribed an integrated optical circuit (3) comprising waveguides (8). capable of channeling and transmitting light, characterized in that it comprises the following steps:

. preparing an organic-inorganic or hybridizable organic-inorganic matrix (2) by two-photon absorption and shaping it as a block (2);

. inserting at least two integrated connections (10) at the edge of the matrix block (2) (4);

. embodiment within the volume of the matrix block (2) of the waveguides (8) of the optical integrated circuit (3), starting and ending at these integrated connections (10), by a localized photopolymerization by absorption at two photons, non-solitonic photopolymerization induced by a laser beam (59) focused within the matrix block (2) and having a focal point (60) moving relative to the matrix block (2) (4) according to the waveguide pattern (8) to be made;

. polymerizing the entire remaining volume of the block (2) by exposure to white light.

2. A method of producing an optical integrated optical circuit block according to the preceding claim characterized in that the step of preparing the matrix (4) comprises the mixing and / or grafting of the various constituents of this matrix.

3. Process for producing an integrated optical circuit optical unit according to any one of the preceding claims, characterized in that the step of forming the die (4) and the step of inserting the integrated connections (10) take place simultaneously.

4. A method of producing an optical unit with integrated optical circuit according to any one of the preceding claims characterized in that it further comprises a step of pre-controlled polymerization of the volume of the matrix (2), prior to l step of producing guides of the optical integrated circuit (3) by photopolymerization by two-photon absorption.

5. A method of producing an optical block with integrated optical circuit according to any one of the preceding claims, characterized in that the step of producing the waveguides (8) of the optical integrated circuit (3) by light-curing absorption two-photon is preceded by a step of locating the absolute position of the end (5) of the integrated connections (10).

6. Process for producing an integrated optical circuit optical unit according to the preceding claim, characterized in that the identification step comprises:

. the scanning by the laser beam (59) of photopolymerization of two orthogonal planes to the axis of the optical fiber (6) serving as integrated connection (10), these planes being both located a little before the end thereof ;

. the detection of the fluorescence emitted at each point of these two planes;

. calculating the center of the core of the fiber (6) at each of these planes; and

. determining the equation describing the core of the fiber (6) in its end portion.

7. Method of making a block optical optical integrated circuit according to any one of the preceding claims characterized in that the step of producing the waveguides (8) of the optical integrated circuit (3) by photopolymerization by two-photon absorption is achieved by means of an optical assembly of modified confocal microscopy.

8. A method of producing an optical block with integrated optical circuit according to the preceding claim characterized in that the photopolymerization by two-photon absorption is performed by means of a femtosecond laser (56), whose light beam (59) is focused by the objective (53) of the microscope at any point in the volume of the block (2).

9. A method of producing an optical unit with integrated optical circuit according to any one of the preceding claims characterized in that it further comprises a step of observation and characterization of the optical circuit (3) produced.

10. A method of producing an optical unit with integrated optical circuit according to any one of the preceding claims characterized in that it further comprises a step of placing electrodes (24).

11. A method of producing an optical unit with integrated optical circuit according to the preceding claim characterized in that the step of placing electrodes (24) comprises placing the matrix (4) between two conductive glass plates on which are the electrodes (24).

12. Optical block integrated optical circuit characterized in that it is achieved by implementing the method according to any one of the preceding claims.

An integrated optical circuit optical block formed of a matrix block (2) in which is inscribed an integrated optical circuit (3) comprising at least one optical element (9) formed of waveguides (8). capable of channeling and transmitting light, characterized in that the matrix is composed at least partially of organic materials and in that the optical circuit (3) is the result of a localized photopolymerization of the matrix (4) by absorption at two photons.

14. Optical block integrated optical circuit according to the preceding claim characterized in that the matrix (4) comprises chromophore molecules.

15. Optical integrated optical circuit block according to claim 13 or 14 characterized in that it further comprises at least two integrated connections (10) for connecting the integrated optical circuit (3) to the optical fiber connection transmitting the light signal. .

16. Optical integrated optical circuit block according to the preceding claim characterized in that at least one of the integrated connections (10) is an optical fiber section (6) of which one of the ends (5) is integrated in the block ( 2).

17. Optical integrated optical circuit block according to any one of claims 13 to 16 characterized in that the optical circuit (3) comprises at least one Y-divider (13).

18. Optical integrated optical circuit block according to any one of claims 13 to 17 characterized in that the optical circuit (3) comprises at least one interferometer Mach-Zehnder type (17).

19. optical optical integrated circuit unit according to any one of claims 13 to 18 characterized in that it further comprises at least one electrode (24).