FR2681436A1 - Method of installing a thin-film optical device on an optical element, and resulting optical component - Google Patents

Abstract

The invention relates to a method of installing, on an optical element, an optical device produced by thin layers on a substrate (support) and also relates to a resulting optical component. The method is characterised in that the said optical device (4) is produced on a transfer coating (2), deposited beforehand on the said substrate (3) or comprises this transfer coating as a first layer, and is positioned in place on the said optical element with the said substrate, but held in place without the said substrate. Application: optical component, in particular a wavelength multiplexer/demultiplexer.

Description

Method for placing an optical device in thin layers on an optical element and resulting optical component
The present invention relates to a method for installing an optical device produced by thin layers on an optical transmission element, as well as to the optical component resulting from the implementation of this method.

 This optical device produced by thin layers is an optical filter for separation and selection of wavelengths or an anti-reflection structure. I1 consists of a stack of thin layers, produced by vacuum evaporation. This treatment has a high number of ~ 4lattions and is of long duration.

 The optical element can be an optical fiber, or an optical waveguide integrated into a substrate, or any other optical element such as a lens, in particular.

 The installation of such optical devices on a waveguide for example is currently carried out according to two possible known methods.

 One of these known methods consists in depositing this optical device directly on the end of the waveguide which is to receive it. Several waveguides are introduced at the same time into an evaporation frame, for the installation of the suitable optical device directly on each of them. The high manipulations during this common processing can then be different according to the different optical devices produced on the different waveguides. After treatment, the resulting optical components are tested. Those whose thin film deposition is defective or the stack does not have the expected characteristics and performance are lost. This method of direct deposit in place is cumbersome. It is only advantageous for a large number of components treated simultaneously, and for these almost identical components and whose stacks are in a reduced number of layers, themselves not very complex.

 The second known method consists in depositing the thin layers no longer directly on the end of the waveguide concerned but on an auxiliary substrate, made of glass and of the thin blade type, and to put and maintain in place on the guide d 'waves stacking thin layers, with the blade that carries it.

 An optical component obtained by this second method is described in particular in the article "High-performance guided- wave multi / demultiplexer based on novel design using embedded gradient-index waveguides in glass" published in Electronics Letters August 27, 1987 - vol.23 nO 18. The resulting optical component is a multiplexer / demultiplexer with optical waveguides integrated in a glass substrate and with filters in thin layers arranged with their support plate on the selective ports of these guides. For the installation of these filters with their support blade, microfentes, of precisely defined width and depth passing through these selective accesses, are provided in the substrate transversely to the guides.

The blade and the filter that it carries are mounted and held in place in each microfente using an optical adhesion agent.

 This second method has the advantage compared to the first of being able to test the optical devices in thin layers before their installation on the waveguides. By cons it requires to resolve the difficulty of implementation, without altering the performance of the component. In particular, it must solve the technical problems posed by the production of the microfentes and the precise positioning of the blade with its optical device in the microfente and transverse to the access of the guide (s). In addition, the blade thus integrated into the filter and the resulting component creates a diffusion of the guided light which it receives. It leads to losses and therefore to a significant attenuation of transmitted light.

 The object of the present invention is to benefit from the advantages of these two known methods and to avoid their drawbacks.

 It relates to a method for installing an optical device in thin layers on an optical element, consisting in carrying out an optical processing step for depositing the thin layers of said optical device on a support, followed by a final step. for transferring and holding in place using an optical agent for adhering said optical device to an access of said optical element, characterized in that it consists, moreover, in carrying out an initial phase of deposition on said support a so-called transfer coating, of relatively low adhesion to said support, for deposition in said processing step of said optical device on said transfer coating thus forming a low adhesion interface between this optical device and said support, and in that said final step further consists in detaching said support from said optical device in place.

 The transfer coating is in particular a silver-based material or a zinc sulfide.

 Said initial step is independent of the phases of evaporation of said thin layers in said treatment step or is a first of said phases of evaporation.

 This method may also include an additional step, analogous to said final step and carried out after it, of adding a new optical device to the one already in place.

 The invention also relates to an optical component resulting from the implementation of this method, comprising at least one optical element and at least one optical device produced by thin layers and retained in place on the corresponding optical element by an optical agent adhesion, characterized in that it exclusively comprises said optical device, with said optical agent of adhesion between it and said corresponding optical element, but without support on which this optical device has been previously produced.

 The characteristics and advantages of the present invention will emerge from the description given below with reference to the attached drawings. In these drawings - FIGS. 1 and 2 illustrate the steps of the method for installing an optical device produced by thin layers on an optical fiber and on an integrated optical waveguide, according to the present invention, - FIG. 3 represents an optical component resulting from the implementation of the method according to the present invention.

 Figures 1 and 2 illustrate the two essential steps, noted A for the first and B for the second, of the method according to the invention, with in Figure 1 the optical element consisting of an optical fiber 1 and in Figure 2 l optical wave element consisting of an optical guide integrated 10 into a glass substrate 11.

 In these figures 1 and 2, these steps A and B are analogous and described simultaneously.

 Step A is called the optical processing step. It consists in carrying out, in an initial phase of this step, the deposition of a so-called transfer coating 2 on a support 3, then in multiple phases of the aforementioned known evaporation operation, the deposition of a stack of thin layers constituting a desired optical device 4 on this transfer coating. The transfer coating then forms a weak adhesion interface between the optical device and the support.

 The support 3 is preferably for subsequent tests, a glass slide. Its dimensions, including its thickness, are arbitrary, they are sufficient for its easy gripping and subsequent handling. The blade has optical transmission characteristics well known for subsequent testing.

 The coating material 2 is preferably silver-based or is a zinc sulfide. Depending on the nature of this material, this initial phase of step A is independent or not of the evaporation operation. Thus, in an independent initial phase, a silver or silver-based layer is deposited on the support. As a variant, a first layer of zinc sulfide is deposited on the support at the start of the evaporation operation itself, this first layer constituting the transfer coating then belonging to the optical device 4. This is translated by the dotted line between the transfer coating and the optical device proper, in Figures 1 and 2.

 At the end of this step, each optical device 4 on its support 3 is tested. The optical devices on their support which do not have the desired characteristics are eliminated. They are, moreover, selected before mounting on the optical element or elements, in order to obtain the desired resulting optical component.

 The following final step B is called the transfer and holding step of the optical device, at the end of the optical fiber 1 or of the waveguide 10, according to these two examples considered. It is illustrated broken down into two phases Bl and B2. Phase B1 is the implementation phase. In this phase B1 an optical adhesion agent 5 is first of all deposited on the end of the optical element concerned and / or on the free face of the optical device 4, then the optical device on its support is positioned at the end of this optical element. The support 3 is retained in suitable gripping and handling means shown diagrammatically at 7, during this phase B1.

 Phase B2 is that of holding the optical device 4 in place without its support, which is separated by traction using the gripping and handling means.

 According to the transfer coating 2 adopted, it is noted that the silver-based material acts as a release layer which is easily dissociated from the support as from the optical device and is completely eliminated thereon, for example by etching with solvent. On the other hand, zinc sulphide, which constitutes the initial thin optical layer of the optical device, dissociates easily from the support. This transfer coating, eliminated or belonging to the stack of thin layers, has therefore been illustrated in dotted lines in this phase B2. It is specified that this initial thin optical layer controlled in the operating cycle of the evaporation operation is extremely slim. As a result, the possible presence of the transfer coating in the optical device in place on the optical element brings only almost zero and negligible diffusion and / or propagation losses, which are incommensurate with the losses that gives the same thin glass slide of the solution known from the known art indicated above.

 Advantageously, the optical device 4 is made of dimensions greater than those useful when it is considered in place on the waveguide or the optical fiber which will receive it. I1 is cut substantially to the peripheral dimensions of this optical element, before or after its installation depending on the type of optical element and the network or structure to which this optical element belongs.

 As illustrated in FIG. 2 only, it is noted that the two phases B1 and B2 of this final step can be renewed for the setting up and holding in place in an additional final step C of a second optical device 4 ′ on that already 4 in place. These two optical devices 4 and 4 ′ are held together by an optical adhesion agent 5 ′ similar to the agent 5. They constitute a new overall optical device, of desired new function resulting from those of the two optical devices which constitute it.

 Of course also the optical device in place can be replaced pr: n other, by cutting by the adhesion plane that in place on the optical element and by putting and maintaining this other device, according to phases B1 and B2 ci -before.

 FIG. 3 illustrates an optical component resulting from the implementation of the method described above. This optical component is a wavelength multiplexer / demultiplexer in integrated optics. I1 has two integrated optical waveguides 20 and 20 'in a glass substrate 21, which are coupled to each other by a first of their ports on one of the edges of the substrate and each have their second access on the opposite edge of the substrate. I1 is also with a first optical device produced by thin layers 24, on the first accesses coupled to each other of these waveguides and with a second optical device produced by thin layers 24 ′ on the second access of one waveguides 20 ′. These two devices 24 and 24 ′ are two filters, produced according to step A and mounted and held in place according to phases BI and B2 of the process according to the inversion of the optical component, they are with the optical agent of adhesion 3 and 25 ′ and possibly with their transfer coating (felt) when this is integrated into each filter in step A, but without the support on which each of them was produced .

 The first filter 24 is transparent at a first wavelength and reflecting at a second. The second filter 24 'has the opposite function.

 Of course, one and / or the other of these two filters may consist of two superimposed elementary filters, placed one on the other according to the method of the invention.

Claims (11)

1 / Method for installing an optical device in thin layers on an optical element consisting in carrying out an optical processing step for depositing the thin layers of said optical device on a support, followed by a final step of transfer and holding in place using an optical agent for adhering said optical device to an access of said optical element, characterized in that it consists, moreover, in carrying out an initial phase of deposition on said support with a coating said transfer, of relatively low adhesion to said support, for the deposition in said step of processing the thin layers of said optical device on said transfer coating thus forming an interface of low adhesion between said optical device and said support, and in that said final step further consists in detaching said support from said optical device in place. 2 / A method according to claim 1, characterized in that it consists in using to constitute said transfer coating an optical material of less adhesion to said support than said optical device produced on it. 3 / A method according to claim 2, characterized in that said optical material is a zinc sulfide. 4 / Method according to one of claims 1 and 2, characterized in that said initial phase is the first of the evaporation phases constituting said optical processing step. 5 / A method according to claim 1, characterized in that it consists in using to form said transfer coating a release material of low adhesion on said support and on said optical device, and easy to completely eliminate on said optical device after separation of said support. 6 / A method according to claim 5, characterized in that said chosen material is based on silver. 7 / A method according to one of claims 5 and 6, characterized in that said initial phase is independent of phases of evaporation of said thin layers of the optical device in said processing step. 8 / A method according to one of claims 1 to 7, characterized in that it consists in using, to constitute said support, an optical support of any dimensions but of known light transmission characteristics, for tests of said optical device on said support. 9 / A method according to one of claims 1 to 8, characterized in that it further consists in adapting the dimensions of said optical device produced on said support, by cutting it substantially to the peripheral dimensions of the access of said optical element, after or before it is put on and kept in place on this access. 10 / Method according to one of claims 1 to 9, characterized in that it consists in remaking identically an additional final step, adding on said optical device already in place a new additional optical device defining with that in place an overall optical device having desired new optical characteristics. 11 / optical component resulting from the implementation of the method according to one of claims 1 to 10, comprising at least one optical element and at least one optical device produced by thin layers and retained in place on the corresponding optical element by a optical adhesion agent, characterized in that it exclusively comprises said optical device (4, 24, 24 '), with said optical adhesion agent (5, 25, 25') between it and said corresponding optical element (1 , 10, 20, 20 '), but without support on which this optical device was previously produced.