CA2041128A1 - Slot-coupling of optical waveguide to optical waveguide devices - Google Patents

Abstract

SLOT-COUPLING OF OPTICAL WAVEGUIDE
TO OPTICAL WAVEGUIDE DEVICES
ABSTRACT
An optical waveguide device adaptable to be coupled with a similar optical waveguide device through commensurate slots on the devices, the slots guiding the ends of the respective waveguides into contact with each other, and into properly aligned optical coupling.

Description

20411~8 SLOT-COUPLING OF OPTICAL WAVEGUIDE
TO OPTICAL ~AVEGUIDE DEVICES
5 1 . E-~ e 1 d of t he ~,,~y~
Thiq invention relates to optical waveguide devices capable of being coupled with each other through matching slots on each device. This greatly facilitates the alignment of the waveguides. The instant inventlon also relates to methods of making such optlcal devices.

2 . Ba~ Q~ the Tnve-lt~orl In optical communication systems, messages are transmitted typically through optical fibers by carrier waves of optical frequenc$es that are ~enerated by sources, such as lasers or light emitting diodes. There is much current interest in such optical communicatlon systems because they offer several advantages over other communication systems, such as having a greatly increased number of channel-~ of communication and the ability to use other materlals besides expensive copper cables for transmitting messages.
As the development of optical circuits proceeded, it became necessary to have optical waveguide devices which could couple, divide, swltch and modulate the optical waves from one optical fiber to another, or from one waveguide device to another. For example devices see U.S. Patents 3,689,264, 4,609,252 and 4,637,681.
Connectlng optical devlces to one another ha~
tradltionally been a problem. One method is to fuse or melt fibers or other conflguratlons, for example, together 80 that llght from one flber or conflguratlon can pass to the connected fiberQ or configuration~
However, ln such a fu~lon proces~ it ls difflcult to control the extent of fuslon and the exact geometry and reproduclbility of the final structure.

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2 2 0 41 ~2 8 3. ~ummary of t~e Tnvent ~ on The instant invention 19 directed to optical waveguide devices capable of being coupled with each other through matching slots on each device. This greatly facilitates the alignment of the waveguides.
More particularly, this ~nvention pertains to an optical waveguide device adaptable to be connected to a similar optical waveguide device, comprising: terminal edge; a first pair of opposite external surfaces, substantially parallel to each other, and extending away from the terminal edge; and a waveguide positioned equidistantly between the first pair of the opposite external surfaces, and having an end point and a center axis, the center axis forming an angle greater than zero with the termlnal edge; the device also having a thickness, and a through-slot extending in a direction substantially parallel to the direction of the waveguide, the through-slot starting at the terminal edge and extending adequately within the device as to meet the end of the waveguide, the through-slot having a width, and a center axis coinciding with the center axis of the wavegulde, the through-slot confined by a second pair of opposite side surfaces, substantially parallel to each other and to the center axis of the waveguide, and substantially perpendicular to the first pair of surfaces with the requirement that the width of the through-slot is not excessively smaller than the thickne~s of the matching device; and an lnternal surface meeting with and being substantially perpendicular to the flrst and the second pairs of surfaces, the lnternal ~urface having a center point, the center point coincidlng wlth the end of the wavegulde, 80 that when the through-slot of the optical waveguide device is coupled with a slmllar slot of a second similar device, the ends of the respective 3 204112~3 waveguides come in contact, and the center axes of the waveguides substantially coincide.
Preferably, the width of the through-slot is adequately smaller than the thickness of the device, so S that when the optical waveguide device is connected to a similar device through coupling of their respective through-slots, a tight and secure fit ls created. Also preferably, the optical waveguide device comprises a laminate of a middle photopolymer layer containing the waveguide, and two external photopolymer layers having the same thickness.
The instant invention also relates to methods of making such optical devices. More particularly it pertains to a method of coupling two optical waveguide devices, each optical device having a terminal edge, a first pair of opposite surfaces substantially parallel to each other, and a waveguide positioned equidistantly between the opposite surfaces, the waveguide having a center axis forming an angle with the terminal edge different from zero, comprising the steps of: forming a through-slot in a direction substantially parallel to the directlon of the waveguide, the through-slot ~tarting at the terminal edge of each device and extending adequately within the device to remove at least part of the waveguide and form an end on the waveguide, in a way that the through-slot has a center axis coinciding with the center axis of the waveguide, and a second pair of opposite slde surfaces, substantlally parallel to each other and to the center aX19 of the wavegulde, and substantially perpendlcular to the flrst pair of surface~ wlth the requirement that the wldth of the through-slot 19 not exce~slvely smaller than the thickness of the device, and an internal surface meetlng wlth and being perpendlcular to the second palr of surfaces, the lnternal surface havlng a Z04112~3 center point, the center point coinciding with the end of the waveguide; and, inserting the slot of one device into a similar slot of a second device in a way that the ends of the respective waveguides come in contact, and the center axes of the waveguides substantially coincide. It iY preferable to adhere the respective waveguide ends of the two devices to each other with an adhesive photopolymer composition.

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The reader's understanding of practical implementation of preferred embodiments of the invention will be enhanced by reference to the following detailed description taken in coniunction with perusal of the lS drawing figures, whereln:
Figure 1 i-~ a perspective view of a photohardenable film removably adhered to a support.
Figure 2a is a schematic repreQentation of a preferred way for forming an optical waveguide in a film on a support.
Figure 2b is a ~chematic representation of a second preferred way for forming an optical waveguide having a Y configuration in a film on a support.
Figure 2c is a schematic representation of a third preferred way for forming an optical waveguide having a different configuration in a film on a -~upport.
Figure 3 depicts an optlonal step of flooding the film having a waveguide on a support wlth light.
Figure 4 shows a laminated structure comprlslng from top to bottom a support, a photohardenable layer, a film havlng a waveguide, and another support.
Figure 5 illustrates an optional step of flooding the Qtructure of Figure 4 with light.
Figure 6 19 the structure of Figure 4 or 5 with one of the supports remo~ed.

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20~ 8 Figure 7 is a perspective vlew of an optical waveguide device compri~ing from top to bottom a support, a photohardenable or photohardened layer, a film having a waveguide, a photohardenable layer, and a S ~upport.
Figure 8 shows the step of hardening the device of Figure 7 by floodinq it with light.
Figure 9 Qhows the step of hardening the element of Flgure 7 or the device of Figure 8 by heating it.
Figure 10 is a perspective view of an optical waveguide device for use in integrated optical systems, the device comprising from top to bottom a first hardened layer, a hardened film having a waveguide, and a second hardened layer.
I5 Figure 11 shows the step of stabilizing the device of Figure 10 by heating it.
Figure 12 is a perspective vie of two optical waveguide devices having through-slots before they have been connected.
Figure 13 is a perspectlve view of the two optical waveguide device~ shown in Figure 12 after they have been connected over their through-slots.
Figure 14 Qhows a cross-sectional view of a slot including an enlarged outer region.
S. Deta~led ne~cr~t~on of the Tnvent~ o~
This invention pertains to optical waveguide devices capable of being coupled with each other through special matching ~lots on each devlce. This greatly facllltates the allgnment of the waveguides embedded in different devices and alleviates the need for accurate and very expenQive equipment, whlch 18 otherwlse requlred for the wavegulde alignment. The lnstant lnvention also relates to method~ of makinq such optlcal devices.

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Although any type of optical wavegulde devices having the waveguide embedded equidiqtantly from their outside surfaces may be uQed in accordance with this invention, the deviceQ de-qcribed in the detailed d~scussion of Figures 1 - 11 lend themselves to inherently more accurate positioning of a waveguide regarding the "equidistance" requirement, and therefore they are preferred. The through-slots, which are carved according to the instant inventlon on the optical waveguide deviceQ are described in the discussion of Figures 12 and 13.
It should be under-qtood that although the Figures illustrate only elementary optical waveguide devices for simplicity purposes, the degree of complexity of the lS individual devices does not have adverse consequences with regard to the present invention.
Throughout the following detailed description, similar reference numeral~ refer to similar parts in all Figures of the drawing. In additlon, the word "element"
is used to denote a constituent of a final optical waveguide device.
Referring to Figure 1, an eIement is illustrated comprising a substantially dry photohardenable film 1 removably adhered to a support 2. The film 1 has a first surface 3 and a second Qurface 4. The support similarly has a first surface 5 and a second surface 6.
The first surface 5 of the support 2 is removably adhered to the first surface 3 of the fllm 1. The surfaces 3, 4, 5 and 6 of the fllm 1 and the support 2 are preferably qubQtantia}ly flat.
The fllm 1 may have a thickness ln the range of 2 micrometers through 15 micrometer~ or above, preferably ln the range of 4.5 micrometers through 8.0 micrometers, and more preferably about 5.3 micrometers.

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Referring to Figures 2a, 2b, and 2c, the first step of the method of of making the preferred devices according to the present invention comprises exposing to light at least a first region 7 of the film 1 S polymerizing at least one monomer in the film 1 and changing the refractive index of the region 7 to form at least a first optical waveguide. The term waveguide ls defined by those skilled in this art to include the entire area that transmits radiant energy. This technically includes some area ~ust around the exposed region can by considered to substantially be the waveguide. In theory, the waveguide formation is believed to be due to a self-focusing property of the film material. Upon exposure to light, a polymerization reaction is induced in the exposed region. It is believed that there i9 interdiffusion between the exposed and unexposed regions, at least near the interface of these regions.
This lnterdiffusion changes and typically increases the density of the exposed region raising its refractive index creating a lens-like expoqed region directing the light in a self focused fashion to create a narrow smooth walled waveguide of approximately the same dimension as a mask area or light beam width. Three ways for performing this first step are illustrated in Figures 2a, 2b and 2c.
In Figure 2a, a focused laQer light source 8 exposes the region 7 to form the wavegulde. A
translational mechanlsm 9 ls connected to the laser llght source 8 and/or the support 2 for moving the laser llght source 8, the support 2 or both, to create the waveguide having a desired and/or predetermlned pattern.
Here, the exposed region 7 has a substantially elongated box configuration having an optlcal axis 10 through the the longitudinal center of the region 7. A physical ' ' ' cro~s section of the exposed reglon 7 perpendicular to the optical or center axis 10 is substantially rectangular. On both sides of the region 7 are remaining unexposed regions 11 of the film 1.
S Figure 2b shows an alternate way for exposing a region 7`. Here, a non-focused laser light source 8` is generally directing actlnic radlation toward the element of Figure 1. An opaque ma3k 12 is positioned between the laser light source 8 and the film 1, typically contacting and covering the second fllm surface 4. The mask 12 has at least a patterned area 13 therein through which actinic radiation from the light source 8' exposes region 7'. The patterned area can have any desired configuration, including the substantially Y
lS configuration shown in Figure 2b.
Exposlng the region 7` through this area 13, results in the creation of a waveguide having a sub~tantially Y configuration. Described more generically, the region can have one end adapted to inlet or outlet light connected to a plurality of ends (e.g., 2, 3, 4...~ adapted to inlet or outlet light. As in the Figure 2a case, there are remaining unexposed regions 11` in the film 1.
A third way for performing the exposlng step of the present method i~ illustrated in Figure 2c. Here, actinic radiation from a light source B`` exposes a first region 7`` and a second region 7``` of the film 1 through an opaque mask 12`. Thi9 mask 12` has first and second areas 13` and 13`` for the light to pass through exposing regions 7`` and 7```, respectlvely. The second area 13`` approaches and is ln part parallel to the first area 13`. Thus, after exposure, the exposed second region 7``` and the corresponding wavegulde. ~s a result, the waveguides can be positloned to exhibit evanescent couplinq of light in~ected into one of the , ~ :
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20411:~8 waveguides by gradually leaking or coupling the in~ected light into the other waveguide.
In each of these preferred ways, after exposure, the first and second surfaces 3 and 4 of the film 1 remain substantially flat. This facilitates subsequent laminating of layers on the film surfaces. As such, Figures 2a, 2b and 2c illustrate the making of optical waveguide elements, useful in making optical waveguide devlces, which in turn are useful ln integrated optical systems.
Figure 3 illustrates an optlonal step which follows the exposing step. The element resulting from the exposure step can be flooded with light, such as broadband ultraviolet light. This polymerizes some of at least one monomer in the film and typically most or all of one or all of the monomers in the film. This may allow for eaqy removal or attachment of the support 2.
This resulting optical waveguide element can similarly be used in making optical waveguide devices, which devices are preferably used in the present invention.
Next, referring to Figure 4, a flrst substantially dry photohardenable layer 14 is laminated to the second film surface 4. The first layer 14 has first and second surfaces 15 and 16, respectively. The first layer 14 first ~urface 15 is laminated to the second film surface 4 by placing them in intimate contact and controllably applying pressure with rollers to remove air between the film 1 and layer 14. The flrst layer 14 i5 tacky. If the optlonal floodlng step lllustratod ln Flgure 3 19 not performed, then the fllm 1 19 al90 tacky. Thus, the fllm 1 and flrst layer 14 easily adhere to one another.
A support 17 19 removably adhered to the second surface 16 of the flrst layer 14. Figure 4 illustrates another optical waveguide element useful ln maklng optical ~ .
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waveguide devices, which devices are preferably used in the present inventlon.
Figure 5 shows an optional flooding step similar to that illustrated in Figure 3, except the element being S flooded is modifled as described in relation to Figure 4. The element resulting from the first lamination step can be flooded with light, such as broadband ultraviolet light. This polymerizes some of at least one monomer (and typically most or all of one or all of the monomers) in the first layer 14 and further polymerizes some of the at least one monomer ln the film 1 (if not already polymerized by a previous flooding step).
Extensive crosslinking or polymerization occurs between the monomer (9) of the layer 14 ad~acent to the monomer(s) of the film 1 forming a diffuse boundary line or region. The resulting optical waveguide element is also useful in making an optical waveguide device in accordance with this inventlon.
Figure 6 shows the element after the next step of removing the support 2 from the film 1 first surface 3.
Then, referring to Figure 7, a second substantially dry photohardenable layer 18 is laminated to the film 1 fir~t surface 3. The second layer 18 has first and second surfaces 19 and 20, respectively. The second layer 18 first surface 19 is laminated to the film first surface 3 by placing the in intimate contact and controllably applying pressure with rollers removing air between the film 1 and second layer 8. The sec-ond layer surfaces 19 and 20 are tacky and, thus, oasily adhere to the fllm 1. A support 21 ls removably adhered to the second layer second ~urface 20.
Figure 8 illustrates a step of hardenlng the structure depicted in Figure 7 by ~looding it with light, such as broadband ultravlolet light. Throughout this application, the term "broadbend ultraviolet light"

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Z0411~8 means llght ln the ~pectral reglon of about 350 through 400 nanometers. Thls step occurs for minutes, preferably 5, but can last longer. If thls is the first flooding step, then this ls the first polymerization of S at least one monomer ~and tvpically most or all of one or all monomers) in the remaining regions 11 in the film 1 and the first and second layers 14 and 18, respectively. It further polymerizes the at least one monomer in the region 7 of the film 1. If this 19 not the first flooding step, it polymerizes at least one monomer in the second layer and continues polymerizing the at least one monomer in the rest of the element.
Some crosslinking or polymerization occurs between the previously polymerized film 1 and the monomer(s) ln the second layer 18 forming a boundary line or region that is more evident than if the film 1 had not previously been flooded with light. Further, if this is not the first flooding step, for instance if buffer layer 14 was previously hardened by flooding it wlth light as illustrated ln Figure 5, then it would be preferred to harden the film 1 and the buffer layer 18 of the element lllustrated in Figure 8 by flooding light first through support 21, layer 18, film 1, layer 14, and then support 17. In other words, the structure should be flooded such that light passes through unhardened layers or film~ before previously hardened ones.
Furthermore, any one or all of the buffer layers and the fllm with a waveguide formed thereln can be hardened by floodlng them wlth llght before tho layers or fllm are lamlnated to the other parts. A devlce results havlng at least one burled channel wavegulde ln a laminated and photohardened matrix useful ln lntegrated optlcal systems.
Flgure 9 lllustrates another posslble step of hardening the structure depicted in Flgure 7 by heating .
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12 20~ 8 it. Actually, the layers and film can be heated before, in combination with, after, or in lleu of the light flooding step to harden of further harden the device.
This heating step occurs at a temperature in the range S of about 50C through 200C and preferably in the range of about 100C through 150C for a duration of minutes, preferably 5.
Photohardenable compositions are typically less sensitive to temperatures up to 100C than above 100C.
}0 However, hardening may be initiated as low as 50C of held at the temperature for a sufficlent period of time.
As the temperature is increased beyond 100C, thermally initiated hardening increases significantly.
After the hardening step, a maximum refractive index increase in the localized waveguide region as measured by an ASUJENA Interphako microscope occurs in the film in the range of 0.001 through 0.40 measured at 546 nanometers wavelength. The localized refractive index increase, n, may be derived by conventional shearing interference microscopy techniques and is calculated assuming a uniform index shift through the film such that n is effectively an average using the following equations:
f~ ~ ~nd f b a~
b ' ~nd where d - assumed waveguide thickness, typically the fllm thickne~s a - waveguide frlnge shift b - fringe spacing - 0.546 ~, wavelength of llght in the microscope .

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Z04~128 This local~zed refractive index ~ncrease is contrasted and iQ not to be confused with a refractive index modulation measured from gratings prepared holographically, such a described in U.S. patent application Serial Number 07/144,355 filed January 15, 198B.
After the hardening step, the wavegulde is tranQparent in the range of 0.6 through 1.6 micrometers wavelength. It ls effectlvely transparent at 1.3 micrometers for single mode operation. Also after the hardening step, the maximum refractive index of the matrix except in and near the waveguide is in the range of 1.45 through 1.60 measured at 632 nanometers depending on formulation and/or extent of interlayer d~ffusion from ad~oining layers or film of different indexes. The refractive index is determined by using an ABBE refractometer manufactured by Karl Zeiss.
The supports 17 and 21 can be removed from the device resulting from the hardening step as shown ln Figure 10.
It has been found that a time delay of 5 to 120 minutes, preferably 20 to 30 minutes, after each flooding step and before removal of support sheets facilitate interlayer diffusion and polymerization.
Figure 11 shows an optional, but preferred, step of stabilizing the device shown in Figure 10 by heating it, typically after the hardening step. This heating step similarly occur~ at a temperature ln the range of about 50C thorough 200C and preferably ln the range of about 30 100C through 150C. However, thls stablllzlng step occurs longer than the hardenlng step. Preferably the stabilizing step occurs in the range of about 20 minutes through 2 hours and more preferably for about an hour.
This heatlng makes the devlce more envlronmentally stable ensuring water and other elementQ ln the ., ~ .

20~1128 environment will not interfere with proper operation of the device. Further, this heating provides thermal -qtabilization of optical and mechanical properties allowing operation of the resulting device over a wide range of temperatures without modification of the device properties.
In the device of Figure 10 or 11, the first and ~econd layers 14 and 18, respectively, have equal thicknesses since the fllms 14 and 18 are substantially identical, thus inherently fulfilling the "equidistance"
requirement. It is preferabie for the purposes of this invention to select and cut the pieces of films 14 and 18 from ad~acent areas of the ~ame roll of film, in order to ensure identical thickness.
One of the advantages of this arrangement is the ease of adding one or more substantially dry photohardenable or photohardened layers on each side with or without a waveguide or grating, and build up any deQired thickness, still fulfilling the "equidistance"
requirement.
All layers can be made out of the same materlal as the film. Then the hardened device matrix is substantially homogeneous in composition and refractive index except in and near the waveguide. Preferably, however, after the hardening ~tep, the waveguide has a refractive index about 0.005 and 0.060 greater than the hardened film and about 0.001 to 0.025 greater than the hardened layers. Of course, regardless of whether different materials are used for dlfferent layers and the film, the composltlon and refractlve index ln each exposed reglon i9 substantially homogeneous ln compo~ltlon and refractlve lndex.
Figure 12 lllu-~trate~ in a perspectlve view an optlcal wavegulde devlce~ 30 and a matchlng slmllar optlcal waveguide device 30', preferably both made :
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; -~0~ll2a according to the preceding di~cus~ion. The devices have similar configuration, and they are adaptable to be connected or coupled to each other. Device 30 has a terminal edge 32, and a first pair of opposite external 5 surfaces 34 and 36, which are substantially parallel to each other, and they extend away from the terminal edge 32. There i8 provided also a waveguide 7, which should be positioned equidistantly between the first pair of opposite surfaces 34 and 36. The waveguide 7 has an 10 end-point 40 and an optlcal or center axis A-A'. The center axis A-A' forms an angle with the terminal edge 32, which should have a value different than zero, and should preferably be a substantially right angle. The thickness of the optical device 30 is defined as the 15 distance between the parallel and opposite surfaces 34 and 36.
The optical waveguide device 30 has also a through-slot 42 which extends in a genéral direction substantially parallel to the direction of the waveguide 20 7, which is the same as the direction of its center axis A-A'. As a matter of fact, the through-slot has a center axis (not shown) which coincides with the center axis A-A' of the waveguide 7. The through-slot 42 starts at the terminal edge 32, and it extends 2 5 adequately within the device 30 as to meet the end point 40 of the wavegulde 7. The slot 42 is conflned by a second pair of opposlte surfaces 46 and 48 which are in a general way substantially parallel to each other and to the center axls A-A' of the wavegulde 7. It 19 30 requlred that the wldth of the through-slot, deflned as the distance separating the opposite surfaces 46 and 48, may not be excessively smaller than the thickness of the matching device 30'. By this lt 19 meant that the width of the slot must not be 80 much smaller than the 5 thlckness of the matchlng device 30' as to produce .
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20411;~8 deleterlous effects when it i8 inserted into a respective slot 42' of device 30'. Such deleterious effects may be breakage, cracking, excessive stress, misalignment, and the like, occurring to one or both devices. Although the wldth of the through-slot 42 may be larger than the thicknes~ of the matching device 30', the primary advantage of this lnventlon of automatically achieving outstanding alignment will be minimized.
Thus, it iQ preferable that the width of the slot 42 equals the thickness of the matching device. It is more preferable that the thickness of the through-slot 42 is adequately smaller, in a trapezoidal manner, than the thickness of the matching device 30', so that when the optical waveguide device 30 is connected to the matching lS device 30' through coupling of their respective through-slots 42 and 42', a tight and secure fit is created. By "trapezoidal manner" it i~ meant that the through-slot 42 is slightly less wide ih the region disposed towards the terminal edge 32 as compared to the region disposed toward the inside of the device 30. Two lips 50 and 52 may be provided for facilitating the insertion of one device into the other at their respective ~lots 42 and 42'. ~he lips may have rounded edge~ for easier insertlon of one slot into another.
The through-slot 42 is al~o confined by an internal surface 54, which meets with and is perpendicular to both the first pair of surfaces 34 and 36, and to the second pair of surfaces 46 and 48. The lntornal surface 54 has a center polnt 56, whlch colncldes wlth the end 40 of the wavegulde 42.
In this manner, when the through-slot 42 of the optlcal waveguide device 30 19 coupled wlth a similar slot 42' of the matchlng simllar devlce 30', the ends 40 and 90' of the respective waveguldes 7 and 7' come ln . . . : . -. ..
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2041~2817 contact, and the center or optlcal axes of the waveguides ~ubstantially coinclde.
Figure 13 shows the manner in which two devices are positioned , when the slot one of them 30, has been inserted completely into the slot of another similar device 30' so that the corresponding ends 40 and 40' of their respective waveguides 7 and 7' come in contact with each other.
Since simple mechanical contact may leave spots of the waveguide end~, which spots may still remaln apart from each other, lt is highly preferab}e that a liquid is placed between the ends of the waveguldes to fill such spots. This liquid should have a refractive index as close as possible to the refractive index of the lS waveguides. It 18 preferable that this liquid possesses adhesive characteristics in order to secure the two respective devices in place. It is even more preferable that the curing of the adhesive liquid is a photohardenable one, and thus ls cured by a photohardening mechanism. This is preferred not only because most of the steps of making the devlces of the lnstant invention lnvolve actlnlc radiation, but also and mos~t importantly because by selecting similar or in general appropriate monomer~ or ollgomerQ, initiators, and other ad~uncts, in appropriate amounts, one may approximate and match the desirable refractive index with higher accuracy and broader formulatlon and condltlon latitude. The technlque of using such adheslve formulatlons may be applled not only for the devlces of the present lnventlon, but also ln any other ca~e, where the free ends of two embedded waveguldes come in contact for the purposes of coupling, including connectors, couplers, splitters, fiber embedded waveguides, and the llke, as well as comblnatlons thereof.

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~ lB 2041128 Monomers, oligomers, polymerQ, initiators, chain transfer agents and other constituents llke the ones used for the fabrication of the devices described herein may also be used for making the optlcally matching liquid, which preferably is also an adhesive when photohardened. Of course, any other materials may be used aQ long as the requirement of matchlng as close as possible the refractlve index of the waveguides under consideratlon ls met.
It ls preferable that the through-slot is ablated by the use of a laser, and more preferably by an excimer la~er. A method for provlding exclmer ablated fiber channels for passive (wlthout need of allgnment equipment) coupllng lnvolves a computer controlled lmage processing and positioning system. The excimer laser is masked by a rectangular aperture and is pro~ected onto the optical waveguide device though a 15x reduction lens.
The rectangular aperture's width is ad~usted until the correct channel width for passive coupling is achieved. For preferred present applications, this width is -112 ~m wide (as measured by the computer) at the optical waveguide device plane. A "sample" channel is created away from the work area. This sample channel is digitized and analyzed for width; the center and angular orientatlon 19 determined by the image processing system, then this lmage is stored as the reference that will be used to align all of the wavegulde~. At this polnt a wavegulde 19 brought into the fleld of vlew and the optlcal wavegulde devlce 19 allgned laterally and rotatlonally, lteratively, untll wlthln tolerance of the reference channel allgnment (~/-0.5 ~m laterally, ~/- 0.25 degrees rotatlonally). Then the actual channel to thls wavegulde is ablated; fluence -2.5 J/cm2, repetltlon rate lOHz, 30 sec. Thls .
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20411~8 procedure is repeated using the stored reference fiber channel image on the rest of the waveguides to be processed.
The photohardenable base and buffer layers used herein are thermoplastic compositions which upon exposure to actinic radiation from crosslinks or polymers of high molecular weight to change the refractive index and rheological character of the composition(s). Preferred photohardenable materials are photopolymerizable composltions, such as disclosed ln United States Patent 3,65~,526 ~Haugh) and more preferred materials are described copending appllcation Serial Numbers 07/144,355, 07/144,281 and 07/144,B40, all filed January 15, 1988 and all assigned to E. I. du Pont de Nemours and Company, Incorporated. In these materials, free radical additlon polymerization and crosslinking of a compound containing one or more ethylenically unsaturated groups, usually in a terminal position, hardens and inQolubilizes the composition.
The sensitivity of the photopolymerizable composition is enhanced by tbe photoinitiatlng sy~tem which may contain a component which 3ensltizes~the composition to predetermined radiation sources, e.g., visible light.
Conventionally a binder is the most ~ignificant component of a substantially dry photopolymerizable base or layer ln terms of what physical properties the base or layer will have while being used in the lnvention.
The binder serves BS a containlng medlum for the monomer and photolnitlator prior to exposure, provldes the base llne refractlve lndex, and after exposure contributes to the physical and refractive index characterlstlcs needed for the base layer of buffer layer. Cohesion, adhesion, flexibility, dlffusiblllty, tensile strength, in addltion to lndex of refractlo~ are some of the many .
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20411;;~8 properties whlch determine if the binder is sultable for use in the base layer or the buffer layer.
Dry base or layer photohardenable elements contemplate to be equivalent are photodlmerizable or S photocrosslinkable compositions such as disclosed in United States Patent 3,526,504 (Celeste) or those compositions in which hardening is achieved by a mechanism other than the free radical initiated type identified above.
While the photopolymerizable base or layer is a solid sheet of uniform thickness it is compo~ed of three ma~or components, a solid solvent soluble performed polymeric material, at lea~t one liquid ethylenically unsaturated monomer capable of addition polymerization to produce a polymeric material with a refractive lndex substantially different from that of the performed polymeric material, or binder, and a photoinitiator system activatable by actinic radiation. Although the base or layer i9 a solid composition, components interdiffuse before, during and after imaglng exposure until they are fixed or destroyed by a final uniform treatment u-~ually by a further uniform exposure to actinic radiation. Interdiffusion may be further promoted by incorporation into the composition of an otherwise inactive plasticizer.
In addition to the liquid monomer, the composition may contain solid monomer components capable of interdiffuslng ln the solid composition and reacting with the liquld monomer to form a copolymer wlth a refractlve index shlfted from that of the blnder.
In the preferred compo~ltlons for use as the base layer or buffer layer~ ln thl~ lnvention, the preformed polymeric material and the llquld monomer are selected so that either the preformed polymeric material or the monomer contains one or more moleties taken from the group consisting essentially of substituted or un~ubstituted phenyl, phenoxy, naphthyl, naphthyloxy, heteroaromatic groups containing one to three aromatic rings, chlorine, and bromine and wherein the remaining S component is substantially free of the specified moleties. In thè instance when the monomer contains these moieties, the photopolymerizable system hereinafter is identified as a "Monomer Oriented System`' and when the polymeric material contains these moieties, the photopolymerizable system hereinafter is identified as a "Binder Oriented System. n The stable, solid, photopolymerizable compositions preferred for this invention will be more fully described by reference to the "Monomer Oriented System`' and "Binder Oriented System.`' The Monomer Oriented System is preferred for the base layer.
The monomer of the Monomer Oriented System is a liquid, ethylenically unsaturated compound capable of addition polymerization and having a boiling point above 100C.. The monomer contains either a phenyl, phenoxy, naphthyl, naphthoxy, heteroaromatic group containing one to three aromatic rings, chlorine or bromine. The monomer contains at least one such moiety and may contain two or more of the same or different moieties of the group, provided the monomer remains liquid.
Contemplated as equivalent to the groups are substituted groups where the substitution may be lower alkyl, alkoxy, hydroxy, carboxy, carbonyl, amino, amido, ~mido or combinations thereof provlded the monomer remains liquld and diffusible in the photopolymerizable layer.
Preferred liquld monomers for use ln the Monomer Orlented System of this lnvention are 2-phenoxyethyl acrylate, 2-phenoxyethyl methacrylate, phenol ethoxylate acrylate, l-(p-chlorophenoxy) ethyl, p-chlorophenyl acrylate, phenyl acrylate, l-phenylethyl acrylate, di(2-22 20411Z8acryloxyethyl) ether of b~phenol-A, and 2-(2-naphthyloxy) ethyl acrylate.
While monomers useful in this invention are liquids, they may be used in admlxture with a second solid monomer of the same type, e.g., N-vinyl-carbazole, ethylenically unsaturated carbazole monomers such as disclosed in ~3~ml5~y ~d~tion, Vol. 18, pp. 9-18 (1979) by H. Kamagawa et al., 2-naphthyl acrylate, penta-chlorophenyl acrylate, 2,4,6-tribromophenyl acrylate, and bisphenol A diacrylate, 2-(2-naphthyloxy) ethyl acrylate, and N-phenyl maleimide.
The solvent soluble polymeric material or binder of the Monomer Oriented System i8 substantlally free of phenyl, phenoxy, naphthyl, naphthyloxy, heteroaromatic group containing one to three aromatic rings, chlorine and bromine.
Preferred blnders for use ~n the Monomer Oriented system of this invention are cellulose acetate butyrate polymers; acrylic polymers and lnter polymers including polymethyl methacrylate, methyl methacrylate/methacrylic acid and methylmethacrylate/acrylate acid copolymers, terpolymers of methylmethacrylate/C2-C4 alkyl acrylate or methacrylate/acryllc or methacrylic acid; polyvinyl-acetate; polyvinyl acetal, polyvlnyl butyral, polyvinylormal; and as well as mixtures thereof.
The monomers of the Binder Orlented System ls a liquid ethyIenically unsaturated compound capable of addltion polymerlzatlon and havlng a bolllnq point above 100C. The monomer i8 substantially free of moletles taken from the group conslstlng essentlally of phenyl, phenoxy, naphthyl, naphthyloxy, heteroaromatlc group contalnlng one to three aromatlc rings, chlorlne and bromine.

Z04~12~

Preferred liquid monomers for use in Binder Oriented Systems of this invention include decanediol diacrylate, iso-bornyl acrylate, triethylene glycol diacrylate, diethyleneglycol diacrylate, triethylene glycol dimethacrylate, ethoxyethoxyethyl acrylate, triacrylate ester of ethoxylated trimethylolpropane, and 1-vinyl-2-pyrrolldinone.
While monomerQ u~ed ln Binder Oriented Systems are liquids, they may be used ln admixture with a ~econd solid monomer of the same type, e.g., N-vlnyl-caprolactam.
The solvent qoluble polymeric material or binder of the Binder Oriented system contains in its polymeric structure moieties taken from the group consisting essentially of phenyl, phenoxy, naphthyl naphthyloxy or heteroaromatic group containing one to three aromatic rings as well as chloro or bromo atoms. Contemplated as equivalent to the groups are substituted groups where the ~ubstitution may be lower a-lkyl, alkoxy, hydroxy, carboxy, carbonyl, amido, imido or combinations thereof provided the binder remains solvent soluble and thermopla~tic. The moietie~ may form part of the monomeric unitq whlch constitute the polymeric binder or may be grated onto a pre-prepared polymer or interpolymer. The binder of this type may be a homopolymer or it may be an interpolymer of two or more separate monomeric units wherein at least one of the monomeric units contains one of the moieties ldentified above.
Preferred binders for use ln the Blnder Orlented System lnclude polystyrene, poly (styrene/acrylo-nitrile~, poly~styrene~methyl methacrylate), and polyvinyl benzal as well a9 ~dmlxtures thereof.
The ~ame photoinitlator ~y~tem actlvatab}e by actinic radiatlon may be used ln either the Monomer . , .

20411~

Oriented System or the Blnder Orlented System.
Typically the photoinitiator sy~tem will contain a photoinitiator and may contain a sensitizer which extends the spectral response into the near U.V. region and the visible spectral regions.
Preferred photoinitlator~ include C~M-HABI, l.e., 2-(Q-chlorophenyl)-4,5-bis(m-methoxyphenyl)-imidazole dimer; Q-Cl-HABI, i.e., 1,1'-biimidazole, 2,2'-bis-(~-chlorophenyl)-4,4',5,5'-tetraphenyl-; and TCTM-HABI, i.e., lH-imldazole, 2,5-bl~(Q-chlorophenyl)-4-3,4-dlmethoxyphenyl-, dimer each of which is typically used with a hydrogen donor, e.g., 2-mercaptobenzoxazole.
Preferred sensitizers include the following:
DBC, i.e., Cyclopentanone, 2,5-bis-(diethylamino)-15 2-methylphenyl)methylene); -DEAW, i.e., Cyclopentanone, 2,5-bis-(~4-(diethylamlno)-phenyl)methylene); and Dimethoxy-JDI, i.e., lH-inden-l-one, 2,3-dihydro-5,6-dimethoxy-2-((2,3,6,7-tetrahydro-lH,5H-benzo[i,~]qulnolizine-9-yl)-methylene)-.
The solid photopolymerizable compositions of this invention may contain a plasticizer. Plasticizers of thls invention may be used in amounts varying from about 2% to about 20% by weight of the compositions preferably 5 to 15 wt. %.
Preferred plasticizers for use in ~imple cellulose acetate butyrate systems are triethyleneglycol dicaprylate, tetrAethyleneglycol diheptanoate, diethyl adipate, Bri~ 30 and trls-~2-ethylhexyl)phosphate.
Slmllarly, trlethyleneglyco dlcaprylate, dlethyl adlpate, Brl~ 30, and trls~2-ethylhexyl)-phosphate are preferred in ~Monomer Oriented Systems" where cellulose acetate butyrate 1~ the binder.
Other components ln addition to;those described above can be present ln the photopolymerlzable .

2041~28 compositions in varying amount-~. Such components lnclude: ultraviolet radiatlon absorbing material, thermal stabilizers, hydrogen donors, oxygen scavengers and release agents.
Amounts of ingredient~ in the photopolymerizable compositions will generally be within the following percentage ranges baqed on total weight of the photopolymerlzable layer: monomer, 5-50%, preferably 15-35%; lnitiator 0.1-~0~, preferably 1-5%; binder, 25-75%, preferably 45-65~; plasticizer, 0-25~, preferably 5-15%;
other ingredients 0-5%, preferably 1-4%.
The supports can be any subqtance transparent to actinic radiation that provide~ sufficient support to handle the combined base and layer. Preferably the support is transparent to light in the spectral region of 0.6 through 1.6 micrometerq wavelengths. The term n~upport~ iQ meant to include natural or ~ynthetic -qupports, preferably one which is capable of existing in a flexible or rigid film or sheet form. For example, the support or substrate could be a sheet or film of ~ynthetic organic reqin, or a composite of two or more materials. Speciflc substrates include polyethylene terephthalate film, e.g., resln-Aubbed polyethylene terephthaiate film, flame or electrostatic discharge treated polyethylene terephthalate film, glass, cellulose acetate film, and the like. The thickness of the supports has no particular importance 80 long as lt adequately supports the film or layer removably adhered to lt. A support thickness of about twenty-five ~25) to flfty ~50) mlcrometers uslng polyethylene terephthalate provide~ sufflclent rlgidity.
The following examples are provlded as an illustratlon of how such a devlce may be made, but does not llmlt, the lnventlon.

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2041~28 xa2~
A substantially dry photohardenable (active~ film ~base or waveguide layer) of about 5.3 nm thick, having the ingredients listed in Table I, coated on a 25 nm thick clear polyethylene terephthalate support, ln approxlmately a 3 inch X 4 inch sectlon, 1~ exposed to broad band ultraviolet light in the spectral range of 350 to 400 nm through a conventional chrome-plated glass photo-ma~k to produce a 1 X 4 (one wavegulde end to four waveguide ends or four to one) coupler wavegulde pattern. After expo~ure and then an appropriate delay time of about 15 minute~, the mask i8 removed.
Next, a first substantially dry photohardenable layer (inner buffer layer) of about 30 nm thick, having the ingredients listed in Table II, coated on a 25 nm thick clear polyethylene terephthalate support, is laminated to the film surface over the waveguide, and is subsequently flooded with broadband ultraviolet light in the qpectral range on 350 to 400 nanometers. The film support ls then removed by mechanical stripping.
Next, a second photohardenable layer (inner buffer layer) of identical composition and structure, as the first buffer layer, with ~upport, is laminated to the opposite surface of the film (base or waveguide layer) and flooded as above.
In subsequent steps, the supports attached to the buffer layers are removed. Seguentially, a third and fourth buffer layer ~outer buffer layers) of a compositlon a8 shown ln Tablo III, and a structure aY
the other buffer layers are lamlnated to the first and second buffer layers, respectively, with flooding between each lamlnatlon and sub~eguent removal of the buffer layer support to form an optlcal wavegulde devlce having a burled channel waveguide.

.. ~ . - ~ ;. , --: , - 2041~8 The resultant device is heated at 100C for 60 minutes to achieve thermal stability.

B~SE OR WAVEGUIDE LAYER

~9~EDIE~ WEIGHT %
Cellulose acetate butyratel 56.54 Phenoxyethyl acrylate 35.00 Triethyleneglycol dicaprylate 5.00 10 Q-Cl HABI1 1.00 2-Mercaptobenzoxazole 1.89 Sensitizing dye (DEAW) 3 0.56 2,6-Di-t-butyl-4-methylphenol 1 Eastman type CAB 531-1 2 l.l'-bis-biimidazole, 2,2'-bis-o-chlorophenyl-4,4',5,5'-tetraphenyl; CAS 1707-68-2 3 2,5-bis(~4-diethylamino)-phenyl]methylene)cyclopentanone ,-.

-- .. .
: :

.
.
.
, 20411;~3 28 :
TAB't.~! T I
~:R LAYER
~i~ Wl;'.TGRT %
Poly(vinylacetate~, MW 500,000,66.04 Phenol ethoxylate monoacrylate,17.02 tO Ethoxylated bisphenol A diacrylate,3.00 N-Vinyl carbazole 7.94 15 Q-Cl-HABI1 3.69 4-Methyl-rH-1,2,4-triazole-3-thlol, 2.09 FC-4302 0.19 Sen~iti ing dye (DAW)3 1 1,1'-bis-biimidazole, 2,2'-bis-o-ch}orophenyl-4,4',5,5'-tetraphenyl; CAS 1707-68-2 2 fluoroallphatic polymeric esters, 3M Company, St. Paul, MN
3 2,5-bls~[4-(diethylamino)-phenyl]methylene)cyclo-pentanone .
.

204~ 8 ~EIII
OUTER BUFFF.R L~YER.
WF'. I GT~T %
Cellulose acetate butyrate1 57.11 5 Phenoxyethyl acrylate 38.00 Q-Cl HABI2 2-Mercaptobenzoxazole 1.89 _____________________ 1 Eastman type CAB 531-1 2 1,1'-bis-blimidazole, 2,2'-bis-o-chlorophenyl-4,4',5,5'-tetraphenyl: CAS 1707-68-2 ~L~
An optical waveguide device of the category described in Example 1 was made by using the materials shown in Tables IV, V, and VI.
The total thickness of the device was approximately 123 microns +/- 1 micron, with an embedded straight single-mode waveguide having dimensions 7.5 microns +/- 0.2 micron in both waveguide layer thickness and waveguide width. The guide operated single mode at 1300 nm with a typical loss of 0.4 to 0.5 dB/cm.
Two ablated slots were created at each side of the device, using an excimer Iaser with optical feedback control for positioning. The positlons of the slots were such 80 that their center axes coincided with the center or optlcal axes of the respectlve waveguldes.
The created slots were approxlmately 121 +/- 1 micron wide, wlth a slight trapezoldal profile of the order of 5 degrees sloped sldes of the slot. The exclmer laser wavelength was 248 nm. Using approxlmately 360 mllli~oules per pulse and a 10-hertz rep rate, lt took 30 seconds to create the indivldual 910t. A key polnt 19 that the ablated ~lot was ~llghtly smaller by a few microns than the material thickness, -~o that the two ..
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204~ 8 inserted slots could snugly fit onto the material of the adjoining piece.
The length of each slot was approximately 470 microns. An enlarged outer region 60 was also created, as shown in Figure 14, having a length of approximately 470 microns. The outer region 60, with a width of approximately 375 microns, was used for general alignment and aid in microtoming the terminal edge without distorting the narrow slot region. Typically, one could have outer regions having lengths of 300 to 1000 microns for insertion to create the slot couple.
In this particular case, the length of 470 microns was completely satisfactory. Bowever, it should be noted that although in this example, use of outer regions 60 was made, the most preferred configuration is the one shown in Figures 12 and 13, wherein the outer region 60 is replaced by the pair of beveled edges 50 and 52. The beveled configuration facilitates insertion of one slot to another. In addition rounding of the beveled edges is also preferred.
In this example, the device made above with two ablated slots at each end, was first cut in half and the slots were inserted into each other, with the plane of the two section-~ 90 degrees from each other.
The slots were easily inserted by hand, creating an accurate alignment of the two single-mode waveguides for each of the two sections. Optical 109~ was evaluated by using a butt-coupled fiber to the outside edge of one of the sections and looking at the near-field output using an IR camera focused on the output edge of the output section.
When initially placed together with no refracting index matching, the total inQertion loss waQ
approxlmately 2.5 dB, but once the optlcally matching adhesive having the formulation shown in Table VII was 204~8 placed into the slot-coupled region and totally polymerized, the loss was 1.4 dB total insertion. This includes the estimated 0.9 to 1.1 dB linear guide loss for the 2.23 cm long guide from input to output through both sections. Typical butt-coupled loss is of the order 0.4 +/- 0.1 dB and thus the expected loss of the system was 1.2 minimum to 1.6 maximum, or typically 1.4.
Since the absolute insertion loss measurement was 1.4 dB, we conclude that the slot couple additional loss was close to 0 and at maximum 0.2 dB.
The optically matching adhesive, which was inserted into the slot through capillary action, covered all intersection surfaces, and it was polymerized us~ng Teck ~ite UV source for approximately 5 minutes. The two ~ntersecting sections were then placed in a nitrogen atmosphere and exposed for 14 hours under fluorescent lights to ensure complete polymerization of the liquid optically matching adhesive, which gave a permanently bonded waveguide-to-waveguide couple.
For the folowing tables, the following definitions apply:
Q-Cl-HABI l,l'-biimidazole, 2,2'-bis[o-chlorophenyl]-4,4',5,5'-tetra-phenyI-; CAS 1707-68-2 MMT 4-methyl-4H-1,2,4-triazole-3-thiol;

Photomer~4039 phenol ethoxylate monoacrylate;
CAS 56641-05-5; Henkel Process Chemical Company 30 Sartomer 349 ethoxylated blsphenol A diacrylate;
CAS 24447-78-7; Sartomer Company, West Chester, PA
CAB cellulose acetate butyrate DEAW 2,5-bl~([4-(diethylamino)-phenyl~methylene)cyclopentanone . .

., .

'~:

204~ 8 TDMA Triethylene glycoldimethacrylate BHT Butylated hydroxy toluene Irgacure~651 2,2-dimethoxy-2-phenylacetophenone Polyox~WSR-3000 Surfactant (Un$on Carbide Corp.) 5 Petrarch M8550 Methacryloxypropyl trimethoxy Yilane ~a~I~ TV

% by wt.
0 Polyox WSRN-3000 1.00 CAB 531-1 55.41 Photomer 4039 34.94 Sartomer 349 4.99 MMT 1.90 1 5 Q-Cl--HABI 1.00 DEAW 0,55 BHT 0.01 3M FC-430 0.20 TABLE V

% by wt.
Polyox WSRN-3000 45.00 CAB 531-1 S5.92 Photomer 4039 23.45 Sartomer 349 10.20 : Q-Cl-H~ABI 0.97 Ethyl Michler'~ ~etone 0.49 Benzophenone 2.91 TDMA 5.10 , .

.

. , 2041~8 'rABT.E VI
Outer ~uf~er Layer % hV wt.
CAB 381-20 47.50 Photomer 4039 20 . 00 Sartomer 349 8.50 TDMA 21.00 Irgacure 651 3.00 1 0 'rA~LE VII
ODtically Matching Adhes~ve % by wt.

Photomer 4039 12 . 5 Irgacure 651 2 :-Petrarch M B550 12 ~ ~

Examples demonstrating the operation of the instant ~ .
invention have been glven for lllustration purposes only, and ~hould not be construed a-q re~tricting the scope or limits of this invention in any way other than ls recited ln the:appended claims.

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Claims (33)

1. An optical waveguide device adaptable to be connected to a matching similar optical waveguide device, comprising:
a pair of opposite surfaces;
an enclosed waveguide having a center-axis, an end point and a guiding direction, the waveguide being positioned equidistantly between the opposite surfaces;

a through-slot extending in a direction substantially parallel to the direction of the waveguide, so that when the through-slot of the optical waveguide device is coupled with a similar slot of a second similar device, the end-points of the respective waveguides come in contact, and the center-axes of the waveguides substantially coincide.

2. An optical waveguide device as defined in claim 1, wherein the width of the through-slot is substantially equal to the thickness of the matching device.

3. An optical waveguide device as defined in claim 1, wherein the width of the through-slot is adequately smaller in a trapezoidal manner than the thickness of the matching device, so that when the optical waveguide device is connected to the matching device through coupling of their respective through-slots, a tight and secure fit is created.

4. An optical waveguide device as defined in claim 1, comprising a laminate of a middle photopolymer layer containing the waveguide, and two external photopolymer layers having the same thickness.

5. An optical waveguide device as defined in claim 1, coupled with a second similar device through an adhesive photopolymer composition.

6. An optical waveguide device as defined in claim 3, coupled with the matching similar device through an adhesive photopolymer composition.

7. An optical waveguide device as defined in claim 4, coupled with the matching similar device through an adhesive photopolymer composition.

8. An optical waveguide device adaptable to be connected to a matching similar optical waveguide device, comprising:
a terminal edge;
a first pair of opposite external surfaces, substantially parallel to each other, and extending away from the terminal edge; and a waveguide positioned equidistantly between the first pair of the opposite external surfaces, and having an end point and a center axis, the center axis forming an angle greater than zero with the terminal edge;

the device also having a through-slot extending in a direction substantially parallel to the guiding direction of the waveguide, the through-slot starting at the terminal edge and extending within the device so as to meet the end of the waveguide, the through-slot having a center axis coinciding with the center axis of the waveguide, the through-slot confined by a second pair of opposite side surfaces, substantially parallel to each other and to the center axis of the waveguide, and substantially perpendicular to the first pair of surfaces with the requirement that the width of the through-slot is substantially the same as the thickness of the matching device, and an internal surface meeting with and being substantially perpendicular to the first and the second pairs of surfaces, the internal surface having a center point, the center point coinciding with the end of the waveguide, so that when the through-slot of the optical waveguide device is coupled with a similar slot of a second similar device, the ends of the respective waveguides come in contact, and the center axes of the waveguides substantially coincide.

9. An optical waveguide device as defined in claim 8, wherein the angle formed by the center axis of the through-slot and the terminal edge is a substantially right angle.

10. An optical waveguide device as defined in claim 8, wherein the width of the through-slot is slightly smaller, with a trapezoidal geometry, than the thickness of the matching device, so that when the optical waveguide device is connected to the matching device through coupling of their respective through-slots, a secure fit is accomplished.

11. An optical waveguide device as defined in claim 8, comprising a laminate of a middle photopolymer layer containing the waveguide, and two external photopolymer layers having the same thickness.

12. An optical waveguide device as defined in claim 8, coupled with a second similar device through an adhesive photopolymer composition.

13. An optical waveguide device as defined in claim 10, coupled with the matching similar device through an adhesive photopolymer composition.

14. An optical waveguide device as defined in claim 11, coupled with the matching similar device through an adhesive photopolymer composition.

15. A method of coupling two optical waveguide devices, each optical device having a thickness, a pair of opposite surfaces, and a waveguide positioned equidistantly between the opposite surfaces, the waveguide having a direction, an end-point and a center-axis, comprising the steps of:

forming a through-slot in a direction substantially parallel to the direction of the waveguide; and inserting the through-slot of one device into a through-slot of the second device in a way that the end-points of the respective waveguides come in contact, and the center axes of the waveguides substantially coincide.

16. A method as defined in claim 15, wherein the forming step of the through-slot is conducted by ablating with a laser.

17. A method as defined in claim 16, wherein the laser is an excimer laser.

18. A method as defined in claim 15, wherein the width of the through-slot of each device is substantially equal to the thickness of the respective device.

19. A method as defined in claim 15, wherein the width of the through-slot of each device is adequately smaller than the thickness of the respective device, so that when the two optical waveguide devices are coupled, a tight and secure fit is created.

20. A method as defined in claim 15, wherein at least one of the optical waveguide devices comprises a laminate of a middle photopolymer layer containing the waveguide, and two external photopolymer layers having the same thickness.

21. A method as defined in claim 15, further comprising the step of adhering the respective waveguide ends of the two devices to each other with an adhesive photopolymer composition.

22. A method as defined in claim 19, further comprising the step of adhering the respective waveguide ends of the two devices to each other with an adhesive photopolymer composition.

23. A method as defined in claim 20, further comprising the step of adhering the respective waveguide ends of the two devices to each other with an adhesive photopolymer composition.

24. A method of coupling two optical waveguide devices, each optical device having a terminal edge, a first pair of opposite surfaces substantially parallel to each other, and a waveguide positioned equidistantly between the opposite surfaces, the waveguide having a center axis forming an angle with the terminal edge different than zero, comprising the steps of:

forming a through-slot in a direction substantially parallel to the direction of the waveguide, the through-slot starting at the terminal edge of each device and extending adequately within the device to remove at least part of the waveguide and form an end on the waveguide, in a way that the through-slot has a center axis coinciding with the center axis of the waveguide, a second pair of opposite side surfaces, substantially parallel to each other and to the center axis of the waveguide, and substantially perpendicular to the first pair of surfaces with the requirement that the width of the through-slot is not excessively smaller than the thickness of the device, and an internal surface meeting with and being perpendicular to the second pair of surfaces, the internal surface having a center point, the center point coinciding with the end of the waveguide; and inserting the slot of one device into a similar slot of a second device in a way that the ends of the respective waveguides come in contact, and the center axes of the waveguides substantially coincide.

25. A method as defined in claim 24, wherein the forming step of the through-slot is conducted by ablating with a laser.

26. A method as defined in claim 25, wherein the laser is an excimer laser.

27. A method as defined in claim 24, wherein the angle formed by the center axis of the through-slot and the terminal edge is a substantially right angle.

28. A method as defined in claim 24, wherein he width of the through-slot of each device is substantially equal to the thickness of the respective device.

29. A method as defined in claim 24, wherein the width or the through-slot of each device is adequately smaller than the thickness of the respective device in a trapezoidal manner, so that when the two optical waveguide devices are coupled, a tight and secure fit is created.

30. A method as defined in claim 24, wherein at least one of the optical waveguide devices comprises a laminate of a middle photopolymer layer containing the waveguide, and two external photopolymer layers having the same thickness.

31. A method as defined in claim 24, further comprising the step of adhering the respective waveguide ends of the two devices to each other with an adhesive photopolymer composition.

32. A method as defined in claim 29, further comprising the step of adhering the respective waveguide ends of the two devices to each other with an adhesive photopolymer composition.

33. A method as defined in claim 30, further comprising the step of adhering the respective waveguide ends of the two devices to each other with an adhesive photopolymer composition.