JP2002533776A - Method for manufacturing optical device using purified adhesive in optical path - Google Patents

Abstract

(57) [Summary] A method for manufacturing an optical device using a strong purified adhesive as a binder is disclosed. Impurity particles greater than 0.1 micrometers are removed from the liquid precursor material prior to polymerization or crosslinking. Impurity particles are separated from the precursor by applying a high gravitational centrifugal force. A refining adhesive is used to bond the optical components located in the optical path of the device to one another. The refined adhesive withstands damage from the high power laser since impurity particles that would otherwise absorb and scatter the laser light have been removed from the adhesive.

Description

DETAILED DESCRIPTION OF THE INVENTION

BACKGROUND OF THE INVENTION This application is based on US Provisional Patent Application No. 60 / 114,356, filed December 29, 1998, which claims the priority date of this application.

[0002] 1. FIELD OF THE INVENTION The present invention relates generally to methods for manufacturing multi-component optical devices, and more particularly, to methods for removing impurity particles from polymeric adhesives used in methods for manufacturing multi-component optical devices.

[0003] 2. TECHNICAL BACKGROUND Organic polymers are used in many optical applications where high transparency is required at specific wavelengths. In applications where high pulse laser power can be experienced, such as in optical amplifiers, the material of choice was glass. Currently, techniques such as fusion splicing and laser welding are used to connect fibers and other glass components. However, as optical device design is more complex than ever,
There is a need for simple and less expensive alternatives.

In one approach that has been considered, polymers have been used as adhesives to bond various waveguide and optical components together. Polymers are attractive materials because they have optical and mechanical properties that allow them to be used as binders in the optical path. However, certain designers and researchers have discovered that polymeric adhesives are undesirable due to their low laser damage threshold. Under certain conditions, experiencing pulsing and transients from about 100 MW / cm ² to about 100 GW / cm ² results in the adhesive becoming scorched and damaged.
It has been determined that one of the major causes of polymer adhesive failure under these conditions is the presence of superabsorbent impurity particles. The damage started at the location of the impurities. The impurity particles absorbed at least 5 to 10 times more energy at 1550 nm than the surrounding medium, depending, of course, on the actual composition of the impurity particles. Therefore, in order to use a polymer adhesive in the optical path of a high-power laser, it is absolutely necessary to find a method for removing these impurity particles.

[0005] In another approach, a method of purifying macromolecules that has proven successful has been to filter low viscosity monomers prior to polymerization. This method has produced polymers with higher laser damage thresholds. FIG. 1 is a graph showing the relationship between the laser threshold damage (Ed) of a polymeric adhesive and the pore size of a filter used to remove impurity particles in the adhesive. As FIG. 1 clearly shows, when the pore size of the impurity particles was reduced from about 16 micrometers to about 0.22 micrometers, the damage resistance of the polymer adhesive was improved by about 3.5 times. Further improvements could be achieved if particles smaller than 0.22 micrometers could be removed. However, the improvements that can be achieved using filtration techniques are limited. One of the limitations of filtration is that it is very difficult to filter out particles smaller than 0.2 micrometers. Second, as the size of the particles becomes smaller, the pressure and heat required to filter these particles becomes extremely high. Finally, if the viscosity of the adhesive precursor is too high, filtration can no longer be performed.

Therefore, development of a polymer optical path adhesive that is resistant to damage by high power lasers is highly desirable. Such adhesives provide several design and manufacturing advantages over fusion welding, laser welding, and other techniques currently used to connect glass components.

SUMMARY OF THE INVENTION Accordingly, the present invention discloses a method for removing impurity particles from a polymeric precursor material by using high gravity centrifugation techniques as an alternative to filtration. This technique offers advantages over current polymer adhesive methods in that impurity particles having a diameter of 0.1 micrometer or more can be removed and the laser damage threshold is increased by about a factor of 10. Furthermore, the present invention does not require high pressure and high temperature to remove particles in the 0.1 micrometer range and is not limited by the viscosity of the liquid precursor.

[0008] One aspect of the present invention is a method of manufacturing an optical device used to transmit light. The optical device includes a plurality of optical components each having an optical path.
The method for manufacturing an optical device includes the following steps. An adhesive precursor is provided. A high centrifugal force is applied to the adhesive precursor to remove light scattering impurity particles, thereby producing a purified adhesive. Each of the plurality of optical components is bonded to at least one other of the plurality of optical components by a purification adhesive to form an optical device.

[0009] In another aspect, the invention includes an optical device for transmitting an optical signal generated by a high power laser. The optical device includes a plurality of optical components. Each of the plurality of optical components has an optical path through which an optical signal passes. A refining adhesive is applied to a portion of each of the plurality of optical components in the optical path. The refining adhesive bonds each of the plurality of optical components to at least one other of the plurality of optical components. This purified adhesive has no impurity particles of 0.1 μm or more.

[0010] In another aspect, the invention includes a method of transmitting an optical signal generated by a high power laser through an optical device. The optical device includes a plurality of optical components,
Here, each of the plurality of optical components has an optical path. A method of transmitting an optical signal includes applying a purified adhesive to a portion of each of a plurality of optical components in an optical path. The refining adhesive binds each of the plurality of optical components to at least one other of the plurality of optical components and has no impurity particles of 0.1 μm or more. The method of transmitting an optical signal also includes directing the optical signal generated by the high power laser into an optical device such that the optical signal passes through the optical path.

[0011] Additional features and advantages of the invention will be set forth in the detailed description that follows, and in part will be readily apparent to those skilled in the art from the description, or may be learned from the detailed description, patents that follow. It will be appreciated by practicing the invention described herein, including the claims, as well as the accompanying drawings.

The above general description and the following detailed description are merely exemplary of the invention, and are intended to provide an overview or concept to understand the nature and features of the invention as set forth in the claims. It will be understood that this is intended. The attached drawings are
Included for a further understanding of the invention, included herein and forming a part thereof. The drawings illustrate various embodiments of the invention, and together with the description, serve to explain the principles and operation of the invention.

DETAILED DESCRIPTION In accordance with the present invention, a method for removing impurity particles from a liquid polymeric precursor material prior to polymerization or crosslinking is disclosed. The method includes rotating a precursor liquid at a predetermined speed for a predetermined time in a high gravity centrifuge to separate desired particles. Polymers produced from purified precursors using this centrifugation technique are resistant to damage by high power laser pulses and their transients. This means that from the precursor material
This is achieved by separating impurity particles of 0.1 micrometers or more. FIG.
4 is a graph showing the improvement of the laser damage threshold realized by the present invention. Both the first and second embodiments of the present invention discussed below provide a laser damage threshold that is about 10 times greater than that of a polymeric adhesive developed by using other techniques utilized to date. Having.

The relationship between settling velocity, viscosity, and particle density in the Stokes flow region can be created using the following equation:

[0015]

(Equation 2) Here, v _c is the sedimentation rate of the centrifugal field, [rho _c is the density of the impurity particles, [rho _m is the density of the liquid precursor medium, D _p is the diameter of impurity particles, omega is the centrifuge , R is the radius of the centrifuge, and μ is the viscosity of the liquid precursor medium. One skilled in the art knows from equation (1) that the rotation speed and the rotation time vary depending on the viscosity of the liquid precursor and the density difference between the particles and the liquid precursor. Typically,
For low viscosity precursors, shorter times are required. As the viscosity of the precursor increases, the rotation time increases accordingly. Generally, the viscosity of the adhesive precursor ranges from 100 cps to 2,000 cps, but the invention should not be considered as limited thereto. It should be noted that the present invention is particularly useful if the liquid precursor is too viscous to filter. According to equation (1), the higher the angular velocity, the faster the sedimentation velocity. It should also be noted that the effectiveness of centrifugation depends on the density difference between the particles and the liquid. There is a direct correlation between density difference and settling velocity. The method of the present invention is less effective when the density difference is small, and is more effective when the density difference is large. If the density difference is small, the sedimentation rate will be low and the process will take longer to complete.

In a first embodiment of the present invention, a one-part liquid adhesive precursor material is pipetted into an even number of holding tubes. The only requirement for a one-part adhesive is that it be liquid. The holding tube is located in a holding mount in the centrifuge. The centrifuge is operated at a predetermined rotation speed for a predetermined time based on the performance of the centrifuge and the equation (1). Once spinning is complete and the particles are separated, the liquid is removed from the upper half of the centrifuge tube with a syringe or pipette to extract the purest liquid from the tube. 0.
Light scattering impurity particles of 1 μm or more remain at the bottom of the centrifuge tube and are discarded.

The centrifuge tube can be of any suitable well-known type. Fixed-angle-head-rotor type centrifuges are suitable because they can produce the high gravity required for this application. When using an ultracentrifuge,
Powers of about 50,000 to 100,000 G can be achieved. There are more expensive centrifuges on the market that can produce 1,000,000 G of power. With this centrifuge, the spin time can be reduced to a few minutes.

As embodied herein and shown in FIG. 3, optical device 10 is a multi-component device that includes a first component 20 and a second component 40. These components are joined together using an adhesive 30 that has been purified using the process described above. As shown in FIG.
Refining adhesive 30 is applied to components in optical path 50 of device 10. Thereafter, the adhesive is cured.

The optical components 20 and 40 can be of any suitable well-known type, for example, the waveguide 20 coupled to a green lens 40 is shown. Purifying adhesive 30 can be used to couple the fiber to a planar waveguide or a green lens. Those skilled in the art will be able to bond any optical components together using adhesive 30;
It will be appreciated that the adhesive does not degrade with high power laser damage.

The adhesive precursor may be of any suitable well-known type. The reactive precursor can also have any monofunctional or multifunctional groups attached for chemical crosslinking. The one-part adhesive system used in the first embodiment is:
It is a light curable, thermosetting, or RTV (room temperature vulcanizing) curable adhesive. For example, low weight polymers (oligomers) with functional groups attached for chemical crosslinking
The material can be used as a photocurable adhesive precursor. The photocurable precursor comprises a solution of an uncured liquid precursor and a photopolymerization initiator. When exposed to light energy, the photoinitiator reacts with the liquid to cure the solution. The functional group may include an epoxy, epoxy acrylate, or epoxy methacrylate terminal group. On the other hand, low molecular weight fluorinated or non-fluorinated organic precursors with epoxy, cycloaliphatic epoxy, or acrylate functional end groups can be used. The precursor used can be a low molecular weight liquid monomer prior to polymerization. Further, the precursor can be an inorganic polymer such as a silicone oligomer having two or more cycloaliphatic epoxy functional groups.
This material is suitable for both photocurable and RTV curing methods. The number and type of functional groups can vary based on the end use contemplated for the optical device. Precursors having one or more functional groups can be used to obtain the desired mechanical and optical properties.

EXAMPLE 2 A centrifuge tube having a capacity of 2 ml is filled with the precursor. The precursor consisted of an epoxy precursor having a viscosity of 100 cp and a density of 0.9638 g / cm ³ . Polymer impurity particles are dispersed in the liquid. According to the principles of the present invention, particles having a diameter of 0.1 μm or more should be removed from the precursor liquid. The density of the polymer particles of 0.1 μm is 1.05 g
/ Cm ³ . The height of the fluid in the tube is 1 from the bottom of the tube to the meniscus of the fluid.
It is .5cm. Thus, the maximum distance the particles have to settle is 1.5 cm when traveling from the meniscus to the bottom. Knowing the distance that the particles have to travel, for example 1.5 cm, allows the calculation of the rotation time required for the particles to settle to the bottom of the tube. A rotation at a speed of 13,500 rpm is converted to an angular speed of 1,414 radians / second. The radius of the centrifuge is 9.5 cm. Then 0.091
Equation (1) is used to calculate a sedimentation velocity equal to × 10 ⁻⁶ cm / sec. At this rate, the particles settle 1.5 cm in 46 hours. Once spinning is complete and the particles are separated, the purified liquid is extracted from the tube. Apply adhesive to some of the components in the light path,
By joining them, the components are combined. Thereafter, light energy is applied to the adhesive and light cured.

In a second embodiment of the present invention, a two-part liquid adhesive precursor material is utilized. In a two-part system, the liquid precursor and the curing agent are separately purified according to the method described above. Therefore, the centrifugation process described above is performed twice. After the light scattering impurity particles of 0.1 μm or more have been removed from both materials, the two liquids are mixed and applied to the optical components.

The two-part adhesive precursor and curing agent may be of any suitable well-known type. The reactive precursor can also have any monofunctional or multifunctional groups attached for chemical crosslinking. These precursors described above with respect to the first embodiment of the present invention may be used in the two-part system of the second embodiment of the present invention. Curing agents such as amines or anhydrides can be used.

As embodied herein and shown in FIG. 3, optical device 10 is a multi-component device that includes a first component 20 and a second component 40. These components are bonded together using an adhesive 30 that has been purified using the process described above. As shown in FIG. 3, a mixture 30 of the purified adhesive and curing agent is applied to some of the components in the optical path 50 of the device 10 and cured. This two-part system must be applied to the optical components immediately after mixing. This is because the curing agent reacts with the precursor immediately thereafter. The mixture can be cured at room temperature or cured by the application of heat. Applying thermal energy to the adhesive reduces the cure time. As described above with respect to the first embodiment, one skilled in the art can use this two-part adhesive system to bond any optical components together, and the adhesive will degrade due to high power laser damage. It will be understood that not.

Since the same precursor material used in the first embodiment is also used in the second embodiment, the second example describing the liquid precursor purification technique is the same, and therefore Do not repeat. As described above, equation (1) is used to determine the rotation speed and rotation time of the amine or anhydride curing agent. This step is, of course, not necessary for one-part systems.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit and scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.

While the preferred embodiments of the method and optical device 10 described above have been described in detail with reference to the drawings, those skilled in the art will recognize the method and optical device 10 without departing from the spirit and scope of the claims. It will be understood that various modifications, changes and adaptations can be made to. Thus, it is intended that the present invention cover such modifications, changes and adaptations as fall within the scope of the appended claims and their equivalents.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the laser damage threshold of a polymeric adhesive and the size of impurity particles.

FIG. 2 is a graph illustrating the improvement in laser damage threshold achieved according to the present invention.

FIG. 3 is a perspective view showing details of the manufacture of the multi-component optical device.

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Claims (31)

[Claims] 1. A method of manufacturing an optical device for transmitting light, the optical device comprising a plurality of optical components each having an optical path, wherein a liquid adhesive precursor comprising light scattering impurity particles is provided. Applying a high centrifugal force to the liquid adhesive precursor to remove the light scattering impurity particles, thereby producing a purified adhesive; and using the purified adhesive to convert each of the plurality of optical components into the plurality of optical components. Combining the at least one of the components with the other to form the optical device. 2. The method of claim 1, wherein applying a high centrifugal force comprises removing light scattering impurity particles having a size greater than about 0.1 micrometers. 3. The method of claim 2, wherein said bonding step comprises curing said refining adhesive. 4. The method according to claim 3, wherein the purified adhesive is a two-part chemical system composed of a purified adhesive precursor and a purified curing agent. 5. The method of claim 4 including the step of mixing said purified adhesive precursor with said purified hardener to form said purified adhesive. 6. The method according to claim 5, wherein the purified adhesive precursor is a liquid precursor having a monofunctional group bonded thereto. 7. The method according to claim 5, wherein the purified adhesive precursor is a liquid precursor to which a polyfunctional group is bonded. 8. The method of claim 5, wherein said curing agent is selected from the group consisting of amines or anhydrides. 9. The method of claim 4, wherein the step of curing the adhesive is performed at room temperature. 10. The method of claim 4, wherein the step of curing the purified adhesive is performed by applying heat to the adhesive. 11. The method according to claim 3, wherein the refining adhesive is a one-part system.
The described method. 12. The method according to claim 11, wherein said curing step includes light curing.
The described method. 13. The method according to claim 11, wherein said curing step includes heat curing.
The described method. 14. The method of claim 11, wherein said curing step comprises room temperature vulcanization (RTV). 15. The method according to claim 11, wherein the purified adhesive is a liquid precursor to which a polyfunctional group is bonded. 16. The method according to claim 11, wherein the purified adhesive is a liquid precursor having a monofunctional group attached thereto. 17. The method of claim 2, wherein said purified adhesive is formed from an organic adhesive precursor. 18. The method according to claim 17, wherein the organic adhesive precursor is a low molecular weight polymer having a functional group selected from the group consisting of epoxy, epoxy acrylate, and epoxy methacrylate. 19. The method of claim 17, wherein said organic adhesive precursor is a low molecular weight oligomer having a functional group selected from the group consisting of epoxy, epoxy acrylate, and epoxy methacrylate. 20. The method of claim 17, wherein the organic adhesive precursor is a low molecular weight monomer having a functional group selected from the group consisting of epoxy, epoxy acrylate, and epoxy methacrylate. 21. The method of claim 17, wherein the organic adhesive precursor is a fluorinated organic precursor having a functional end group selected from the group consisting of epoxy, epoxy acrylate, and epoxy methacrylate. Method. 22. The organic adhesive precursor according to claim 17, wherein the organic adhesive precursor is a non-fluorinated organic precursor having a functional end group selected from the group consisting of epoxy, epoxy acrylate, and epoxy methacrylate. the method of. 23. The method according to claim 17, wherein a monofunctional group is bonded to the organic adhesive precursor. 24. The method according to claim 17, wherein a polyfunctional group is bonded to the organic adhesive precursor. 25. The method of claim 2, wherein said purified adhesive is formed from an inorganic adhesive precursor. 26. The method of claim 25, wherein the inorganic precursor is a silicone oligomer having at least one cycloaliphatic epoxy functionality attached. 27. The method according to claim 25, wherein a monofunctional group is bonded to the inorganic adhesive precursor. 28. The method according to claim 25, wherein a polyfunctional group is bonded to the inorganic adhesive precursor. 29. The step of applying a high centrifugal force comprises the following equation:Rotating the centrifuge at a predetermined angular velocity for a predetermined time according to
Where v_cIs the sedimentation velocity of the centrifugal field, ρ_cIs the density of the impurity particles, ρ _m Is the density of the liquid precursor medium and D_pIs the diameter of the impurity particles, and ω is the
Is the angular velocity of the centrifuge, r is the radius of the centrifuge, and μ is the viscosity of the liquid precursor medium.
3. The method according to claim 2, wherein the degrees are degrees. 30. The method of claim 2, wherein the bonding step includes applying the purified adhesive to selected portions of the plurality of optical components disposed in an optical path of the optical device. the method of. 31. The method of claim 2, wherein said light scattering impurity particles comprise a partially polymerized mass of said adhesive precursor.