OPTICAL CONNECTION AND MANUFACTURING METHOD THEREFOR

Description

BACKGROUND OF THE INVENTIONField of the Invention

[0001] The present invention relates to an optical interconnection and a method for making the same, and more particularly to an optical interconnection comprising a rod and a wire.Description of the Prior Art

[0002] High-density photonic integrated circuits based on the assembly of nanoscale photonic elements are new future technologies that can go beyond the limits of electronic integrated circuits. Over the past decade, a variety of nanoscale photonic elements have been developed to achieve high-density photonic integrated circuits. The development of a technology for interconnecting these elements is a key challenge that is most fundamental for realizing nanoscale photonic integration. The most promising approach for interconnecting nanoscale elements is to integrate a wire waveguide between two spaced elements to allow evanescent coupling between them.

[0003] Up to now, technology for integrating wire optical waveguides has relied on the in-plane manual assembly of pre-synthesized wires. However, in-plane assembly has a problem in that the loss of light from a wire to a substrate occurs, and manual assembly using a microprobe or the like has problems in that the process is very complicated and a wire is likely to be damaged during the process.

[0004] In a conventional art, the direction of light is changed using a prism lens or the like, and then spaced contacts are interconnected by optical fibers (see Han-Soon Lee et al., Optics Express 22(10) 11778-11787 (2014)). In this case, light emitted from VCSEL should be aligned with the prism lens, and the light emitted therefrom should be aligned accurately with the optical fiber core. However, since the diameter of the optical fiber core is as small as about 10 µm, many defects occur due to mechanical errors occurring during alignment.

[0005] To overcome this problem, an active alignment method is used, but this method requires a lot of time and cost and still shows a significant defect rate. In addition, a device that is used in this method necessarily requires a prism device, and for this reason, there is a limitation in reducing the size.

[0006] Korean Patent No. 10-15583736 discloses an optical interconnection method in which a wire is three-dimensionally grown directly at a desired position. In this case, there is a problem in that light loss occurs because the wire is tilted and positioned while the wire is connected directly between the contacts.

[0007] The patent document JP H11 174260 A discloses a method for forming an optical transmission line. This document discloses a capillary 16 being lowered, poly methyl methacrylate(PMMA) 21 being connected to an optical transmission end and the capillary 16 being elevated for about several mm. Thereafter, the PMMA 21 is cut at the optical transmission end and the projection 41 composed of the PMMA 21 is formed at the optical transmission end. After forming the solidified projection 41, the capillary 16 is moved in a circular arcuate shape from a light emitting element to the projection 41 formed at the optical transmission end of an optical waveguide and the line is formed by the PMMA 21. An optical transmission line is formed without pressing the line formed by the PMMA 21 connected to the light emitting element to the optical transmission end of the optical waveguide. Thus, both end parts of the optical transmission line are formed in the shape of being extended vertically to a substrate and the utilization efficiency of the light is improved.SUMMARY OF THE INVENTION

[0008] In a conventional art in which a wire (optical fiber) is formed in a separate process and then used in optical interconnection, there is a problem in terms of process and cost (for example, because a control device such as a prism lens is required). The present invention has been made in order to solve this problem, and it is an object of the present invention to provide a technology that makes a wire and, at the same time, interconnects spaced contacts.

[0009] Another object of the present invention is to provide an optical interconnection comprising a rod and a wire, which can minimize the optical loss in the connection between a contact and / or the wire and / or the rod.

[0010] The present invention is directed to an optical interconnection as described in claim 1.

[0011] Other advantageous and non-limitative features of the optical interconnection according to the invention are listed in claims 2 to 6

[0012] The present invention is also directed to a method for making an optical interconnection as described in claim 7.

[0013] Other advantageous and non-limitative features of the method according to the invention are listed in claims 8 and 9.BRIEF DESCRIPTION OF THE DRAWINGS

[0014] FIG. 1(a) is a schematic view illustrating optical interconnections made according to the present invention. FIG. 1(b) and FIG. 1(c) are schematic view illustrating optical interconnections according to embodiments which are not part of the present invention. FIG. 2 shows an optical microscope image of a rod made according to the present invention. FIG. 3 depicts optical microscope images showing optical interconnections of an example of the present invention and a comparative example, respectively. FIG. 4 depicts optical microscope images showing light scattering in an example of the present invention and a comparative example. FIG. 5 is a graph comparing the optical signal characteristics of an example of the present invention and a comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0015] All technical terms that are used in the present invention have the following definitions unless otherwise defined, and have the same meanings as commonly understood by those skilled in the art.

[0016] As used herein, the term "meniscus" means a curve that is formed in the surface of a liquid within a tube as a result of surface tension. The curve is concave or convex depending on the nature of the liquid.

[0017] As used herein, the term "first contact" means a portion that emits light. For example, the term includes a light source such as LED or LD, or means and devices for emitting light (including transmitting light), such as waveguides, optical fibers or the like. As used herein, the term "second contact" means a portion that receives the light that passed through an optical interconnection. For example, the term includes a direct light detection means such as a photodetector (PD), or means and devices for receiving light (including transmitting light), such as waveguides, optical fibers or the like.

[0018] The present invention is directed to an optical interconnection for optical connection between a first contact and a second contact, the optical interconnection comprising a rod and a wire. Particularly, the optical interconnection according to the present invention is defined by the features of claim 1.

[0019] The rod according to the present invention is formed on the first contact and the second contact. Considering the characteristics of the making method, the optical loss in the second contact portion may occur more. For this reason, in order to reduce the optical loss in this portion, the wire made according to the present invention comprises the rod formed on the second contact.

[0020] FIG. 1(a) is a schematic view showing optical interconnections made according to the present invention. Specifically, FIG. 1(a) shows rods 11 and 12 formed on a first contact 14 and a second contact 15, respectively, and a wire 13 interconnecting the rods 11 and 12.

[0021] FIG. 1(b) and FIG. 1(c) are schematic views showing optical interconnections according to embodiments which are not part of the invention. Specifically, FIG. 1(b) shows a rod 11, formed on a first contact 14, and a wire 13 interconnecting the rod 11 and a second contact 15 (no rod is formed on the second contact 15); and FIG. 1(c) shows a rod 12, formed on a second contact 15, and a wire 13 interconnecting a first contact 14 and the rod 12 (no rod is formed on the first contact 14).

[0022] In one embodiment not forming part of the claimed invention, the rod may have a cylindrical shape. The rod according to the present invention has a truncated cone shape such that the outer circumferential surface of the rod becomes narrower as the rod extends upward.

[0023] Particularly, the outer circumferential surface of the rod has an angle of more than - 35° to less than +35°, preferably -10° or more to +10° or less, with respect to the vertical axis of the rod. As used herein, the expression "vertical axis of the rod" means an axis perpendicular to the bottom of the rod (which is a portion coming in contact with the contact), and is shown as z-axis in FIG. 2. FIG. 3 shows an optical microscope image of a rod made according to the present invention. As used herein, the expression "vertical axis of the rod" means an axis vertical perpendicular to a direction in which the rod grows, that is, a surface on which the rod is formed.

[0024] For example, when light is to be transmitted in one direction from the first contact to the second contact, the rod on the second contact may have a reverse truncated cone shape such that the outer circumferential surface becomes narrower downward, in order to focus the light.

[0025] However, considering the fact that the size of the contact that emits and receives light is generally larger than the size of the optical interconnection and also considering the adhesion of the optical interconnection to the contact, the rod has a shape such that the outer circumferential surface thereof becomes narrower as it extends upward. Specifically, the outer circumferential surface of the rod may have an angle of less than 35° (not including 0°), preferably 10° or less (not including 0°), with respect to the vertical axis of the rod.

[0026] In addition, the height of the rod is 0.5 µm to 100 µm. If the height of the rod is less than 0.5 µm, the effect of reducing optical loss by the rod cannot be obtained, and if the height is more than 100 µm, it can affect the shape, size and the like of the resulting product. However, the height of the rod may be controlled considering the size of the rod, the wire, a substrate (chip) or the like, the distance between the contact, etc.

[0027] The bottom diameter of the rod is 0.5 µm to 500 µm. The bottom diameter of the rod may be controlled depending on the size of the contact from which light is emitted, and the quantity of light emitted.

[0028] The rod according to the present invention may be made by a method comprising the following steps: a) filling a rod material solution into a micropipette; b) aligning the micropipette with a first or second contact; c) forming a meniscus of the rod material solution; and d) making a rod by evaporating the solvent from the rod material solution while lifting the micropipette in a direction perpendicular to the surface of the contact.

[0029] Hereinafter, each step of the method for making the rod will be described in detail.

[0030] First, the step of filling a rod material solution into a micropipette is performed. As used herein, the rod material solution means a solution containing a material that forms the rod. Examples of the rod material solution include all materials capable of forming a meniscus, and include most organic compounds. Specifically, as the material that forms the rod, polystyrene, methyl polymethacrylate, or polycarbonate may be used, and perfluorinated compounds (PFCs) such as CYTOP (amorphous fluoropolymer), polyimides, or epoxy compounds such as SU-8, may also be used. In addition, organic conductive polymers (π-conjugated polymers) may also be used, which are characterized in that their electrical and optical properties can be freely controlled by chemical doping. As the solvent of the rod material solution, an easily evaporating material (volatile material) may be used, and examples of the solvent include all materials that are used in the art.

[0031] The micropipette may be prepared to have a desired diameter by use of a pipette puller.

[0032] Next, the step of aligning the micropipette with a first or second contact is performed. Preferably, the micropipette is coaxially aligned such that the lengthwise axis of the micropipette lies in line with an axis perpendicular to the surface of the first or second contact. For alignment, the x-axis and the y-axis are preferably aligned using two optical lenses. When only one optical lens is used, coaxial alignment will be difficult due to errors occurring in other directions, and the rod which is to be grown using the micropipette will also not be coaxially aligned and grown, and thus the optical transmission loss in the connection will increase. For coaxial alignment, optical lenses for the x-axis and the y-axis are located perpendicular to each other.

[0033] Next, the step of forming a meniscus of the rod material solution is performed. In this step, the micropipette filled with the rod material solution is spaced apart from one end of an optical fiber so that the rod material solution forms a meniscus.

[0034] Finally, the step of making a rod by evaporating the solvent from the rod material solution while lifting the micropipette in a direction perpendicular to the surface of the contact is performed.

[0035] When the micropipette is lifted while maintaining a spacing capable of inducing a meniscus of the rod material solution, the dissolved material is solidified to form a cylindrical shape while the liquid in the micropipette evaporates quickly. The micropipette is lifted in the direction in which light is emitted, that is, a direction perpendicular to a portion in which the rod comes in contact with the contact.

[0036] In one embodiment, the micropipette may be lifted while gradually increasing or reducing the lifting speed so that the outer circumferential surface of the rod will have a shape becoming narrower as the rod extends upward. The lifting speed (withdrawal speed) may be controlled considering the angle with respect to the vertical axis of the rod, the height of the height of the rod, etc.

[0037] In another embodiment, the pressure that is applied to the micropipette may be controlled so that the outer circumferential surface of the rod will have a shape becoming narrower as the rod extends upward. If the pressure that is applied into the micropipette is increased, the diameter of the rod becomes larger increase while the amount of rod material solution discharged will increase, and if the pressure that is applied into the micropipette is decreased, the diameter of the rod becomes smaller while the amount of rod material solution discharged will decrease.

[0038] In addition, the optical interconnection according to the present invention may comprise a wire extending from the first contact or the rod formed on the first contact so as to transmit an optical signal toward the second contact or the rod formed on the second contact.

[0039] Preferably, the lengthwise axis of the wire according to the present invention is perpendicular to the surface of the first contact, the second contact or the rod, or the lengthwise axis of the wire has an angle of less than 35° with respect to an axis perpendicular to the surface of the first contact, the second contact or the rod, which comes in contact with the wire. In other words, according to the present invention, the contact portion between the wire and the first contact (or the rod formed on the first contact) or the second contact (or the rod formed on the second contact) is formed to have an angle of 0° to 35°, preferably 0° (i.e., perpendicular), with respect to an axis perpendicular to the surface of the first contact or the second contact. As the angle approaches 0°, it is advantageous for optical interconnection because no light scattering occurs. As used herein, the expression "lengthwise axis of the wire" means the central axis of the wire or the central axis in the direction in which the wire grows.

[0040] The diameter of the wire is 500 µm or less, and preferably, may be equal to or smaller than the diameter of the rod.

[0041] Particularly, the wire according to the present invention may be made by a method comprising the following steps: a) filling a wire material solution into a micropipette; b) coaxially aligning the lengthwise axis of the micropipette with an axis perpendicular to the surface of the first contact or the top surface of the rod disposed on the first contact; c) forming a meniscus of the wire material solution; d) making a wire by evaporating the solvent from the wire material solution while lifting the micropipette; and e) brining the micropipette into contact with the second contact or the top of the rod disposed on the second contact.

[0042] Hereinafter, each step of the method for making the wire will be described in detail.

[0043] First, the step of filling a wire material solution into a micropipette is performed.

[0044] As used herein, the expression "wire material solution" means a solution containing a material capable of forming the wire. Examples of the wire material solution include all materials capable of forming a meniscus, and include most organic compounds. Specifically, as the material capable of forming the wire, polystyrene, methyl polymethacrylate, or polycarbonate may be used, and perfluorinated compounds (PFCs) such as CYTOP (amorphous fluoropolymer), polyimides, or epoxy compounds such as SU-8, may also be used. In addition, organic conductive polymers (π-conjugated polymers) may also be used, which are characterized in that their electrical and optical properties can be freely controlled by chemical doping. As the solvent of the wire material solution, an easily evaporating material (volatile material) may be used, and examples of the solvent include all materials that are used in the art.

[0045] Next, the step of coaxially aligning the micropipette with the top of the first contact or the rod formed on the first contact is performed. When the rod is formed on the first contact, the micropipette is preferably coaxially aligned with both an axis perpendicular to the surface of the first contact and the vertical axis of the rod formed on the first contact. For coaxial alignment, the x-axis and the y-axis are aligned using two optical lenses, like the method for making the rod.

[0046] Next, the step of forming a meniscus of the rod material solution is performed.

[0047] Next, the step of making a wire by evaporating the solvent from the rod material solution while lifting the micropipette is performed.

[0048] Specifically, when the micropipette is lifted while maintaining a spacing capable of inducing a meniscus of the wire material solution, the dissolved material is solidified to form a cylindrical shape while the liquid in the micropipette evaporates quickly. The lifting direction is determined considering the distance between the spaced first and second contacts, the lifting speed, etc., and should be controlled such that the direction of a certain portion of the wire made does not abruptly change. In particular, the lifting direction should be controlled so as to minimize the optical loss in the wire portion connected to the contact and / or the rod.

[0049] Finally, the step of brining the micropipette into contact with the second contact or the top of the rod disposed on the second contact is performed.

[0050] The rod and the wire may be made of the same material or different materials, preferably the same material.

[0051] The methods for making the rod and the wire are the same in principle in that they use a meniscus. These methods include the contents described in the manufacturing method of other parts except for the parts specifically mentioned. In addition the present invention includes the contents disclosed in Korean Patent No. 10-15583736.

[0052] The optical interconnection of the present invention may be applied to a part having spaced contacts which need to be optically interconnected.

[0053] When contacts are interconnected by a wire without using a wire, the wire will not be formed in a perpendicular direction on the surface of the contacts, but will be formed to be tilted in the lifting direction of the micropipette (i.e., a direction not perpendicular to the contacts), and for this reason, the optical coupling loss in the contact portion (the connection between the wire and the contact) will occur.

[0054] The optical interconnection according to the present invention is made by two separate processes: a first process of making the rod by lifting the micropipette in a direction perpendicular to the contact; and a second process of making the wire by lifting the wire in another contact in a direction not perpendicular to the contact. This can minimize the optical loss occurring in the connection.

[0055] The present invention is also directed to a method for making an optical interconnection three-dimensionally interconnecting a first contact and a second contact by a wire. Specifically, the method comprises the steps of: a) filling a rod material solution into a micropipette; b) coaxially aligning the lengthwise axis of the micropipette with an axis perpendicular to the surface of the contact; c) forming a meniscus of the rod material solution; d) making a rod by evaporating the solvent from the rod material solution while lifting the micropipette in a direction perpendicular to the surface of the contact; e) filling a wire material solution into a micropipette; f) coaxially aligning the lengthwise axis of the micropipette of step e) with an axis extending from the first contact or the lengthwise axis of the rod formed on the first contact; g) forming a meniscus of the wire material solution; h) making a wire by evaporating the solvent from the wire material solution while lifting the micropipette; and i) bringing the micropipette into contact with either the second contact spaced apart from the first contact or the top of the rod disposed on the second contact.

[0056] In addition, additional treatment for enhancing adhesion may be performed on the connection between the contact and the rod or between the contact and the wire or between the rod and the wire. Namely, before step a) or e) of the method for making the optical interconnection, additional treatment for enhancing adhesion may be performed on the portion to be connected (the contact or the rod), and it may be performed using any method known in the art.

[0057] Hereinafter, the present invention will be described in detail with reference examples. However, these examples are for illustrative purposes only and the scope of the present invention is not limited thereto.Preparation of Example

[0058] Polystyrene powder was dissolved in a xylene solvent at a concentration of 0.5 wt% to prepare a rod material solution. The rod material solution was filled into a micropipette having a tip diameter of 0.5 µm. The micropipette was brought into contact with a first contact to form a meniscus of the rod material solution outside the opening of the micropipette. Rod growth was performed while controlling the lifting speed of the micropipette, thereby forming a rod having a bottom diameter of about 10 µm, a top diameter of about 8 µm, a height of about 6 µm, and an angle of 10° with respect to the vertical axis of the rod. The same rod was formed on a second contact in the same manner as described above. The spacing between the first contact and the second contact was about 500 µm.

[0059] Polystyrene powder was dissolved in a xylene solvent at a concentration of 0.5 wt% to prepare a wire material solution. The wire material solution was filled into the same micropipette as described above, and then was brought into contact with the top of the rod formed on the first contact, thereby forming a meniscus. While the micropipette was lifted to remove the solvent, a wire was grown. The formed wire had a diameter of about 8 µm. The micropipette was brought into contact with the top of the rod formed on the second contact of the chip, thereby obtaining an optical interconnection comprising the wire.Preparation of Comparative Example

[0060] Polystyrene powder was dissolved in a xylene solvent at a concentration of 0.5 wt% to prepare a wire material solution. The wire material solution was filled into a micropipette having a tip diameter of 0.5 µm. The micropipette filled with the solution was brought into contact with a first contact of a chip to form a meniscus of the wire material solution outside the opening of the micropipette. While the micropipette was lifted to remove the solvent, a wire was grown. The micropipette was brought into contact with a second contact of the chip, thereby obtaining an optical interconnection comprising the wire. The formed wire had a diameter of about 8 µm, and the spacing between the first contact and the second contact was about 500 µm.Experimental Example 1: Comparison of Optical Microscope Images of Optical Interconnections

[0061] FIG. 3(a) is an optical microscope image showing the connection between the second contact, the rod and the wire, and FIG. 3(b) is an optical microscope image showing the connection between the second contact and the wire. FIGS. 4(a) and 4(b) are optical microscope images used to measure light scattering in the connection when light was passed through the optical interconnections of the example and the comparative example, respectively. In the example of the present invention, in which the rod was formed followed by formation of the wire, it can be seen that the wire had an angle of about 10° with respect to the axis perpendicular to the surface of the chip (FIG. 3(a)), and little or no light scattering occurred (FIG. 4(a)). However, in the comparative example in which no rod was formed, it can be seen that the wire had an angle of 35° with respect to the axis perpendicular to the surface of the chip (FIG. 3(b)), and significant light scattering occurred (FIG. 4(b)).Experimental Example 2: Comparison of Optical Signal Characteristics of Optical Interconnections

[0062] FIG. 5 is a graph comparing the optical signal characteristics of the example of the present invention and the comparative example. As can be seen therein, the comparative example had a transmission value of about -27 dB, whereas the example had a transmission value of about -21 dB, which was 6 dB higher than that of the comparative example. This suggests that the optical signal intensity of the example is about 4-fold higher than that of the comparative example.

[0063] As described above, the optical interconnection according to the present invention makes it possible to eliminate or minimize an optical loss that can be caused by the connection between the contact and the rod and / or the wire.

[0064] Furthermore, the optical interconnection according to the present invention shows improved optical signal characteristics due to a reduction in coupling loss.

[0065] In addition, the optical interconnection according to the present invention can be made in a simpler manner than a conventional art, and thus is advantageous in terms of cost and process. In addition, it is easily applied even to miniaturized products.

Claims

1. An optical interconnection for interconnecting a first contact (14) and a second contact (15), which need to be optically interconnected, the optical interconnection comprising: a first rod (11) formed on the first contact (14) that emits light; a second rod (12) formed on the second contact (15) that receives or transmits light; and a wire (13) extending from the first rod (11) formed on the first contact (14) so as to transmit an optical signal toward the second rod (12) formed on the second contact (15), wherein each of the first (11) and the second (12) rods has a truncated cone shape such that the outer circumferential surface of each rod (11, 12) becomes narrower as each rod (11, 12) extends upward, and each of the first (11) and the second (12) rods has a height ranging from 0.5 µm to 100 µm and a bottom diameter ranging from 0.5 µm to 500 µm, and the wire has a diameter of 500 µm or less.

2. The optical interconnection of claim 1, wherein the outer circumferential surface of each rod (11, 12) has an angle of less than 35° not including 0° with respect to a vertical axis of each rod (11, 12).

3. The optical interconnection of claim 1, wherein the outer circumferential surface of each rod( 11, 12) has an angle of 10° or less not including 0° with respect to a vertical axis of each rod (11, 12).

4. The optical interconnection of claim 1, wherein a lengthwise axis of the wire (13) is perpendicular to a surface of the first contact (14), the second contact (15) or the rod (11, 12).

5. The optical interconnection of claim 1, wherein the rod (11) is made by a method comprising the steps of: a) filling a rod material solution into a micropipette; b) coaxially aligning a lengthwise axis of the micropipette with an axis perpendicular to a surface of the contact (14, 15); c) forming a meniscus of the rod material solution; and d) making the rod (11) by evaporating a solvent from the rod material solution while lifting the micropipette in a direction perpendicular to the surface of the contact (14).

6. The optical interconnection of claim 1, wherein the wire is made by a method comprising the steps of: a) filling a wire material solution into a micropipette; b) coaxially aligning a lengthwise axis of the micropipette with a lengthwise axis of the rod (11) formed on the first (14) contact; c) forming a meniscus of the wire material solution; d) making the wire (13) by evaporating a solvent from the wire material solution while lifting the micropipette; and e) brining the micropipette into contact with the top of the rod (12) disposed on the second contact 15).

7. A method for making an optical interconnection three-dimensionally interconnecting a first contact (14) and a second contact (15) by a wire (13), the method comprising the steps of: a) filling a rod material solution into a micropipette; b) coaxially aligning a lengthwise axis of the micropipette with an axis perpendicular to a surface of the contact (14); c) forming a meniscus of the rod material solution in the coaxially aligned state; d) making a rod (13) by evaporating a solvent from the rod material solution while lifting the micropipette in a direction perpendicular to the surface of the contact (14); e) filling a wire material solution into a micropipette; f) coaxially aligning a lengthwise axis of the micropipette of step e) with an axis perpendicular to a top surface of the rod (11) disposed on the first contact (14); g) forming a meniscus of the wire material solution; h) making a wire (13) by evaporating a solvent from the wire material solution while lifting the micropipette; and i) bringing the micropipette into contact with the top of the rod (12) disposed on the second contact (15), wherein the rod (11) has a truncated cone shape such that the outer circumferential surface of the rod (11) becomes narrower as the rod (11) extends upward, and the rod (11) has a height ranging from 0.5 µm to 100 µm and a bottom diameter ranging from 0.5 µm to 500 µm, and the wire has a diameter of 500 µm or less.

8. The method of claim 7, wherein step d) comprises controlling a lifting speed of the micropipette such that an outer circumferential surface of the rod (11) has a truncated conical shape becoming narrower as the rod extends upward.

9. The method of claim 7, wherein step d) comprises controlling a pressure that is applied to the micropipette such that an outer circumferential surface of the rod (11) has a truncated conical shape becoming narrower as the rod (11) extends upward.