CN118915245A - Optical fiber coupling structure and optical fiber and chip welding method thereof - Google Patents

Abstract

The present invention discloses an optical fiber coupling structure and an optical fiber and chip welding method thereof, and belongs to the technical field of optical fiber and wavelength division multiplexer chip coupling structure. The optical fiber coupling structure of the present invention includes a wavelength division multiplexer chip, a metal seat, an optical fiber holder, an optical fiber sleeve, a chip base, an optical fiber, and an optical fiber array; wherein the optical fiber holder and the chip base are placed on the upper surface of the metal seat, the optical fiber holder and the metal seat are connected by laser welding, a wavelength division multiplexer chip is arranged above the chip base, the opening of the optical fiber holder is directly opposite to the chip output end, the bottom of the optical fiber holder is against the bottom of the chip base, the optical fiber and the optical fiber sleeve are coaxially arranged, the optical fiber sleeve passes through the optical fiber holder to achieve limiting, and the optical fiber array is fixed to the chip base. The present invention fixes the optical fiber sleeve by laser welding to ensure that the optical fiber and the wavelength division multiplexer chip are aligned horizontally and vertically. Finally, the chip base is adjusted again, and the chip base is fixed by laser welding to achieve stable and accurate connection between the optical fiber and the wavelength division multiplexer chip.

Description

A fiber coupling structure and a fiber and chip welding method thereof

Technical Field

The invention relates to the technical field of optical fiber and wavelength division multiplexer chip coupling structure, and in particular to an optical fiber coupling structure and an optical fiber and chip welding method.

Background Art

Wavelength division multiplexing devices such as multimode interferometers, arrayed waveguide gratings, and Mach-Zehnder interferometers are indispensable parts of optical fiber communication networks. In RF photonic systems, the application demand for high-efficiency and high-power broadband wireless systems in the Sub15GHz golden spectrum will grow rapidly in the future. Breakthroughs in the relevant technologies of microwave photonic core devices for high-power and high-efficiency analog RF fronthaul networks and photodetector direct-driven antennas will become particularly important. High input optical power requires a stable connection between the optical chip and the optical fiber, while high efficiency requires efficient coupling between the optical chip and the optical fiber to reduce losses. Conventional optical chips and optical fibers are coupled using a curing agent. As introduced in "Ranno, L., et al. (2022). "Integrated Photonics Packaging: Challenges and Opportunities." ACS Photonics 9(11): 3467-3485.", this method deteriorates the stability of the curing agent used to connect the optical fiber and the device under high power input, affecting the coupling quality and increasing the input loss. In severe cases, the optical chip will be damaged and unable to work normally. Most of the research on fiber coupling focuses on the coupling between laser and fiber, such as the solution disclosed in the patent application with the announcement number CN108879318A and the invention name "A semiconductor laser packaging structure and its welding method". Another example is the free light emission packaged laser introduced in the document "Yi-Cheng, H., et al. (2005). "A novel fiber alignment shift measurement and correction technique in laser-welded laser module packaging." Journal of Lightwave Technology 23(2):486-494." Due to the working characteristics of the laser, the optical chip and the optical fiber only need single-end coupling, which is less difficult than the wavelength division multiplexer that needs to couple the input and output two end faces. On the other hand, due to the increased difficulty of coupling due to the miniaturization of the device, the input/output coupling technology of passive optical chips such as precision optical fiber and wavelength division multiplexer can reduce the insertion loss of optical devices. Although there is a solution proposed in the patent application with publication number CN103323919A and invention name “Optical assembly for precisely aligning optical components with optical fibers” that can precisely align optical components with optical fibers, the process is complicated and the coupling requires special devices to complete, which makes the operation difficult. Therefore, a new chip and optical fiber coupling method for wavelength division multiplexing devices with simple structure and easy operation is needed.

Summary of the invention

The purpose of the present invention is to provide a coupling structure and a coupling method of an optical fiber and a wavelength division multiplexer chip with low loss, stable coupling and high coupling accuracy in a high power input application scenario based on actual needs.

In one aspect, the present invention discloses a fiber coupling structure, which includes a metal seat, a fiber holder, a fiber sleeve, a chip base, a wavelength division multiplexer chip, an optical fiber, and an optical fiber array;

The optical fiber holder and the chip base are placed on the upper surface of the metal base. The optical fiber holder and the chip base are both in a "J" shape and are fixed to the upper surface of the metal base through the bottom of the optical fiber holder and the bottom of the chip base respectively. The height of the optical fiber holder is greater than the height of the chip base. A wavelength division multiplexer chip is arranged above the chip base.

The optical fiber and the optical fiber sleeve are coaxially arranged, and the inner diameter of the optical fiber sleeve is not less than the outer diameter of the optical fiber. The optical fiber sleeve passes through the optical fiber holder to face the wavelength division multiplexer chip, and the optical fiber sleeve located in the optical fiber holder is fixedly connected to the optical fiber holder;

The chip input end of the wavelength division multiplexer chip is connected to the optical fiber array fixed on the chip base, and the chip output end of the wavelength division multiplexer chip is connected to the optical fiber in the optical fiber sleeve passing through the optical fiber fixture.

Furthermore, the chip base upper surface size is larger than the chip size of the wavelength division multiplexer chip, the chip output end face of the wavelength division multiplexer chip is flush with the edge of the chip base upper surface, and the distances between the two sides of the wavelength division multiplexer chip and the two edges of the chip base upper surface are equal.

Furthermore, the connection between the optical fiber and the optical fiber array and the wavelength division multiplexer chip can be swapped, the opening of the optical fiber holder is opposite to the chip input end face of the wavelength division multiplexer chip, the chip input end of the wavelength division multiplexer chip is used to connect to the optical fiber passing through the optical fiber holder, and the chip output end of the wavelength division multiplexer chip is used to connect to the optical fiber array.

Furthermore, the length of the upper surface of the chip base is 5 to 7 mm greater than the length of the chip.

Furthermore, the height of the optical fiber holder is 4 to 5 mm greater than the height of the chip base.

Furthermore, the materials of the metal seat, the optical fiber holder, the optical fiber sleeve and the chip base are all made of var alloy.

Furthermore, windows are provided on the side surfaces of the chip base and/or the extended surfaces of the side surfaces located on the upper surface of the metal base, so as to increase the adjustment welding points and increase the adjustment welding dimensions.

Furthermore, the side surface of the chip base is in a shape similar to an "X" character, and two groups of welding fixing points are respectively arranged on the left and right sides of the "X"-shaped side surface to weld the chip base to the upper surface of the metal base.

On the other hand, the present invention also discloses a method for welding an optical fiber and a chip used in the optical fiber coupling structure of the present invention, which comprises the following steps:

A) Mounting the wavelength division multiplexer chip on the chip base;

B) trimming the optical fiber connector so that the optical fiber connector does not exceed the limited length of the optical fiber cladding, which is 1 to 5 mm;

C) Use a curing agent to permanently connect the optical fiber and the optical fiber sleeve;

D) Fixing the optical fiber holder to the metal base by laser welding;

E) Use a clamp to hold the chip base against the fiber holder, use a precision adjuster to pass the fiber sleeve through the fiber holder, use a microscope to observe the lateral distance between the optical fiber and the output end of the wavelength division multiplexer chip, adjust the position of the chip base, and when the optical axis of the optical fiber is aligned with the chip output waveguide, press down the wavelength division multiplexer chip mounted on the chip base to temporarily fix it;

F) Connect the other end of the optical fiber to the laser and place the near-infrared imaging microscope on the input end face of the wavelength division multiplexer chip;

G) Turn on the laser, observe the output status through a near-infrared imaging microscope, adjust the position of the optical fiber sleeve, and when the output channel of the wavelength division multiplexer chip shows a light spot, use two symmetrical laser beams to weld the optical fiber sleeve and the optical fiber holder to achieve permanent connection between the optical fiber sleeve and the optical fiber holder;

H) releasing the pressure on the wavelength division multiplexer chip, adjusting the chip base by observing the output of the near-infrared imaging microscope, and pressing down the temporarily fixed wavelength division multiplexer chip when the near-infrared microscopic imaging shows the emission channel spot;

1) Connect the fiber array to the optical power meter, use a precision adjuster to clamp the fiber array, and when the output optical power is maximum, fix the fiber array to the wavelength division multiplexer chip;

J) Use two symmetrical laser beams to laser weld the chip base to the metal base to release the pressure on the wavelength division multiplexer chip.

Furthermore, if the light falling phenomenon occurs, the chip base is adjusted using adjustment solder to find the best coupling position.

Since the wavelength division multiplexer is a passive optical device, light waves can propagate in both directions, so the optical fiber and chip welding method of the present invention is also applicable to the wavelength division multiplexer and optical fiber coupling with the optical fiber as the input end and the optical fiber array as the output end.

Furthermore, in step D), when the optical fiber holder is fixed to the metal seat by laser welding, at the same time, spot welding is performed on both sides of the bottom of the optical fiber holder to ensure that the optical fiber holder is not offset in the direction perpendicular to the axial direction of the optical fiber. After fixing the front pair of welding points, the rear pair is fixed.

Furthermore, in step G), when the optical fiber sleeve is fixedly welded to the optical fiber holder by laser welding, at the same time, both sides of the opening of the optical fiber holder are spot welded simultaneously to ensure that the optical fiber holder is not offset in the direction perpendicular to the axial direction of the optical fiber, and the rear pair of welding points are fixed after the front pair of welding points are fixed.

When the output channel of the wavelength division multiplexer chip shows a light spot, two symmetrical laser beams are used to weld the optical fiber sleeve and the optical fiber holder to achieve permanent connection between the optical fiber sleeve and the optical fiber holder;

The technical solution provided by the present invention brings at least the following beneficial effects:

Compared with the existing coupling structure, the fiber coupling structure of the present application first adjusts the lateral position of the chip base after fixing the fiber holder to achieve rough alignment in the horizontal direction, and then adjusts the height of the fiber sleeve in the fiber holder to achieve fine alignment between the fiber and the chip. Since the fiber sleeve forms thermal deformation and offset after cooling after laser welding, the coupling efficiency will decrease. After the fiber part is fixed, it is necessary to adjust the chip base again to achieve additional dimensional adjustment. The fiber and chip welding method provided by the present invention enables the obtained fiber coupling structure to complete the efficient docking of the chip and the fiber array by only adjusting the fiber array after the fiber is fixed. Compared with the fiber holder, the chip base is larger in size, and the chip offset is smaller after laser welding. The use of symmetrical laser welding, combined with the restriction of the coupling structure on the chip base, can effectively prevent the base from shifting during welding. In addition, after the chip base and the fiber sleeve are laser welded, the adjustment weld can be used to adjust the offset caused by deformation for a second time, which can achieve a higher precision adjustment than the input fiber by laser welding alone.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

FIG1 is a schematic diagram of the optical fiber coupling structure of the present application.

FIG. 2 is a top view of the optical fiber holder of the present application.

FIG. 3 is a schematic diagram of the laser welding portion of the optical fiber sleeve and the optical fiber holder of the optical fiber coupling structure of the present application.

FIG. 4 is a schematic diagram of a fiber-coupled structure chip base of the present application.

Figure numerals: 1, chip base; 2, optical fiber holder; 3, optical fiber sleeve; 4, metal seat; 5, wavelength division multiplexer chip; 6, optical fiber; 7, optical fiber array; 11 and 12 are different fixed point pairs on the chip base for welding the metal seat, 21 and 22 are different fixed point pairs on the optical fiber holder for welding the metal seat; 23 and 24 are different fixed point pairs on the optical fiber holder for welding the optical fiber sleeve.

DETAILED DESCRIPTION

To make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be described in detail and completely in conjunction with the drawings in the implementation of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings can be arranged and designed using different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the present application for protection, but merely represents selected embodiments of the present invention.

As shown in Fig. 1, the fiber coupling structure of the present application includes a metal seat 4, a fiber holder 2, a fiber sleeve 3, a chip base 1, a wavelength division multiplexer chip 5, an optical fiber 6 and an optical fiber array 7; wherein the fiber holder 2 and the chip base 1 are respectively fixedly connected to the upper surface of the metal seat 4 through their bottoms, and the height of the fiber holder 2 is greater than the height of the chip base 1. Preferably, in this embodiment, the fiber holder 2 and the chip base 1 are respectively welded and fixed to the upper surface of the metal seat 4 based on their bottoms. A wavelength division multiplexer chip 5 is arranged above the chip base 1, the opening of the optical fiber holder 2 is directly opposite to the chip output end face of the wavelength division multiplexer chip 5, the optical fiber 6 is coaxially arranged with the optical fiber sleeve 3, and the inner diameter of the optical fiber sleeve 3 is not less than the outer diameter of the optical fiber 1, the optical fiber sleeve 3 passes through the optical fiber holder 2 to face the wavelength division multiplexer chip 5, and the optical fiber sleeve 3 located in the optical fiber holder 2 is fixedly connected to the optical fiber holder 2; the chip input end of the wavelength division multiplexer chip 5 is connected to the optical fiber array 7 fixed on the chip base 1, and the chip output end of the wavelength division multiplexer chip 5 is connected to the optical fiber 6 in the optical fiber sleeve 3 passing through the optical fiber holder 2. Preferably, the upper surface size of the chip base 1 is larger than the chip size of the wavelength division multiplexer chip 5, the chip output end face of the wavelength division multiplexer chip 5 is flush with the upper surface edge of the chip base 1, and the two sides of the wavelength division multiplexer chip 5 are equidistant from the two edges of the upper surface of the chip base 1. In addition, in the specific implementation, the metal seat 4, the optical fiber holder 2, the optical fiber sleeve 4, and the chip base 1 are all made of Kovar alloy, which is easy to weld, has strong thermal conductivity and a small thermal expansion coefficient, and can reduce positional deviation after laser welding.

The present application provides a method for welding an optical fiber and a chip for the above optical fiber coupling structure, comprising the following steps:

Mount the wavelength division multiplexer chip 5 on the chip base 1. When mounting, it should be noted that the chip output end surface of the wavelength division multiplexer chip 5 is flush with the upper surface edge of the chip base 1, and the two sides of the wavelength division multiplexer chip 5 are equidistant from the two edges of the chip base 1;

After trimming the optical fiber connector, the optical fiber 6 is inserted into the optical fiber sleeve 3 and fixed with a curing agent;

The optical fiber holder 2 is fixed to the metal seat 4 by laser welding, as shown in FIG2 , using two symmetrical laser beams to first weld the fixed point pair 21 and then weld the fixed point pair 22;

Use a clamp to hold the chip base 1 against the optical fiber holder 2 to prevent the chip base 1 from moving in the axial direction of the optical fiber, use a precision adjuster to pass the optical fiber sleeve 3 through the optical fiber holder 2, use a microscope to observe the lateral distance between the optical fiber 6 and the chip output end face of the wavelength division multiplexer chip 5, keep the chip base 1 against the optical fiber holder 2 while adjusting the position of the chip base 1, and when the optical axis of the optical fiber 6 is aligned with the output waveguide of the wavelength division multiplexer chip 5, press down the wavelength division multiplexer chip 5 mounted on the chip base 1 to temporarily fix it to prevent the lateral distance from shifting;

Connect the other end of the optical fiber 6 to the laser, place the near-infrared imaging microscope on the chip input end face of the wavelength division multiplexer chip 5, then turn on the laser, observe the output status through the near-infrared imaging microscope, adjust the position of the optical fiber sleeve 3, and when the output channel of the wavelength division multiplexer chip 5 shows a light spot, use two beams of symmetrical laser welding to permanently connect the optical fiber sleeve 3 to the optical fiber holder 2, as shown in Figure 3, first weld the two fixed points 23 and then weld the two fixed points 24. The use of symmetrical lasers can well suppress the horizontal movement of the optical fiber sleeve 3 and reduce the difficulty of subsequent adjustments. After fixing the optical fiber holder 2 and the optical fiber sleeve 3, release the clamp.

The next step is to align the wavelength division multiplexer chip 5 and the optical fiber array 7. First, release the pressure on the wavelength division multiplexer chip 5, and adjust the chip base 1 by observing the output of the near-infrared imaging microscope. When the near-infrared microscopic imaging shows the emission channel spot, press down the temporarily fixed wavelength division multiplexer chip 55 to ensure that the alignment can be completed by inputting the laser signal at the chip input end. Connect one channel of the optical fiber array 7 to the optical power meter, use the precision regulator to clamp the optical fiber array 7, and fix the optical fiber array 7 to the wavelength division multiplexer chip 5 when the output optical power is the maximum. By fixing the chip base 1 to adjust the position of the optical fiber array 7, the coupling efficiency from the output end of the wavelength division multiplexer chip 5 to the optical fiber array 7 can be improved.

After the optical fiber array 7 is fixed on the chip base 1, the relative position of the chip base 1 and the optical fiber holder 2 is adjusted again to the maximum output optical power, and the chip base 1 is laser welded to the metal base 4 using two symmetrical laser beams, as shown in FIG4 , first welding the fixing point 11 and then welding the fixing point 12. Because the chip base size is larger than the optical fiber holder, the chip offset after laser welding is smaller, and the offset after laser welding can be more accurately corrected during subsequent adjustment welding. Since both adjustments use symmetrical lasers, the relative displacement of the optical fiber 6 and the wavelength division multiplexer chip 5 in the horizontal direction is greatly reduced. Therefore, for the optical fiber sleeve, only the vertical direction needs to be adjusted by adjusting the welding, which reduces the difficulty of adjustment and improves the alignment accuracy.

In the present application, the optical fiber holder 2 and the chip base 1 are placed on the upper surface of the metal base 4, and the optical fiber holder 2 and the metal base 4 are connected by laser welding. A wavelength division multiplexer chip 5 is arranged above the chip base 1, and the opening of the optical fiber holder 2 is directly opposite to the chip output end face of the wavelength division multiplexer chip 5. The bottom of the optical fiber holder 2 is against the bottom of the chip base 1, and the optical fiber 6 is coaxially arranged with the optical fiber sleeve 3. The optical fiber sleeve 3 passes through the optical fiber holder 2 to achieve position limiting, and the optical fiber array 7 is fixed to the chip base 1. The optical fiber sleeve 3 is fixed by laser welding to ensure the lateral and longitudinal alignment of the optical fiber 6 and the wavelength division multiplexer chip 5. Finally, the chip base 1 is adjusted again, and the chip base 1 is fixed by laser welding to achieve a stable and accurate connection between the optical fiber 6 and the wavelength division multiplexer chip 5.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

The above are only some embodiments of the present invention. For those skilled in the art, several modifications and improvements can be made without departing from the creative concept of the present invention, which all belong to the protection scope of the present invention.

Claims (10)

1. The optical fiber coupling structure comprises a metal seat, an optical fiber fixer, an optical fiber sleeve, a chip base, a wavelength division multiplexer chip, optical fibers and an optical fiber array, and is characterized in that the optical fiber fixer and the chip base are arranged on the upper surface of the metal seat, the optical fiber fixer and the chip base are in a similar shape and are respectively fixed on the upper surface of the metal seat through the bottom of the optical fiber fixer and the bottom of the chip base, the height of the optical fiber fixer is larger than the height of the chip base, and the wavelength division multiplexer chip is arranged above the chip base;

The opening of the optical fiber fixer is opposite to the chip output end face of the wavelength division multiplexer chip, the length of the bottom of the chip base is longer than that of the top of the chip base, and the bottom of the optical fiber fixer is propped against the bottom of the chip base;

The optical fiber and the optical fiber sleeve are coaxially arranged, the inner diameter of the optical fiber sleeve is not smaller than the outer diameter of the optical fiber, the optical fiber sleeve penetrates through the optical fiber fixer to be opposite to the wavelength division multiplexer chip, and the optical fiber sleeve positioned in the optical fiber fixer is fixedly connected with the optical fiber fixer;

The chip input end of the wavelength division multiplexer chip is connected with the optical fiber array fixed on the chip base, and the chip output end of the wavelength division multiplexer chip is connected with the optical fibers in the optical fiber sleeve passing through the optical fiber fixer.

2. The optical fiber coupling structure of claim 1, wherein the upper surface of the chip base has a size greater than the chip size of the wavelength division multiplexer chip, the chip output end face of the wavelength division multiplexer chip is flush with the edge of the upper surface of the chip base, and the two sides of the wavelength division multiplexer chip are equidistant from the two edges of the upper surface of the chip base.

3. The optical fiber coupling structure of claim 1, wherein the optical fibers and the optical fiber array are connected to the wavelength division multiplexer chip in a reciprocal manner, the opening of the optical fiber holder is opposite to the chip input end face of the wavelength division multiplexer chip, the chip input end of the wavelength division multiplexer chip is connected to the optical fibers passing through the optical fiber holder, and the chip output end of the wavelength division multiplexer chip is connected to the optical fiber array.

4. The optical fiber coupling structure of claim 1, wherein the upper surface of the chip base has a length greater than 5-7 mm of the chip length.

5. A fiber coupling structure according to claim 1, wherein the fiber holder has a height greater than 4-5 mm of the height of the chip base.

6. The optical fiber coupling structure of claim 1 wherein the metal base, the fiber holder, the fiber sleeve and the chip base are all made of a vaive alloy.

7. The optical fiber coupling structure according to claim 1, wherein the side surface of the chip base and/or the extension surface of the side surface on the upper surface of the metal base are/is provided with windows.

8. The optical fiber coupling structure of claim 1, wherein the open ends of the fiber holder are respectively provided with a pair of welding fixation points for welding the fiber optic ferrule disposed within the fiber holder.

9. The optical fiber coupling structure of claim 1, wherein the side surface of the chip base is shaped like a Chinese character 'ji', and a welding fixing point is respectively arranged at the left and right sides of the side surface of the Chinese character 'ji' to weld the chip base to the upper surface of the metal base.

10. A method of optical fiber and die bonding for an optical fiber coupling structure according to any one of claims 1 to 9, comprising the steps of:

a) Mounting the wavelength division multiplexer chip on a chip base;

b) Trimming the fiber splice so that the fiber splice does not exceed a defined length of the fiber cladding, the defined length being 1-5 mm;

C) Connecting the optical fiber with the optical fiber sleeve by adopting a curing agent;

D) Fixing the optical fiber fixer to the metal seat by laser welding;

E) The chip base is propped against the optical fiber fixer by using a clamp, the optical fiber sleeve passes through the optical fiber fixer by using a precision regulator, the transverse distance between the optical fiber and the output end of the wavelength division multiplexer chip is observed by using a microscope, the position of the chip base is adjusted, and after the optical axis of the optical fiber is aligned with the output waveguide of the chip, the wavelength division multiplexer chip attached to the chip base is pressed down to temporarily fix the optical fiber;

f) Connecting the other end of the optical fiber with a laser, and placing a near infrared imaging microscope on the input end face of the wavelength division multiplexer chip;

G) Opening laser, observing output conditions through a near infrared imaging microscope, adjusting the position of the optical fiber sleeve, and welding the optical fiber sleeve and the optical fiber fixer by using two symmetrical lasers when the emergent channel of the wavelength division multiplexer chip displays light spots;

H) Releasing the pressure on the wavelength division multiplexer chip, adjusting a chip base by observing the output of the near infrared imaging microscope, and pressing down the temporarily fixed wavelength division multiplexer chip when the near infrared imaging microscope displays the emergent channel light spots;

I) One path of the optical fiber array is connected into an optical power meter, a precise regulator is used for clamping the optical fiber array, and when the output optical power is maximum, the optical fiber array and the wavelength division multiplexer chip are fixed;

J) And (3) using two symmetrical lasers to weld the chip base on the metal base by laser, and releasing the pressure on the wavelength division multiplexer chip.