End face coupler and manufacturing method thereof

Abstract

The invention discloses an end face coupler and a manufacturing method thereof, the end face coupler comprises a first waveguide, a second waveguide, a third waveguide, a fourth waveguide, a fifth waveguide and a sixth waveguide, when an external optical fiber outputs an optical signal to the first waveguide, the fourth waveguide expands the first waveguide, and the fifth waveguide expands the sixth waveguide; the fifth waveguide and the sixth waveguide evolve optical signals transmitted in the end face coupler in the vertical direction, so that mode fields of the optical signals are gradually distributed in the first waveguide in a concentrated mode and then transmitted to the second waveguide in the transmission direction of the optical signals, the loss of the optical signals transmitted to the second waveguide is reduced, and the transmission efficiency of the optical signals is improved. The fourth waveguide, the fifth waveguide and the sixth waveguide are formed by forming grooves in the lower cladding by adopting an etching process, depositing doped silicon dioxide in the grooves and on the lower cladding and performing chemical mechanical polishing treatment, and the first waveguide, the second waveguide and the third waveguide are formed by etching after deposition; the coupler has the advantages of low coupling loss and simple manufacturing process.

Description

Technical Field

[0001] The invention relates to an end face coupler, and in particular to an end face coupler and a manufacturing method thereof. Background Art

[0002] The high refractive index difference quartz-based / silicon-based silica planar optical waveguide has the characteristics of large tolerance and small temperature drift. It is an ideal material for making optical waveguide devices such as wavelength division multiplexers and optical switches. It has been widely used in the manufacture of optical waveguide devices in data centers, backbone networks and 5G fronthaul. However, the height of the high refractive index difference silica waveguide is only 3 to 4 μm, while the mode field diameter of the optical fiber is about 9 μm. If the optical waveguide device prepared with the high refractive index difference silica waveguide is directly coupled with the optical fiber, the coupling loss will be relatively high due to the large mode field mismatch. Insertion loss is the core indicator of all optical waveguide devices, so the researchers proposed using end couplers to reduce the coupling loss between the optical fiber and the optical waveguide device prepared with the high refractive index difference silica waveguide.

[0003] Existing end couplers are mainly based on waveguide grating structure, multi-layer cone structure or grayscale mask structure. The end coupler based on waveguide grating structure is a planar processing structure. Although the manufacturing process is simple, its height expansion capability is limited and the coupling loss is large. The end coupler based on multi-layer cone structure and the end coupler based on grayscale mask structure can achieve the expansion of the height mode field and the coupling loss is small, but their manufacturing process is complicated. Summary of the invention

[0004] One of the technical problems to be solved by the present invention is to provide an end face coupler which has low coupling loss and simple manufacturing process.

[0005] The technical solution adopted by the present invention to solve one of the above technical problems is: an end face coupler, comprising an upper cladding, a lower cladding and a waveguide core layer, wherein the upper cladding is located above the lower cladding, the waveguide core layer is arranged between the upper cladding and the lower cladding, and is wrapped by the upper cladding and the lower cladding, the waveguide core layer comprises a first waveguide, a second waveguide and a third waveguide, the materials of the first waveguide, the second waveguide and the third waveguide are all doped silicon dioxide, the third waveguide is a single-mode waveguide, and the first waveguide is used for The optical signal transmitted by the external optical fiber is coupled to the end coupler, and the second waveguide is used to evolve the mode field of the optical signal transmitted in the end coupler in a horizontal plane perpendicular to the transmission direction of the optical signal, so that the optical signal mode can match the third waveguide, and the third waveguide is used to output the optical signal to the rear-end optical waveguide device. The waveguide core layer also includes a fourth waveguide, a fifth waveguide and a sixth waveguide. The materials of the fourth waveguide, the fifth waveguide and the sixth waveguide are all doped with silicon dioxide. The fifth waveguide and the sixth waveguide are respectively located below the first waveguide, the fourth waveguide is used to expand the first waveguide to reduce the mode field mismatch between the end coupler and the external optical fiber, the fifth waveguide and the sixth waveguide are used to evolve the optical signal transmitted in the end coupler in the up and down directions, so that the mode field of the optical signal is gradually concentrated and distributed in the first waveguide along the optical signal transmission direction, the fourth waveguide, the fifth waveguide and the sixth waveguide are formed by forming a groove in the lower cladding by an etching process, and then depositing doped silicon dioxide in the groove and on the lower cladding and performing chemical mechanical polishing. After the fourth waveguide, the fifth waveguide and the sixth waveguide are formed, the first waveguide, the second waveguide and the third waveguide are deposited on the lower cladding, the fourth waveguide, the fifth waveguide and the sixth waveguide to form a doped silicon dioxide layer, and the same portion as the first waveguide, the second waveguide and the third waveguide is retained at the corresponding position in the doped silicon dioxide layer, and the other portions are etched away.

[0006] Compared with the prior art, the end coupler of the present invention has the advantage that the fourth waveguide, the fifth waveguide and the sixth waveguide are additionally arranged in the waveguide core layer, and the materials of the fourth waveguide, the fifth waveguide and the sixth waveguide are all doped with silica, so that the fourth waveguide, the fifth waveguide and the sixth waveguide are located below the first waveguide, and are combined with the first waveguide, the second waveguide and the third waveguide to form the core structure of the end coupler. When the external optical fiber outputs an optical signal to the first waveguide, the fourth waveguide extends the first waveguide and is coupled with the external optical fiber together with the first waveguide, so that the end face height coupled with the optical fiber can be extended to 5-7 μm, and the matching degree with the optical fiber mode field (about 6-9 um) is higher, that is, the end face mode field of the end coupler and the optical fiber mode field have a larger overlap integral, thereby reducing the mode field mismatch between the end coupler and the external optical fiber. When the first waveguide and the fourth waveguide are coupled with the optical fiber, the optical signal will enter the first waveguide and the fourth waveguide for transmission at the same time, and the fifth waveguide and the sixth waveguide are coupled to the optical signal transmitted in the end coupler along the The optical signal mode field of the optical signal is gradually concentrated and distributed in the first waveguide along the transmission direction of the optical signal, and then transmitted to the second waveguide, thereby reducing the loss of the optical signal transmitted to the second waveguide. The second waveguide then evolves the mode field of the optical signal transmitted in the end face coupler in a horizontal plane perpendicular to the transmission direction of the optical signal, so that the optical signal mode matches the third waveguide and can be transmitted to the rear-end optical waveguide device through the third waveguide. In addition, the fourth waveguide, the fifth waveguide and the sixth waveguide are formed by forming a groove in the lower cladding by an etching process, and then depositing doped silicon dioxide in the groove and on the lower cladding and performing chemical mechanical polishing. The first waveguide, the second waveguide and the third waveguide are formed by depositing doped silicon dioxide on the lower cladding, the fourth waveguide, the fifth waveguide and the sixth waveguide to form a doped silicon dioxide layer, and then adopting an etching process. That is, only two etching processes are used in the manufacturing process of the end face coupler of the present invention. Therefore, the end face coupler of the present invention has low coupling loss and a simple manufacturing process.

[0007] Furthermore, the first waveguide is a rectangular parallelepiped structure, the thickness of the first waveguide is along the up-down direction, the length is along the transmission direction of the optical signal in the end face coupler, the length direction of the first waveguide is defined as the left-right direction, the width direction of the first waveguide is defined as the front-back direction, and the plane that makes the first waveguide front-to-back symmetric is called the first symmetry plane; the second waveguide is located on the right side of the first waveguide, the second waveguide is an isosceles trapezoidal structure, the second waveguide is front-to-back symmetric about the first symmetry plane, and the cross-section of the second waveguide along the horizontal plane is An isosceles trapezoid, wherein the lower base of the isosceles trapezoid is located on the left side of the upper base thereof and both extend in the front-to-back direction, the length direction of the second waveguide is in the left-right direction, the thickness direction is in the up-down direction, and the width direction is in the front-to-back direction, the upper end surface of the second waveguide is in the same plane as the upper end surface of the first waveguide, the lower end surface of the second waveguide is in the same plane as the lower end surface of the first waveguide, the left end width of the second waveguide is equal to the right end width of the first waveguide, and the left end surface of the second waveguide is integrally formed with the right end surface of the first waveguide and completely overlaps; the third waveguide The third waveguide is located on the right side of the second waveguide, the third waveguide is a rectangular parallelepiped structure, the third waveguide is symmetrical about the first symmetry plane, the length direction of the third waveguide is along the left-right direction, the thickness direction is along the up-down direction, and the width direction is along the front-back direction. The upper end surface of the third waveguide is located in the same plane as the upper end surface of the second waveguide, the lower end surface of the third waveguide is located in the same plane as the lower end surface of the second waveguide, the width of the third waveguide is equal to the right end width of the second waveguide, and the left end surface of the third waveguide is equal to the right end surface of the second waveguide. The fourth waveguide is an isosceles trapezoidal structure, the fourth waveguide is symmetrical about the first symmetry plane, the cross section of the fourth waveguide along the vertical plane is an isosceles trapezoid, the lower base of the isosceles trapezoid is located on the upper side of its upper base, both extend along the front-to-back direction, and the length of its upper base is greater than the width of the first waveguide, the left end face of the fourth waveguide and the left end face of the first waveguide are located in the same plane, the upper end face of the fourth waveguide is fixedly connected to the lower end face of the first waveguide and is in a fitted state; the length direction of the fourth waveguide is along the left-right direction;The fifth waveguide is located on the right side of the fourth waveguide, the fifth waveguide is a trapezoidal gradient structure, the fifth waveguide is symmetrical front-to-back with respect to the first symmetry plane, the fifth waveguide has an upper end face, a lower end face, a left end face, a right end face, a front end face and a rear end face which are distributed in the upper, lower, left, right, front and rear directions and connected in sequence, the upper end face of the fifth waveguide is an isosceles trapezoid, the isosceles trapezoid is symmetrical front-to-back with respect to the first symmetry plane, its lower base is located on the left side of its upper base, and its lower base length is equal to the lower base length of the right end face of the fourth waveguide, and its upper base length is less than the width of the first waveguide, the lower end face of the fifth waveguide is an isosceles triangle, and the isosceles triangle is symmetrical front-to-back with respect to the first symmetry plane, the left end face of the fifth waveguide is an isosceles trapezoid, the isosceles trapezoid is symmetrical front-to-back with respect to the first symmetry plane, and its upper base is located below its lower base, the fifth waveguide The right end face of the fifth waveguide is an isosceles triangle, and the isosceles triangle is symmetrical front-to-back with respect to the first symmetry plane. The front end face and the rear end face of the fifth waveguide are both quadrilaterals, and the front end face and the rear end face of the fifth waveguide are symmetrical front-to-back with respect to the first symmetry plane. The front end face of the fifth waveguide and the front end face of the fourth waveguide are located in the same plane, the rear end face of the fifth waveguide and the rear end face of the fourth waveguide are located in the same plane, the upper end face of the fifth waveguide and the upper end face of the fourth waveguide are located in the same plane, the lower end face of the fifth waveguide and the lower end face of the fourth waveguide are located in the same plane, the left end face of the fifth waveguide and the right end face of the fourth waveguide are integrally formed and completely overlap, and the upper end face of the fifth waveguide is fixedly connected to the lower end face of the first waveguide and is in a fitted state; the length of the fifth waveguide is along the left-right direction, the width is along the front-to-back direction, and the thickness is along the up-down direction;The sixth waveguide is located on the right side of the fifth waveguide, the sixth waveguide is a triangular pyramid structure, the sixth waveguide is symmetrical about the first symmetry plane, the sixth waveguide has an upper end face, a front end face, a rear end face and a left end face which are distributed in the upper, front, rear and left directions and connected in sequence, the upper end face of the sixth waveguide is an isosceles triangle, and the isosceles triangle is symmetrical about the first symmetry plane, the left end face of the sixth waveguide is an isosceles triangle, and the isosceles triangle is symmetrical about the first symmetry plane, the front end face and the rear end face of the sixth waveguide are both triangles, and the front end face and the rear end face of the sixth waveguide are The sixth waveguide is symmetrical with respect to the first symmetry plane, the upper end face of the sixth waveguide is located in the same plane as the upper end face of the fifth waveguide, the upper end face of the sixth waveguide is fixedly connected to the lower end face of the first waveguide and is in a fitted state, the front end face of the sixth waveguide is located in the same plane as the front end face of the fifth waveguide, the rear end face of the sixth waveguide is located in the same plane as the rear end face of the fifth waveguide, the left end face of the sixth waveguide is integrally formed with the right end face of the fifth waveguide and completely overlaps, the right end of the sixth waveguide is located in the same plane as the right end face of the first waveguide, and the length of the sixth waveguide is along the left-right direction. ;

[0008] Furthermore, the materials of the upper cladding layer and the lower cladding layer are both silicon dioxide, and the refractive index of the doped silicon dioxide is 0.45% to 2.5% higher than the refractive index of the silicon dioxide.

[0009] Furthermore, the thickness H1 of the first waveguide is 3.5 μm, the width W1 is 11.3 μm, the length W of the lower base of the left end face of the fourth waveguide is 1.2 μm, the thickness H of the fourth waveguide in the up-down direction is 5.4 μm, the length L3 of the second waveguide is 380 μm, the length L4 of the third waveguide is 100 μm, the length L1 of the fifth waveguide is 600 μm, the length L2 of the sixth waveguide is 800 μm, the length L5 of the fourth waveguide is 100 μm, and the angle β between the rear end face of the sixth waveguide and the horizontal plane is 73.3°.

[0010] The second technical problem to be solved by the present invention is to provide a method for manufacturing an end face coupler which can produce an end face coupler with low coupling loss and simple manufacturing process.

[0011] The technical solution adopted by the present invention to solve the second technical problem is: a method for manufacturing an end face coupler, comprising the following steps:

[0012] Step 1, preparing a quartz substrate as a lower cladding layer;

[0013] Step 2, coating a photoresist on the upper surface of the quartz substrate, wherein the photoresist completely covers the upper surface of the quartz substrate;

[0014] Step 3, using a photolithography method to prepare a pattern consistent with the overall structural cross-section of the fourth waveguide, the fifth waveguide and the sixth waveguide in the photoresist of step 2, and using a developing method to remove the photoresist outside the pattern;

[0015] Step 4, etching the lower cladding layer by using an inductively coupled plasma etching process, wherein the portion of the lower cladding layer not covered by the photoresist is etched away, and a preset groove is etched in the lower cladding layer, wherein the inclination angle of the side wall of the etched groove is equal to the angle β between the rear end face of the sixth waveguide and the horizontal plane;

[0016] Step 5, depositing doped silicon dioxide in the groove and on the lower cladding layer by plasma enhanced chemical vapor deposition, wherein the groove is filled with doped silicon dioxide and a first doped silicon dioxide layer is formed on the lower cladding layer;

[0017] Step 6, performing chemical mechanical polishing from the first doped silicon dioxide layer downwards until a lower cladding layer of a preset thickness and the overall structure of the fourth waveguide, the fifth waveguide and the sixth waveguide are obtained;

[0018] Step 7, depositing a doped silicon dioxide material on the lower cladding layer, the fourth waveguide, the fifth waveguide and the sixth waveguide to form a second doped silicon dioxide layer;

[0019] Step 8, coating a photoresist on the upper surface of the second doped silicon dioxide layer, wherein the photoresist completely covers the upper surface of the second doped silicon dioxide layer;

[0020] Step 9, according to the structures of the first waveguide, the second waveguide and the third waveguide and the positional relationship between the first waveguide, the second waveguide and the third waveguide and the fourth waveguide, the fifth waveguide and the sixth waveguide, a pattern consistent with the overall structure formed by the first waveguide, the second waveguide and the third waveguide is prepared in the photoresist of step 8 by photolithography, and the photoresist outside the pattern is removed by development;

[0021] Step 10, etching away the portion of the second doped silicon dioxide layer not covered by the photoresist by an inductively coupled plasma etching process, and the remaining portion forms the first waveguide, the second waveguide and the third waveguide;

[0022] Step 11: depositing silicon dioxide on the lower cladding, the first waveguide, the second waveguide and the third waveguide to form an upper cladding.

[0023] Compared with the prior art, the manufacturing method of the end face coupler of the present invention has the advantages that the first waveguide, the second waveguide, the third waveguide, the fourth waveguide, the fifth waveguide and the sixth waveguide are formed by adopting two etching processes, the manufacturing process is simple, and in the manufactured end face coupler, the fourth waveguide, the fifth waveguide and the sixth waveguide form the core structure of the end face coupler with the first waveguide, the second waveguide and the third waveguide. When the external optical fiber outputs the optical signal to the first waveguide, the fourth waveguide extends the first waveguide and couples with the external optical fiber together with the first waveguide, so that the end face height coupled with the optical fiber can be extended to 5-7 μm, and the matching degree with the optical fiber mode field (about 6-9 um) is higher, that is, the end face mode field of the end face coupler and the optical fiber mode field have a larger overlap integral, thereby reducing the end face coupler and the optical fiber mode field. The mode field of the external optical fiber is mismatched. When the first waveguide and the fourth waveguide are coupled with the optical fiber, the optical signal will enter the first waveguide and the fourth waveguide for transmission at the same time. The fifth waveguide and the sixth waveguide evolve the optical signal transmitted in the end face coupler in the up and down directions, so that along the transmission direction of the optical signal, the mode field of the optical signal is gradually concentrated and distributed in the first waveguide and then transmitted to the second waveguide, reducing the loss of the optical signal transmitted to the second waveguide. The second waveguide then evolves the mode field of the optical signal transmitted in the end face coupler in a horizontal plane along a direction perpendicular to the transmission direction of the optical signal, so that the optical signal mode matches the third waveguide and can be transmitted to the rear-end optical waveguide device through the third waveguide. Therefore, the manufacturing method of the end face coupler of the present invention can prepare an end face coupler with low coupling loss, and the manufacturing process is simple.

[0024] Furthermore, in the step 4, when the lower cladding is etched by the inductively coupled plasma etching process, the RF power is 1950W, the bias power is 220W, and the etching gas is CF 4 , the protective gas is C 4 F 8 , C.F. 4 The flow rate is 100 sccm, C 4 F 8 The flow rate is 20 sccm. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The three-dimensional structure of the waveguide core layer of the end coupler of the present invention Figure 1 ;

[0026] Figure 2 The three-dimensional structure of the waveguide core layer of the end coupler of the present invention Figure 2 ;

[0027] Figure 3 The three-dimensional structure of the waveguide core layer of the end coupler of the present invention Figure 3 ;

[0028] Figure 4A top view of the waveguide core layer of the end coupler of the present invention Figure 1 ;

[0029] Figure 5 It is a front view of the waveguide core layer of the end coupler of the present invention;

[0030] Figure 6 A top view of the waveguide core layer of the end coupler of the present invention Figure 2 ;

[0031] Figure 7 for Figure 6 Side view at mid-section 1;

[0032] Figure 8 for Figure 6 Side view at mid section 2;

[0033] Fig. 9 A diagram showing the coordination between the waveguide core layer of the end coupler of the present invention and the optical fiber;

[0034] Fig.10 is a flow chart of a method for manufacturing an end face coupler of the present invention;

[0035] Fig.11 The electron microscope images of the grooves with different opening widths in the method for manufacturing the end face coupler of the present invention are shown;

[0036] Fig.12 A diagram showing the groove etching depths at different opening widths in the method for manufacturing the end face coupler of the present invention;

[0037] Fig.13 The end face of the end face coupler of the present invention is Fig. 9 Light field distribution diagram of the YZ section;

[0038] Fig.14 The end face of the end face coupler of the present invention is Fig. 9 Light field distribution diagram of the XZ section;

[0039] Fig.15 This is a transmission spectrum line simulation result diagram of the end coupler of the present invention. DETAILED DESCRIPTION

[0040] The present invention discloses an end face coupler, which will be described in further detail below in conjunction with the embodiments of the accompanying drawings.

[0041] Embodiment 1: Figures 1 to 4As shown, an end face coupler includes an upper cladding, a lower cladding and a waveguide core layer, wherein the upper cladding is located above the lower cladding, the waveguide core layer is arranged between the upper cladding and the lower cladding, and is wrapped by the upper cladding and the lower cladding, the waveguide core layer includes a first waveguide 004, a second waveguide 005 and a third waveguide 006, the materials of the first waveguide 004, the second waveguide 005 and the third waveguide 006 are all doped with silica, the third waveguide 006 is a single-mode waveguide, the first waveguide 004 is used to couple with an external optical fiber, and the optical signal transmitted by the external optical fiber is connected to the end face coupler The second waveguide 005 is used to evolve the mode field of the optical signal transmitted in the end face coupler in a horizontal plane along a direction perpendicular to the optical signal transmission direction, so that the optical signal mode can match the third waveguide 006, and the third waveguide 006 is used to output the optical signal to the back-end optical waveguide device. The waveguide core layer also includes a fourth waveguide 001, a fifth waveguide 002 and a sixth waveguide 003. The materials of the fourth waveguide 001, the fifth waveguide 002 and the sixth waveguide 003 are all doped silicon dioxide. The fourth waveguide 001 is respectively located below the first waveguide 004, and is used to expand the first waveguide 004 to reduce the mode field mismatch between the end coupler and the external optical fiber. The fifth waveguide 002 and the sixth waveguide 003 are used to evolve the optical signal transmitted in the end coupler in the up and down directions, so that the mode field of the optical signal is gradually concentrated in the first waveguide 004 along the optical signal transmission direction. The fourth waveguide 001, the fifth waveguide 002, and the sixth waveguide 003 are formed by etching grooves in the lower cladding layer, and then the grooves and the lower cladding layer are formed. After depositing doped silicon dioxide and performing chemical mechanical polishing, after the fourth waveguide 001, the fifth waveguide 002 and the sixth waveguide 003 are formed, the first waveguide 004, the second waveguide 005 and the third waveguide 006 are formed by depositing doped silicon dioxide on the lower cladding, the fourth waveguide 001, the fifth waveguide 002 and the sixth waveguide 003 to form a doped silicon dioxide layer, and retaining portions with the same shapes as the first waveguide 004, the second waveguide 005 and the third waveguide 006 at corresponding positions in the doped silicon dioxide layer, and etching away other portions.

[0042] In this embodiment, the fourth waveguide 001, the fifth waveguide 002 and the sixth waveguide 003 are combined with the first waveguide 004, the second waveguide 005 and the third waveguide 006 to form the core structure of the end face coupler. When the external optical fiber outputs an optical signal to the first waveguide 004, the fourth waveguide 001 extends the first waveguide 004 and couples with the external optical fiber together with the first waveguide 004, so that the end face height coupled with the optical fiber can be extended to 5-7 μm, and the matching degree with the optical fiber mode field (about 6-9 μm) is higher, that is, the end face mode field of the end face coupler and the optical fiber mode field have a larger overlap integral, thereby reducing the mode field mismatch between the end face coupler and the external optical fiber and reducing the coupling loss. When the first waveguide 004 and the fourth waveguide 001 are coupled with the optical fiber, the optical signal will enter the first waveguide 004 and the fourth waveguide 001 for transmission at the same time. The fifth waveguide 002 and the sixth waveguide 003 evolve the optical signal transmitted in the end face coupler in the up and down directions, so that the optical signal transmission along the optical signal is transmitted. direction, the mode field of the optical signal is gradually concentrated and distributed in the first waveguide 004 and then transmitted to the second waveguide 005, thereby reducing the transmission loss of the optical signal transmitted to the second waveguide 005. The second waveguide 005 then evolves the mode field of the optical signal transmitted in the end face coupler in a horizontal plane along a direction perpendicular to the optical signal transmission direction, so that the optical signal mode matches the third waveguide 006, and can be transmitted to the back-end optical waveguide device through the third waveguide 006. In addition, the fourth waveguide 001, the fifth waveguide 002 and the sixth waveguide 003 are formed by forming grooves in the lower cladding by an etching process, and then depositing doped silicon dioxide in the grooves and on the lower cladding and performing chemical mechanical polishing. The first waveguide 004, the second waveguide 005 and the third waveguide 006 are formed by depositing doped silicon dioxide on the lower cladding, the fourth waveguide 001, the fifth waveguide 002 and the sixth waveguide 003 to form a doped silicon dioxide layer and then adopting an etching process. Only two etching processes are used, and the manufacturing process is simple.

[0043] Embodiment 2: This embodiment is basically the same as Embodiment 1, except that: in this embodiment, Figures 5 to 9As shown, the first waveguide 004 is a rectangular parallelepiped structure, the thickness of the first waveguide 004 is along the up-down direction, and the length is along the transmission direction of the optical signal in the end face coupler. The length direction of the first waveguide 004 is defined as the left-right direction, and the width direction of the first waveguide 004 is defined as the front-to-back direction. The plane that makes the first waveguide 004 front-to-back symmetric is called the first symmetry plane; the second waveguide 005 is located on the right side of the first waveguide 004, and the second waveguide 005 is an isosceles trapezoidal structure. The second waveguide 005 is front-to-back symmetric about the first symmetry plane, and the cross section of the second waveguide 005 along the horizontal plane is an isosceles trapezoid , the lower base of the isosceles trapezoid is located on the left side of its upper base, and both extend in the front-to-back direction, the length direction of the second waveguide 005 is along the left-right direction, the thickness direction is along the up-down direction, and the width direction is along the front-to-back direction, the upper end surface of the second waveguide 005 and the upper end surface of the first waveguide 004 are located in the same plane, the lower end surface of the second waveguide 005 and the lower end surface of the first waveguide 004 are located in the same plane, the left end width of the second waveguide 005 is equal to the right end width of the first waveguide 004, and the left end surface of the second waveguide 005 and the right end surface of the first waveguide 004 are integrally formed and completely overlap; the third waveguide 006 Located on the right side of the second waveguide 005, the third waveguide 006 is a rectangular parallelepiped structure. The third waveguide 006 is front-to-back symmetrical about the first symmetry plane. The length direction of the third waveguide 006 is along the left-right direction, the thickness direction is along the up-down direction, and the width direction is along the front-to-back direction. The upper end surface of the third waveguide 006 and the upper end surface of the second waveguide 005 are located in the same plane, the lower end surface of the third waveguide 006 and the lower end surface of the second waveguide 005 are located in the same plane, the width of the third waveguide 006 is equal to the right end width of the second waveguide 005, and the left end surface of the third waveguide 006 is equal to the right end surface of the second waveguide 005. The fourth waveguide 001 is an isosceles trapezoidal structure, the fourth waveguide 001 is symmetrical about the first symmetry plane, the cross section of the fourth waveguide 001 along the vertical plane is an isosceles trapezoid, the lower base of the isosceles trapezoid is located on the upper side of the upper base, both extend along the front-to-back direction, and the length of the upper base is greater than the width of the first waveguide 004, the left end face of the fourth waveguide 001 and the left end face of the first waveguide 004 are located in the same plane, the upper end face of the fourth waveguide 001 and the lower end face of the first waveguide 004 are fixedly connected and in a fitting state; the length direction of the fourth waveguide 001 is along the left-right direction;The fifth waveguide 002 is located on the right side of the fourth waveguide 001. The fifth waveguide 002 is a trapezoidal gradient structure. The fifth waveguide 002 is symmetrical front-to-back about the first symmetry plane. The fifth waveguide 002 has an upper end face, a lower end face, a left end face, a right end face, a front end face and a rear end face which are distributed in the upper, lower, left, right, front and rear directions and connected in sequence. The upper end face of the fifth waveguide 002 is an isosceles trapezoid, which is symmetrical front-to-back about the first symmetry plane. Its lower base is located on the left side of its upper base, and its lower base length is equal to the lower base length of the right end face of the fourth waveguide 001, and its upper base length is less than the width of the first waveguide 004. The lower end face of the fifth waveguide 002 is an isosceles triangle, and the isosceles triangle is symmetrical front-to-back about the first symmetry plane. The left end face of the fifth waveguide 002 is an isosceles trapezoid, which is symmetrical front-to-back about the first symmetry plane, and its upper base is located below its lower base. The right end face of the fifth waveguide 002 The front face of the fifth waveguide 002 is an isosceles triangle, and the isosceles triangle is front-to-back symmetrical about the first symmetry plane. The front end face and the rear end face of the fifth waveguide 002 are both quadrilaterals, and the front end face and the rear end face of the fifth waveguide 002 are front-to-back symmetrical about the first symmetry plane. The front end face of the fifth waveguide 002 and the front end face of the fourth waveguide 001 are located in the same plane, the rear end face of the fifth waveguide 002 and the rear end face of the fourth waveguide 001 are located in the same plane, the upper end face of the fifth waveguide 002 and the upper end face of the fourth waveguide 001 are located in the same plane, the lower end face of the fifth waveguide 002 and the lower end face of the fourth waveguide 001 are located in the same plane, the left end face of the fifth waveguide 002 and the right end face of the fourth waveguide 001 are integrally formed and completely overlap, and the upper end face of the fifth waveguide 002 is fixedly connected to the lower end face of the first waveguide 004 and is in a fitted state; the length of the fifth waveguide 002 is along the left-right direction, the width is along the front-to-back direction, and the thickness is along the up-down direction;The sixth waveguide 003 is located on the right side of the fifth waveguide 002. The sixth waveguide 003 is a triangular pyramid structure. The sixth waveguide 003 is symmetrical front-to-back about the first symmetry plane. The sixth waveguide 003 has an upper end face, a front end face, a rear end face and a left end face which are distributed in the upper, front, rear and left directions and connected in sequence. The upper end face of the sixth waveguide 003 is an isosceles triangle, and the isosceles triangle is symmetrical front-to-back about the first symmetry plane. The left end face of the sixth waveguide 003 is an isosceles triangle, and the isosceles triangle is symmetrical front-to-back about the first symmetry plane. The front end face and the rear end face of the sixth waveguide 003 are both triangles. The front end face and the rear end face of the sixth waveguide 003 are about The first symmetry plane is front-to-back symmetrical, the upper end face of the sixth waveguide 003 and the upper end face of the fifth waveguide 002 are located in the same plane, the upper end face of the sixth waveguide 003 and the lower end face of the first waveguide 004 are fixedly connected and in a fitted state, the front end face of the sixth waveguide 003 and the front end face of the fifth waveguide 002 are located in the same plane, the rear end face of the sixth waveguide 003 and the rear end face of the fifth waveguide 002 are located in the same plane, the left end face of the sixth waveguide 003 and the right end face of the fifth waveguide 002 are integrally formed and completely overlap, the right end of the sixth waveguide 003 and the right end face of the first waveguide 004 are located in the same plane, and the length of the sixth waveguide 003 is along the left-right direction. ;

[0044] In this embodiment, the materials of the upper cladding layer and the lower cladding layer are both silicon dioxide, and the refractive index of the doped silicon dioxide is 0.45% to 2.5% higher than the refractive index of the silicon dioxide.

[0045] In this embodiment, the thickness H1 of the first waveguide 004 is 3.5 μm, the width W1 is 11.3 μm, the length W of the bottom of the left end surface of the fourth waveguide 001 is 1.2 μm, the thickness H of the fourth waveguide 001 in the up-down direction is 5.4 μm, the length L3 of the second waveguide 005 is 380 μm, the length L4 of the third waveguide 006 is 100 μm, the length L1 of the fifth waveguide 002 is 600 μm, the length L2 of the sixth waveguide 003 is 800 μm, the length L5 of the fourth waveguide 001 is 100 μm, and the angle β between the rear end surface of the sixth waveguide 003 and the horizontal plane is 73.3°.

[0046] In this embodiment, the mode field matching of the end coupler mainly includes three parts. The first part is the matching of the optical fiber and the end face: by filling doped silicon oxide in the groove formed by etching to form the fourth waveguide 001, and depositing the first waveguide 004 at the same time, the end face of the end coupler (the end face formed by the left end face of the first waveguide 004 and the fourth waveguide 001) can be extended to 5-7μm in height (dimensions in the up-down direction), which is more matched with the optical fiber mode field (about 6-9um), that is, the end face mode field of the end coupler and the optical fiber mode field have a larger overlap integral. The second part is the longitudinal mode field compression evolution, which mainly uses the gradual change of the groove depth formed by inclined etching to achieve the gradual change of the height of the end coupler (dimensions in the up-down direction), thereby achieving the gradual change of the mode field in height. The third part is to achieve the transition of the wide waveguide mode field to the conventional waveguide mode field by slowly reducing the width of the end coupler (dimensions in the front-back direction). The fourth waveguide 001, the fifth waveguide 002 and the sixth waveguide 003 all adopt a gradient structure, and grooves with inclined surfaces matching the fourth waveguide 001, the fifth waveguide 002 and the sixth waveguide 003 are obtained by etching obliquely, and then the grooves are filled to obtain the fourth waveguide 001, the fifth waveguide 002 and the sixth waveguide 003, which simplifies the manufacturing process while reducing the coupling loss.

[0047] The present invention also discloses a method for manufacturing the end face coupler. The method for manufacturing the end face coupler of the present invention is further described in detail below in conjunction with the embodiments of the accompanying drawings.

[0048] Example: Fig.10 As shown, a method for manufacturing an end face coupler comprises the following steps:

[0049] Step 1, preparing a quartz substrate as a lower cladding layer;

[0050] Step 2, coating a photoresist on the upper surface of the quartz substrate, wherein the photoresist completely covers the upper surface of the quartz substrate;

[0051] Step 3, using a photolithography method to prepare a pattern consistent with the overall structural cross-section of the fourth waveguide 001, the fifth waveguide 002 and the sixth waveguide 003 in the photoresist of step 2, and using a developing method to remove the photoresist outside the pattern;

[0052] Step 4, etching the lower cladding layer by using an inductively coupled plasma etching process, wherein the portion of the lower cladding layer not covered by the photoresist is etched away, and a preset groove is etched in the lower cladding layer, wherein the inclination angle of the side wall of the etched groove is equal to the angle β between the rear end face of the sixth waveguide and the horizontal plane;

[0053] Step 5: Deposit doped silicon dioxide in the groove and on the lower cladding layer by plasma enhanced chemical vapor deposition, so that the groove is filled with doped silicon dioxide and a first doped silicon dioxide layer is formed on the lower cladding layer;

[0054] Step 6, chemical mechanical polishing is performed downward from the first doped silicon dioxide layer until a lower cladding layer of a preset thickness and the overall structure of the fourth waveguide 001, the fifth waveguide 002 and the sixth waveguide 003 are obtained;

[0055] Step 7, depositing a doped silicon dioxide material on the lower cladding, the fourth waveguide 001, the fifth waveguide 002 and the sixth waveguide 003 to form a second doped silicon dioxide layer;

[0056] Step 8, coating a photoresist on the upper surface of the second doped silicon dioxide layer, wherein the photoresist completely covers the upper surface of the second doped silicon dioxide layer;

[0057] Step 9, according to the structures of the first waveguide 004, the second waveguide 005 and the third waveguide 006 and the positional relationship between the first waveguide 004, the second waveguide 005 and the third waveguide 006 and the fourth waveguide 001, the fifth waveguide 002 and the sixth waveguide 003, a pattern consistent with the overall structure formed by the first waveguide 004, the second waveguide 005 and the third waveguide 006 is prepared in the photoresist of step 8 by photolithography, and the photoresist outside the pattern is removed by development;

[0058] Step 10, etching away the portion of the second doped silicon dioxide layer not covered by the photoresist by an inductively coupled plasma etching process, and the remaining portion forms the first waveguide 004, the second waveguide 005 and the third waveguide 006;

[0059] Step 11: deposit silicon dioxide on the lower cladding, the first waveguide 004, the second waveguide 005 and the third waveguide 006 to form an upper cladding.

[0060] In this embodiment, in the actual manufacturing process, when the line width of the lithography machine process is large, the tip width of the mask cannot infinitely approach 0. In the actual process, the tip will be arc-shaped or square-shaped, and a step will be generated during the etching process, so that the height of the sixth waveguide does not completely gradually change to 0. Therefore, the shape of the groove is inconsistent with the required shape (tip portion) of the right end of the sixth waveguide. Therefore, in step 4, a corresponding margin space is preset for the groove to adapt to the current existing lithography machine process and reduce the precision requirements for the current existing lithography machine process. After depositing doped silicon dioxide, the doped silicon dioxide at the margin space is removed by chemical mechanical polishing to form the fourth waveguide 001, the fifth waveguide 002 and the sixth waveguide 003, so that the tip height of the sixth waveguide can transition to close to 0, ensuring the manufacturing accuracy of the sixth waveguide 003; wherein, generally, the height of the groove reserved margin is the tip width*tanβ, and the tip width refers to the tip width of the formed mask, which is appropriately selected according to the actual lithography machine.

[0061] In this embodiment, the thickness H1 of the first waveguide 004 is 3.5 μm, the width W1 is 11.3 μm, the length W of the bottom of the left end face of the fourth waveguide 001 is 1.2 μm, the thickness H of the fourth waveguide 001 in the up-down direction is 5.4 μm, the distance L3 between the right end of the sixth waveguide 003 and the plane where the right end face of the second waveguide 005 is located is 380 μm, the length L4 of the third waveguide 006 is 100 μm, the length L1 of the fifth waveguide 002 is 600 μm, the length L2 of the sixth waveguide 003 is 800 μm, the length L5 of the fourth waveguide 001 is 100 μm, and the angle β between the rear end face of the sixth waveguide 003 and the horizontal plane is 73.3°.

[0062] In this embodiment, when the lower cladding is etched by inductively coupled plasma etching in step 4, the RF power is 1950W, the bias power is 220W, and the etching gas is CF 4 , the protective gas is C 4 F 8 , C.F. 4 The flow rate is 100 sccm, C 4 F 8 The flow rate is 20 sccm.

[0063] In this embodiment, when doped silicon dioxide is deposited in the groove and on the upper cladding by plasma enhanced chemical vapor deposition, not only the overall structure of the fourth waveguide 001, the fifth waveguide 002 and the sixth waveguide 003 is formed in the groove, but also a first doped silicon dioxide layer is formed on the upper cladding. The first doped silicon dioxide layer is then removed by chemical mechanical polishing, which can avoid the introduction of large stress due to the large area of ​​thick film in the process of forming the second doped silicon dioxide layer, thereby avoiding warping and cracking.

[0064] In this embodiment, electron microscope images of the grooves with different opening widths are shown in FIG. Fig.11 As shown in Figure 2, the groove etching depth diagrams under different opening widths are shown in Figure 2. Fig.12 As shown; analysis Fig.11 and Fig.12 It can be seen that the method for manufacturing the end face coupler of the present invention can form grooves matching the overall structure of the fourth waveguide 001, the fifth waveguide 002 and the sixth waveguide 003 with high precision through inclined etching without requiring additional operations.

[0065] In order to verify the performance of the present invention, the time-domain finite difference method is used to simulate the end coupler of the present invention. During the simulation process, a single-mode optical fiber is used to connect the end face of the end coupler. The dimensions of the end coupler of the present invention are as follows: W = 1.2μm, H = 5.4μm, β = 73.3°, H1 = 3.5μm, W1 = 11.3μm, L1 = 600μm, L2 = 800μm, L3 = 380μm, L4 = 100μm, L5 = 100μm. The TE single-mode light field is input from the optical fiber, and the end face of the end coupler of the present invention is along the Fig. 9 The light field distribution diagram of the YZ section is as follows Fig.13 As shown; the end face of the end face coupler of the present invention is along Fig. 9 The light field distribution diagram of the XZ section is as follows Fig.14 As shown. Fig.13 and Fig.14 It can be seen that the end coupler of the present invention can achieve mode field widening or narrowing in the width direction (along the front-to-back direction) and the height direction (along the up-down direction), and can achieve a mode field of 10μm*8μm, which is close to the optical fiber mode field. By monitoring the TE single-mode component power at the right single-mode waveguide (the third waveguide 006), the transmission spectrum line simulation result of the end coupler of the present invention is obtained as shown in the figure below: Fig.15 Analysis Fig.15 It can be seen that the normalized loss of the end face coupler of the present invention is less than 0.29 dB / facet, and the coupling loss is relatively low.

[0066] In summary, the end face height of the end face coupler of the present invention coupled with the optical fiber can be extended to 5-7 μm, with a higher matching degree with the optical fiber mode field (about 6-9 μm), and has a lower coupling loss. The manufacturing method thereof only needs to adopt two etching processes, and the manufacturing process is simple. The excess part formed in the groove caused by the wide line width in the photolithography process can be polished away by the chemical mechanical polishing method to form the fourth waveguide, the fifth waveguide and the sixth waveguide with higher dimensional accuracy, so that the deep groove etching process of the groove does not require a high-precision photolithography process, which greatly reduces the cost. Therefore, the end face coupler of the present invention and its manufacturing method can not only have low coupling loss and simple manufacturing process, but also have the advantages of low cost, significant effect, and broad application prospects.

Claims

1. An end coupler, comprising an upper cladding, a lower cladding and a waveguide core layer, wherein the upper cladding is located above the lower cladding, the waveguide core layer is arranged between the upper cladding and the lower cladding, and is wrapped by the upper cladding and the lower cladding, the waveguide core layer comprises a first waveguide, a second waveguide and a third waveguide, the materials of the first waveguide, the second waveguide and the third waveguide are all doped silica, the third waveguide is a single-mode waveguide, the first waveguide is used to couple with an external optical fiber, and connect the optical signal transmitted by the external optical fiber to the end coupler, the second waveguide is used to evolve the mode field of the optical signal transmitted in the end coupler in a horizontal plane perpendicular to the transmission direction of the optical signal, so that the optical signal mode can match the third waveguide, and the third waveguide is used to output the optical signal to a rear-end optical waveguide device, characterized in that The waveguide core layer also includes a fourth waveguide, a fifth waveguide and a sixth waveguide. The materials of the fourth waveguide, the fifth waveguide and the sixth waveguide are all doped with silica. The fourth waveguide, the fifth waveguide and the sixth waveguide are respectively located below the first waveguide. The fourth waveguide is used to expand the first waveguide to reduce the mode field mismatch between the end coupler and the external optical fiber. The fifth waveguide and the sixth waveguide are used to evolve the optical signal transmitted in the end coupler in the up and down directions so that the mode field of the optical signal is gradually concentrated and distributed in the first waveguide along the transmission direction of the optical signal. The fourth waveguide, the fifth waveguide and the sixth waveguide are used to evolve the optical signal transmitted in the end coupler in the up and down directions so that the mode field of the optical signal is gradually concentrated and distributed in the first waveguide along the transmission direction of the optical signal. The fifth waveguide and the sixth waveguide are formed by forming grooves in the lower cladding by an etching process, and then depositing doped silicon dioxide in the grooves and on the lower cladding and performing chemical mechanical polishing. After the fourth waveguide, the fifth waveguide and the sixth waveguide are formed, the first waveguide, the second waveguide and the third waveguide are formed by depositing doped silicon dioxide on the lower cladding, the fourth waveguide, the fifth waveguide and the sixth waveguide to form a doped silicon dioxide layer, and retaining portions with the same shapes as the first waveguide, the second waveguide and the third waveguide at corresponding positions in the doped silicon dioxide layer, and etching away other portions.

2. An end coupler according to claim 1, characterized in that The first waveguide is a rectangular parallelepiped structure, the thickness of the first waveguide is along the up-down direction, the length is along the transmission direction of the optical signal in the end face coupler, the length direction of the first waveguide is defined as the left-right direction, the width direction of the first waveguide is defined as the front-back direction, and the plane that makes the first waveguide front-back symmetrical is called the first symmetry plane; The second waveguide is located on the right side of the first waveguide, the second waveguide is an isosceles trapezoid structure, the second waveguide is symmetrical front-to-back about the first symmetry plane, the cross section of the second waveguide along the horizontal plane is an isosceles trapezoid, the lower base of the isosceles trapezoid is located on the left side of its upper base, and both extend in the front-to-back direction, the length direction of the second waveguide is along the left-right direction, the thickness direction is along the up-down direction, and the width direction is along the front-to-back direction, the upper end surface of the second waveguide is located in the same plane as the upper end surface of the first waveguide, the lower end surface of the second waveguide is located in the same plane as the lower end surface of the first waveguide, the left end width of the second waveguide is equal to the right end width of the first waveguide, and the left end surface of the second waveguide is integrally formed with the right end surface of the first waveguide and completely overlaps; The third waveguide is located on the right side of the second waveguide, the third waveguide is a rectangular parallelepiped structure, the third waveguide is front-to-back symmetrical about the first symmetry plane, the length direction of the third waveguide is along the left-right direction, the thickness direction is along the up-down direction, and the width direction is along the front-to-back direction. The upper end surface of the third waveguide and the upper end surface of the second waveguide are located in the same plane, the lower end surface of the third waveguide and the lower end surface of the second waveguide are located in the same plane, the width of the third waveguide is equal to the right end width of the second waveguide, and the left end surface of the third waveguide and the right end surface of the second waveguide are integrally formed and completely overlap. The fourth waveguide is an isosceles trapezoidal structure, the fourth waveguide is symmetrical front-to-back about the first symmetry plane, the cross section of the fourth waveguide along the vertical plane is an isosceles trapezoid, the lower base of the isosceles trapezoid is located on the upper side of its upper base, both extend along the front-to-back direction, and the length of its upper base is greater than the width of the first waveguide, the left end face of the fourth waveguide and the left end face of the first waveguide are located in the same plane, the upper end face of the fourth waveguide is fixedly connected to the lower end face of the first waveguide and is in a fitted state; the length direction of the fourth waveguide is along the left-right direction; The fifth waveguide is located on the right side of the fourth waveguide, the fifth waveguide is a trapezoidal gradient structure, the fifth waveguide is symmetrical front-to-back with respect to the first symmetry plane, the fifth waveguide has an upper end face, a lower end face, a left end face, a right end face, a front end face and a rear end face which are distributed in the upper, lower, left, right, front and rear directions and connected in sequence, the upper end face of the fifth waveguide is an isosceles trapezoid, the isosceles trapezoid is symmetrical front-to-back with respect to the first symmetry plane, its lower base is located on the left side of its upper base, and its lower base length is equal to the lower base length of the right end face of the fourth waveguide, and its upper base length is less than the width of the first waveguide, the lower end face of the fifth waveguide is an isosceles triangle, and the isosceles triangle is symmetrical front-to-back with respect to the first symmetry plane, the left end face of the fifth waveguide is an isosceles trapezoid, the isosceles trapezoid is symmetrical front-to-back with respect to the first symmetry plane, and its upper base is located below its lower base, the fifth waveguide The right end face of the fifth waveguide is an isosceles triangle, and the isosceles triangle is symmetrical front-to-back with respect to the first symmetry plane. The front end face and the rear end face of the fifth waveguide are both quadrilaterals, and the front end face and the rear end face of the fifth waveguide are symmetrical front-to-back with respect to the first symmetry plane. The front end face of the fifth waveguide and the front end face of the fourth waveguide are located in the same plane, the rear end face of the fifth waveguide and the rear end face of the fourth waveguide are located in the same plane, the upper end face of the fifth waveguide and the upper end face of the fourth waveguide are located in the same plane, the lower end face of the fifth waveguide and the lower end face of the fourth waveguide are located in the same plane, the left end face of the fifth waveguide and the right end face of the fourth waveguide are integrally formed and completely overlap, and the upper end face of the fifth waveguide is fixedly connected to the lower end face of the first waveguide and is in a fitted state; the length of the fifth waveguide is along the left-right direction, the width is along the front-to-back direction, and the thickness is along the up-down direction; The sixth waveguide is located on the right side of the fifth waveguide, the sixth waveguide is a triangular pyramid structure, the sixth waveguide is symmetrical about the first symmetry plane, the sixth waveguide has an upper end face, a front end face, a rear end face and a left end face which are distributed in the upper, front, rear and left directions and connected in sequence, the upper end face of the sixth waveguide is an isosceles triangle, and the isosceles triangle is symmetrical about the first symmetry plane, the left end face of the sixth waveguide is an isosceles triangle, and the isosceles triangle is symmetrical about the first symmetry plane, the front end face and the rear end face of the sixth waveguide are both triangles, and the front end face and the rear end face of the sixth waveguide are The sixth waveguide is symmetrical with respect to the first symmetry plane, the upper end face of the sixth waveguide and the upper end face of the fifth waveguide are located in the same plane, the upper end face of the sixth waveguide is fixedly connected to the lower end face of the first waveguide and is in a fitted state, the front end face of the sixth waveguide and the front end face of the fifth waveguide are located in the same plane, the rear end face of the sixth waveguide and the rear end face of the fifth waveguide are located in the same plane, the left end face of the sixth waveguide and the right end face of the fifth waveguide are integrally formed and completely overlap, the right end of the sixth waveguide and the right end face of the first waveguide are located in the same plane, and the length of the sixth waveguide is along the left-right direction.

3. An end coupler according to claim 2, characterized in that The materials of the upper cladding layer and the lower cladding layer are both silicon dioxide, and the refractive index of the doped silicon dioxide is 0.45% to 2.5% higher than that of the silicon dioxide.

4. An end coupler according to claim 2, characterized in that The thickness of the first waveguide is H1=3.5μm, and the width is W1=11.3μm. The length of the lower base of the left end face of the fourth waveguide is W=1.2μm. The thickness of the fourth waveguide in the up-down direction is H=5.4μm. The length of the second waveguide is L3=380μm. The length of the third waveguide is L4=100μm. The length of the fifth waveguide is L1=600μm. The length of the sixth waveguide is L2=800μm. The length of the fourth waveguide is L5=100μm. The angle β between the rear end face of the sixth waveguide and the horizontal plane is 73.3°.

5. The method for manufacturing an end coupler according to any one of claims 1 to 4, characterized in that The following steps are involved: Step 1, preparing a quartz substrate as a lower cladding layer; Step 2, coating a photoresist on the upper surface of the quartz substrate, wherein the photoresist completely covers the upper surface of the quartz substrate; Step 3, using a photolithography method to prepare a pattern consistent with the overall structural cross-section of the fourth waveguide, the fifth waveguide and the sixth waveguide in the photoresist of step 2, and using a developing method to remove the photoresist outside the pattern; Step 4, etching the lower cladding layer by using an inductively coupled plasma etching process, wherein the portion of the lower cladding layer not covered by the photoresist is etched away, and a preset groove is etched in the lower cladding layer, wherein the inclination angle of the side wall of the etched groove is equal to the angle β between the rear end face of the sixth waveguide and the horizontal plane; Step 5, depositing doped silicon dioxide in the groove and on the lower cladding layer by using a plasma enhanced chemical vapor deposition method, wherein the groove is filled with doped silicon dioxide, and a first doped silicon dioxide layer is formed on the lower cladding layer; Step 6, performing chemical mechanical polishing from the first doped silicon dioxide layer downwards until a lower cladding layer of a preset thickness and the overall structure of the fourth waveguide, the fifth waveguide and the sixth waveguide are obtained; Step 7, depositing a doped silicon dioxide material on the lower cladding layer, the fourth waveguide, the fifth waveguide and the sixth waveguide to form a second doped silicon dioxide layer; Step 8, coating a photoresist on the upper surface of the second doped silicon dioxide layer, wherein the photoresist completely covers the upper surface of the second doped silicon dioxide layer; Step 9, according to the structures of the first waveguide, the second waveguide and the third waveguide and the positional relationship between the first waveguide, the second waveguide and the third waveguide and the fourth waveguide, the fifth waveguide and the sixth waveguide, a pattern consistent with the overall structure formed by the first waveguide, the second waveguide and the third waveguide is prepared in the photoresist of step 8 by photolithography, and the photoresist outside the pattern is removed by development; Step 10, etching away the portion of the second doped silicon dioxide layer not covered by the photoresist by an inductively coupled plasma etching process, and the remaining portion forms the first waveguide, the second waveguide and the third waveguide; Step 11: depositing silicon dioxide on the lower cladding, the first waveguide, the second waveguide and the third waveguide to form an upper cladding.

6. The method for manufacturing an end coupler according to claim 5, characterized in that In the step 4, when the lower cladding is etched using the inductively coupled plasma etching process, the RF power is 1950w, the bias power is 220w, the etching gas is CF4, the protective gas is C4F8, the CF4 flow rate is 100sccm, and the C4F8 flow rate is 20sccm.

Images