Method for manufacturing optical connection member, and optical connection member

Abstract

This manufacturing method is provided with a preparation step, a laser irradiation step, and a focal point movement step. The light intensity distribution of the irradiated femtosecond laser light is determined by a coordinate axis having the center of the laser light as the origin, and the beam diameter of the light intensity distribution is given to be within the range of-0.5 to + 0.5 on the coordinate axis with respect to the shape of the light intensity distribution. The average light intensity AV0 in the coordinate axis range of-0.1 to + 0.1 is 70% to 99% of both the average light intensity AV-in the coordinate axis range of-0.3 to-0.1 and the average light intensity AV + in the coordinate axis range of + 0.1 to + 0.3.

Description

Technical Field

[0001] The present disclosure relates to a method for manufacturing an optical connecting component and the optical connecting component.

[0002] This application claims priority based on Japanese Patent Application No. 2023-026425, filed on February 22, 2023, the entirety of which is hereby incorporated by reference into this specification based on the contents thereof. Background Art

[0003] Generally speaking, optical connecting components are used as optical signal transceiver components in optical communications. Regarding the manufacturing method of the optical connecting component, for example, non-patent documents 1 to non-patent documents 5 disclose a technology for forming an optical waveguide based on a drawing method using a femtosecond laser light source. Specifically, non-patent document 1 discloses a technology for forming a core that becomes a waveguide by a single scan drawing of a femtosecond laser. In addition, non-patent document 2 discloses a technology for forming a core with a square cross-sectional shape by multiple scan drawings of a femtosecond laser. In addition, non-patent document 3 introduces a refractive index increase mechanism (compression) based on irradiation of a femtosecond laser, non-patent document 4 introduces a refractive index increase mechanism (rearrangement of composition) based on irradiation of a femtosecond laser, and non-patent document 5 introduces a mechanism for forming a nano-grating periodic structure based on irradiation of a femtosecond laser.

[0004] Prior art literature

[0005] Non-patent literature

[0006] Non-Patent Literature 1: Dezhi Tan, et al., “Femtosecond laser writing low-loss waveguides in silica glass: highly symmetrical mode field and mechanism of refractive index change,” Optical Materials Express, Vol. 11, No. 3, pp. 848-857.

[0007] Non-patent document 2: Y. Nasu, et al., “Low-loss waveguides written with femtosecond laser for flexible interconnection in a planar light-wave circuit”, Optics Letters, Vol. 30, pp. 723-725 (2005).

[0008] Non-patent document 3: ENG Lezer and E. Mazur, “Ultrafast-laser driven micro-explosions in transparent materials”, Appl. Phys. Lett. Vol. 71, No. 7, pp. 882-884 (1997).

[0009] Non-patent document 4: Y. Liu, et al., “Micromodification of element distribution in glass using femtosecond laser irradiation”, OPTICS LETTERS, Vol. 34, No. 2, pp. 136-138 (2009).

[0010] Non-patent document 5: Y. Shimotsuma, et al., “Self-organized nanogratings in glass irradiated by ultrashort light pulses”, PHYSICAL REVIEW LETTERS, Vol. 91, No. 24, pp. 247405-1 to 247405-4 (2003).

[0011] Non-Patent Document 6: S. Masaaki, et al., “Improved phase hologram design for generating symmetric light spots and its application for laser writing of waveguides,” OPTICS LETTERS, Vol. 36, No. 7, April 1, 2011, pp. 1065-1067.

[0012] Non-Patent Document 7: Keiji Fuse, “Beam Shaping for Advanced Laser Materials Processing,” Laser Technik Journal, pp. 19-22 (2015).

[0013] Non-Patent Literature 8: S. Hasegawa, et al., “Holographic vector wave femtosecond laser processing”, International Journal of Optomechatronics, p. 73 (2014).

[0014] Non-patent document 9: Payne. FP, et al., “A theoretical analysis of scattering loss from planar optical waveguides”, Optical and Quantum Electronics, vol. 26 (1994) pp. 977-986. Summary of the Invention

[0015] The manufacturing method of an optical connecting component disclosed herein comprises a preparation step, a laser irradiation step, and a focal point movement step. In the preparation step, a silica-based glass component is prepared. In the laser irradiation step, a femtosecond laser beam having energy to induce a light-induced refractive index change in the glass component and a pulse width of 500 fs or less after beam shaping is focused and irradiated into the interior of the glass component via a focusing lens. In the focal point movement step, the focal point position of the femtosecond laser beam is moved relative to the glass component. Furthermore, by linking the laser irradiation step and the focal point movement step, a continuous refractive index change region is formed within the glass component, functioning as an optical waveguide. The light intensity distribution of the irradiated femtosecond laser beam is determined by a coordinate axis with the center of the femtosecond laser beam as its origin, wherein the coordinate axis passes through the center of gravity of the femtosecond laser beam irradiation region at the focal point position and extends in a direction orthogonal to the direction of movement of the focal point position relative to the glass component. The shape of the light intensity distribution satisfies the following three conditions. The first condition is that the beam diameter of the femtosecond laser beam is given a range on the coordinate axis of greater than -0.5 and less than +0.5. The second condition is that the light intensity of the femtosecond laser be greater than that of a Gaussian beam with the same laser light intensity in the ranges from -∞ to -0.1 and +0.1 to +∞. The third condition is that the average light intensity AV0 in the range from -0.1 to +0.1 is 70% to 99% of both the average light intensity AV- in the range from -0.3 to -0.1 and the average light intensity AV+ in the range from +0.1 to +0.3. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a flowchart for explaining an example of a method for manufacturing the optical connecting component of the present disclosure.

[0017] Figure 2 This is a diagram for illustrating a configuration example of a manufacturing apparatus for implementing the manufacturing method of the optical connecting component disclosed herein and for explaining laser scanning.

[0018] Figure 3 These are diagrams used to explain various beam shaping optical systems and beam spot shapes.

[0019] Figure 4 It is a diagram showing the beam shape of a Gaussian beam used for forming an optical waveguide and the cross section of the formed optical waveguide.

[0020] Figure 5 This diagram shows the relationship between the beam shape of the laser light used in the manufacturing method of the present disclosure and the cross-sectional shape of the optical waveguide to be formed. DETAILED DESCRIPTION

[0021] [Problems to be Solved by the Present Disclosure]

[0022] The inventors investigated the aforementioned prior art and discovered the following problem. While the technique disclosed in Non-Patent Document 1 successfully formed an optical waveguide using a single scan of a femtosecond laser, it failed to control the waveguide's width. Consequently, the resulting waveguide was elongated relative to the laser irradiation axis, while its width was narrow to approximately 2 μm or less. Consequently, coupling loss of light propagating within the waveguide increased.

[0023] In contrast, the technology of non-patent document 2 has successfully formed an optical waveguide by multiple scanning strokes of a femtosecond laser. In the multiple scanning strokes, the femtosecond laser irradiated along the beam irradiation axis is scanned 20 times in a staggered manner in a direction orthogonal to the beam irradiation axis, thereby controlling the width of the optical waveguide. However, the time required to form an optical waveguide is 20 times longer than that required by a single scanning stroke. It should be noted that the following technology is introduced in non-patent document 6: using holographic technology, a femtosecond laser is used to generate multiple branch beams of diffracted light beams, and multiple optical waveguides are simultaneously produced in a glass component by irradiating these branch beams. In this way, in the technology of non-patent document 6, the optical waveguide is formed by only one scan, so it is difficult to maintain the necessary width of the optical waveguide, and there is a problem of a significant decrease in the productivity of the optical connection components containing the optical waveguide.

[0024] The present disclosure provides an optical connecting component and a method for manufacturing the optical connecting component, which facilitates the control of the shape of an optical waveguide provided in the optical connecting component and can significantly increase the productivity of the optical connecting component.

[0025] [Effects of the Present Disclosure]

[0026] According to the method for manufacturing an optical connecting component disclosed herein, the shape of the optical waveguide provided in the glass member can be easily controlled, and productivity can be significantly increased.

[0027] [Description of Embodiments of the Present Disclosure]

[0028] First, the contents of the embodiments of the present disclosure will be individually listed and described.

[0029] The manufacturing method of the optical connecting component disclosed in the present invention is as follows:

[0030] (1) A method for manufacturing an optical connecting component includes a preparation step, a laser irradiation step, and a light-converging point movement step. In the preparation step, a silica-based glass component is prepared. In the laser irradiation step, a femtosecond laser having energy that causes a light-induced refractive index change in the glass component and a pulse width of 500 fs or less after beam forming is focused and irradiated into the interior of the glass component via a focusing lens. In the light-converging point movement step, the light-converging point position of the femtosecond laser is moved relative to the glass component. In addition, by linking the laser irradiation step and the light-converging point movement step, a continuous refractive index change region that functions as an optical waveguide is formed inside the glass component. The light intensity distribution of the irradiated femtosecond laser light is determined by a coordinate axis with the center of the femtosecond laser light as the origin, wherein the coordinate axis passes through the center of gravity of the light-converging point region of the femtosecond laser light at the light-converging point position and extends in a direction orthogonal to the direction of movement of the light-converging point position relative to the glass component. The shape of the light intensity distribution satisfies the following three conditions. The first condition is that the beam diameter of the femtosecond laser light is given to a range on the coordinate axis that is greater than -0.5 and less than +0.5. The second condition is that the light intensity of the femtosecond laser be greater than that of a Gaussian beam with the same laser light intensity in the ranges from -∞ to -0.1 and +0.1 to +∞. The third condition is that the average light intensity AV0 in the range from -0.1 to +0.1 is 70% to 99% of both the average light intensity AV- in the range from -0.3 to -0.1 and the average light intensity AV+ in the range from +0.1 to +0.3.

[0031] This configuration facilitates control of the shape of the optical waveguide provided in the glass member and significantly increases productivity.

[0032] (2) In the above (1), the light intensity of the femtosecond laser light may be increased in the range of -∞ to -0.1 on the coordinate axis and in the range of +0.1 to +∞ on the coordinate axis compared to the light intensity of a Gaussian beam having the same laser light quantity. This configuration facilitates control of the shape of the optical waveguide provided in the glass member and significantly increases productivity.

[0033] (3) In the above (1) or (2), the shape of the light beam irradiation area at the focal point position may have a first maximum width Zd along the moving direction and a second maximum width Yd along a direction perpendicular to the moving direction, and a ratio Yd / Zd (the second maximum width Yd to the first maximum width Zd) may be greater than or equal to 2 and less than or equal to 15. In this case, the width of the optical waveguide formed by a single scan can be easily controlled.

[0034] (4) In any of (1) to (3) above, the optical system for beam shaping may be any one element selected from the group consisting of liquid crystal on silicon (LCoS), a diffractive optical element (DOE), an aspherical lens, and a cylindrical lens, or a combination of a plurality of elements selected from the group. In this case, the shape of the beam irradiation area at the focal point position can be shaped into any desired shape.

[0035] (5) In any of the above (1) to (4), the refractive index change region may be a quadrilateral in a plane perpendicular to the direction of movement of the focal point relative to the glass member. This rounds off the light intensity distribution of the propagation mode, thereby improving the coupling efficiency with a single-mode fiber (SMF).

[0036] The optical connection components disclosed herein are as follows:

[0037] (6) An optical connecting component manufactured by any one of the manufacturing methods described in (1) to (5), wherein the shape of the refractive index change region may be a quadrilateral in a plane perpendicular to the direction of movement of the focal point position relative to the glass component.

[0038] (7) In the above (6), the refractive index inside the quadrilateral may be uniform. This can reduce propagation loss.

[0039] Each aspect listed above in the [Description of Embodiments of the Present Disclosure] column can be applied to each of all the remaining aspects, or can be applied to all combinations of the remaining aspects.

[0040] [Details of the embodiments of the present disclosure]

[0041] The following describes in detail the manufacturing method and specific structure of the optical connecting component disclosed herein with reference to the accompanying drawings. It should be noted that the present disclosure is not limited to these examples but is set forth in the claims, which are intended to encompass all modifications within the meaning and scope of the claims. In the description of the drawings, identical elements are denoted by the same reference numerals, and duplicate descriptions are omitted.

[0042] Figure 1 This is a flowchart for explaining an example of a method for manufacturing the optical connecting component 100 of the present disclosure. Figure 2 This is a diagram for illustrating a configuration example of a manufacturing apparatus for implementing the manufacturing method of the optical connecting component 100 disclosed herein and for explaining laser scanning (in Figure 2 In Figure 2 The upper part (in Figure 2 In the figure, it is written as "structure") and shows an example of the structure of the manufacturing device. Figure 2 The lower part (in Figure 2 , denoted as “laser scanning”) shows the laser scanning in the laser irradiation process.

[0043] Figure 2 The manufacturing device shown in the upper part includes a femtosecond laser 20, a laser driving unit 25 for driving the femtosecond laser 20, a beam shaping optical system 30 for shaping the beam spot of the femtosecond laser into an arbitrary shape, an XYZ stage 40, a stage driving unit 45 for driving the XYZ stage 40, and a control unit 50 for controlling the operation of these parts.

[0044] The laser driving unit 25 controls the power and repetition frequency of the pulsed laser (hereinafter referred to as "femtosecond laser") output from the femtosecond laser 20 according to the instructions from the control unit 50. As a result, the femtosecond laser 20 can output a femtosecond laser having a pulse width of several hundred femtoseconds or less. In particular, the femtosecond laser with a pulse width of several hundred femtoseconds or less can have a peak power of 10 5 W / cm 2 Above. In addition, in order to make the refractive index and structure of the optical waveguide formed inside the glass material smooth, the repetition frequency of the output femtosecond laser can be 10kHz or more. The glass component 10 to be the main body of the optical component is placed on the device mounting surface of the XYZ stage 40. The glass component 10 is a glass that can produce a refractive index change Δnp caused by pressure or both Δnp and a refractive index change Δnd caused by structure by laser irradiation, such as silica-based glass. Silica-based glass refers to glass with silicon dioxide (SiO2) as the main component and contains more than 50% SiO2. It can be undoped glass, germanium (Ge)-doped glass, co-doped glass of Ge and boron (B), etc. More specifically, it can be glass that does not contain dopants other than Ge, or glass co-doped with B and Ge. In addition, these glasses can also be quartz glass, phosphate glass, halide glass, and sulfide glass. The femtosecond laser light output from the femtosecond laser 20 is focused by the beam shaping optical system 30 onto the interior of the glass member 10 disposed on the XYZ stage 40, that is, onto a focal point 35 located on the YZ plane. This forms a refractive index variation region 15 serving as an optical waveguide within the glass member 10, resulting in the optical connecting component 100. It should be noted that the axis along the laser scanning direction is defined as the Z axis. The axis perpendicular to the Z axis and perpendicular to the laser irradiation surface of the glass member 10 is defined as the X axis. The axis perpendicular to the scanning direction and perpendicular to both the Z and X axes is defined as the Y axis.

[0045] The stage driving unit 45 drives the XYZ stage 40 according to the instruction from the control unit 50, so that the device mounting surface of the XYZ stage 40 moves along the X-axis direction, the Y-axis direction and the Z-axis direction. Figure 2 During the laser scanning shown in the lower section, the position of the focal point 35 of the femtosecond laser moves relative to the glass member 10. The control unit 50 controls the actions of the laser driver 25 and the stage driver 45 as described above to create a refractive index change region 15 with an arbitrary pattern within the glass member 10. It should be noted that the arbitrary pattern corresponds to the shape of the optical waveguide projected onto the YZ plane, taking into account the depth information of the X axis. Through the above steps, the optical connecting component 100, which serves as an optical component, is manufactured.

[0046] Next, the optical connecting component 100 provided with an optical waveguide is manufactured using the manufacturing apparatus having the above-described structure. Figure 1 The flowchart of FIG. 1 illustrates the manufacturing method of the optical connecting component 100 of the present disclosure. It should be noted that in the following description, as an example of the manufacturing method of the optical connecting component 100, the case of manufacturing a three-dimensional optical waveguide device having a refractive index change region 15 with an arbitrary pattern to become an optical waveguide is described.

[0047] The manufacturing method of the optical connecting component 100 of the present disclosure comprises a preparation step and an optical waveguide manufacturing step. First, in the preparation step, a parallel plate glass is prepared as the glass member 10 to be the optical connecting component 100 (step ST10).

[0048] In the optical waveguide manufacturing process, a refractive index change region 15 of an arbitrary pattern forming an optical waveguide is formed inside the prepared glass component 10. Specifically, after step ST10 is completed, the prepared glass component 10 is immediately placed on the device mounting surface of the XYZ stage 40 and irradiated with a femtosecond laser (step ST20). The control unit 50 controls the laser driving unit 25 so that a femtosecond laser having energy that causes a light-induced refractive index change inside the glass component 10 and a repetition frequency of 10 kHz or more is output from the femtosecond laser 20. The femtosecond laser output from the femtosecond laser 20 is focused into the interior of the glass component 10 by the beam shaping optical system 30. It should be noted that the beam shaping optical system 30 shapes the beam spot of the input femtosecond laser into a predetermined shape. A light-induced refractive index change is formed in the beam irradiation area at the focal point 35 of the femtosecond laser. When the laser irradiation of the predetermined portion of the glass member 10 is completed, the control unit 50 controls the stage driving unit 45 to move the position of the glass member 10 provided on the device mounting surface of the XYZ stage 40 (step ST30). Figure 2 As shown in the lower section, the position of the glass member 10, the position of the focal point 35 of the femtosecond laser, or both the setting position and the focal point position are continuously or intermittently changed, thereby moving the position of the focal point 35 of the femtosecond laser inside the glass member 10.

[0049] It should be noted that the laser irradiation process of step ST20 and the light-converging point moving process of step ST30, that is, the operation control of the laser driving unit 25 and the stage driving unit 45 by the control unit 50, are returned to the state in which the laser irradiation process of step ST20 and the light-converging point moving process of step ST30 are returned to the state in which the laser irradiation process of step ST20 and the light-converging point moving process of Figure 1 At the time indicated by point C in FIG, the irradiation conditions are changed or repeated under the same conditions until the pre-designed optical waveguide pattern is formed within the glass member 10 (step ST40). When the refractive index change region 15 of the glass member 10 is formed (step ST40), the glass member 10 is annealed to perform an aging treatment, etc., to maintain a long-term change in the refractive index (step ST50). After the above steps, an optical connecting component having an internal optical waveguide is obtained.

[0050] Regarding the beam shaping optical system 30, for example, Figure 3 As shown in FIG, the optical system including aspheric lenses, the optical system composed of a focusing lens and a cylindrical lens, DOE (Diffractive Optical Element), etc. DOE includes LCoS (Liquid Crystal on Silicon). Here, the glass type with fixed refractive index modulation is called DOE, and the LCoS with variable refractive index modulation is called holographic optical element. It should be noted that in Figure 3 The top section (in Figure 3 In FIG, “aspheric lens” is referred to as “aspheric lens”) and shows the structure of the optical system including the aspheric lens 110. Figure 3 The second paragraph (in Figure 3 In FIG, it is written as "cylindrical lens + focusing lens" to show the composition of the optical system composed of a cylindrical lens and a focusing lens. Figure 3 The third paragraph (in Figure 3 In FIG, “DOE” is shown as a “DOE”) showing the structure of the optical system including the DOE. Figure 3 The bottom section (in Figure 3 , referred to as "holographic optical element") shows the structure of an optical system including a holographic optical element.

[0051] Figure 3The first optical system utilizing an aspheric lens, shown in the top section, includes an aspheric lens 110. It should be noted that a beam shaper 111 may be provided upstream or downstream of the aspheric lens 110 as needed. The total light intensity distribution (hereinafter referred to simply as "light intensity distribution") of the femtosecond laser light output from the aspheric lens 110 is defined at the beam waist BW, which is located at the focal point 35 and is included in the YZ plane. Furthermore, the femtosecond laser beam spot corresponds to a beam irradiation area 350 having a first maximum width Zd along the Z-axis and a second maximum width Yd (≥Zd) along the Y-axis.

[0052] Figure 3 The second optical system composed of a focusing lens and a cylindrical lens shown in the second paragraph includes a focusing lens 121 and a cylindrical lens 122. Like the above-mentioned "aspheric lens" optical system, it outputs a femtosecond laser having a beam spot having a beam irradiation area 350 with a width Yd along the Y-axis direction and a width Zd (≤Yd) along the Z-axis direction.

[0053] Figure 3 The third optical system composed of a focusing lens and a DOE shown in the third section includes a DOE 131 and a focusing lens 132. The DOE 131 inputs the femtosecond laser from the femtosecond laser 20 and outputs a group of branched beams with various beam arrangement patterns. The focusing lens 132 focuses the multiple branched beams output from the DOE 131 into the interior of the glass member 10 while maintaining the beam arrangement pattern. Figure 3 The fourth optical system composed of a focusing lens and a holographic optical element shown in the bottom section includes an LCoS 141 as a holographic optical element and a focusing lens 142. The LCoS 141 inputs a femtosecond laser from the femtosecond laser 20 and outputs a branch beam group with various beam arrangement patterns. The focusing lens 142 focuses the multiple branch beams output from the LCoS 141 into the interior of the glass member 10 while maintaining the beam configuration pattern. For example, when five branch beams are output from the DOE 131 or the LCoS 141, as shown in FIG. Figure 3 As shown in the third and right sides of the bottom section of FIG, the beam spots #1 to #5 of these branched beams can be spatially separated so that the centers of the spots are arranged along the Y-axis direction. In this case, the beam spots #1 to #5 constitute the beam irradiation area 350.

[0054] As described above, it is known that a refractive index variation region that serves as an optical waveguide can be formed within a glass member by a drawing method using a femtosecond laser light source (Non-Patent Documents 3 and 4). Furthermore, it has been proposed to improve productivity by branching a femtosecond laser into a plurality of diffracted beams using a holographic diffraction element or the like, and simultaneously forming a plurality of optical waveguides using each of the plurality of branched beams composed of these diffracted beams (Non-Patent Document 6).

[0055] On the other hand, in an embodiment of the present disclosure, the light beam irradiation area 350 is defined on the beam waist BW included in the YZ plane where the focal point 35 exists. In this light beam irradiation area 350, the focusing power in the Z-axis direction is set to the diffraction limit or near it. In contrast, the focusing power in the Y-axis direction is set to be weaker than the focusing power in the Z-axis direction. For example, when the beam diameter in the Z-axis direction is set to 1, the beam diameter in the Y-axis direction is greater than 2 and less than 15, that is, the ratio Yd / Zd is greater than 2 and less than 15. The beam diameter defined along the Y-axis direction on the beam waist BW, that is, the beam width is 1 / e of the maximum light intensity that exists across the center of the beam. 2 The distance between the locations.

[0056] Specifically, femtosecond laser Figure 3 The beam shaping optical system 30 shown focuses light to the inside of the glass component 10, and forms a refractive index change region 15 inside the glass component 10 by driving the XYZ stage 40. The wavelength of the laser is, for example, in the range of -10 nm to +10 nm based on 1030 nm, or in the range of -10 nm to +10 nm based on 1060 nm, or in the range of second harmonic generation (SHG) of each wavelength range, or third harmonic generation (THG) of each wavelength range. The pulse width of the laser is less than 500 fs. The repetition frequency is greater than 100 kHz and less than 5 MHz. Below, Figure 4 An example of Gaussian beam irradiation is shown in FIG. Figure 5 An example of an embodiment of the present disclosure is shown in FIG.

[0057] Figure 4 is a diagram showing the beam shape of a Gaussian beam used for forming an optical waveguide and the cross section of the formed optical waveguide (in Figure 5 In

[15] , it is referred to as "Formation of optical waveguide (Gaussian beam)"). Figure 4 The upper part (in Figure 4 In FIG, “beam shape” is indicated as “beam shape”) showing a beam irradiation area 350 of a Gaussian beam defined on the YZ plane, a light intensity distribution 350Y along the central axis of the beam irradiation area 350 parallel to the Y axis, and a light intensity distribution 350Z along the central axis of the beam irradiation area 350 parallel to the Z axis. Figure 4 The lower part (in Figure 4 , denoted as "cross section of optical waveguide") shows the cross section of the optical waveguide having Figure 4 The cross section of the optical waveguide formed by the irradiation of the light beam with the light intensity distribution shown in the upper section is along Figure 2 The lower section shows a cross section of the II line optical waveguide.

[0058] like Figure 4 As shown in the upper part of FIG, the beam irradiation area 350 defined on the beam waist BW is Figure 3 The beam shaping optical system 30 shown performs beam shaping. That is, the femtosecond laser irradiated to the interior of the glass component 10 is a Gaussian beam whose beam diameter along the Z-axis direction is set to about 1 μm or less and whose beam diameter along the Y-axis direction is set to 2 μm or more and 10 μm or less. The Gaussian beam itself has a light intensity distribution 350Y along the Y-axis direction and a light intensity distribution 350Z along the Z-axis direction. It should be noted that the light intensity distribution 350Y is a light intensity distribution centered on the axis AXz parallel to the Z axis of the two axes orthogonal to the center of gravity of the beam irradiation area 350, and the light intensity distribution 350Z is a light intensity distribution centered on the axis AXy parallel to the Y axis. By irradiating this Gaussian beam, a light having Figure 4 The refractive index change region 150 has a cross-sectional shape shown in the lower section. The refractive index change region 150 functions as an optical waveguide. Figure 4 In the example shown in the lower section, the NA (Numerical Aperture) of the focusing lens used in the beam shaping optical system 30 is 0.40 to 0.55. The wavelength of the incident light beam is 1030 nm, or 515 nm for its SHG. The pulse width is 100 fs to 450 fs. The scanning speed is 0.01 mm / sec to 10 mm / sec. The pulse energy is 30 nJ to 1000 nJ. The repetition frequency is 100 kHz to 5 MHz. The position of the focal point 35 is set at a depth of 50 μm to 250 μm from the surface of the glass member 10.

[0059] according to Figure 4 From the cross-sectional shape of the refractive index change region 150 shown in the lower section, it can be seen that a single beam scan resulted in a 9.2 μm optical waveguide width. It can be seen that by adjusting the laser power, the optical waveguide width can be controlled to be greater than 3 μm and less than 10 μm. It should be noted that Figure 4 In the light intensity distribution 350Y in the Y-axis direction shown in the upper section, the outline of the refractive index change region 150 formed by irradiation with a Gaussian beam is shown by a dotted line for reference. That is, the outline of the refractive index change region 150 is superimposed on the light intensity distribution 350Y in the Y-axis direction according to the scale. It can be seen from this that there is a modification threshold for forming a modified region that becomes the refractive index change region 150 inside the glass component 10, and the cross-sectional shape of the refractive index change region 150 is roughly consistent with the shape of the light intensity distribution 350Y, except for the central portion extending along the X-axis direction. On the other hand, Figure 4The cross-sectional shape of the refractive index variation region 150 shown in the lower section is elongated in the X-axis direction. Consequently, high-order modes are generated in the X-axis direction, making it unusable for single-mode optical waveguides. Therefore, it is necessary to set an appropriate laser intensity that takes this modified shape into account.

[0060] Furthermore, as described above, the central portion of refractive index variation region 150 exhibits a more significantly modified shape compared to the shape of light intensity distribution 350Y. In particular, as described in Non-Patent Documents 3 and 4, it is known that electrons excited by multiphoton absorption on the side irradiated with laser light further increase in number due to nonlinear absorption. Therefore, it is speculated that the high light intensity distribution in the central region, due to absorption of the irradiated laser light, further modifies the shape.

[0061] When the laser is irradiated to the interior of the glass component 10 under the above conditions, an irradiation side modification region different from the refractive index change region 150 is generated on the irradiation side of the laser. It is known that a nano grating of about several hundred nm is formed in the irradiation side modification region, and the nano grating is formed perpendicularly to the polarization of the irradiated laser (non-patent document 5). It should be noted that the beam shaping technology is disclosed in non-patent document 7, and the formation of the nano grating by relying on the polarization of multiple light beams after multi-branching is pointed out in non-patent document 8. Therefore, the refractive index change region 150 is set as an optical waveguide, and the irradiation side modification region located on the irradiation side of the laser can be regarded as an optical cladding. Due to the existence of the nano grating with periodic refractive index fluctuations of the optical cladding, there is a problem of increasing the propagation loss. It should be noted that the relationship between the propagation loss and the different periods of the refractive index is disclosed in non-patent document 9.

[0062] Figure 5 The relationship between the beam shape of the laser beam used in the manufacturing method of the present disclosure and the cross-sectional shape of the optical waveguide formed is shown in FIG. Figure 5 In the embodiment, it is described as "Formation of optical waveguide (this embodiment)"). Figure 5 The upper part (in Figure 5 In the figure, the light intensity distribution in the Y-axis direction is shown as Figure 4 The light intensity distribution 350Y shown in the upper section corresponds to the light intensity distribution 350P of the laser light used in the method for manufacturing the optical waveguide of the present disclosure. Figure 5 The lower part (in Figure 5 , denoted as "cross section of optical waveguide") shows the cross section of the optical waveguide having Figure 5 The cross section of the optical waveguide formed by the irradiation of the light beam with the light intensity distribution shown in the upper section is along Figure 2 The lower section shows a cross section of the II line optical waveguide.

[0063] like Figure 4 As shown in the upper portion of FIG, the shape of the refractive index change region 150 formed by laser irradiation matches the shape of the light intensity distribution 350Y in the Y-axis direction, except for the central portion. This means that by adjusting the shape of the intensity distribution of the irradiated femtosecond laser light, the cross-sectional shape of the refractive index change region 15 formed within the glass member 10 by laser irradiation can be controlled to a desired shape.

[0064] In the embodiments of the present disclosure, Figure 5 As shown in the upper part of FIG, the femtosecond laser irradiated to the glass member 10 has a light intensity distribution 350P in the Y-axis direction. The light intensity distribution 350P of the femtosecond laser is defined by a coordinate axis with the position of the axis AXz representing the center of the femtosecond laser as the origin, wherein the coordinate axis passes through the center of gravity of the femtosecond laser beam irradiation area 350 at the position of the focal point 35 and extends along the Y-axis direction orthogonal to the scanning direction. In addition, on the coordinate axis along the Y-axis, the beam diameter of the femtosecond laser is given in the range of greater than -0.5 and less than +0.5. That is, 1 / e of the maximum light intensity of the beam will be 2 The beam width at the position is set to 1. In addition, based on the light intensity distribution 350Y in the Y-axis direction of the Gaussian beam shown by the dotted line, the light intensity distribution 350P bulges in the direction indicated by the arrow S2 in the range of -∞ to -0.1, is recessed in the direction indicated by the arrow S1 in the range of -0.1 to +0.1, and bulges in the direction indicated by the arrow S2 in the range of +0.1 to +∞.

[0065] More specifically, in light intensity distribution 350P, the light intensity of the femtosecond laser increases in the range of -∞ to -0.1 and the range of +0.1 to +∞ compared to the light intensity of a Gaussian beam with the same laser light quantity. Furthermore, the average light intensity AV0 in the range of -0.1 to +0.1 can be within a range of 70% to 99% of both the average light intensity AV- in the range of -0.3 to -0.1 and the average light intensity AV+ in the range of +0.1 to +0.3.

[0066] By setting the light intensity distribution 350P of the irradiated femtosecond laser light to the above range, the cross-sectional shape of the refractive index change region 15 formed inside the glass member 10 can be changed from Figure 5The shape of the refractive index change region 150 shown on the left side of the cross-sectional shape shown in the lower section is close to the cross-sectional shape of the refractive index change region 15B shown on the right side. That is, the refractive index change region 150 shown on the left side is provided with an oblique line region 150A extending in the X-axis direction. This causes the generation of high-order modes in the X-axis direction. On the other hand, when the average light intensity AV0 in the range of -0.1 to +0.1 is set to less than 99% of the average light intensity AV- in the range of -0.3 to -0.1 and the average light intensity AV+ in the range of +0.1 to +0.3, as shown in FIG. Figure 5 The portion of the oblique line region 150A corresponding to the refractive index change region 150 on the left can be reduced, as shown in the lower section and the center of the refractive index change region 15A. － If both AV and AV+ are low, Figure 5 The formation of the portion of the oblique line region 150A corresponding to the refractive index change region 150 on the left can also be reduced, just like the refractive index change region 15B shown in the lower section and on the right side. That is, an optical waveguide can be manufactured in which the cross-sectional shape of the refractive index change region 15 is a quadrilateral. As a result, the light intensity distribution of the propagation mode is rounded, and the coupling efficiency with the SMF can be improved. In addition, the width required for the cross-sectional shape of the refractive index change region 15 can be maintained, thereby increasing the productivity of the optical waveguide. In the multiple scanning drawing method, when the core is scanned horizontally, the etching shape of the modified layer inside the core is reflected to present a comb-tooth shape parallel to the direction of the light beam irradiation axis. The etching shape inside the core of this method does not present a comb-tooth shape, but presents a boundary with or without modification, and its interior is etched in a manner with a uniform refractive index. As a result, the propagation loss can be reduced.

[0067] Description of Reference Numerals

[0068] 10: Glass components;

[0069] 15, 15A, 15B: refractive index change region;

[0070] 20: Femtosecond laser;

[0071] 25: laser driver;

[0072] 30: beam shaping optical system;

[0073] 35: Spotlight;

[0074] 40: XYZ stage;

[0075] 45: stage driving unit;

[0076] 50: Control Department;

[0077] 100: optical connection components;

[0078] 110: Aspheric lens;

[0079] 111: beam shaper;

[0080] 121: focusing lens;

[0081] 122: cylindrical lens;

[0082] 131:DOE;

[0083] 132: focusing lens;

[0084] 141:LCoS;

[0085] 142: focusing lens;

[0086] 350: beam irradiation area;

[0087] 350Y, 350Z, 350P: light intensity distribution; #1 to #5: beam spot;

[0088] BW: waistband.

Claims

1. A method for manufacturing an optical connecting component, comprising: A preparation step of preparing a silica-based glass component; a laser irradiation step of irradiating the interior of the glass member with a femtosecond laser having an energy that causes a light-induced refractive index change in the glass member and a beam-shaped pulse width of 500 fs or less through a focusing lens; and The focusing point moving step is to move the focusing point position of the femtosecond laser relative to the glass member. The laser irradiation step and the light-converging point movement step are linked together to form a continuous refractive index change region inside the glass member. The light intensity distribution of the femtosecond laser is determined by a coordinate axis with the center of the femtosecond laser as the origin, wherein: The coordinate axis passes through the center of gravity of the femtosecond laser beam irradiation region at the focal point position and extends in a direction orthogonal to the moving direction of the focal point position relative to the glass member. Regarding the shape of the light intensity distribution, the beam diameter of the femtosecond laser is given a range on the coordinate axis of not less than -0.5 and not more than +0.

5. The average light intensity AV0 in the range of -0.1 to +0.1 on the coordinate axis is 70% to 99% of both the average light intensity AV- in the range of -0.3 to -0.1 and the average light intensity AV+ in the range of +0.1 to +0.3 on the coordinate axis.

2. The method for manufacturing an optical connecting component according to claim 1, wherein: In the range of −∞ to −0.1 on the coordinate axis and the range of +0.1 to +∞ on the coordinate axis, the light intensity of the femtosecond laser light increases compared to the light intensity of a Gaussian beam with the same laser light amount.

3. The method for manufacturing an optical connecting component according to claim 1 or 2, wherein: The shape of the light beam irradiation area at the focal point position has a first maximum width Zd along the moving direction and a second maximum width Yd along a direction perpendicular to the moving direction. A ratio Yd / Zd of the second maximum width Yd to the first maximum width Zd is greater than or equal to 2 and less than or equal to 15.

4. The method for manufacturing an optical connecting component according to any one of claims 1 to 3, wherein: The optical system for beam shaping includes at least one of a diffractive optical element (DOE), an aspherical lens, and a cylindrical lens.

5. The method for manufacturing an optical connecting component according to any one of claims 1 to 4, wherein: The refractive index change region has a quadrilateral shape within a plane perpendicular to a moving direction of the light-converging point position with respect to the glass member.

6. An optical connecting component manufactured by the method for manufacturing an optical connecting component according to any one of claims 1 to 5, wherein: The refractive index change region has a quadrilateral shape within a plane perpendicular to a moving direction of the light-converging point position with respect to the glass member.

7. The optical connecting component according to claim 6, wherein: The refractive index inside the quadrilateral is uniform.

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