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WO2024176840A1 - Composant de connexion optique et procédé de fabrication de composant de connexion optique - Google Patents

Composant de connexion optique et procédé de fabrication de composant de connexion optique Download PDF

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Publication number
WO2024176840A1
WO2024176840A1 PCT/JP2024/004200 JP2024004200W WO2024176840A1 WO 2024176840 A1 WO2024176840 A1 WO 2024176840A1 JP 2024004200 W JP2024004200 W JP 2024004200W WO 2024176840 A1 WO2024176840 A1 WO 2024176840A1
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Prior art keywords
glass member
refractive index
optical waveguide
optical
region
Prior art date
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PCT/JP2024/004200
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English (en)
Japanese (ja)
Inventor
重博 長能
学 塩▲崎▼
哲也 中西
芳夫 早崎
智士 長谷川
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Utsunomiya University
Sumitomo Electric Industries Ltd
Original Assignee
Utsunomiya University
Sumitomo Electric Industries Ltd
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Application filed by Utsunomiya University, Sumitomo Electric Industries Ltd filed Critical Utsunomiya University
Priority to CN202480013019.1A priority Critical patent/CN120712503A/zh
Priority to JP2025502262A priority patent/JPWO2024176840A1/ja
Publication of WO2024176840A1 publication Critical patent/WO2024176840A1/fr
Anticipated expiration legal-status Critical
Pending legal-status Critical Current

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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
    • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
    • G02B6/122—Basic optical elements, e.g. light-guiding paths
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
    • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
    • G02B6/13—Integrated optical circuits characterised by the manufacturing method

Definitions

  • the present disclosure relates to an optical connecting component and a method for manufacturing an optical connecting component.
  • Non-Patent Documents 1 to 5 disclose a method for manufacturing such optical connection parts, which is a technique for forming an optical waveguide by a drawing method using a femtosecond laser light source.
  • Non-Patent Document 1 discloses a technique for forming a core that becomes a waveguide by single-scan drawing with femtosecond laser light.
  • Non-Patent Document 2 discloses a technique for forming a core having a square cross-sectional shape by multi-scan drawing with femtosecond laser light.
  • Non-Patent Document 3 discloses a technique for forming a core that becomes an optical waveguide by using multiple branched beams of the same polarization.
  • Non-Patent Document 4 introduces a mechanism for increasing the refractive index by irradiation with femtosecond laser light (compression)
  • Non-Patent Document 5 introduces a mechanism for increasing the refractive index by irradiation with femtosecond laser light (rearrangement of composition)
  • Non-Patent Document 6 introduces a mechanism for forming a nano-grating periodic structure by irradiation with femtosecond laser light.
  • Non-Patent Document 7 also introduces a technique for creating three optical waveguides simultaneously by using multi-point irradiation with a hologram. Note that the technique in Non-Patent Document 8 can be used for beam shaping, and Non-Patent Document 9 reports the formation of a polarization-dependent nanograting by controlling the polarization of a multi-branched beam using two LCoS sheets.
  • the optical connection component disclosed herein comprises a silica-based glass member and an optical waveguide disposed inside the glass member and having a refractive index higher than that of the glass member.
  • one or more modified regions having a refractive index lower than that of the glass member excluding the optical waveguide are formed in the upper layer region of the glass member, and the average correlation length of the nanograting formed in the layer composed of the one or more modified regions is shorter than 100 nm.
  • FIG. 1 is a flow chart for explaining an example of a manufacturing method for an optical connecting component according to the present disclosure.
  • FIG. 2 is a diagram showing an example of the configuration of a manufacturing apparatus for carrying out the manufacturing method of the optical connecting component of the present disclosure.
  • FIG. 3 is a diagram for explaining various beam shaping optical systems.
  • FIG. 4 is a diagram for explaining laser light scanning for forming an optical waveguide and for explaining one configuration example of an optical connecting part to be manufactured.
  • FIG. 5 is a diagram showing the observation result of the modified shape in the cross section of the optical waveguide.
  • FIG. 6 is a diagram showing the results of calculations for evaluating the side roughness of an optical waveguide.
  • Non-Patent Document 1 has succeeded in forming an optical waveguide by single-scan drawing of femtosecond laser light, but the width of the optical waveguide is not controlled. That is, the shape of the obtained optical waveguide is long with respect to the laser irradiation axis, while the lateral direction of the optical waveguide is narrow, about 2 ⁇ m or less. This increases the coupling loss of light propagating through the optical waveguide.
  • Non-Patent Document 7 discloses a technique in which a single laser beam is divided into multiple diffracted light beams by combining a femtosecond laser and a hologram technique, and multiple optical waveguides are simultaneously written using these multiple diffracted light beams.
  • the sufficient width of the optical waveguide cannot be maintained, so that the coupling loss of light propagating through the optical waveguide increases.
  • Non-Patent Document 2 has succeeded in forming an optical waveguide by multi-scan drawing with femtosecond laser light.
  • multi-scan drawing the femtosecond laser light irradiated along the beam irradiation axis is scanned 20 times while being shifted in a direction perpendicular to the beam irradiation axis, thereby controlling the width of the optical waveguide.
  • the time required to form one optical waveguide is 20 times longer than that of single-scan drawing, which poses the problem of a significant decrease in the productivity of optical connection parts including optical waveguides.
  • the present disclosure provides an optical connection component in which the propagation loss in the optical waveguide is effectively reduced, and provides a manufacturing method for an optical connection component that makes it easy to control the shape of the optical waveguide provided in the optical connection component and allows the productivity of the optical connection component to be significantly increased.
  • an optical connection component can be obtained in which the propagation loss in the optical waveguide is effectively reduced.
  • it is possible to easily control the shape of the optical waveguide provided in the optical glass member and to significantly increase the productivity.
  • the optical connecting part of the present disclosure includes: (1) A silica-based glass member and an optical waveguide provided inside the glass member and having a refractive index higher than that of the glass member.
  • one or more modified regions having a refractive index lower than that of the glass member excluding the optical waveguide are formed in the upper layer region of the glass member, and the average correlation length of the nanograting formed in the layer composed of the one or more modified regions is controlled to be shorter than 100 nm.
  • the upper layer region of the glass member is defined as a region located between the optical waveguide and the laser irradiation surface of the glass member irradiated with laser light for forming the optical waveguide, for example, femtosecond laser light, in a cross section of the glass member perpendicular to the longitudinal direction of the optical waveguide.
  • the correlation length of the nanograting means the periodic length of the periodic refractive index fluctuation with respect to the propagation axis coinciding with the longitudinal direction of the optical waveguide in one or more modified regions.
  • a layer composed of one or more modified regions is generated in a region that can be substantially regarded as an optical cladding, and in this optical cladding, various nanogratings having periodicity along the longitudinal direction of the optical waveguide, a direction perpendicular to the longitudinal direction, and a direction inclined to the longitudinal direction, and nanostructures with random periodic directions are formed.
  • nanogratings and nanostructures in the layer composed of such modified regions greatly affects the increase in propagation loss of the optical waveguide in the optical connection component.
  • the average correlation length of the nanogratings formed in the layer of the modified region is controlled to 100 nm or less, and this configuration effectively reduces the increase in propagation loss of the optical waveguide formed in the glass member.
  • one or more modified regions are also created in the upper layer of the actual optical cladding, and in some cases, the various nanogratings and nanostructures with random periodic directions described above are present in some of the interior.
  • the number of modified regions that can be confirmed in the cross section of the glass member may be 100 or less. In this case, too, the increase in propagation loss of the optical waveguide formed in the glass member is effectively reduced.
  • the method for producing an optical connection component includes: (3) The method includes a preparation step, a laser irradiation step, and a focal point moving step.
  • a silica-based glass member is prepared.
  • a laser irradiation step a femtosecond laser with a pulse width of 500 fs or less is used, which has an energy amount that causes a change in the refractive index of the glass member due to photo-induced induction.
  • the plurality of branched beams are condensed and irradiated inside the glass member through a condenser lens.
  • the focal point positions of the plurality of branched beams are moved relative to the glass member.
  • the polarizations of adjacent diffracted beams among the diffracted beams that respectively constitute the plurality of branched beams are different.
  • the beam shaping element may be a DOE (Diffractive Optical Element).
  • DOEs include LCoS (Liquid Crystal on Silicon).
  • a glass type with non-variable refractive index modulation is referred to as a DOE, and a variable type is referred to as an LCoS.
  • LCoS Light Crystal on Silicon
  • the beam shaping element may be composed of multiple LCoS or multiple glass-type DOEs. This configuration makes it possible to selectively change the polarization state of the diffracted light of the multiple branched beams.
  • FIG. 1 is a flow chart for explaining an example of a method for manufacturing the optical connection part 100 of the present disclosure.
  • FIG. 2 is a diagram showing an example of the configuration of a manufacturing device for carrying out the method for manufacturing the optical connection part 100 of the present disclosure.
  • the manufacturing apparatus shown in FIG. 2 includes a femtosecond laser 20, a laser driver 25 for driving the femtosecond laser 20, a beam shaping optical system 30 for shaping the beam spot of the femtosecond laser light into an arbitrary shape, an XYZ stage 40, a stage driver 45 for driving the XYZ stage 40, and a controller 50 for controlling the operation of each of these components.
  • the laser driver 25 controls the power and repetition frequency of the pulsed laser light (hereinafter, referred to as "femtosecond laser light”) output from the femtosecond laser 20 according to instructions from the controller 50.
  • femtosecond laser light the pulsed laser light
  • the femtosecond laser 20 output femtosecond laser light having a pulse width of several hundred femtoseconds or less.
  • the femtosecond laser light having a pulse width set to several hundred femtoseconds or less can have a peak power of 10 5 W/cm 2 or more.
  • the repetition frequency of the output femtosecond laser light may be 10 kHz or more in order to smooth the refractive index and structure of the optical waveguide formed inside the glass material.
  • a glass member 10 to be the main body of the optical component is placed on the device mounting surface of the XYZ stage 40.
  • the glass member 10 is a silica-based glass that can generate a pressure-induced refractive index change ⁇ np and both ⁇ np and structure-induced refractive index change ⁇ nd by laser light irradiation.
  • Silica-based glass is a glass mainly composed of silicon dioxide (SiO 2 ) and contains 50% or more of SiO 2. For example, it may be glass without impurities, germanium (Ge)-doped glass, or glass co-doped with Ge and boron (B). These glasses may also be silica-based glass, phosphate-based glass, halide glass, or sulfide glass.
  • the femtosecond laser light output from the femtosecond laser 20 is focused by the beam shaping optical system 30 on the inside of the glass member 10 placed on the XYZ stage 40, that is, on the focusing point 35 located on the YZ plane.
  • a refractive index change region 15 is formed as an optical waveguide inside the glass member 10, and an optical connection part 100 is obtained.
  • the stage driver 45 drives the XYZ stage 40 in accordance with instructions from the controller 50 so that the device mounting surface of the XYZ stage 40 moves along the X-axis, Y-axis, and Z-axis directions.
  • This configuration enables laser scanning, and the position of the focal point 35 of the femtosecond laser light moves relative to the glass member 10.
  • the controller 50 controls the operations of the laser driver 25 and the stage driver 45 as described above, thereby creating a refractive index change region 15 of an arbitrary pattern inside the glass member 10.
  • the arbitrary pattern corresponds to the shape of the optical waveguide projected onto the YZ plane taking into account the depth direction information of the X-axis.
  • an optical connection part 100 provided with an optical waveguide is manufactured using a manufacturing apparatus having the above-described structure.
  • the manufacturing method of the optical connection part 100 disclosed herein will be described with reference to the flowchart of FIG. 1.
  • a case will be described in which a three-dimensional optical waveguide device is manufactured in which a refractive index change region 15 of an arbitrary pattern that serves as an optical waveguide is fabricated.
  • the manufacturing method of the optical connection part 100 disclosed herein is composed of a preparation process and an optical waveguide manufacturing process.
  • a glass member 10 such as a parallel plate glass, that will become the optical connection part 100 is prepared (step ST10).
  • a refractive index change region 15 of an arbitrary pattern that will become an optical waveguide is fabricated inside the prepared glass member 10.
  • the prepared glass member 10 is immediately placed on the device mounting surface of the XYZ stage 40 after completion of step ST10, and is irradiated with femtosecond laser light (step ST20).
  • the control unit 50 controls the laser driving unit 25 so that femtosecond laser light having an energy amount that causes a photoinduced refractive index change inside the glass member 10 and a repetition frequency of 10 kHz or more is output from the femtosecond laser 20.
  • the femtosecond laser light output from the femtosecond laser 20 is focused inside the glass member 10 by the beam shaping optical system 30.
  • the beam shaping optical system 30 shapes the beam spot of the input femtosecond laser light into a predetermined shape.
  • a photoinduced refractive index change is formed in the beam irradiation region at the focusing point 35 of this femtosecond laser light.
  • the position of the installation position of the glass member 10, the position of the focal point 35 of the femtosecond laser light, or both the installation position and the focal point position are continuously or intermittently changed, thereby moving the position of the focal point 35 of the femtosecond laser light inside the glass member 10.
  • step ST20 and the focal point movement process in step ST30 are repeated while changing the irradiation conditions or under the same conditions, returning to the point indicated by point C in FIG. 1, until the predesigned optical waveguide pattern is formed inside the glass member 10 (step ST40).
  • step ST40 Once the formation of the refractive index change region 15 in the glass member 10 is completed (step ST40), the glass member 10 is annealed for aging treatment or the like so that the relative refractive index difference ⁇ n does not change for a long period of time (step ST50).
  • FIG. 3 is a diagram for explaining various beam shaping optical systems (marked “beam shaping optical system” in FIG. 3).
  • Beam shaping optical system 30 is composed of a beam shaping element and a condenser lens. Examples of beam shaping elements include a DOE and a hologram optical element using LCoS.
  • the upper part of FIG. 3 shows the configuration of an optical system that includes a DOE as a beam shaping element.
  • the lower part of FIG. 3 shows the configuration of an optical system that includes a hologram optical element as a beam shaping element.
  • a femtosecond laser beam is combined with a beam shaping element such as a hologram optical element to generate multiple branched beams, each of which is composed of diffracted light, from the femtosecond laser beam.
  • the multiple branched beams are focused inside the glass member 10 via a focusing lens, and a refractive index change region 15 that serves as an optical waveguide is formed inside the glass member 10 by moving the XYZ stage.
  • the effective wavelength of the laser beam is in the range of -10 nm or more to +10 nm or less based on 1030 nm, the range of -10 nm or more to +10 nm or less based on 1060 nm, or second harmonic generation (SHG) or third harmonic generation (THG) in each wavelength range.
  • the effective pulse width is 500 fs or less.
  • the effective repetition frequency is 100 kHz or more to 5 MHz or less.
  • the femtosecond laser light is split by a pair of beam shaping elements that generate diffracted light of different polarizations, such as a pair of DOE131A and DOE131B, or a pair of LCoS141A and LCoS141B.
  • a set of PBS (polarizing beam splitters) 133A and PBS 133B, a set of DOE 131A and DOE 131B as beam shaping elements, a set of mirrors 134A and 134B for optical path deflection, and a focusing lens 132 are provided.
  • the 45-degree linear polarization is converted into a 0-degree polarization component and a 90-degree polarization component by PBS 133A.
  • the 0-degree polarization component is input from PBS 133A to DOE 131A
  • the 90-degree polarization component is input from PBS 133B via mirror 134A to DOE 131B.
  • DOE 131A to which the 0-degree polarization component is input produces diffracted light L0 consisting only of the 0-degree polarization component, and diffracted light L0 reaches PBS 133B from DOE 131A.
  • the 90-degree polarized component is input to the DOE 131B, diffracted light L90 consisting only of the 90-degree polarized component is obtained, and the diffracted light L90 travels from the DOE 131B to the mirror 134B and reaches the PBS 133B.
  • the diffracted light L0 and the diffracted light L90 are combined by the PBS 133B, and finally, a plurality of diffracted light groups, in which the polarization state differs by 90 degrees between adjacent diffracted lights, that is, a plurality of branched beams, are generated.
  • the combined plurality of branched beams are focused at the focusing point 35 on the beam waist BW via the focusing lens 132.
  • a pair of LCoS 141A and LCoS 141B are prepared as beam shaping elements, and a condenser lens 142 is prepared.
  • a condenser lens 142 is prepared.
  • LCoS 141A in order to convert only the 0-degree polarization component of the output polarization components into diffracted light L0, the phase distribution of LCoS 141A is formed by controlling the liquid crystal orientation, so that only the 0-degree polarization component is converted into diffracted light L0 and the 90-degree polarization component is reflected as it is. Furthermore, in LCoS 141B, the 0-degree polarized diffracted light L0 is reflected as it is, while only the 90-degree polarization component is converted into diffracted light L90, and finally, multiple diffracted lights with polarization states differing by 90 degrees between adjacent diffracted lights, i.e., multiple branch beams, are generated. The multiple branched beams from LCoS 141B are focused at a focusing point 35 on the beam waist BW via a focusing lens 142.
  • the diffraction gratings of the elements that make up the beam shaping element are adjusted so that the multiple branch beams obtained from a single input laser beam are converted into diffracted beams with linear polarization of 0 degrees and 90 degrees. This allows the polarization state of the diffracted beams that each make up the multiple branch beams to be controlled so that adjacent diffracted beams have different polarization states of 0 degrees and 90 degrees.
  • Non-Patent Document 11 reports that it is possible to control the inclination of radial polarization and linear polarization by inserting a ⁇ /2 wave plate between the first LCoS and the second LCoS and inserting a ⁇ /4 wave plate between the second LCoS and the condenser lens.
  • the beam shaping optical system may be constructed by combining the set of LCoS 141A and LCoS 141B shown in the lower part of FIG. 3 with the set of LCoS in Non-Patent Document 11. If the number of LCoS included in the beam shaping optical system increases, it becomes possible to increase the degree of freedom in selecting the polarization of the branched diffracted light.
  • irradiation of multiple branched beams according to the present disclosure with different polarization states between adjacent branched beams acts in a direction that breaks the periodicity of the nanograting formed in the upper layer region 150 adjacent to the optical waveguide, making it possible to reduce propagation loss in the optical waveguide.
  • the beam irradiation according to the present disclosure results in periodicities with different angles being formed in the upper layer region 150 adjacent to the optical waveguide, which is effective in substantially shortening the correlation length of the nanograting.
  • FIG. 4 is a diagram for explaining laser light scanning for forming an optical waveguide and for explaining one example of the configuration of an optical connection part to be manufactured (in FIG. 4, this is labeled "waveguide formation”).
  • the upper part of FIG. 4 shows a configuration for drawing a refractive index change region 15 that becomes an optical waveguide within a glass member 10 by scanning a laser light across the glass member 10.
  • the lower part of FIG. 4 shows the structure of an optical connection part 100 obtained through laser light scanning.
  • a beam shaping element a DOE, LCoS, etc., as shown in FIG. 3, are used.
  • a plurality of branched beams are irradiated into the inside of the glass member 10 through the laser irradiation surface 10A while being shifted by an interval ⁇ y in the Y-axis direction.
  • These branched beams move relatively along a scanning direction that coincides with the Z-axis direction or a direction shifted by a predetermined angle from the Z-axis, and an optical connection part 100 is obtained in which a refractive index change region 15 that becomes an optical waveguide is formed.
  • This method is effective because it can obtain the width of the optical waveguide as designed.
  • FIG. 4 shows an example of an XY cross section of the refractive index change region 15 provided inside the glass member 10 by this laser irradiation process.
  • the example shown in this XY cross section is near the refractive index change region 15 obtained by irradiating the glass member 10 with a plurality of branched beams whose polarization states are consistent, and a plurality of modified regions 15A are formed in the refractive index change region 15 and the upper layer region 150 adjacent to the refractive index change region 15.
  • multiple modified regions 15B different from modified region 15A are formed in areas closer to the laser irradiated surface 10A than modified region 15A due to interference between adjacent branched beams.
  • the refractive index change region 15 when forming the refractive index change region 15 to be the optical waveguide inside the glass member 10, in addition to paying attention to the light intensity distribution in the vicinity of the focal point 35 that directly contributes to the structure of the optical waveguide, it is also necessary to pay attention to the interference in the overlapping region of the multiple branched beams in the upper layer region 150 between the laser irradiation surface 10A and the focal point 35.
  • Figure 5 shows the results of observing the modified shape at the cross section of the optical waveguide due to laser light scanning (in Figure 5, this is marked as "modified shape of waveguide cross section").
  • the middle of Figure 5 shows the results of observing the modified region 15A when the spacing ⁇ y2 of the 13 branched beams branched by the pair of LCoS141A and LCoS141B shown in the bottom of Figure 3 as beam shaping elements is set to 2.2 ⁇ m.
  • the lower part of Figure 5 shows the observation results of modified region 15A when the spacing ⁇ y3 between the 13 branched beams branched by the pair of LCoS141A and LCoS141B shown in the lower part of Figure 3 as beam shaping elements is set to 4.4 ⁇ m.
  • the NA of the prepared focusing lens is 0.40 or more and 0.55 or less.
  • the wavelength of each branch beam is 515 nm, and the pulse width is 100 fs or more and 450 fs or less.
  • the scanning speed is 0.01 mm/sec or more and 10 mm/sec or less.
  • the pulse energy is 30 nJ or more and 1000 nJ or less.
  • the repetition frequency is 100 kHz or more and 5 MHz or less.
  • the depth from the laser irradiation surface 10A to the inside of the glass member 10 (the distance to the focusing point 35) is 5 ⁇ m or more and 500 ⁇ m or less.
  • the modified region corresponding to the refractive index change region 15 that becomes the optical waveguide has a refractive index higher than that of the glass member 10. Between the refractive index change region 15 and the laser irradiation surface 10A, a modified region 15A having a refractive index lower than that of the glass member 10 excluding the refractive index change region 15 is formed. When the modified regions that constitute part of the refractive index change region 15 are connected along the Y-axis direction, an optical waveguide is formed.
  • the sizes of the modified regions that constitute part of the refractive index change region 15 and the modified region 15A become different, and it can be seen that a complex modified structure is formed in the upper layer region 150 located between the laser irradiation surface 10A and the refractive index change region 15.
  • a modified region 15B other than the modified region 15A exists, and it is considered that the state where the modified threshold is exceeded is reflected by the intensification due to the interference of the multiple branched beams.
  • the modified region 15B has a refractive index similar to that of the modified region 15A, that is, a refractive index lower than that of the glass member 10 excluding the refractive index change region 15.
  • a region that is brighter than both the modified region 15A and the modified region 15B and has a brightness similar to that of the refractive index change region 15 can be confirmed between the modified region 15B and the refractive index change region 15.
  • this high brightness region has a refractive index similar to that of the refractive index change region 15, that is, a refractive index higher than that of the glass member 10.
  • the upper layer region 150 between the refractive index change region 15 and the laser irradiation surface 10A will contain a mixture of modified region 15A and modified region 15B, as well as a region with a refractive index similar to that of the refractive index change region 15.
  • the modified region constituting the refractive index change region 15 functions as an optical waveguide, but the modified region 15A and a part of the modified region 15B form a layer with a thickness of about 5 ⁇ m in the upper layer region 150 directly above the refractive index change region 15 that becomes the optical waveguide.
  • various nanogratings having periodicity are formed along the longitudinal direction of the refractive index change region 15 and the direction intersecting the longitudinal direction.
  • a nanostructure with a random directionality of the period is formed. Propagation loss is reduced by shortening the period of the nanograting in the modified region 15A.
  • the number of modified regions 15A and 15B formed directly above the refractive index change region 15 that can be confirmed in the XY cross section may be 10 to 100, 1 to 9, or 0.
  • the modified regions 15A and 15B are confirmed by observing the XY cross section of the refractive index change region 15 provided in the glass member 10 with a microscope while irradiating it with transmitted light.
  • the modified regions 15A and 15B are defined as regions of the glass member 10 that have a brightness that is 10% or more lower than the brightness of the non-modified region excluding the refractive index change region 15, the modified regions 15A, and the modified regions 15B, and have a maximum diameter of 0.5 ⁇ m or more.
  • the total number of modified regions 15A and 15B is determined by counting the number of regions identified by the above-mentioned microscope observation in the XY cross section.
  • FIG. 6 shows the results of calculations for evaluating the side roughness of an optical waveguide (in FIG. 6, this is labeled "Roughness evaluation of waveguide side surface”).
  • the upper part of FIG. 6 shows the specifications of types 1 to 3.
  • the lower part of FIG. 6 shows the relationship between the correlation length Lc and the roughness ⁇ of the optical waveguide side surface.
  • graph G610 shown in the lower part of FIG. 6 shows the calculation results for type 1 shown in the upper part of FIG. 6
  • graph G620 shows the calculation results for type 2
  • graph G630 shows the calculation results for type 3.
  • Non-Patent Document 6 The relationship between the optical propagation loss and the period of different refractive indexes is shown in FIG. 6 as a result of calculation based on the description in Non-Patent Document 10.
  • the roughness ⁇ at which the propagation loss is 0.1 dB/cm was obtained by considering only scattering on the side surface of the optical waveguide.
  • the calculation of roughness ⁇ focuses only on modified region 15A in the upper layer region 150, which is directly related to the transmission loss.
  • the wavelength is 1.55 ⁇ m
  • the cladding refractive index, which corresponds to the refractive index of the glass member 10 is 1.45.
  • d [ ⁇ m] is the waveguide width
  • ⁇ n [%] is the relative refractive index difference of the optical waveguide to the cladding refractive index
  • b is the normalized propagation constant of the optical waveguide
  • ⁇ c [ ⁇ m] is the cutoff wavelength of the optical waveguide
  • MFD [ ⁇ m] is the mode field diameter of the optical waveguide.
  • the horizontal axis is the correlation length Lc, which indicates the periodic length when there is a random fluctuation component periodicity, or the periodic length when there is a roughly constant fluctuation component periodicity.
  • the roughness ⁇ required to reduce the propagation loss to 0.1 dB/cm or less is different depending on the conditions shown in the upper part of Figure 6. However, the tendency is roughly consistent, and it can be seen that the propagation loss is most sensitive to the fluctuation of roughness ⁇ in the vicinity of 100 ⁇ m. In other words, the smaller the periodicity of the correlation length Lc is, such as 100 ⁇ m or less, the less sensitive the transmission loss is to the fluctuation of roughness ⁇ .
  • the nanograting period can be shortened, that is, by controlling the average correlation length to be shorter than 100 nm, it becomes possible to achieve low loss in the optical waveguide.
  • the modified region 15A surrounding it can be regarded as an optical cladding.
  • the periodic refractive index fluctuation of this optical cladding increases the propagation loss.
  • This nanograting is known to be formed perpendicular to the incident polarization, and when multiple branched beams have the same polarization, this leads to the growth of the nanograting formation.
  • the length of the periodicity of the nanograting formed in the optical cladding region the so-called correlation length Lc, varies depending on the wavelength, pulse energy, scanning speed, etc. of each branched beam, but it has been reported to be 100 nm or more and 700 nm or less (Non-Patent Document 11).
  • Non-Patent Document 11 shows laser drawing conditions for shortening the correlation length Lc of the nanograting, but even the minimum correlation length has a period of at least about 100 nm, which is insufficient for reducing propagation loss.
  • the manufacturing method disclosed herein controls the average correlation length of various nanogratings formed near the core to be shorter than 100 nm by making the polarization states of adjacent diffracted lights among the diffracted lights that respectively constitute multiple branch beams different.

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Abstract

Un composant de connexion optique selon la présente invention comprend un élément en verre et un guide d'ondes optique. Dans une région de couche supérieure de l'élément en verre, positionnées entre le guide d'ondes optique et une surface d'irradiation laser de l'élément en verre dans une section transversale de l'élément en verre, une ou plusieurs régions modifiées (15A) ayant un indice de réfraction inférieur à celui du guide d'ondes optique et inférieur à celui de l'élément en verre à l'exclusion du guide d'ondes optique sont formées. La longueur de corrélation moyenne d'un nanoréseau dans une couche composée de la région modifiée est inférieure à 100 nm.
PCT/JP2024/004200 2023-02-22 2024-02-07 Composant de connexion optique et procédé de fabrication de composant de connexion optique Pending WO2024176840A1 (fr)

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CN202480013019.1A CN120712503A (zh) 2023-02-22 2024-02-07 光连接部件和光连接部件的制造方法
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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20030035640A1 (en) * 2001-08-16 2003-02-20 Mark Dugan Method of index trimming a waveguide and apparatus formed of the same
JP2020510538A (ja) * 2017-03-07 2020-04-09 ローベルト ボツシユ ゲゼルシヤフト ミツト ベシユレンクテル ハフツングＲｏｂｅｒｔ Ｂｏｓｃｈ Ｇｍｂｈ レーザ加工用の放射を成形するための方法及び装置
WO2022255261A1 (fr) * 2021-05-31 2022-12-08 住友電気工業株式会社 Procédé de production de guide d'ondes optique et guide d'ondes optique

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20030035640A1 (en) * 2001-08-16 2003-02-20 Mark Dugan Method of index trimming a waveguide and apparatus formed of the same
JP2020510538A (ja) * 2017-03-07 2020-04-09 ローベルト ボツシユ ゲゼルシヤフト ミツト ベシユレンクテル ハフツングＲｏｂｅｒｔ Ｂｏｓｃｈ Ｇｍｂｈ レーザ加工用の放射を成形するための方法及び装置
WO2022255261A1 (fr) * 2021-05-31 2022-12-08 住友電気工業株式会社 Procédé de production de guide d'ondes optique et guide d'ondes optique

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