Optical module and method for manufacturing optical module

Abstract

An exemplary optical module (10) according to the present disclosure is provided with: an optical fiber block (100) having a space (121) in which an optical fiber (30) is disposed; an optical waveguide circuit (200) having an optical waveguide (210); a thermosetting adhesive (50) provided to an optical axis section which is a section through which light passes at connection end faces of the optical fiber block (100) and the optical waveguide circuit (200); and a first groove (125) provided to the optical fiber block (100). The first groove (125) intersects a space (121) extending along the optical fiber (30) and communicates with the space (121) at the intersection.

Description

Optical module and method for manufacturing the optical module

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

[0002] Silica-based planar lightwave circuits (PLCs) are often used in the field of optical communications. PLCs can be used as optical modules by connecting a fiber array, which is an array of multiple optical fibers, to one or both of the optical input and output terminals. In recent years, the practical application of PLCs that handle wavelengths in the visible light range, which are shorter than the wavelength range used in optical communications, has also been considered.

[0003] JP 2014-48628 A JP 2017-54110 A

[0004] A. Nakao, et al. , “Integrated waveguide-type red-green-blue beam combiners for compact projection-type displays”, Optics Communications 330 (2014) 45-48J. Sakamoto, et al. , “Compact and low-loss RGB coupler using mode-conversion waveguides”, Optics Communications 420 (2018) 46-51

[0005] When using visible light wavelengths in an optical module, the dust collection effect can be significant in a structure in which an air gap is provided between the optical fiber core and the PLC waveguide. If the dust collection effect is significant, optical properties such as the mode field diameter (MFD) can change over time in a way that is not expected in the wavelength range used in optical communications, and connection loss can increase.

[0006] In order to suppress the dust collection effect, it has been considered to use, for example, an ultraviolet (UV) curing adhesive for the connection between the optical fiber core and the PLC waveguide, but the UV curing adhesive can absorb light in the visible light range (for example, light in the blue wavelength range close to UV light), which can increase the connection loss.

[0007] On the other hand, if an adhesive of a different type or material than the UV-curing adhesive is used in the connection part, it may be more difficult to ensure optical axis alignment in the connection part than when a UV-curing adhesive is used, and the dust collection effect may also be insufficiently suppressed.

[0008] An exemplary object of the present disclosure is to provide an optical module and a method for manufacturing the optical module that can easily ensure optical axis alignment and suppress dust collection effects.

[0009] Therefore, an optical module according to one aspect of the present disclosure includes an optical fiber block having a space in which an optical fiber is arranged, an optical waveguide circuit having an optical waveguide, a thermosetting adhesive provided in an optical axis portion which is a portion through which light passes at the connection end face between the optical fiber block and the optical waveguide circuit, and a first groove provided in the optical fiber block, the first groove intersecting the space extending along the optical fiber and communicating with the space at the portion where it intersects with the space.

[0010] Furthermore, a method for manufacturing an optical module according to one aspect of the present disclosure is a method for manufacturing an optical module having an optical fiber block having a space in which an optical fiber is arranged, and an optical waveguide circuit having an optical waveguide, wherein the optical fiber block has a first groove that intersects with the space extending along the optical fiber and communicates with the space at the portion that intersects with the space, and the manufacturing method includes the steps of applying a thermosetting adhesive to an optical axis portion that is a portion through which light passes at the connection end face between the optical fiber block and the optical waveguide circuit, heating the thermosetting adhesive under conditions that do not completely harden the adhesive to temporarily harden it, placing the optical fiber in the space and adhering the end face of the optical fiber to the thermosetting adhesive in a temporarily hardened state, and reheating the temporarily hardened thermosetting adhesive to completely harden it.

[0011] FIG. 1 is a top view showing an exemplary configuration of an optical module according to embodiment 1. FIG. 2 is a perspective view of a glass substrate (lower block) constituting the optical fiber block according to embodiment 1. FIG. 3 is a top view showing another exemplary configuration of the optical module according to embodiment 1. FIG. 4 is a top view of a glass substrate (lower block) constituting the optical fiber block according to embodiment 1. FIG. 5 is a perspective view of a glass substrate (upper block) constituting the optical fiber block according to embodiment 1. FIG. 6 is a perspective view of an optical fiber block according to embodiment 1. FIG. 7 is a diagram for explaining an exemplary method of manufacturing the optical module according to embodiment 1. FIG. 8 is a diagram for explaining an exemplary method of manufacturing the optical module according to embodiment 1. FIG. 9 is a diagram for explaining an exemplary method of manufacturing the optical module according to embodiment 1. FIG. 10 is a perspective view showing an exemplary configuration of a capillary as an optical fiber block according to embodiment 2.

[0012] Hereinafter, embodiments will be described in detail with reference to the drawings. However, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the present disclosure, and are not intended to limit the subject matter described in the claims. Furthermore, more detailed descriptions than necessary may be omitted. For example, detailed descriptions of well-known matters or redundant descriptions of substantially identical configurations may be omitted.

[0013] Furthermore, in the drawings, identical or corresponding elements are appropriately designated by the same reference numerals. The drawings are schematic, and the dimensional relationships or ratios of elements may differ from reality. The drawings may also include portions in which the dimensional relationships or ratios differ. When numerical values ​​are used in the following description, they are merely examples, and other numerical values ​​may be used in addition or instead.

[0014] <Summary> Silica-based PLCs are used, for example, in the field of optical communications because they can realize functions such as optical branching, optical switching, and wavelength multiplexing or demultiplexing on a small chip. For example, a PLC can be used as an optical fiber module by connecting a fiber array (which may also be called an "optical fiber block") in which multiple optical fibers are arranged to one or both of the optical input and output ends.

[0015] For example, an ultraviolet (UV) curing adhesive may be used to connect (or fix) the PLC to the fiber array (see, for example, Patent Document 1). In recent years, practical application of PLC has been considered not only for wavelengths used in optical communications but also for wavelengths in the visible light range (see, for example, Non-Patent Documents 1 and 2).

[0016] For example, in analytical devices such as fluorescence microscopes, flow cytometers, or ophthalmoscopes, in order to irradiate a single spot with light of multiple visible wavelengths, spatial optical systems such as lenses and / or dichroic mirrors are used to combine the light emitted from a visible light source (e.g., a laser diode (LD)) into a single beam.

[0017] In devices that use such visible light wavelengths, by using an optical fiber module in which a fiber array is connected to a PLC that has the function of multiplexing multiple visible light wavelengths, it is possible to reduce the size of the device and / or improve its resistance to vibration.

[0018] Here, when a UV-curing adhesive, which is commonly used in optical communication applications, is used to connect a PLC for visible light applications to a fiber array, for example, the adhesive may be altered by light of the visible light wavelength, which is the operating wavelength (or wavelength used), resulting in a decrease in light transmittance, because the UV wavelength and the visible light wavelength are close to each other.

[0019] One example of a structure or method for preventing such deterioration of adhesive is the air gap method (see, for example, Patent Document 2). In the air gap method, a groove is formed in the fiber array to prevent the adhesive from entering the light propagation region, and adhesive is applied outside the groove to connect to the PLC.

[0020] However, although the air gap method can suppress a decrease in light transmittance due to deterioration of the adhesive, since high-density light is emitted from the end of the optical fiber into the air gap, the end face of the optical fiber may be deteriorated, for example, due to the dust collection effect.

[0021] Deterioration of the optical fiber end face can change the pattern or light intensity distribution of the emitted beam near the optical fiber end face, called the NFP (Near Field Pattern), which can change the connection loss between the PLC and the fiber array and, as a result, can reduce the light transmittance.

[0022] Furthermore, even when adhesives made of acrylic resin, epoxy resin, or silicone-based materials are used, the NFP may change, which may result in a change in connection loss.When using polysilazane adhesives, which are used for coating applications, the degree of cure shrinkage is greater than that of the above-mentioned materials, which may result in the generation of voids.

[0023] Therefore, the use of an adhesive that does not contain a material that absorbs blue light, such as a heat-curable adhesive, is being considered. However, the heat-curable adhesive takes longer to harden than the UV-curable adhesive.

[0024] For example, the curing time of a UV-curable adhesive is from several minutes to several tens of minutes, whereas the curing time of a thermosetting adhesive is from several hours to several tens of hours. Therefore, if the UV-curable adhesive is simply replaced with a thermosetting adhesive, the optical axis alignment between the optical fiber core and the PLC waveguide is likely to be displaced during the thermal curing process.

[0025] Furthermore, the more the thermosetting adhesive comes into contact with oxygen, the more accelerated the curing reaction becomes. Therefore, if the area where the thermosetting adhesive comes into contact with air in the applied area is very small, it is difficult to cure the adhesive to the extent that it can achieve visible light resistance.

[0026] Therefore, by-products generated during the curing reaction process (hereinafter referred to as "reaction by-products") may not completely vaporize and may remain in the region or portion (hereinafter referred to as "optical axis portion") through which light passes between the optical fiber core and the PLC waveguide that are optically aligned. If reaction by-products remain in the optical axis portion, a dust collection effect may occur in the optical axis portion.

[0027] Hereinafter, several exemplary embodiments of an optical module and a manufacturing method thereof that can easily ensure optical axis alignment and suppress the dust collection effect will be described.

[0028] 1 is a top view showing an exemplary configuration of an optical module 10 according to a first embodiment, in which an optical fiber block 100 is connected to a PLC 200, which is an example of an optical waveguide circuit. Note that Fig. 1 does not show a glass substrate 104 (described later with reference to Figs. 5 and 6 ) provided on the upper surface of a glass substrate 102 in the optical fiber block 100. The term "optical fiber block" may be read as "fiber array."

[0029] In FIG. 1, the X-axis, Y-axis, and Z-axis correspond to directions along the width, thickness (or height), and length of the optical module 10 or optical fiber block 100, respectively, and the Z-axis is also the direction along the propagation direction of light (same below).

[0030] In addition, in this embodiment 1, the light propagating through the optical fiber block 100 and the PLC 200 is, for example, light of a short wavelength equal to or less than the blue wavelength (approximately 488 nm), at which the influence of the dust collection effect and / or the change in refractive index of the light-transmitting portion is more pronounced than at other wavelengths.

[0031] The optical fiber block 100 includes a glass substrate 102 and an optical fiber 30 disposed (e.g., positioned and fixed) on the glass substrate 102. For example, silica glass or borosilicate glass such as Tempax may be used for the glass substrate 102. The optical fiber 30 is, for example, a single-mode fiber having one core 302 (see FIG. 2 ).

[0032] 2, n V-grooves 121 (n is an integer of 1 or more, and n=3 in the example of FIG. 2) extending in the Z-axis direction are arranged in the X-axis direction on the XZ plane on the glass substrate 102. As illustrated in FIGS. 2 to 4, an optical fiber 30 or an alignment fiber 40 is placed and positioned in each V-groove 121. Note that the V-groove 121 refers to a groove recessed in a V shape from the top surface of the glass substrate 102 downward in the Y-axis direction when viewed in cross section on the XY plane.

[0033] Fig. 1 shows an example in which one optical fiber 30 is arranged in n=1 V-groove 121. On the other hand, Fig. 2 and Fig. 3 show an example in which an optical fiber 30 is arranged in the central V-groove 121 of n=3 V-grooves 121 arranged in the X-axis direction, and an alignment fiber 40 is arranged in each of the two V-grooves 121 on either side of the central V-groove 121 in the X-axis direction.

[0034] 4 shows an example in which, of n=3 V-grooves 121 lined up in the X-axis direction, the central V-groove 121 has no optical fiber 30 placed therein, and the two V-grooves 121 on either side in the X-axis direction each have an aligning fiber 40 placed therein. Note that the gap (space) in the V-groove 121 at the portion that does not contact the outer periphery of the optical fiber 30 or the aligning fiber 40 serves as an air gap layer. Note that, in the optical fiber block 100, the space formed by the V-groove 121 may be referred to as a space 121 for convenience.

[0035] With the optical fiber 30 or the alignment fiber 40 positioned relative to the V-groove 121, a glass substrate 104 such as that shown in FIG. 5 is provided so as to cover at least a portion of the upper surface of the glass substrate 102, as illustrated in FIG. 6.

[0036] For example, the optical fiber block 100 is produced by adhesively fixing the glass substrate 102 and the glass substrate 104 together, sandwiching the optical fiber 30 and the alignment fiber 40, which are positioned along the V-groove 121 in the glass substrate 102, above and below in the Y-axis direction.

[0037] However, in the first embodiment, the glass substrate 104 can be adhesively fixed to the glass substrate 102 after the glass substrate 102 and the PLC 200 are adhesively fixed to each other, as will be described later.

[0038] The glass substrate 104 provided on the upper surface of the glass substrate 102 may be made of quartz glass, as with the glass substrate 102, or may be made of borosilicate glass such as Tempax. The glass substrate 104 is bonded and fixed to the glass substrate 102 by, for example, a UV-curable adhesive.

[0039] As illustrated in Figure 5, the glass substrate 104 may be provided with multiple grooves 141 that have a depth recessed in the Z-axis direction from the side surface of the glass substrate 104 (e.g., the connection end surface to the PLC 200) and extend in the Y-axis direction.

[0040] Each of the grooves 141 is provided, for example, in a portion that avoids a region where light propagates (hereinafter also referred to as an "optical axis portion") on the connection end surface to the PLC 200. Furthermore, when the glass substrate 104 and the glass substrate 102 are adhesively fixed together, each of the grooves 141 exemplarily communicates with a groove 123 (described later) that is provided in the glass substrate 102, as shown in FIG.

[0041] Hereinafter, for convenience, the glass substrates 102 and 104 constituting the optical fiber block 100 may be referred to as the "lower block 102" and the "upper block 104," respectively. By bonding the bottom surface of the upper block 104 to the top surface of the lower block 102, for example, the bonding area between the optical fiber block 100 and the PLC 200 increases, and therefore the fixing strength of the optical fiber block 100 can be increased.

[0042] As shown in FIGS. 1 and 3, the optical fiber block 100 and the PLC 200 are fixed by bonding their connection end faces together using a UV-curable adhesive 70 and a heat-curable adhesive 50, for example.

[0043] For example, the UV-curable adhesive 70 is applied partially (e.g., dripped or painted) to an area at the connection end face between the optical fiber block 100 and the PLC 200, avoiding the area where light propagates (hereinafter also referred to as the "optical axis portion").

[0044] For example, on the connecting end surface of the lower block 102 with the PLC 200, grooves 123 extending along the Y-axis direction are provided on both sides of the X-axis direction in an area that does not overlap with the optical axis portion, and UV-curing adhesive 70 is applied to the portion of the end surface that is outside the grooves 123 in the X-axis direction.

[0045] When the lower block 102 and the upper block 104 are adhesively fixed to each other, the groove 123 communicates with the groove 141 of the upper block 104, as illustrated in Fig. 6. The presence of the groove 123 and the groove 141 that communicate in the Y-axis direction makes it possible to prevent or suppress the UV-curable adhesive 70 from passing over the groove 123 and the groove 141 and entering the optical axis portion when the optical fiber block 100 and the PLC 200 are adhesively fixed to each other, as illustrated in Fig. 1 or 3. In other words, the groove 123 and the groove 141 each function as an adhesive blocking groove (or groove structure) that prevents the UV-curable adhesive 70 from entering the optical axis portion.

[0046] When the UV-curable adhesive 70 is cured, it forms a layer of the UV-curable adhesive 70 (hereinafter, for convenience, may be referred to as a "UV-curable adhesive layer 70") interposed between the connection end face of the optical fiber block 100 and the connection end face of the PLC 200. The UV-curable adhesive layer 70 may also function as a spacer that creates a partial gap layer including the optical axis portion between the connection end face of the optical fiber block 100 and the connection end face of the PLC 200.

[0047] Although the size of each of the grooves 123 and 141 is not particularly limited, it is sufficient if the width in the X-axis direction is about 100 μm or more and the depth in the Z-axis direction is about 100 μm or more. Note that the grooves 123 and 141 are not limited to extending in the Y-axis direction, and may alternatively or additionally be formed to extend in, for example, the X-axis direction.

[0048] 1 or 3, the thermosetting adhesive 50 is applied to the optical axis portion at the connection end surface between the optical fiber block 100 and the PLC 200. For example, an adhesive that does not contain a material that can absorb blue light (such as a carbon-carbon bond that is easily degraded by UV light) may be applied as the thermosetting adhesive 50. A non-limiting example of such a thermosetting adhesive 50 is a thermosetting adhesive with high UV resistance that is used as an encapsulant for light-emitting diodes (LEDs).

[0049] The thermosetting adhesive 50 is thermally cured to form a layer of the thermosetting adhesive 50 that optically couples the end face of the optical fiber 30 to the end face of the waveguide (core) 210 of the PLC 200. For convenience, the layer of the thermosetting adhesive 50 may also be referred to as the "thermosetting adhesive layer 50" below.

[0050] In relation to the thermosetting adhesive 50, the lower block 102 is provided with a groove 125 recessed in the Y-axis direction from the top surface of the lower block 102, as shown in Figures 1 to 4, for example. The groove 125 can be provided in a position in the Z-axis direction close to the connection end surface with respect to the PLC 200, in other words, the bonding surface of the thermosetting adhesive 50. As a non-limiting example, the groove 125 may be provided in a position approximately 50 to 100 micrometers (μm) away from the bonding surface of the thermosetting adhesive 50 in the Z-axis direction.

[0051] Moreover, groove 125 exemplarily extends in a direction (for example, the X-axis direction, which is a perpendicular direction) intersecting the extension direction (Z-axis direction) of V-groove 121, and communicates with V-groove 121 at the portion where it intersects with V-groove 121. Therefore, for example, thermosetting adhesive 50 for fixing the optical axis portion that has flowed into V-groove 121 due to capillary action is drawn into groove 125 and is allowed to escape along the X-axis direction.

[0052] This prevents or inhibits the thermosetting adhesive 50 from flowing out along the V-groove 121 extending in the Z-axis direction and remaining in the V-groove 121. Therefore, the groove 125 can have a volume large enough to draw the thermosetting adhesive 50 that has flowed into the V-groove 121 into the internal space of the groove 125 and prevent the thermosetting adhesive 50 from flowing out along the V-groove 121, for example.

[0053] The shape, size, and / or depth of the groove 125 may be determined as appropriate within a range or condition that ensures the volume. As a non-limiting example, the groove 125 may have a concave shape in a cross-sectional view along the YZ plane, and its depth in the Y-axis direction may be deeper than the depth of the V-groove 121.

[0054] 1 to 4, a groove 127 may be additionally provided in the lower block 102 at a position sufficiently separated in the Z-axis direction from the groove 125, for example, at a position close to the end face on the opposite side in the Z-axis direction from the bonding surface formed by the thermosetting adhesive 50. Note that the grooves 125, 127, and 123 are non-limiting examples of the first groove, the second groove, and the third groove, respectively.

[0055] Groove 127 is recessed in the Y-axis direction from the top surface of lower block 102, extends in a direction intersecting the extension direction (Z-axis direction) of V-groove 121 (for example, the X-axis direction, which is perpendicular), and is connected to V-groove 121 at the portion where it intersects with V-groove 121.

[0056] The groove 127 communicating with the V-groove 121 can suppress or prevent, for example, the UV-curable adhesive 72 used to fix the optical fiber 30 at the end face opposite in the Z-axis direction from the connection end face to the PLC 200 from flowing out along the V-groove 121. For example, the UV-curable adhesive 72 for fixing the optical fiber 30 that has flowed into the V-groove 121 by capillary action is drawn into the groove 127 and is released along the X-axis direction.

[0057] Therefore, the groove 127 can have a volume large enough to draw the UV-curable adhesive 72 that has flowed into the V-groove 121 into the internal space of the groove 127 and prevent the UV-curable adhesive 72 from flowing out along the V-groove 121 toward the optical axis portion.

[0058] As long as the volume is ensured, the shape, size, and / or depth of groove 127 may be determined appropriately. As a non-limiting example, groove 127 may have a concave shape in a cross-sectional view along the YZ plane, similar to groove 125, and its depth in the Y-axis direction may be deeper than the depth of V-groove 121. Furthermore, groove 125 or groove 127 may have another shape, such as a polygon, a circle, an ellipse, or a shape that includes a partial curve, in a cross-sectional view along the YZ plane.

[0059] Considering the respective functions of groove 125 and groove 127 described above, groove 125 may be provided at a Z-axis position where it is easy to draw in the thermosetting adhesive 50 from V-groove 121, and groove 127 may be provided at a Z-axis position where it is easy to draw in the UV-curing adhesive 72 from V-groove 121.

[0060] Each of the grooves 125 and 127 may be a single groove that communicates with the multiple V-grooves 121 aligned in the X-axis direction, and may be formed by the same processing method, such as etching, to have the same shape, size, and / or depth. In this case, it is possible to reduce processing costs compared to, for example, when the grooves 125 and 127 are individually processed and formed to have different shapes, sizes, and / or depths.

[0061] In addition, the lower block 102 may have one or more additional grooves extending in the X-axis direction equivalent to groove 125 or groove 127 arranged side by side in the Z-axis direction between groove 125 and groove 127.

[0062] Increasing the number of grooves aligned in the Z-axis direction in the lower block 102 can increase, for example, the amount of the thermosetting adhesive 50 or the UV-curing adhesive 72 that can escape from the V-groove 121. On the other hand, the physical strength of the lower block 102 can decrease. Therefore, the number of grooves aligned in the Z-axis direction in the lower block 102 can be determined based on this trade-off relationship.

[0063] Furthermore, when multiple grooves 125 or grooves 127 are formed, the spacing (or pitch) of the individual grooves in the Z-axis direction may depend on the Z-axis distance from the application point of the heat-curable adhesive 50 or UV-curable adhesive 72 on the lower block 102.

[0064] For example, the spacing in the Z-axis direction of the grooves 125 or 127 may be set shorter in an area closer to the application location of the thermosetting adhesive 50 or UV-curing adhesive 72. Setting the spacing in this manner can improve the ability (or accuracy) to draw in and release the thermosetting adhesive 50 or UV-curing adhesive 72 that has flowed (or leaked) into the V-groove 121.

[0065] In addition, in the first embodiment, groove 125 and groove 127 are each formed to extend in the X-axis direction perpendicular to the extension direction (Z-axis direction) of V-groove 121, but the present disclosure is not limited to this. For example, groove 125 or groove 127 may be formed to extend in an oblique direction shifted from the direction (X-axis direction) perpendicular to the extension direction (Z-axis direction) of V-groove 121 in the XZ plane.

[0066] 2 to 4, the alignment fiber 40 is disposed in the V-groove 121 on each side in the X-axis direction of the optical fiber 30. However, the V-groove 121 in which the alignment fiber 40 is disposed (in other words, the position in the X-axis direction) may be selected appropriately depending on, for example, the ease of performing optical axis alignment.

[0067] For example, if the distance in the X-axis direction of the two alignment fibers 40 is too close, it becomes difficult to align them in parallel, so a V-groove 121 for arranging the alignment fibers 40 may be selected within a range that allows easy optical axis alignment. Note that a method that does not use the alignment fibers 40 may be used for optical axis alignment.

[0068] 1 to 6, the grooves 123 and 141 for blocking the UV-curable adhesive 70 are provided on the connection end surface of the optical fiber block 100 for connecting to the PLC 200. However, the present disclosure is not limited to this, and for example, grooves for blocking the UV-curable adhesive 70 may be provided at corresponding positions on the connection end surface on the PLC 200 side.

[0069] <Method of Manufacturing Optical Module> Next, an exemplary method of manufacturing (or fabricating) the optical module 10 described above will be described with reference to FIGS.

[0070] 7, the connection end face of the lower block 102 and the connection end face of the PLC 200 are aligned using two alignment fibers 40. After the alignment is complete, UV-curable adhesive 70 is dripped (or applied) on the outer side of the groove 123 in the X-axis direction, and UV light is irradiated onto the UV-curable adhesive 70, thereby bonding and fixing the PLC 200 to the lower block 102.

[0071] As the UV-curable adhesive 70 hardens, it becomes a UV-curable adhesive layer 70 interposed between the PLC 200 and the lower block 102, creating a gap layer in a partial region including the optical axis portion between the PLC 200 and the lower block 102.

[0072] By adhesively fixing the PLC 200 and the lower block 102, for example, positional misalignment of the optical axis portion is prevented or suppressed in a later process of applying the thermosetting adhesive 50 to the optical axis portion and hardening the thermosetting adhesive 50.

[0073] Furthermore, the UV-curing adhesive 70 is blocked by the groove 123 so as not to flow into the optical axis portion, and therefore, it is possible to prevent the UV-curing adhesive 70 from changing the light transmission characteristics of the optical axis portion.

[0074] 8, the thermosetting adhesive 50 is dripped (or applied) onto the optical axis portion, and then heated to harden the thermosetting adhesive 50. At this stage, the upper block 104 is not yet bonded to the lower block 102, so that the thermosetting adhesive 50 can be easily dripped (or applied) onto the optical axis portion. The amount of the thermosetting adhesive 50 dripped may be small enough so that it does not overflow the groove 125 and flow into the V-groove 121, for example.

[0075] The thermosetting adhesive 50 dropped or applied to the optical axis portion may flow into the V-groove 121 due to capillary action. However, the thermosetting adhesive 50 that has flowed into the V-groove 121 is drawn into, for example, a groove 125 that is deeper than the depth of the V-groove 121, and is released in a direction along the groove 125 (X-axis direction), which is a direction different from the extension direction of the V-groove 121 (Z-axis direction).

[0076] Therefore, the thermosetting adhesive 50 can be suppressed or prevented from flowing beyond the groove 125 along the V-groove 121 in the Z-axis direction, and the placement or insertion of the optical fiber 30 into the V-groove 121 can be suppressed or prevented from being hindered by the thermosetting adhesive 50.

[0077] Furthermore, the heat treatment of the thermosetting adhesive 50 at this stage may be performed under conditions (for example, temperature and / or time) such that the thermosetting adhesive 50 is in a partially cured state in which it is not completely cured.

[0078] The reaction by-products generated during this pre-curing are vaporized and released in the gap layer including the space of the V-groove 121, while the oxygen consumed in the curing is supplied in a sufficient amount to promote the curing reaction from the gap layer including the V-groove 121. Therefore, the pre-curing time of the thermosetting adhesive 50 can be shortened, and it is also possible to suppress or prevent the reaction by-products from remaining in the optical axis portion and causing a dust-collecting effect.

[0079] Furthermore, by leaving the thermosetting adhesive 50 in a provisionally hardened state, for example, in a later process, it becomes easier to place the optical fiber 30 in the V-groove 121 and align the optical axis between the core 302 of the optical fiber 30 and the waveguide (core) 210 of the PLC 200.

[0080] After the thermosetting adhesive 50 has been temporarily hardened, as illustrated in Figure 9, the optical fiber 30 is placed in the V-groove 121 where the alignment fiber 40 is not placed, and the optical axis of the optical fiber 30 is adjusted to a position where the coupling efficiency to the waveguide (core) 210 of the PLC 200 is maximized.

[0081] At this stage, the thermosetting adhesive 50 has not completely hardened, and therefore the thermosetting adhesive 50 easily deforms at the portion in contact with the end face of the optical fiber 30. Therefore, it is possible to closely fix (this may also be referred to as "temporarily fix") the end face of the optical fiber 30 to the thermosetting adhesive 50 without any gaps.

[0082] After adjusting the optical axis of the optical fiber 30 and temporarily fixing it, the thermosetting adhesive 50 is reheated and completely hardened, so that the PLC 200 and the lower block 102 are bonded and fixed together by the thermosetting adhesive 50 in addition to the UV-curing adhesive 70.

[0083] Thereafter, as illustrated in FIG. 10, the optical fiber 30 is fixed with a UV-curable adhesive 72 to the end face of the lower block 102 on the opposite side in the Z axis direction from the connection end face between the PLC 200 and the lower block 102 .

[0084] At this time, capillary action may cause the UV-curable adhesive 72 to flow into the gap between the optical fiber 30 and the V-groove 121 and possibly enter the optical axis portion. However, the UV-curable adhesive 72 that has flowed into the V-groove 121 may be drawn into a groove 127 that is deeper than the depth of the V-groove 121, and escape in a direction (X-axis direction) along the groove 127, which is a direction different from the extension direction (Z-axis direction) of the V-groove 121.

[0085] This makes it possible to suppress or prevent the UV-curable adhesive 72 that has flowed into the V-groove 121 from flowing beyond the groove 127 and out along the V-groove 121 in the Z-axis direction toward the PLC 200. This makes it possible to suppress or prevent the UV-curable adhesive 72 from reaching the optical axis portion and unintentionally entering the optical axis portion.

[0086] The upper block 104 illustrated in FIG. 5 may be adhesively fixed to the lower block 102, for example, with a UV-curable adhesive, as illustrated in FIG. 6, after any of the steps illustrated in FIGS. 7 to 10.

[0087] For example, the adhesive fixation of the upper block 104 to the lower block 102 may be performed before dripping (or applying) the thermosetting adhesive 50 in FIG. 8, or may be performed after the thermosetting adhesive 50 has been temporarily hardened.

[0088] Furthermore, the adhesive fixation of the upper block 104 to the lower block 102 may be performed before or after placing or inserting the optical fiber 30 into the V-groove 121 of the lower block 102 in FIG.

[0089] Furthermore, adhesive fixing of the upper block 104 to the lower block 102 may be performed before or after fixing the optical fiber 30 with the UV-curable adhesive 72 in FIG.

[0090] The upper block 104 and the lower block 102 can be bonded together by applying a UV-curable adhesive to the XZ surface on the opposite side of the Z axis (the direction away from the optical axis) from the groove 127. This makes it possible to prevent or inhibit the UV-curable adhesive from flowing into the optical axis.

[0091] Such adhesive fixation between the upper block 104 and the lower block 102 can be performed, for example, after a step of temporarily curing the thermosetting adhesive 50, and preferably after a step of completely curing the thermosetting adhesive 50. This is because, when the upper block 104 is not present relative to the lower block 102, the thermosetting adhesive 50 is more likely to come into contact with air, which can accelerate the curing of the thermosetting adhesive 50.

[0092] As described above, according to the first embodiment, the lower block 102 constituting the optical fiber block 100 is provided with a (first) groove 125 that extends in a direction intersecting (e.g., perpendicular to) the extension direction of the V-groove 121 and communicates with the V-groove 121 at the intersection.

[0093] Therefore, even if the thermosetting adhesive 50 applied to the optical axis portion when bonding the optical fiber block 100 and the PLC 200 flows into the V-groove 121, the thermosetting adhesive 50 can be drawn from the V-groove 121 into the groove 125 and escaped.

[0094] Therefore, it is possible to prevent the thermosetting adhesive 50 from remaining in the V-groove 121, which would hinder the placement of the optical fiber 30 in the V-groove 121 and make it difficult to adjust the optical axis of the optical fiber 30 relative to the PLC 200.

[0095] Furthermore, since the thermosetting adhesive 50 is applied to the optical axis portion through which light (e.g., blue light) passes, it is possible to prevent or suppress the influence of the dust collection effect that may occur in the case of the air gap method.

[0096] Furthermore, it is possible to prevent or suppress the decrease in the refractive index of the UV-curable adhesive that may occur when a UV-curable adhesive is used in the optical axis section, and the absorption of blue light that may occur when other adhesives are used, thereby effectively reducing the optical waveguide loss in the optical axis section.

[0097] In addition, a (second) groove 127 is provided in the lower block 102 at a position close to the end face on the opposite side of the Z-axis direction from the adhesive surface bonded by the thermosetting adhesive 50, the (second) groove 127 extending in a direction different from the extension direction of the V-groove 121 (for example, a perpendicular direction) and communicating with the V-groove 121 at the intersection.

[0098] Therefore, even if the UV-curable adhesive 72 for fixing the optical fiber 30 flows into the V-groove 121, the UV-curable adhesive 72 can be drawn from the V-groove 121 into the groove 127 and escaped. This makes it possible to suppress or prevent the UV-curable adhesive 72 from unintentionally flowing into the optical axis portion.

[0099] 11 is a perspective view showing an exemplary configuration of an optical fiber block 100A according to embodiment 2. The optical fiber block 100A shown in FIG. 11 is a capillary that can be connected to a PLC 200 in place of the optical fiber block 100 of embodiment 1.

[0100] The capillary 100A has, for example, one or more (three in the example of Figure 11) hole portions 131 (which may also be referred to as "fiber insertion holes 131") through which the optical fibers 30 are inserted, arranged in the X-axis direction in the same manner as the arrangement of the V-grooves 121 described above.

[0101] Each fiber insertion hole 131 has an inner diameter large enough to insert the optical fiber 30 therethrough, and is connected in the Z-axis direction. As the material of the capillary 100A, for example, quartz glass or borosilicate glass may be used, as in the case of the glass substrate 102 or 104 described above.

[0102] Grooves 123a extending along the Y-axis direction are provided on both sides of the X-axis direction on one of the surfaces of the capillary 100A facing each other in the Z-axis direction (for example, the end surface connected to the PLC 200).

[0103] The groove 123a corresponds to, for example, the groove 123 in the first embodiment, and is a groove for blocking the UV-curable adhesive 70 so as to prevent the UV-curable adhesive 70 from passing over the groove 123a and entering the hole portion 131 (optical axis portion). Therefore, the UV-curable adhesive 70 is applied to the end surface in the X-axis direction on the outer side than the groove 123a.

[0104] The groove 123a can prevent or suppress the UV-curable adhesive 70 from going beyond the groove 123a and entering the optical axis portion when the capillary 100A and the PLC 200 are bonded and fixed with the UV-curable adhesive 70.

[0105] Furthermore, grooves 125a and 127a having a depth in the Y-axis direction from the bottom surface of capillary 100A are provided on one of the opposing surfaces in the Y-axis direction (e.g., the bottom surface) of capillary 100A. Each of grooves 125a and 127a extends in a direction (e.g., the X-axis direction) intersecting the extension direction of hole 131 of capillary 100A and communicates with hole 131 at the intersection.

[0106] Groove 125a corresponds to, for example, groove 125 in embodiment 1, and when the thermosetting adhesive 50 applied to the optical axis portion flows into hole portion 131 due to capillary action, it plays a role in drawing the thermosetting adhesive 50 from hole portion 131 and releasing it in the direction along groove 125a.

[0107] On the other hand, groove 127a corresponds to groove 127 in embodiment 1, and when the UV-curable adhesive 72 for fixing the optical fiber 30 flows into the hole portion 131 due to capillary action, it serves to draw the UV-curable adhesive 72 from the hole portion 131 and release it in the direction along groove 127a.

[0108] Each of grooves 125a and 127a can be formed, for example, by a dicer or the like on the Y-axis direction below hole portion 131 so as to communicate with hole portion 131 of capillary 100A, and an opening that is open toward the Y-axis direction can be formed.

[0109] The depth in the Y-axis direction of each of grooves 125a and 127a communicating with hole 131 may be a depth that reaches the lower end of the outer diameter of hole 131, or a depth that exceeds the lower end of the outer diameter of hole 131 but does not reach the upper surface of capillary 100A. However, since the deeper the groove depth, the more likely it is that the physical strength of capillary 100A will decrease, the groove depth should be the minimum depth sufficient for communication with hole 131.

[0110] The width in the X-axis direction, position in the Z-axis direction, number in the Z-axis direction, and shape in cross section along the YZ plane of each groove 125a and groove 127a are not particularly limited and may be the same as or similar to those in embodiment 1.

[0111] By using a capillary for the optical fiber block 100A, the manufacturing process of the optical module 10 can be simplified compared to the first embodiment, which uses the optical fiber block 100 configured from the glass substrates 102 and 104. Other effects, such as suppression of dust collection effect, suppression of blue light absorption effect in the optical axis portion, and reduction of optical waveguide loss in the optical axis portion, are the same as or similar to those of the first embodiment.

[0112] Although the first and second embodiments have shown an example (e.g., FIG. 1 ) of the optical module 10 in which the optical fiber block 100 or the capillary 100A is connected to one side of the PLC 200, the present disclosure is not limited to such an embodiment. For example, the optical fiber block 100 illustrated in FIG. 6 or the capillary 100A illustrated in FIG. 11 may be connected to each side of the PLC 200 in the Z-axis direction via a heat-curing adhesive 50 in the optical axis portion and a UV-curing adhesive 70 in the portion avoiding the optical axis portion.

[0113] The term "connect" used in this disclosure may be read as "coupled." "Connected" or "coupled" may be understood to mean any direct or indirect "connection" or "coupling" between two or more elements. For example, the term may also be understood to include an indirect "connection" or "coupling" where one or more intermediate elements are interposed between two elements that are "connected" or "coupled" to each other.

[0114] Any reference to an element followed by a designation such as "first...," "second...," etc. does not limit the quantity or order of those elements. These designations are merely used as a convenient way to distinguish between two or more elements. For example, a reference to a first and a second element does not imply that only two elements may be employed, nor does it imply that the first element must precede the second element in any physical quantity.

[0115] Although the present disclosure has been described in detail above, it is clear to those skilled in the art that the spirit and scope of the present disclosure are not limited to the contents described throughout the present disclosure. The present disclosure can be implemented in modified and altered forms without departing from the spirit and scope of the present disclosure as defined by the claims. Therefore, the description of the present disclosure is intended for illustrative purposes only and does not have any limiting meaning on the spirit and scope of the present disclosure.

[0116] The present disclosure is useful in optical devices, including analytical devices that operate on visible light, such as, for example, a fluorescence microscope, a flow cytometer, or an ophthalmoscope.

[0117] 10 Optical module 30 Optical fiber 40 Alignment fiber 50 Thermosetting adhesive 70, 72 UV-setting adhesive 100 Optical fiber block 100A Optical fiber block (capillary) 102 Glass substrate (lower block) 104 Glass substrate (upper block) 121 V-groove 123, 123a, 125, 125a, 127, 127a, 141 Groove 131 Hole (fiber insertion hole) 200 PLC 210 Waveguide (core) 302 Core

Claims

1. An optical module comprising: an optical fiber block having a space in which an optical fiber is placed; an optical waveguide circuit having an optical waveguide; a thermosetting adhesive provided on an optical axis portion which is a portion through which light passes at the connection end face between the optical fiber block and the optical waveguide circuit; and a first groove provided in the optical fiber block, which intersects with the space extending along the optical fiber and communicates with the space at the portion where it intersects with the space.

2. An optical module as described in claim 1, wherein the optical fiber block comprises: an ultraviolet-curing adhesive for fixing the optical fiber at the end face opposite the connection end face; and a second groove located closer to the opposite end face than the first groove, intersecting the space extending along the optical fiber and communicating with the space at the portion where it intersects with the space.

3. The optical module according to claim 1, wherein the optical fiber block comprises: an ultraviolet-curing adhesive that bonds and fixes the optical fiber block and the optical waveguide circuit in a portion of the connection end face through which the light does not pass; and a third groove provided on at least one of the end faces of the optical fiber block and the optical waveguide circuit that form the connection end face, for blocking the intrusion of the ultraviolet-curing adhesive into the optical axis portion.

4. An optical module as claimed in claim 1 or 2, wherein the space is formed by a V-shaped groove in which the optical fiber is placed, and the groove communicating with the space has a depth greater than the depth from the top surface of the V-shaped groove.

5. An optical module according to any one of claims 1 to 3, wherein the light transmitted through the connection end face is light in the visible light range, and the thermosetting adhesive is made of a material that does not absorb light of blue wavelengths in the visible light range.

6. A method for manufacturing an optical module having an optical fiber block having a space in which an optical fiber is placed, and an optical waveguide circuit having an optical waveguide, wherein the optical fiber block has a first groove that intersects with the space extending along the optical fiber and communicates with the space at the portion that intersects with the space, the manufacturing method comprising the steps of: applying a thermosetting adhesive to an optical axis portion that is a portion through which light passes at the connection end face between the optical fiber block and the optical waveguide circuit; heating the thermosetting adhesive under conditions that do not completely cure the adhesive to temporarily cure it; with the thermosetting adhesive in a temporarily cured state, placing the optical fiber in the space and bringing the end face of the optical fiber into close contact with the thermosetting adhesive; and reheating the temporarily cured thermosetting adhesive to completely cure it.

7. A method for manufacturing an optical module as described in claim 6, wherein the optical fiber block has a second groove that intersects with the space extending along the optical fiber and communicates with the space at the portion that intersects with the space, at a position closer to the end face opposite the connection end face than the first groove, and the manufacturing method further comprises a step of applying an ultraviolet-curing adhesive to fix the optical fiber at the opposite end face between the step of adhering the end face of the optical fiber to the thermosetting adhesive and the step of reheating the thermosetting adhesive to completely harden it.

8. A method for manufacturing an optical module according to claim 6 or 7, further comprising the step of applying an ultraviolet-curing adhesive to the portion of the connection end face through which the light does not pass, prior to the step of applying the thermosetting adhesive, thereby adhesively fixing the optical fiber block and the optical waveguide circuit together.

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