Transparent hard-brittle material thick substrate, laser drilling method and application thereof

Abstract

This invention relates to a thick substrate of a transparent, hard, and brittle material, a laser drilling method therein, and its application. The laser drilling method includes: using a nanosecond laser to drill from a first surface to a second surface of the thick substrate, first forming a tapered segment with a gradually decreasing diameter from the first surface inwards; when the remaining un-drilled thickness is 0.2~0.9mm, adjusting the diameter to a preset diameter and continuing drilling perpendicular to the thick substrate to form a vertical segment connected to the tapered segment, constituting a pre-fabricated channel; then using an ultrafast laser to enlarge the hole along the pre-fabricated channel from the second surface, with a focal point diameter less than 5μm, to enlarge the diameter of the vertical segment to the target diameter, obtaining a micropore. The inlet diameter of the tapered segment on the first surface is at least 10μm larger than the preset diameter, and the target diameter is 2~20μm larger than the preset diameter, and the target diameter is smaller than the inlet diameter on the first surface. Using this method, the error in the diameter of the hole on the second surface of the thick substrate can be kept within ±0.5μm.

Description

Technical Field

[0001] This invention relates to the field of laser processing technology, and in particular to thick substrates of transparent, hard and brittle materials, as well as laser drilling methods and applications thereof. Background Technology

[0002] Fabricating micropores on transparent, hard, and brittle material substrates such as glass, sapphire, quartz, and transparent ceramics is a key process requirement in fields such as optical communication, 3D packaging, MEMS devices, and biomedical detection.

[0003] Currently, one of the most common methods for fabricating micropores on transparent, hard, and brittle material substrates is to modify the substrate using ultrafast lasers such as picosecond or femtosecond lasers, and then immerse the modified area in an acid solution for chemical etching. The preferential corrosion of the modified area by the acid forms the micropores. This method can fabricate micropores with diameters ranging from tens to hundreds of micrometers, offering advantages such as high processing efficiency and good hole wall quality. However, because the etching rate of transparent, hard, and brittle materials is similar in all directions during acid etching, controlling the hole size becomes extremely difficult when the substrate thickness is large. Therefore, this method is currently only applicable to thin substrates with a thickness of 300 μm or less; for thick substrates, it is almost impossible to fabricate micropores that meet the required precision, exhibiting significant limitations.

[0004] With the development of optoelectronic interconnect technology in computing centers, thick substrates with micro-aperture arrays are being used to insert standard communication optical fibers to form fiber optic arrays. Compared to thin substrates, thick substrates have higher mechanical strength and superior optical path stability, ensuring reliable optical alignment and mechanical fixation of the fiber optic array during long-term operation. However, these applications place extremely high demands on the dimensional and positional accuracy of the micro-apertures: taking standard communication optical fibers as an example, the diameter of the aperture's exit end needs to be precisely controlled within the range of the fiber diameter plus a predetermined margin, with an error not exceeding ±0.5μm, to ensure precise fixation of the optical fiber.

[0005] To address the need for micro-hole processing on thick substrates, laser drilling is currently the primary method. However, nanosecond lasers interact primarily with transparent, hard, and brittle materials through thermal effects, resulting in heat-affected zones and chipping dimensions typically ranging from several micrometers to tens of micrometers. In contrast, ultrafast lasers (picosecond or femtosecond) rely on nonlinear effects such as multiphoton absorption and avalanche ionization, requiring extremely high peak power and strict energy thresholds. These two methods differ fundamentally in their physical mechanisms. Based on these differences, it is widely believed that using nanosecond and ultrafast lasers sequentially within the same hole will result in residual thermal cracks and altered layers from the nanosecond laser, compromising the precision of the ultrafast laser's processing and preventing the achievement of high-precision exit hole diameters. Limited by this understanding, current technologies typically employ a single laser approach, either using nanosecond lasers or ultrafast lasers throughout the entire process.

[0006] However, when using ultrafast laser drilling, the laser energy initially acts on the substrate's incident surface, with the hole extending inward from the incident surface. As the drilling depth increases, the laser energy is continuously absorbed and scattered by the hole walls as it passes through the hole, resulting in a significant attenuation of the energy reaching the exit surface. This causes the hole to exhibit a tapered characteristic with a large incident surface and a small exit surface. Therefore, while this method can effectively control the incident hole diameter, it is difficult to precisely control the exit hole diameter within ±0.5 μm.

[0007] However, when using nanosecond laser drilling, there is an inherent contradiction between drilling depth and hole diameter control. As the drilling depth increases, the multiple reflections and scattering effects of the laser beam within the hole channel are significantly aggravated, causing fluctuations in the actual effective spot size and energy density distribution at the bottom of the hole. This effect is particularly pronounced when the drilling depth approaches the total thickness of the substrate, making precise control of the hole diameter at the bottom extremely difficult, and failing to meet the accuracy requirement of an exit hole diameter error not exceeding ±0.5μm.

[0008] Therefore, it is evident that neither ultrafast lasers nor nanosecond lasers can achieve the required precision of an exit hole diameter error of no more than ±0.5 μm on thick substrates of transparent, hard, and brittle materials using single laser drilling. This stringent precision requirement, coupled with the inherent processing difficulty of thick substrates, presents a sharp contradiction and has become a long-standing technical challenge in this field. Summary of the Invention

[0009] Therefore, it is necessary to provide a transparent, hard and brittle thick substrate and its laser drilling method and application to address the above problems, which can ensure that the error of the second surface side hole diameter on the transparent, hard and brittle thick substrate does not exceed ±0.5μm.

[0010] A laser drilling method for a thick substrate made of a transparent, hard, and brittle material includes the following steps:

[0011] A transparent, hard, and brittle material thick substrate is provided, the thick substrate having opposing first and second surfaces;

[0012] A nanosecond laser is used to drill from the first surface toward the second surface, first forming a tapered segment whose diameter gradually decreases from the first surface toward the interior. When the remaining thickness of the un-drilled section is 0.2mm to 0.9mm, the diameter is adjusted to a preset diameter and drilling continues perpendicular to the thick substrate, forming a vertical hole segment connected to the tapered segment, thus constituting a pre-fabricated channel. The inlet diameter of the tapered segment on the first surface is more than 10μm larger than the preset diameter.

[0013] An ultrafast laser is used to expand the hole along the pre-made channel from the second surface. The diameter of the focal spot is less than 5 μm. The diameter of the vertical hole segment is expanded to the target diameter to obtain a microhole. The target diameter is 2 μm to 20 μm larger than the preset diameter and is smaller than the inlet diameter of the first surface.

[0014] This invention decomposes the drilling process of thick substrates into two stages: nanosecond laser roughing and ultrafast laser finishing. The nanosecond laser is incident from the first surface and is responsible for the prefabrication of the tapered and vertical hole sections with large material removal. The ultrafast laser expands the hole along the prefabricated channel from the second surface and is only responsible for the finishing of the hole diameter on the second surface side. The two lasers perform different functions on the same channel, realizing functional decoupling and maximizing strengths while avoiding weaknesses, thus balancing processing efficiency and accuracy. During nanosecond laser drilling, the inlet diameter of the conical section on the first surface is more than 10 μm larger than the preset diameter, giving the sidewall of the conical section sufficient inclination. When the incident laser beam is reflected from the inner wall of the conical section, the large inclination causes the reflected light to tend to propagate towards the second surface, reducing energy loss and ensuring the formation quality of the vertical hole section. When the remaining thickness before drilling is 0.2 mm to 0.9 mm, vertical drilling is switched to ensure that the nanosecond laser heat-affected zone and edge chipping zone are confined to the area away from the second surface, reserving a material layer without thermal damage for ultrafast laser. The difference between the preset diameter and the target diameter is 2 μm to 20 μm, and the focal point diameter during ultrafast laser hole enlargement is less than 5 μm, ensuring that material removal is limited to the submicron level lateral scale, so that the enlargement of the second surface side hole diameter is precisely controlled within the target diameter. The determination of the above features takes into account the multi-physics coupling effect of the nanosecond laser heat-affected zone depth, the effective depth of the ultrafast laser, the material stress release critical point, and the laser energy distribution at the bottom of the deep hole. The parameters are interrelated and mutually restrictive, which together enable the present invention to achieve micro-hole processing with a second surface side aperture error of no more than ±0.5μm on a thick substrate, overcoming the inherent contradiction between precision and thickness in the prior art.

[0015] In one embodiment, the thickness of the thick substrate is 2mm to 5mm;

[0016] And / or, the inlet aperture of the tapered segment on the first surface is 10μm~300μm larger than the preset aperture;

[0017] And / or, when the remaining thickness of the un-drilled portion is 0.2mm~0.5mm, adjust the hole diameter to the preset hole diameter and turn to continue drilling perpendicular to the direction of the thick substrate;

[0018] And / or, the target aperture is 2μm~5μm larger than the preset aperture.

[0019] In one embodiment, the perpendicularity of the vertical hole segment to the second surface is greater than or equal to 87°.

[0020] In one embodiment, the center distance between the vertical hole segment before and after enlargement is less than 2 μm.

[0021] In one embodiment, the minimum aperture of the tapered segment is equal to the aperture of the vertical segment, and the tapered segment and the vertical segment transition smoothly at the junction.

[0022] In one embodiment, the inlet aperture of the tapered segment on the first surface is 140 μm to 160 μm;

[0023] And / or, the preset pore size is 121μm~124μm, and the target pore size is 126μm.

[0024] In one embodiment, the nanosecond laser uses an infrared nanosecond laser with a laser wavelength of 1.0μm to 1.2μm or a green nanosecond laser with a laser wavelength of 510nm to 550nm, with a pulse width of 1ns to 100ns and a repetition frequency of 10kHz to 2000kHz.

[0025] And / or, the ultrafast laser uses an ultraviolet femtosecond laser with a wavelength of 320nm~360nm, an ultraviolet picosecond laser with a wavelength of 320nm~360nm, a green femtosecond laser with a wavelength of 510nm~550nm, or a green picosecond laser with a wavelength of 510nm~550nm, with a pulse width of less than 10ps and a repetition frequency of 10kHz~5MHz.

[0026] A transparent, hard, and brittle thick substrate obtained using the laser drilling method, the transparent, hard, and brittle thick substrate having a plurality of micropores, the micropores penetrating a first surface and a second surface of the transparent, hard, and brittle thick substrate, the micropores including a conical segment located on the first surface side and a vertical hole segment connected to the conical segment, the inlet diameter of the conical segment on the first surface being larger than the diameter of the vertical hole segment.

[0027] In one embodiment, the micropores are arranged in an array.

[0028] An optical fiber array, comprising the aforementioned transparent hard and brittle material thick substrate and optical fibers, wherein the optical fibers pass through and are fixed in micropores of the transparent hard and brittle material thick substrate.

[0029] In this fiber optic array, the micro-holes on the thick substrate of the transparent, rigid material have a large inlet aperture on the first surface side, facilitating smooth fiber insertion; and a high-precision outlet aperture on the second surface side, allowing the fiber to be precisely fixed after passing through the micro-holes. Simultaneously, the high-precision aperture and excellent hole wall quality of the micro-holes ensure the positional accuracy and angular consistency of each fiber in the array, which is beneficial for improving the optical alignment accuracy and long-term operational stability of the fiber optic array. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of this application or the conventional technology, the drawings used in the description of the embodiments or the conventional technology will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 This is a schematic diagram of a laser drilling process according to an embodiment of the present invention;

[0032] Figure 2 This is a schematic diagram of a laser drilling process according to another embodiment of the present invention.

[0033] In the figure: 10, first surface; 20, second surface; 30, tapered section; 40, vertical hole section. Detailed Implementation

[0034] To facilitate understanding of the present invention, it will be described in more detail below. However, it should be understood that the present invention can be implemented in many different forms and is not limited to the embodiments or examples described herein. Rather, these embodiments or examples are provided to make the disclosure of the present invention more thorough and complete.

[0035] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments or examples only and is not intended to limit the invention. The optional scope of the term "and / or" as used herein includes any one of two or more of the related listed items, as well as any and all combinations of the related listed items, including any two related listed items, any more related listed items, or a combination of all related listed items.

[0036] In this invention, numerical ranges are involved. Unless otherwise specified, the numerical ranges are considered continuous and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe features or characteristics, the ranges may be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are included.

[0037] Combination Figure 1 and Figure 2 As shown, the laser drilling method for a thick substrate of a transparent, hard, and brittle material provided by the present invention includes the following steps:

[0038] A transparent, hard, and brittle material thick substrate is provided, the thick substrate having opposing first surface 10 and second surface 20;

[0039] A nanosecond laser is used to drill from the first surface 10 toward the second surface 20, first forming a tapered segment 30 whose diameter gradually decreases from the first surface 10 toward the interior. When the remaining thickness H of the un-drilled section is 0.2mm to 0.9mm, the diameter is adjusted to a preset diameter D3 and drilling continues perpendicular to the thick substrate, forming a vertical hole segment 40 connected to the tapered segment 30, thus forming a pre-fabricated channel. The inlet diameter D1 of the tapered segment 30 on the first surface 10 is more than 10μm larger than the preset diameter D3.

[0040] An ultrafast laser is used to enlarge the hole along the pre-made channel from the second surface 20. The diameter of the focal spot is less than 5μm, and the diameter of the vertical hole segment 40 is enlarged to the target hole diameter D4 to obtain a microhole. The target hole diameter D4 is 2μm to 20μm larger than the preset hole diameter D3, and the target hole diameter is smaller than the inlet hole diameter of the first surface.

[0041] This invention decomposes the drilling process of thick substrates into two stages: nanosecond laser roughing and ultrafast laser finishing. The nanosecond laser, incident from the first surface 10, is responsible for pre-fabricating the tapered section 30 and vertical hole section 40, which have a large material removal volume. The ultrafast laser, originating from the second surface 20, expands the hole along the pre-fabricated channel, focusing solely on finishing the hole diameter on the second surface 20. Its sub-micron-level processing resolution enables precise control of the hole diameter. Thus, the two lasers perform different functions on the same channel, achieving functional decoupling and maximizing strengths while minimizing weaknesses, balancing processing efficiency and precision. Furthermore, the ultrafast laser finishing stage results in a minimal heat-affected zone, smooth hole walls, and minimal edge chipping, ensuring hole wall quality.

[0042] Specifically, when the nanosecond laser drills from the first surface 10 towards the second surface 20, a tapered segment 30 is first formed, with the diameter gradually decreasing from the first surface 10 towards the interior. Since the entrance diameter D1 of the tapered segment on the first surface 10 is more than 10 μm larger than the preset diameter D3, the sidewalls of the tapered segment 30 have sufficient inclination. During nanosecond laser drilling, when the incident laser beam is reflected from the inner wall of the tapered segment 30, the greater the inclination of the sidewall, the more likely the reflected light is to propagate along the channel towards the second surface 20, rather than refracting back to the first surface 10 or laterally bombarding the inner wall of the tapered segment 30. This reduces the propagation loss of laser energy within the tapered segment 30, allowing more laser energy to reach the processing front of the vertical hole segment 40, ensuring the formation quality and dimensional consistency of the vertical hole segment 40.

[0043] When the remaining thickness H of the un-drilled portion is 0.2mm~0.9mm, the hole diameter is adjusted to the preset hole diameter D3 and drilling continues perpendicular to the thick substrate direction, forming a vertical hole segment 40 connected to the tapered segment 30, thus constituting a pre-fabricated channel. This combined operation ensures the geometric consistency of the channel before the tapered segment and the vertical hole segment intersect, providing ideal pre-fabricated channel conditions for subsequent high-precision ultrafast laser hole enlargement. Simultaneously, the control of this remaining thickness confines the heat-affected zone and chipping zone of the nanosecond laser to areas far from the second surface 20, thereby reserving a material layer free from thermal damage for ultrafast laser finishing. If the remaining thickness is greater than 0.9 mm, the required processing depth and material volume of the ultrafast laser increase significantly. Increased processing depth leads to intensified laser energy attenuation and scattering during propagation, compromising the accuracy of the aperture on the second surface 20. If the remaining thickness is less than 0.2 mm, the heat-affected zone and microcrack zone of the nanosecond laser have extended deep into the vicinity of the second surface 20. During ultrafast laser hole enlargement, stress release occurs in this damaged area, causing edge chipping on the second surface 20. Therefore, a remaining thickness range of 0.2 mm to 0.9 mm is a crucial condition for ensuring high-precision hole enlargement within an extremely thin material layer using ultrafast lasers.

[0044] With the nanosecond laser already performing roughing, the difference between the preset aperture D3 and the target aperture D4 is designed to be 2μm~20μm. This allows the ultrafast laser to remove only a thin layer of material from the inner wall of the vertical hole section during the hole enlargement stage. This minimal material removal during enlargement allows the ultrafast laser to correct for potential aperture deviations during the roughing stage. Furthermore, when the ultrafast laser enlarges the hole along the pre-fabricated channel from the second surface 20, the focal point diameter is less than 5μm. The focal point diameter determines the lateral resolution of the laser-material interaction. A focal point diameter of less than 5μm ensures that the material removal during hole enlargement is limited to the sub-micron lateral scale. This allows for precise control of the removal amount while ensuring sufficient material can be removed, ensuring that the aperture enlargement on the second surface 20 side is precisely controlled within the target aperture D4, guaranteeing that the aperture error on the second surface 20 side does not exceed ±0.5μm.

[0045] Therefore, the rapid material removal capability of nanosecond lasers and the submicron-level processing resolution of ultrafast lasers complement each other on the same channel. The control of the critical remaining thickness H reserves ideal finishing conditions for ultrafast lasers. The difference between the inlet aperture D1 and the preset aperture D3 ensures the energy utilization efficiency and the forming quality of the vertical hole segment 40 during the nanosecond laser roughing stage. The difference between the preset aperture D3 and the target aperture D4, combined with the small focal diameter of the ultrafast laser, achieves precision hole enlargement. The determination of the above features comprehensively considers the multi-physics coupling effects of the nanosecond laser heat-affected zone depth, the effective working depth of the ultrafast laser, the stress release critical point of hard, brittle, and transparent materials, and the laser energy distribution at the bottom of the deep hole. The parameters are interrelated and mutually restrictive, enabling the present invention to achieve micro-hole processing on the second surface 20 with a hole diameter error of no more than ±0.5μm on a thick substrate, overcoming the inherent contradiction between precision and thickness in the prior art.

[0046] It is understood that the transparent hard and brittle material described in this invention can be glass, sapphire, quartz, transparent ceramics, etc., such as borosilicate glass, quartz glass, or soda-lime glass.

[0047] The laser drilling method of this invention does not have particular limitations on the thickness of the substrate, and can achieve high-precision micro-hole processing on transparent, hard, and brittle material substrates with a thickness of 2 mm or more. Preferably, the thickness of the substrate is 2 mm to 5 mm. Within this preferred range, stable hole diameter accuracy can be obtained while ensuring processing efficiency.

[0048] In order to balance energy utilization efficiency and the forming quality of the vertical hole segment during the nanosecond laser roughing stage, the inlet aperture D1 of the tapered segment 30 on the first surface 10 is preferably 10μm to 300μm larger than the preset aperture D3, for example, 10μm, 15μm, 20μm, 25μm, 30μm, 35μm, 40μm, 45μm, 50μm, 60μm, 70μm, 80μm, 90μm, 100μm, 150μm, 200μm, 250μm or 300μm larger, and more preferably 10μm to 100μm, 10μm to 50μm, 15μm to 50μm or 15μm to 30μm larger. Similarly, in order to balance machining allowance and removal accuracy during the ultrafast laser finishing stage, the target aperture D4 is preferably 2μm~10μm larger than the preset aperture D3, and more preferably 2μm~5μm larger.

[0049] In order to achieve the best process transition between nanosecond laser roughing and ultrafast laser finishing, preferably, when the remaining thickness H of the undrilled hole is 0.5mm~0.2mm, the hole diameter is adjusted to the preset hole diameter D3 and the drilling direction is turned to be perpendicular to the thick substrate to continue drilling, so as to provide more ideal processing conditions for high-precision hole enlargement by ultrafast laser.

[0050] Optionally, the perpendicularity of the vertical hole segment 40 is greater than or equal to 87°. Perpendicularity refers to the angle of deviation of the centerline of the vertical hole segment relative to the normal to the surface of the thick substrate. A perpendicularity of 90° indicates that the hole is completely perpendicular to the substrate surface, and a perpendicularity greater than or equal to 87° indicates that the angle between the centerline of the hole and the normal direction does not exceed 3°. Controlling the perpendicularity to above 87° can prevent hole skewness, which would lead to uneven hole enlargement on one side during subsequent ultrafast laser enlargement, ensuring the concentricity of the enlarged hole and the unenlarged hole, thereby ensuring the processing accuracy of the exit end hole diameter.

[0051] Optionally, the center distance before and after the vertical aperture segment is enlarged is less than 2 μm. That is, the center distance between the target aperture D4 and the preset aperture D3 is less than 2 μm. This center distance is the offset of the final channel center formed after ultrafast laser enlargement relative to the center of the vertical aperture segment 40 pre-fabricated by nanosecond laser. Controlling the center distance within 2 μm ensures that the amount of enlargement by ultrafast laser on the inner wall of the vertical aperture segment 40 is uniformly distributed along the circumferential direction, avoiding excessive or insufficient enlargement on one side, thereby ensuring the roundness of the aperture on the second surface 20 and meeting the accuracy requirement that the aperture error does not exceed ±0.5 μm.

[0052] When a nanosecond laser drills a hole from the first surface 10 to the second surface 20, there are two possible settings for the minimum diameter of the tapered section 30 and the diameter of the vertical section 40. Specifically, as follows: Figure 1 As shown, in one case, the minimum aperture D2 of the tapered section 30 is equal to the preset aperture D3 of the vertical section 40. In this case, after ultrafast laser enlargement, the transition between the two remains smooth. Figure 2 As shown, another configuration involves the minimum aperture D2 of the tapered segment 30 being greater than the preset aperture D3 of the vertical segment 40. The two segments form a stepped structure at their junction. In this case, after ultrafast laser enlargement, the junction may be a smooth transition or it may still have a stepped structure. To ensure smooth debris removal and processing efficiency during nanosecond laser processing, preferably, the minimum aperture D2 of the tapered segment 30 is equal to the preset aperture D3 of the vertical segment 40, and the tapered segment 30 and the vertical segment 40 have a smooth transition at their junction.

[0053] The aperture parameters of the micropores on the thick substrate can be selected according to the actual application requirements. For example, in one embodiment, the target aperture D4 of the micropore can be set to 126 μm, and correspondingly, the inlet aperture D1 of the tapered segment 30 on the first surface 10 can be set to 140 μm to 160 μm, and the preset aperture D3 of the vertical aperture segment 40 can be set to 121 μm to 124 μm.

[0054] It should be noted that the nanosecond laser used in this invention can be an infrared nanosecond laser with a wavelength of 1.0μm to 1.2μm or a green nanosecond laser with a wavelength of 510nm to 550nm, with a pulse width of 1ns to 100ns and a repetition frequency of 10kHz to 2000kHz. The ultrafast laser used can be an ultraviolet femtosecond laser with a wavelength of 320nm to 360nm, an ultraviolet picosecond laser with a wavelength of 320nm to 360nm, a green femtosecond laser with a wavelength of 510nm to 550nm, or a green picosecond laser with a wavelength of 510nm to 550nm, with a pulse width of less than 10ps and a repetition frequency of 10kHz to 5MHz.

[0055] The present invention also provides a transparent hard and brittle material thick substrate obtained by the laser drilling method, the transparent hard and brittle material thick substrate having a plurality of micropores, and the micropores penetrating the first surface and the second surface of the transparent hard and brittle material thick substrate, the micropores including a conical segment located on the first surface side and a vertical hole segment connected to the conical segment, the inlet diameter of the conical segment on the first surface being larger than the diameter of the vertical hole segment.

[0056] It can be understood that the vertical hole segment in the micro-hole is obtained by expanding the vertical hole segment in the pre-formed channel formed in the nanosecond laser roughing stage with an ultrafast laser, and its hole diameter is expanded from the preset hole diameter to the target hole diameter.

[0057] The micropores of this invention gradually decrease in diameter from the first surface side inwards, transforming into constant-diameter straight holes in the interior, resembling a trumpet-shaped structure. The first surface side has a larger inlet diameter, serving as a guide and introducing element; the second surface side has a high-precision constant-diameter straight hole section, enabling precise fixation of components passing through the micropores. This structure is particularly suitable for applications requiring guidance and introduction at one end and precise fixation at the other.

[0058] It is understood that the distribution of multiple micropores can be controlled according to actual application requirements; for example, multiple micropores can be arranged in an array.

[0059] The present invention also provides an optical fiber array, the optical fiber array comprising the aforementioned transparent hard and brittle material thick substrate and optical fibers, the optical fibers passing through and being fixed in micropores of the transparent hard and brittle material thick substrate.

[0060] In this fiber optic array, the micro-holes on the thick substrate of the transparent, rigid material have a large inlet aperture on the first surface side, facilitating smooth fiber insertion; and a high-precision outlet aperture on the second surface side, allowing the fiber to be precisely fixed after passing through the micro-holes. Simultaneously, the high-precision aperture and excellent hole wall quality of the micro-holes ensure the positional accuracy and angular consistency of each fiber in the array, which is beneficial for improving the optical alignment accuracy and long-term operational stability of the fiber optic array.

[0061] The technical solution of the present invention will be further described below through specific embodiments. However, those skilled in the art will understand that the following embodiments are only for illustrating the present invention and should not be regarded as limiting the scope of the present invention. Unless otherwise specified, specific conditions in the embodiments are performed under conventional conditions or conditions recommended by the manufacturer. Reagents or instruments used without specified manufacturers are all commercially available conventional products.

[0062] Example 1

[0063] A 3mm thick borosilicate glass substrate was selected, and after cleaning and drying, it was fixed on the worktable of the laser processing platform.

[0064] An infrared nanosecond laser (wavelength 1064nm, pulse width 50ns, repetition frequency 50kHz) is used to focus the laser at a predetermined hole location on the first surface of the substrate, drilling the substrate from the first surface to the second surface. During the process, the diameter of the inlet hole on the first surface is 150μm, gradually decreasing from the first surface inwards to form a tapered section. When the drilling depth reaches 2.8mm (i.e., the remaining thickness before drilling is 0.2mm), the hole diameter is adjusted to 123μm, and vertical drilling begins, forming a vertical hole segment connected to the tapered section, constituting a pre-fabricated channel. At this point, the diameter of the vertical hole segment is measured to be 123μm, and the verticality is 88°.

[0065] A picosecond ultraviolet laser (wavelength 355nm, pulse width 10ps, repetition rate 200kHz) was used to incident the laser from the second surface of the substrate, with the focal point diameter controlled at 3μm. Hole enlargement was performed along pre-formed channels from the second surface to the first surface. The diameter of the vertical holes in the pre-formed channels was increased from 123μm to 126μm. The hole diameter was monitored in real time during processing, and processing was stopped when the hole diameter reached 126±0.5μm.

[0066] The fabricated micropores were inspected using high-precision optical measuring equipment. The diameter of the pore on the second surface side was 126.2 μm with an error of +0.2 μm, meeting the accuracy requirement of 126 ± 0.5 μm. The diameter of the pore on the first surface side was 151 μm. The micropores on the second surface side were observed using a scanning electron microscope (SEM). The pore wall roughness (Ra) was ≤0.35 μm, the chipped edge size was <2 μm, the pore roundness was >99%, and there were no significant microcracks or heat-affected zones.

[0067] In addition, the processing efficiency of this embodiment is as follows: nanosecond laser pre-drilling (2.8mm) takes about 2 seconds, ultrafast laser fine reaming (0.2mm) takes about 2 seconds, and a single hole takes about 4 seconds in total.

[0068] Example 2

[0069] A quartz glass substrate with a thickness of 2mm was selected, and after cleaning and drying, it was fixed on the worktable of the laser processing platform.

[0070] A green nanosecond laser (wavelength 532nm, pulse width 20ns, repetition rate 80kHz) is used to focus the laser at a predetermined hole location on the first surface of the substrate, drilling the substrate from the first surface to the second surface. During the process, the diameter of the inlet hole on the first surface is 150μm, gradually decreasing from the first surface inwards to form a tapered segment. When the drilling depth reaches 1.5mm (i.e., the remaining thickness before drilling is 0.5mm), the hole diameter is adjusted to 124μm, and vertical drilling begins, forming a vertical hole segment connected to the tapered segment, constituting a pre-fabricated channel. At this point, the diameter of the vertical hole segment is measured to be 124μm, and the verticality is 89°.

[0071] A green femtosecond laser (wavelength 530nm, pulse width 500fs, repetition rate 500kHz) was used, incident from the second surface of the substrate, with the focal point diameter controlled at 4μm. Hole enlargement was performed along pre-fabricated channels from the second surface to the first surface. The diameter of the vertical holes in the pre-fabricated channels was increased from 124μm to 126μm. The hole diameter was monitored in real time during processing, and processing was stopped when the hole diameter reached 126±0.5μm.

[0072] The microholes were inspected using high-precision optical measuring equipment. The diameter of the hole on the second surface side was 125.8 μm with an error of -0.2 μm, which meets the accuracy requirement of 126 ± 0.5 μm.

[0073] Example 3

[0074] A 5mm thick soda-lime glass substrate was selected, and after cleaning and drying, it was fixed on the worktable of the laser processing platform.

[0075] An infrared nanosecond laser (wavelength 1064nm, pulse width 100ns, repetition frequency 30kHz) is used to focus the laser at a predetermined hole location on the first surface of the substrate, drilling the substrate from the first surface to the second surface. During the process, the diameter of the inlet hole on the first surface is 150μm, gradually decreasing from the first surface inwards to form a tapered segment. When the drilling depth reaches 4.8mm (i.e., the remaining thickness before drilling is 0.2mm), the hole diameter is adjusted to 122μm, and vertical drilling begins, forming a vertical hole segment connected to the tapered segment, constituting a pre-fabricated channel. At this point, the diameter of the vertical hole segment is measured to be 122μm, and the verticality is 88°.

[0076] A green femtosecond laser (wavelength 532nm, pulse width 800fs, repetition rate 300kHz) was used, incident from the second surface of the substrate, with the focal point diameter controlled at 4.5μm. Hole enlargement was performed along pre-formed channels from the second surface to the first surface. The diameter of the vertical hole segment in the pre-formed channel was increased from 122μm to 126μm. The hole diameter was monitored in real time during processing, and processing was stopped when the hole diameter reached 126±0.5μm.

[0077] The microholes were inspected using high-precision optical measuring equipment. The diameter of the hole on the second surface side was 126.1 μm with an error of +0.1 μm, which meets the accuracy requirement of 126 ± 0.5 μm.

[0078] Example 4

[0079] A 2.5mm thick borosilicate glass substrate was selected, and after cleaning and drying, it was fixed on the worktable of the laser processing platform.

[0080] An infrared nanosecond laser (wavelength 1064nm, pulse width 40ns, repetition frequency 60kHz) is used to focus the laser at a predetermined hole location on the first surface of the substrate, drilling the substrate from the first surface to the second surface. During the process, the diameter of the inlet hole on the first surface is 145μm, gradually decreasing from the first surface inwards to form a tapered segment. When the drilling depth reaches 2.0mm (i.e., the remaining thickness before drilling is 0.5mm), the hole diameter is adjusted to 123μm, and vertical drilling begins, forming a vertical hole segment connected to the tapered segment, constituting a pre-fabricated channel. At this point, the diameter of the vertical hole segment is measured to be 123μm, and the verticality is 89°.

[0081] A picosecond ultraviolet laser (wavelength 355nm, pulse width 10ps, repetition rate 400kHz) was used, incident from the second surface of the substrate, with the focal point diameter controlled at 3.5μm. Hole enlargement was performed along pre-fabricated channels from the second surface to the first surface. The diameter of the vertical segments in the pre-fabricated channels was increased from 123μm to 126μm. The hole diameter was monitored in real time during processing, and processing was stopped when the hole diameter reached 126±0.5μm.

[0082] The microholes were inspected using high-precision optical measuring equipment. The diameter of the hole on the second surface side was 126.0 μm with an error of 0 μm, which meets the accuracy requirement of 126 ± 0.5 μm.

[0083] To verify the feasibility and processing stability of the method of the present invention, a borosilicate glass substrate with a thickness of 3 mm was selected, and batch processing tests were carried out according to the method of Example 1. The sample size was 100 microholes. The results of the second surface side hole diameter are shown in Table 1 and Table 2. With the hole center after enlargement as the base point, the distance between the hole center after enlargement and the adjacent hole center after enlargement does not exceed 1 micrometer.

[0084] Table 1

[0085]

[0086] Table 2

[0087]

[0088] As shown in Tables 1 and 2, the micropores processed by the method of the present invention have a pore diameter height concentrated around the target value of 126 μm on the second surface side, with 68% of the pore diameters distributed within the range of 125.9 μm to 126.1 μm (i.e., within ±0.1 μm of error). The pore diameter error of all 100 samples is within ±0.5 μm. The CPK value is 1.85 (>1.33), indicating sufficient process capability and good mass production stability.

[0089] Comparative Example 1

[0090] A 2mm thick borosilicate glass substrate was selected, and after cleaning and drying, it was fixed on the worktable of the laser processing platform.

[0091] An ultraviolet picosecond laser (wavelength 355nm, pulse width 10ps, repetition frequency 200kHz) is used to focus the laser at a predetermined hole position on the second surface of the substrate, and a hole with a diameter of 126μm is drilled from the second surface to the first surface.

[0092] The comparative sample consisted of 50 micropores, and the pore diameter results on the second surface side are shown in Table 3.

[0093] Table 3

[0094]

[0095] Comparative Example 2

[0096] A 2mm thick borosilicate glass substrate was selected, and after cleaning and drying, it was fixed on the worktable of the laser processing platform.

[0097] An infrared nanosecond laser (wavelength 1064nm, pulse width 10ns, repetition frequency 50kHz) is used to focus the laser at a predetermined hole location on the first surface of the substrate, and drilling is performed on the substrate from the first surface to the second surface. During the processing, the diameter of the inlet hole on the first surface is 150μm.

[0098] The comparative sample consisted of 50 micropores, and the pore diameter results on the second surface side are shown in Table 4.

[0099] Table 4

[0100]

[0101] Comparative Example 1 shows that when using an ultrafast laser to directly drill from the second surface to the first surface, the hole diameter on the second surface fluctuates greatly. Comparative Example 2 shows that when using a nanosecond laser to directly drill from the first surface to the second surface, the hole wall is rough, and the chipping size on the second surface is large. The pass rate for both methods is 0%. Therefore, neither using a nanosecond laser to directly drill from the first surface to the second surface nor using an ultrafast laser to directly drill from the second surface to the first surface can meet the accuracy requirement of a hole diameter error not exceeding ±0.5μm.

[0102] Comparative Example 3

[0103] The only difference between Comparative Example 3 and Example 1 is that when the drilling depth reaches 2.0 mm (i.e., the remaining thickness before drilling is 1.0 mm), the diameter of the hole is adjusted to 123 μm, and vertical drilling begins to form a vertical hole segment connected to the conical section, thus constituting a prefabricated channel.

[0104] When the remaining thickness is 1 mm, the required processing depth and amount of material for ultrafast laser processing increase significantly. Due to the increased processing depth, the laser energy attenuates and scatters during propagation, causing the aperture deviation on the second surface side to increase to ±2.8 μm. Furthermore, the increased material removal leads to heat accumulation, resulting in microcracks on the hole walls and a sharp drop in the yield rate to 8%.

[0105] Therefore, when the remaining thickness exceeds 0.9 mm, the processing depth of the ultrafast laser is too large, and the aperture accuracy cannot be guaranteed, proving that 0.9 mm is the upper limit of the critical range of this invention.

[0106] Comparative Example 4

[0107] The only difference between Comparative Example 4 and Example 1 is that when the drilling depth reaches 2.9 mm (i.e., the remaining thickness before drilling is 0.1 mm), the diameter of the hole is adjusted to 123 μm, and vertical drilling begins to form a vertical hole segment connected to the conical section, thus constituting a prefabricated channel.

[0108] When the remaining thickness is 0.1 mm, although the ultrafast laser processing is minimal, the heat-affected zone and microcrack zone from the nanosecond laser pre-drilling have already extended to a depth of less than 0.1 mm. During the subsequent ultrafast laser reaming process, stress release occurs in this damaged area, resulting in a chipping edge greater than 5 μm in the second surface side hole diameter.

[0109] Therefore, when the remaining thickness is less than 0.2 mm, the heat-affected zone of the nanosecond laser has extended to the confluence surface, making it impossible to guarantee the quality of the micropores, thus proving that 0.2 mm is the lower limit of the critical range of this invention.

[0110] Comparative Example 5

[0111] The only difference between Comparative Example 5 and Example 1 is that the diameter of the hole was adjusted to 120 μm, and the hole was drilled vertically upwards to form a vertical hole segment connected to the conical segment, thus forming a prefabricated channel.

[0112] When the diameter of the vertical aperture section is 120 μm, the single-sided aperture expansion amount of the ultrafast laser reaches 3 μm (expanding from 120 μm to 126 μm). Excessive aperture expansion leads to an increase in the number of laser scanning revolutions, and the accumulated heat causes the aperture wall to recast, reducing the roundness to 97%, which does not meet the form and position tolerance requirements of fiber arrays.

[0113] Comparative Example 6

[0114] The only difference between Comparative Example 6 and Example 1 is that the diameter of the hole was adjusted to 125 μm, and the hole was drilled vertically upwards to form a vertical hole segment connected to the conical segment, thus forming a prefabricated channel.

[0115] When the aperture of the vertical aperture section is 125μm, since only 0.5μm of expansion is required on one side, the ultrafast laser is difficult to focus stably at this scale, resulting in an "overburning" phenomenon, which causes the local aperture to abnormally expand to more than 127.5μm.

[0116] Comparative Examples 5 and 6 show that the optimal matching range for seamless integration with ultrafast laser aperture expansion parameters is when the difference between the target aperture and the preset aperture is 2μm to 20μm.

[0117] Comparative Example 7

[0118] The only difference between Comparative Example 7 and Example 1 is that the diameter of the inlet aperture on the first surface is 130 μm during the processing.

[0119] When the inlet aperture of the first surface is 130 μm, the difference between the inlet aperture and the aperture of the vertical section (123 μm) is only 7 μm, which is less than the 10 μm limit specified in this invention, indicating insufficient taper of the tapered section. During nanosecond laser drilling, due to the small inclination of the tapered section sidewall, the propagation direction of the incident laser beam after reflection from the inner wall of the tapered section tends to fold back towards the first surface or laterally bombard the inner wall of the tapered section, increasing the propagation loss of laser energy within the tapered section. Measurement results show that the laser energy reaching the processing front of the vertical section decreases, the diameter consistency of the vertical section deteriorates, and the aperture deviation on the second surface side expands to ±1.8 μm, failing to meet the accuracy requirement of an error not exceeding ±0.5 μm.

[0120] Comparative Example 8

[0121] The only difference between Comparative Example 8 and Example 1 is that the ultraviolet picosecond laser is incident from the second surface of the substrate, and the focal diameter is controlled at 6 μm.

[0122] When the focal spot diameter is 6 μm, the lateral resolution of the ultrafast laser decreases, and material removal during the hole enlargement process cannot be confined to the sub-micron lateral scale. Measurement results show that the aperture deviation on the second surface side expands to ±1.2 μm, failing to meet the accuracy requirement of an error not exceeding ±0.5 μm. Therefore, the focal spot diameter should be controlled below 5 μm.

[0123] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0124] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A laser drilling method for a thick substrate of a transparent, hard, and brittle material, characterized in that, Includes the following steps: A transparent, hard, and brittle material thick substrate is provided, the thick substrate having opposing first and second surfaces; A nanosecond laser is used to drill from the first surface toward the second surface, first forming a tapered segment whose diameter gradually decreases from the first surface toward the interior. When the remaining thickness of the un-drilled section is 0.2mm to 0.9mm, the diameter is adjusted to a preset diameter and drilling continues perpendicular to the thick substrate, forming a vertical hole segment connected to the tapered segment, thus constituting a pre-fabricated channel. The inlet diameter of the tapered segment on the first surface is more than 10μm larger than the preset diameter. An ultrafast laser is used to expand the hole along the pre-made channel from the second surface. The diameter of the focal spot is less than 5 μm. The diameter of the vertical hole segment is expanded to the target diameter to obtain a microhole. The target diameter is 2 μm to 20 μm larger than the preset diameter and is smaller than the inlet diameter of the first surface.

2. The laser drilling method for a thick substrate of a transparent, hard, and brittle material according to claim 1, characterized in that, The thickness of the thick substrate is 2mm to 5mm; And / or, the inlet aperture of the tapered segment on the first surface is 10μm~300μm larger than the preset aperture; And / or, when the remaining thickness of the un-drilled portion is 0.2mm~0.5mm, adjust the hole diameter to the preset hole diameter and turn to continue drilling perpendicular to the direction of the thick substrate; And / or, the target aperture is 2μm~5μm larger than the preset aperture.

3. The laser drilling method for a thick substrate of a transparent, hard, and brittle material according to claim 1, characterized in that, The perpendicularity of the vertical hole segment to the second surface is greater than or equal to 87°.

4. The laser drilling method for a thick substrate of a transparent, hard, and brittle material according to claim 1, characterized in that, The center distance between the vertical hole section before and after enlargement is less than 2μm.

5. The laser drilling method for a thick substrate of a transparent, hard, and brittle material according to claim 1, characterized in that, The minimum diameter of the tapered section is equal to the diameter of the vertical section, and the tapered section and the vertical section transition smoothly at the joint.

6. The laser drilling method for a thick substrate of a transparent, hard, and brittle material according to any one of claims 1 to 5, characterized in that, The inlet aperture of the tapered segment on the first surface is 140μm~160μm; And / or, the preset pore size is 121μm~124μm, and the target pore size is 126μm.

7. The laser drilling method for a thick substrate of a transparent, hard, and brittle material according to any one of claims 1 to 5, characterized in that, The nanosecond laser used is an infrared nanosecond laser with a wavelength of 1.0μm to 1.2μm or a green nanosecond laser with a wavelength of 510nm to 550nm, with a pulse width of 1ns to 100ns and a repetition frequency of 10kHz to 2000kHz. And / or, the ultrafast laser uses an ultraviolet femtosecond laser with a wavelength of 320nm~360nm, an ultraviolet picosecond laser with a wavelength of 320nm~360nm, a green femtosecond laser with a wavelength of 510nm~550nm, or a green picosecond laser with a wavelength of 510nm~550nm, with a pulse width of less than 10ps and a repetition frequency of 10kHz~5MHz.

8. A transparent, hard, and brittle thick substrate obtained by the laser drilling method according to any one of claims 1 to 7, characterized in that, The transparent hard and brittle material thick substrate has a plurality of micropores, and the micropores penetrate the first surface and the second surface of the transparent hard and brittle material thick substrate. The micropores include a conical segment located on the first surface side and a vertical hole segment connected to the conical segment. The inlet diameter of the conical segment on the first surface is larger than the diameter of the vertical hole segment.

9. The transparent, hard, and brittle thick substrate according to claim 8, characterized in that, The micropores are arranged in an array.

10. A fiber optic array, characterized in that, The fiber array includes a transparent, hard, and brittle material thick substrate as described in claim 8 or claim 9, and an optical fiber, wherein the optical fiber passes through and is fixed in a micropore in the transparent, hard, and brittle material thick substrate.

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