JP2004196585A - Method for forming heterogeneous phase within material with laser beam, structure and optical parts - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for forming a heterogeneous phase having a complex two- or three-dimensional shape within a transparent material such as glass by irradiating the interior of the material with a laser beam without using a scanning mechanism. <P>SOLUTION: In the method for forming the heterogeneous phase within a material, a pulsed laser beam is converged on a plurality of desired positions within a material by controlling phase and/or amplitude independently in a plurality of regions of wave fronts of the pulsed laser beam, and parts on which the pulsed laser beam have been converted within the material are altered by photoinduction to form the heterogeneous phase in the plurality of desired positions within the material at the same time. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention provides a method of forming a heterogeneous phase, particularly a two-dimensional or three-dimensional heterogeneous phase, by irradiating a laser beam inside a transparent material such as glass without using a scanning mechanism, and The present invention relates to a structure having a heterogeneous phase inside produced by the method, and an optical component having the structure.
Transparent structures with heterogeneous phases formed by this method are mainly used for optical information processing, optical communication systems, etc., optical filters, multiplexing / demultiplexing elements, polarizing elements, steep bent optical waveguides. It is suitable for optical parts such as an ultra-small coupling / branching, an all-optical switch that actively controls light, an optical arithmetic element, and an optical bistable element.
Moreover, this method is suitable also for forming a reinforcement part in the inside of the transparent material utilized in information processing, an architecture, the energy field | area, etc.
[0002]
[Prior art]
In recent years, with the spread of optical information processing, optical waveguides in which a high refractive index region is formed in a transparent medium such as glass have been manufactured. On the other hand, research and development of photonic crystals, in which a high refractive index region having a period of about the wavelength of light is formed in a transparent medium such as glass and the light is controlled by the structure, are being actively researched and developed. In order to form a portion that becomes a linear circuit in an optical waveguide or a high refractive index phase of a photonic crystal, a material that can be formed in a transparent medium by controlling a region having a higher refractive index than the medium, and the material A method of controlling and forming a region having a large refractive index is necessary. In addition, it is one of the issues to have complicated functions by optical parts and integration, and it is hoped to produce circuit parts of optical parts with complicated two-dimensional shapes and three-dimensional shapes. It is rare.
On the other hand, a transparent material with a small thickness such as a plate shape is often used in information processing, architecture, energy fields and the like. These plate-like transparent materials are used in various environments, and are required to have excellent strength depending on applications, and it is also necessary to provide a reinforcing portion inside the material.
[0003]
A typical method of manufacturing an optical waveguide is SiO₂A region called a core having a refractive index higher than that of the substrate is formed on a substrate glass containing as a main component, the core is processed by a process such as etching, and is embedded again with a material having a refractive index lower than that of the core. It is produced by. Such a method is difficult to manufacture because it requires a very complicated process, and the optical waveguide to be manufactured is limited to a planar shape. Similarly, in the production of photonic crystals so far, several layers of semiconductors are formed on a semiconductor substrate having a high refractive index, fine processing is performed by etching, and a high refractive index portion at a light wavelength level and A structure in which the low refractive index portions are arranged with a period of a wavelength level is formed. Therefore, also in this case, the production is complicated and difficult, and the photonic crystal produced is also limited to a planar shape.
[0004]
As a method for three-dimensionally forming a linear circuit portion of an optical waveguide in glass, for example, a method of forming a high refractive index region in the glass by laser light irradiation is known (see Patent Document 1). . In this method, it is considered that the refractive index of the region is changed by changing the molecular structure of the glass due to the high electromagnetic field of light in the focused irradiation region of the laser light in the glass. In this method, since the refractive index change occurs only in the condensing region, the condensing point is three-dimensionally scanned inside the glass to form a three-dimensional region where the refractive index changes, and the linear shape of the optical waveguide It is possible to configure the circuit portion three-dimensionally. In this method, not only high-refractive-index regions but also laser irradiation is used to generate crystals and increase the density due to various light effects such as heat, photochemical reaction, oxidation / reduction of substances, and non-linear effects. It is known that a heterogeneous phase (called a heterogeneous phase) can be formed in a material by so-called light-induced changes such as bubble generation. In this method, it has also been proposed that an optical component such as a photonic crystal can be produced by using the heterogeneous phase formed.
[0005]
In the method of forming a heterogeneous phase inside the material by irradiation with laser light as described above, in order to increase the power density of the laser light, the pulse time width is pico (10^-12) Seconds to femto (10^-15) Ultra-short pulse lasers that are very narrow in seconds are used. However, because of the laser mechanism, the repetition frequency of the laser pulse is practically limited to 1 kHz to several hundred kHz, so that when a heterogeneous phase having a smooth interface is to be formed, the laser beam condensing point is scanned at high speed. There is a problem that manufacturing throughput (processing amount per hour) is low. In addition, in order to scan the condensing point of the laser beam, a device having a highly accurate moving mechanism is required, and such a device is complicated and expensive.
[0006]
Furthermore, in the above-described method, since a high refractive index region is formed at the condensing point of the laser light, an aggregate of elliptical high refractive index regions generated by one pulse is used as a high circuit such as a linear circuit portion of an optical waveguide. Although the refractive index region is formed, the current ultrahigh pulse laser device with a high power density capable of forming a high refractive index region has many intensity fluctuations for each pulse and low pointing stability. Taking the case of forming a high refractive index region as an example, the conceptual shape of the high refractive index region formed by scanning with laser light is as shown in FIG. 1A. 1B and 1C graphically show the amount of eccentricity and the amount of fluctuation in outer diameter.
As is clear from these graphs, the formed high refractive index region has a large amount of eccentricity and external shape variation, and has a high position accuracy and shape accuracy, as well as a linear circuit portion of an optical waveguide having a smooth interface. The production of the refractive index region is difficult. Therefore, the basic structure of the optical component as shown in FIG. 4, particularly the formation of the optical coupling portions 15 a and 15 b of the directional coupler 17 shown in FIG. 4A and the Y branch portion 15 c of the Y branch waveguide 18 shown in FIG. When used, the positional accuracy and the shape accuracy are insufficient, and the optical characteristics of the obtained optical components vary. For this reason, it has been difficult to achieve a sufficient loss reduction and stable production of the optical waveguide structure.
[0007]
Further, in the field of laser processing, batch formation of processing patterns using an ultrashort pulse laser and a diffractive optical element has been performed (see, for example, Patent Documents 2 to 4). However, these methods are based on beam splitting and two-dimensional imaging, and are limited to sublimation processing (ablation processing). Therefore, it is not intended to form a heterogeneous phase having a complicated two-dimensional shape or a three-dimensional shape inside the material.
[0008]
In addition, a three-dimensional structure forming method by forming a three-dimensional image is used for three-dimensional molding by photocuring of a resin material, patterning on a resist, and the like (see, for example, Patent Document 5 and Patent Document 6). These methods do not disclose a method for controlling phase and / or amplitude in multiple regions of a pulsed laser beam, and relate to the formation of three-dimensional structures for some limited materials, such as photocured materials. Forming a heterogeneous phase using high energy inside a general material (glass, plastic, semiconductor, etc.) in the formation of a linear circuit portion of an optical waveguide or a high refractive index phase of a photonic crystal Is not shown at all, and application to material processing by local heating or material modification is not shown.
[0009]
[Patent Document 1]
JP 9-311237 A
[Patent Document 2]
JP 2000-280085 A
[Patent Document 3]
JP 2001-138083 A
[Patent Document 4]
JP 2001-212800 A
[Patent Document 5]
JP-A-4-267132
[Patent Document 6]
JP-A-8-286591
[0010]
[Problems to be solved by the invention]
In order to solve the above-mentioned problems of the prior art, the present invention irradiates a laser beam inside a material without using a scanning mechanism to form a heterogeneous phase, particularly a heterogeneous phase having a complicated two-dimensional shape or three-dimensional shape. And a structure having a heterogeneous phase in the interior produced by the method, and an optical component having the structure.
The method of the present invention is suitable for forming an optical functional structure having a complicated two-dimensional shape or a three-dimensional shape typified by a circuit portion of an optical waveguide in a transparent material such as glass. It is also suitable for forming a reinforcing part inside a transparent structural material (window material, transparent substrate for display, etc.). Eliminate the low.
[0011]
[Means for Solving the Problems]
In the formation of a heterogeneous phase inside a material by focused irradiation of a pulsed laser beam, the present inventors independently controlled the phase and / or amplitude of a plurality of regions of the wavefront of the pulsed laser beam. It was found that a heterogeneous phase having a complicated two-dimensional shape or a three-dimensional shape can be collectively formed in the material by condensing the laser beam at a plurality of desired positions inside the material.
That is, a continuous pulse is formed by forming a condensing shape inside a material as an aggregate of a plurality of condensing points of a pulse laser beam and / or a continuous condensing point having a certain size such as a linear shape or a curved shape. The laser beam focused part is changed by light induction to form a heterogeneous phase at a plurality of desired positions inside the material, thereby forming a complicated two-dimensional shape inside the material, or tertiary It has been found that heterogeneous phases having an original shape can be formed collectively.
Furthermore, it has been found that by using an ultrashort pulse laser with a pulse width of femtosecond level in the method, not only the positional accuracy and shape accuracy of the heterogeneous phase can be improved, but also the manufacturing throughput can be improved. completed.
[0012]
Therefore, the present invention focuses the pulse laser beam at a plurality of desired positions inside the material by independently controlling the phase and / or the amplitude of the wavefront of the pulse laser beam. A heterogeneous phase inside the material, wherein a heterogeneous phase is collectively formed at a plurality of desired positions inside the material by causing a light-induced change in a portion where the pulse laser beam inside the material is condensed A method of forming a phase is provided.
In the method of the present invention, the plurality of heterogeneous phases formed inside the material may be in a two-dimensional positional relationship with each other inside the material.
In the method of the present invention, the plurality of heterogeneous phases formed in the material may be in a three-dimensional positional relationship with each other in the material.
In the method of the present invention, the plurality of heterogeneous phases may be present continuously in the material and may have a two-dimensional shape or a three-dimensional shape.
[0013]
In the method of the present invention, the spatial power density represented by the following formula is 10 at a desired position in the material.^TenW / cm^Three-10^{twenty four}W / cm^ThreeIt is preferable that the pulsed laser beam is focused to form a heterogeneous phase at a desired position in the material.
Spatial power density (W / cm^Three) = Energy (J) applied to a specific minute volume / irradiation time (seconds) / the minute volume (cm)^Three)
[0014]
In the method of the present invention, the pulse laser beam has a pulse width of 10 femto (10 × 10^-15) 10 pico (10x10)^-12It is preferable that the laser is an ultrashort pulse laser of less than 2 seconds.
[0015]
In the method of the present invention, the material has the following formula in terms of the transmittance T of the pulse laser beam from the surface on which the pulse laser beam is incident to the portion where the pulse laser beam is condensed, to the condensing magnification M: It is preferable that the material satisfies (1) and (2).
T ≧ 100 / M²... (1)
T ≧ (I_th× 2 × 10^-Four) / (I₀× M²) ... (2)
M: (π / 4)^1/2× (Diameter of pulsed laser beam at material incidence) / (Circular root of material collection volume)
I_th: Spatial power density (W / cm) of the pulsed laser beam necessary to form a heterogeneous phase at the focused site in the material^Three)
I₀: Power density (W / cm) of the pulse laser beam on the surface where the pulse laser beam is incident on the material²)
[0016]
In the method of the present invention, it is preferable that the material satisfy the above formulas (1) and (2) with respect to a pulse laser beam having a wavelength of 0.1 to 11 μm.
In the method of the present invention, the material is preferably glass.
[0017]
In the method of the present invention, the heterogeneous phase formed in the material is a phase in which the refractive index with respect to light having a wavelength of 0.1 to 2 μm differs by 0.1% or more with respect to the refractive index in other parts of the material. It is preferable that
In the method of the present invention, the heterogeneous phase formed in the material preferably forms a reinforcing part of the material.
[0018]
In the method of the present invention, the phase and / or amplitude of the pulse laser beam is controlled by at least one selected from the group consisting of a diffractive optical element, a microlens array, a high-order curved mirror, a cylindrical lens, and a high-order curved lens. May be performed.
[0019]
In the method of the present invention, it is preferable that chromatic aberration correction of the pulse laser beam is performed when the pulse laser beam is focused.
In the method of the present invention, it is preferable that a change in the pulse time width of the pulse laser beam, which occurs when the pulse laser beam is condensed, is corrected in advance before entering the material.
[0020]
In the present invention, the pulse laser beam condensed at a desired position inside the material may be further moved relative to the material.
[0021]
The present invention also includes a step of forming a heterogeneous phase at a plurality of desired sites inside a material by the above-described method of the present invention, and condensing a pulsed laser beam at a desired position inside the material. Forming a heterogeneous phase inside the material by moving the focused portion of the beam relative to the material to form a heterogeneous phase due to a light-induced change in the material. Provide a method.
[0022]
The present invention also provides a structure having a heterogeneous phase produced by the method of the present invention.
The present invention also includes the structure of the present invention, and the structure provides an optical component having an optical functional structure.
The optical component preferably has at least one selected from the group consisting of a directional coupler structure, a Y-branch waveguide structure, a Mach-Zehnder interferometer structure, and a ring resonator structure as an optical functional structure.
[0023]
In the present invention, a structure having a heterogeneous phase in the inside has an optical functional structure, and what is formed of the structure is an optical component.
Examples of the structure include a directional coupler structure, a Y-branch waveguide structure, and a photonic crystal.
The component is, for example, an optical waveguide.
In addition, a photonic crystal becomes an optical waveguide by providing a defect portion inside.
[0024]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, although embodiment of this invention is described based on drawing, this invention is not limited to this embodiment.
In the method of the present invention, when a pulse laser beam is irradiated to the inside of a material and a portion irradiated with the pulse laser beam is changed by light induction, a plurality of regions of the pulse laser beam are independently set for each region. By controlling the phase and / or amplitude, the divergence angle and traveling direction of each region of the laser beam are changed, and each region of the pulsed laser beam is irradiated to a plurality of different sites inside the material at once. Thereby, a condensing shape is formed inside the material as an aggregate of condensing points of each part, that is, as an aggregate of a plurality of condensing points.
[0025]
For example, in the case of forming a linearly high-refractive region in the material as shown in FIG. 1D, in the method of the present invention, a plurality of regions on the wavefront of the pulsed laser beam are individually phased. By controlling the amplitude and / or the amplitude to change the divergence angle and the traveling direction of each region of the laser beam, the plurality of regions of the pulsed laser beam can be moved to a plurality of different parts so as to form the linear shape shown in FIG. 1D. Irradiate all at once.
The portion irradiated with the laser beam is changed by the light irradiation to form a heterogeneous phase, specifically, for example, a high refractive region. Therefore, as shown in FIG. 1E and FIG. A highly refractive region having a shape can be formed in a lump.
[0026]
In the conventional method of forming a heterogeneous phase inside the material by scanning the condensing point of the laser beam, the heterogeneous phase is formed as an aggregate of heterogeneous phases formed by one pulse. When a high-density ultrashort pulse laser device is used, since the intensity fluctuation for each pulse is large and the pointing stability is low, the formed heterogeneous phase (FIG. 1A) is as shown in FIGS. 1B and 1C. The position accuracy was poor and the shape accuracy was also poor.
[0027]
On the other hand, in the method of the present invention, the pulse laser beam is focused on a plurality of desired sites inside the material without scanning the laser beam focusing point. A condensing shape as an aggregate of light spots can be collectively formed. As a result, a heterogeneous phase having a desired shape can be collectively formed by changing the portion irradiated with the pulse laser beam inside the material by light induction. In the method of the present invention, the heterogeneous phases are collectively formed in the material, so that it is possible to obtain a heterogeneous phase having higher positional accuracy and shape accuracy than the conventional method of scanning the condensing point of the laser beam.
[0028]
In the method of the present invention, since a heterogeneous phase is formed by irradiating a plurality of focused laser beams to each focused point which preferably has a focused shape, there is a problem when the above-described current ultrashort pulse laser apparatus is used. The influence of the laser beam intensity and pointing fluctuation for each pulse is averaged. Thereby, the influence by the fluctuation | variation of the laser beam for every pulse is reduced, and a heterogeneous phase can be obtained with high position accuracy and shape accuracy.
According to the method of the present invention, since heterogeneous phases are formed in a lump, manufacturing throughput is improved. Furthermore, since a highly accurate moving mechanism for scanning the condensing point of the laser beam is unnecessary, the apparatus can be simplified.
[0029]
In FIG. 1D, a heterogeneous phase having a linear shape is shown as an example of the heterogeneous phase to be formed, but the shape of the heterogeneous phase formed by the method of the present invention is not limited to this. That is, it may be a more complex two-dimensional shape having a curve or a branch, and may be a three-dimensional shape. Furthermore, the shape of the heterogeneous phase is not limited to a single continuous shape, and a plurality of dotted heterogeneous phases may be dispersed two-dimensionally or three-dimensionally inside the material. The method of the present invention that can form a desired shape at once with high positional accuracy and shape accuracy is particularly preferable for forming such a heterogeneous phase having a two-dimensional shape or a three-dimensional shape.
[0030]
1D shows a high refractive region as the heterogeneous phase to be formed, but the heterogeneous phase formed by the method of the present invention is widely different from the heterogeneous phase formed by light-induced changes caused by laser beam irradiation. Including. In addition to changes in the molecular structure of the glass caused by the high electromagnetic field of light, which is thought to form a highly refractive region in the glass material, the light-induced changes include the heat, photochemical reaction, Various light effects such as redox and non-linear effects widely include so-called photo-induced changes such as crystal formation, densification, and bubble generation.
[0031]
2A and 2B are schematic views of typical forms of a laser processing apparatus for forming a heterogeneous phase having a desired shape inside a material using the method of the present invention.
The laser processing apparatus 101 shown in FIG. 2A roughly includes a laser light source (not shown) that emits a pulse laser beam having a desired intensity as a light beam 1 having a certain width, and a plurality of regions of the laser beam. The wavefront control element 5 that independently controls the phase and / or amplitude, and the light condensing function element 8 that condenses a light beam having a certain area in a minute region inside the material 11. With such a configuration, it is possible to irradiate a plurality of desired sites inside the material 11 with the pulsed laser beam 1 at a time. Since the site irradiated with the laser beam changes due to light induction, a plurality of heterogeneous phases 10 can be collectively formed at a desired site inside the material. In FIG. 2A, the plurality of heterogeneous phases 10 exist continuously in the material, and form a continuous three-dimensional shape.
[0032]
Since the laser light source concentrates the pulse laser beam inside the material, particularly inside a transparent material such as a glass material, and causes a light-induced change, it may be able to emit a pulse laser beam with high power density. Therefore, an ultrashort pulse laser with a short pulse width, more specifically, a pulse width at a condensing point of 10 femto (10 × 10^-15) More than 10 pico (10x10)^-12) It is preferable that the laser is an ultrashort pulse laser that takes less than a second. In particular, when the material for forming the heterogeneous phase is a glass material, the pulse width is more preferably 15 femtoseconds or more and 300 femtoseconds or less. If the pulse width is in the above range, the energy per pulse of the pulse laser can be reduced, which is advantageous in terms of energy, and damage due to the irradiation of the laser beam on the part other than the part that forms the heterogeneous phase in the material. There is almost no risk of it occurring.
[0033]
The wavefront of the laser beam emitted from the laser generator is controlled by the wavefront control element 5 so that the phases and / or amplitudes of the plurality of regions are independently controlled. The laser beam 3 is modulated in the divergence angle and the traveling direction by the phase and / or amplitude of each of the plurality of regions independently changing by means such as a diffractive optical element, which will be described later in detail. Here, in order to increase the degree of freedom in changing the phase and / or amplitude, the laser beam may be separated into a plurality of beams by a beam splitter, or widened by a beam expander. 4 schematically shows the wavefront of the laser beam before the phase and / or amplitude is controlled, 6 shows the laser beam wavefront after the phase and / or amplitude is controlled by the wavefront control element 5, and 7 shows the luminous flux corresponding to 6. It is shown in.
[0034]
The wavefront control element 5 is not particularly limited as long as a plurality of regions of the wavefront of the laser beam can be independently controlled in phase and / or amplitude. Specifically, for example, a normal optical control system such as a normal lens, a prism, a reflection mirror, and a condensing mirror, an integrated optical element such as a lens array, a mirror array, and a prism array, or a cylindrical lens, a complicated condensing shape can be obtained. It may be a more complex optical control system such as a higher-order curved lens or a higher-order curved mirror, or a binary phase grating, a multi-level phase grating, a continuous phase grating, a grating type, a phase mask type, or a liquid crystal modulator A phase type hologram or kinoform is calculated from a two-dimensional or three-dimensional cross-sectional image of a heterogeneous phase formed inside the material by a diffractive optical element having amplitude modulation, phase modulation function, etc., and a computer, You may form a condensing shape as a hologram or a kinoform using the said various optical control systems or optical elements.
[0035]
The wavefront control element 5 is particularly preferable if the reflection surface shape of the mirror or the surface shape of the lens and the phase and / or amplitude modulation function of the diffractive optical element are variable. As the wavefront control element 5 having such a variable shape or function, for example, a phase modulation type and / or amplitude phase simultaneous modulation type liquid crystal spatial modulator provided with a driving device, a surface shape variable mirror (deformable mirror), There are variable mirrors, variable diffractive lenses, variable gratings, micromirror arrays with driving devices, and the like using electro-optic effects, acousto-optic effects, and magneto-optic effects. By using these function variable elements, fine correction of the shape of the heterogeneous phase can be easily performed at the time of manufacture, and it is not necessary to prepare a wavefront control element for each heterogeneous phase pattern to be formed. preferable.
[0036]
The laser beam whose phase and / or amplitude is independently controlled in each of the plurality of regions by the wavefront control element 5 is condensed at a desired position inside the material 11 by the condensing function element 8. Since the phase and / or amplitude of the laser beam is independently controlled in each of the plurality of regions, the beam corresponding to each region forms a condensing point 10 at a different portion inside the material 11. Reference numeral 9 schematically shows each light beam to be condensed. And the whole condensing shape 10 is formed as an aggregate | assembly of such a condensing point. In this way, a condensing shape having an arbitrary shape is formed at one time inside the material without scanning the condensing point inside the material, so that the portion where the laser beam inside the material is condensed is photo-induced. It is possible to collectively form heterogeneous phases having a desired shape.
[0037]
The order of the wavefront control element 5 and the condensing function element 8 is limited to disposing the wavefront control element 5 on the upstream side of the laser beam with respect to the condensing function element 8 as in the example illustrated in FIG. 2A. Instead, as shown in FIG. 2B, the order of the wavefront control element 5 and the condensing function element 8 can be changed.
[0038]
The condensing functional element 8 is not particularly limited as long as a light beam having a certain area can be condensed on a desired minute region inside the material. For example, a normal lens, a prism, a reflection mirror, a condensing mirror, etc. It may be a light collection control system.
The wavefront control element 5 and the light condensing function element 8 do not exist as separate elements, but may have both functions. In the case of lenses that can control the laser beam emission direction independently, such as a lens array, a cylindrical lens, and a high-order curved lens, the functions of the wavefront control element 5 and the condensing function element 8 are realized by a single lens. be able to.
[0039]
The combination of the wavefront control element 5 and the condensing functional element 8 is not particularly limited as long as a desired condensing shape can be formed inside the material. Further, the size of the condensing functional element 8 is not particularly limited as long as it has an effective cross-sectional area sufficient to obtain a desired condensing shape.
[0040]
The laser processing apparatus 101 using the method of the present invention may include elements other than the laser light source, the wavefront control element 5 and the condensing function element 8. For example, when a laser light source that irradiates a pulse laser beam with a pulse time width of 300 femtoseconds or less is used, the spectrum spread becomes significant, and the focus shape may be distorted by chromatic aberration. Further, there is a possibility that the pulse width of the laser beam may be widened due to material dispersion or structural dispersion in the material constituting the wavefront control element 5 and the light condensing function element 8 or material dispersion in the material processed by the laser beam. If the pulse width of the laser beam is widened by these, the power density of the laser beam is lowered, and there is a possibility that a heterogeneous phase cannot be formed in the condensed portion. Therefore, when using a laser light source that irradiates a pulse laser with a pulse width of 300 femtoseconds or less, 1) a chromatic aberration correction mechanism for preventing chromatic aberration within the wavelength of the laser, or 2) the inside of the optical control material Changes in the pulse time width of the laser beam (changes in the pulse time width caused by material dispersion) inside the processing material (inside the lenses, mirrors, etc. constituting the wavefront control element 5 and the condensing function element 8) (inversely) The dispersion correction mechanism 2 is provided as necessary to correct the chromatic aberration of the laser beam and / or the pulse width change due to material dispersion or the like before entering the material. It is necessary to correct.
[0041]
Further, the laser processing apparatus 101 preferably has an achromatic structure for correcting chromatic aberration such as achromatic and apochromatic. Furthermore, it is preferable that the laser processing apparatus 101 includes a dispersion generator for generating arbitrary wavelength dispersion such as a prism pair and a grating pair as a dispersion correction mechanism.
[0042]
In the present invention, since a heterogeneous phase is formed inside the material by irradiation with a pulse laser beam, the power density of the pulse laser beam to be used is important.
The power density of the laser beam is usually an amount indicating how much energy is input per unit area per unit time. When the continuous wave laser beam is focused at one point, it is expressed by the following equation.
Power density (W / cm²) = Average power (W) / Condensing area (cm²)
On the other hand, when the pulse laser beam is focused on one point, it is expressed by the following formula.
Power density (W / cm²) = Energy per pulse (J) / pulse width (seconds) / light collection area (cm²)
[0043]
In the case of the present invention, since the spatial distribution of the condensing points inside the material, particularly the spatial distribution of the condensing shape having a three-dimensional shape becomes a problem, the concept of spatial power density is used. FIG. 3 is a diagram for explaining the concept of the spatial power density, and shows the relationship between the condensing functional element 8 and the condensing shape 12 of the laser beam. In FIG. 3, the light condensing function element 8 is formed of a microlens array and also serves as a wavefront control element. As shown in FIG. 3, the condensing shape 12 when condensing and irradiating the material 11 with the condensing functional element 8 is divided into minute volumes 13, and a laser beam 14 condensed on each minute volume 13 is divided. Think about it. The spatial power density is defined by the following formula.
Spatial power density (W / cm^Three) = Energy (J) input to a specific microvolume 13 / irradiation time (seconds) / specific microvolume 13 (cm^Three)
[0044]
In the method of the present invention, the spatial power density of the laser beam at the focused site inside the material is 10^TenW / cm^Three10 or more^{twenty four}W / cm^ThreeThe following is preferable. When the material for forming the heterogeneous phase is a glass material, the spatial power density of the laser beam is 10 depending on the type of glass and the type of light-induced change.¹⁴W / cm^Three10 or more²⁰W / cm^ThreeIt is particularly preferred that When the spatial power density is within the above range, the position accuracy and shape accuracy of the formed heterogeneous phase are high, and the power density of the laser beam is sufficient to form the heterogeneous phase. It should be noted that 10% of the material forms a heterogeneous phase.^{twenty four}W / cm^ThreeWhen a super spatial power density is required, a large laser pulse energy is required, and it is difficult to increase the volume of the heterogeneous phase.
[0045]
Specifically, the relationship between the preferred spatial power density and the energy of the pulsed laser is shown as follows.¹⁸W / cm^ThreeIn the case of using a pulse laser having an energy of 1 pulse of 180 μJ and a pulse width of 100 femtoseconds, the cross-sectional area is 9 μm.², The light can be condensed in a region having a length of 200 μm.
[0046]
Further, in the method of the present invention, the restriction on the repetition frequency of the laser pulse (the number of pulses of the laser beam per second) is greatly relaxed. In the conventional method, when forming a heterogeneous phase with a smooth interface, as many laser pulses as possible are irradiated in order to reduce the influence of fluctuation of the laser pulses by averaging. However, in the method of the present invention, since the positional accuracy and shape accuracy of the heterogeneous phase formed as described above are improved, in principle, the heterogeneous phase can be formed inside the material even with only one pulse. It can be formed. However, the repetition frequency is preferably 5 Hz or more in order to improve manufacturing throughput. The upper limit of the repetition frequency is not particularly limited as long as the spatial power density by one pulse at the focused part can be secured. In practice, an ultrashort pulse laser of several Hz to several tens of MHz can be used. However, in order to improve position accuracy and shape accuracy, it is preferable to form a group of heterogeneous phases forming one two-dimensional shape or three-dimensional shape with several pulses to several thousand pulses. If the repetition frequency is in the above range, each focused spot is irradiated with a plurality of pulses of laser beam, so the intensity of the laser beam and the fluctuation in pointing when the heterogeneous phase is formed are averaged. The effect is reduced.
[0047]
In the method of the present invention, in order to collectively form a heterogeneous phase having a two-dimensional shape or a three-dimensional shape inside the material, compared with a conventional method of forming a heterogeneous phase by scanning the focal point of a laser beam. A heterogeneous phase with high position accuracy and shape accuracy can be formed. In addition, since each laser beam is irradiated with a plurality of pulses of laser beam, the influence of laser beam intensity and pointing fluctuation is reduced, and a heterogeneous phase with high positional accuracy and shape accuracy is formed. be able to. Therefore, a high refractive index region is formed as a heterogeneous phase, and a circuit portion of an optical component that requires high positional accuracy and shape accuracy as shown in FIG. 4, for example, an optical coupling portion of the directional coupler 17 shown in FIG. 4A If the method of the present invention is used to produce 15a, 15b, the Y branching portion 15c of the Y branching waveguide 18 shown in FIG. 4B, etc., it becomes possible to obtain an optical component having more stable optical characteristics.
[0048]
Another advantage of the present invention is that, in order to form a group of heterogeneous phases having a two-dimensional shape or a three-dimensional shape at a time, the condensing point of the laser beam is scanned in the material to form the heterogeneous phase. Compared to this method, these shapes can be formed quickly, and the manufacturing throughput can be improved. Therefore, it is particularly promising as a method of forming a heterogeneous phase having at least one of the following effects inside the transparent material, thereby forming a reinforcing portion inside the material.
・ Effect of reducing the occurrence of cracks from the inside
・ Effect of changing the direction of cracks
・ Effect of suppressing the extension of cracks
[0049]
In the method of the present invention, when the reinforcing part is formed inside the material, it is not necessary to consider the influence due to fluctuation, etc. Further, a plurality of condensing points of the laser beam formed at once may be further scanned and moved relative to the material. By scanning the condensing point of the laser beam formed in a lump, more heterogeneous phases can be formed in the material at a time, and heterogeneous phases can be formed in a wider range. Thereby, the manufacturing throughput can be further improved.
[0050]
It is also effective to use the method of the present invention in combination with the conventional method of scanning the condensing point of the laser beam and moving the condensing point relative to the material. For example, when forming a circuit portion of an optical component as shown in FIG. 4 where high positional accuracy and shape accuracy are required, for example, the optical coupling portions 15a and 15b of the directional coupler 17 shown in FIG. The circuit portion having a complicated shape such as the Y branching portion 15c of the Y branching waveguide 18 shown in FIG. 5 is formed by using the method according to the present invention. By using the conventional method for scanning the optical system, it is possible not only to simplify the manufacturing apparatus while maintaining desired optical characteristics, but also to greatly increase the degree of freedom in designing and manufacturing optical components.
[0051]
According to the present invention, a structure having a heterogeneous phase having a desired shape at a desired position inside is obtained by condensing a laser beam collectively at a plurality of desired sites inside the material by the above-described procedure. can get. The material of such a structure needs to have a small linear absorption coefficient (absorption coefficient when the laser beam power density (laser power / irradiation area) is sufficiently small) with respect to the laser wavelength to be used. Indicates that the transmittance T of the pulse laser beam from the surface on which the pulse laser beam is incident to the point where the pulse laser beam is focused satisfies the following formulas (1) and (2) in relation to the focusing magnification M: It is preferable.
T ≧ 100 / M²... (1)
T ≧ (I_th× 2 × 10^-Four) / (I₀× M²) ... (2)
M: (π / 4)^1/2× (Diameter of pulsed laser beam (cm) at material incidence) / (Condensed volume of material (cm^Three) The cube root)
I_th: Spatial power density (W / cm) of the pulsed laser beam necessary to form a heterogeneous phase at the focal point in the material^Three)
I₀: Power density (W / cm) of the pulse laser beam on the surface where the pulse laser beam is incident on the material²)
[0052]
If the transmittance T is in the above range, the position accuracy and shape accuracy of the heterogeneous phase formed inside the structure are high, and the power density of the laser beam at the focal point causes a light-induced change in the material. Enough. Therefore, a structure having a heterogeneous phase having a desired shape, for example, a two-dimensional shape or a three-dimensional shape, can be suitably obtained at a desired position inside. Moreover, if the transmittance is in the above range, the energy efficiency of the laser beam is excellent, which is preferable.
[0053]
Further, the material of the structure needs to be transparent to the laser beam to be used. Specifically, the transmittance T is a material that satisfies the formulas (1) and (2) with respect to a laser beam having a wavelength of 0.1 to 11 μm that is normally used in processing applications. Therefore, for example, when using a laser beam in the near-infrared region having a wavelength of about 0.8 to 2.5 μm as well as glass, a polymer, and a transparent crystal, the semiconductor material has transparency to the laser beam. Therefore, processing is possible. Among them, glass materials are currently the most practical ultra-short pulse lasers that are practically usable: 1) titanium sapphire laser, 2) YAG laser, or 3) Nd-doped, Yb-doped, or Er-doped fiber laser. It is particularly preferable because it has high permeability, has mechanical and thermal stability, and can contain various functional elements such as rare earths and semiconductors. Examples of the glass material used include oxide glass (quartz glass, silicate glass, borosilicate glass, phosphate glass, aluminum silicate glass, etc.), halide glass, sulfide glass, or chalcogenide glass. .
[0054]
As a heterogeneous phase formed inside such a structure, one of the preferable embodiments is a heterogeneous phase having a refractive index different from that of other parts of the material.
If the structure is made of a single-phase glass material, a difference in refractive index of about several percent of the refractive index of the original glass occurred due to a light-induced reaction such as high density caused by the focused irradiation of the laser beam. It is possible to form a heterogeneous phase. Moreover, in order to form a photonic crystal inside the structure, a glass material capable of forming a region having a larger refractive index difference is necessary, and an example of such a glass material is compound semiconductor glass. In this glass material, a compound having a refractive index of about 2.5 to 3.5 is irradiated by irradiating a glass material having a refractive index of about 1.4 to 2.2 with an ultrashort pulse laser having a pulse width of a femtosecond level. A semiconductor can be formed, and thus a heterogeneous phase having a refractive index difference of several tens of percent or more can be formed. According to the present invention, such a heterogeneous phase having a large refractive index difference can be formed in a desired shape at a desired position inside the structure, and therefore suitable for manufacturing an optical component having an optical functional structure. It is.
[0055]
In the present invention, it is possible to produce optical components such as an optical filter having a complicated optical functional structure, a coupling / branching element, and a multiplexing / demultiplexing element. FIG. 4 shows an example of the basic structure of an optical component by the circuit portion of the optical waveguide. 4A shows a directional coupler structure 17, FIG. 4B shows a Y-branch waveguide structure 18, FIG. 4C shows a Mach-Zehnder interferometer structure 19, and FIG. 4D shows a ring resonator structure 20. These form the basic structure of the optical component in the circuit portion 15 of the optical waveguide. These structures require high accuracy in shape, size, and relative position in order to function stably. For example, in the directional coupler structure 17 shown in FIG. 4A and the ring resonator structure 20 shown in FIG. It is required to do. According to the present invention, an optical component having stable optical characteristics can be manufactured by collectively manufacturing these structures, and such an optical component can be manufactured with a high manufacturing throughput. Furthermore, the optical component has a mechanism that uses a nonlinear optical effect (a phenomenon in which the optical response changes nonlinearly according to the intensity of incident light) and a refractive index modulation mechanism (changes the refractive index of a part of the optical component). It is possible to create an optical component that actively controls light by providing a mechanism that changes the characteristics of the component by locally heating, energizing, or generating sound waves. Thus, for example, since an all-optical switch, an optical arithmetic element, and an optical bistable element are realized, it is possible to manufacture the basic structure of an optical component as shown in FIG. Is important.
[0056]
Another preferred form of the heterogeneous phase formed within the structure is a heterogeneous phase having at least one of the effects described below.
・ Effect of reducing the occurrence of cracks from the inside
・ Effects of changing the direction of crack propagation
・ Effect of suppressing the extension of cracks
Such a heterogeneous phase forms a reinforcing part that improves the strength of the material. Such a material having a reinforcing portion inside, particularly a transparent material, is an information processing field represented by a thin glass substrate for a flat panel display such as a liquid crystal display, a plasma display and an organic EL display, an architectural field such as a window glass, It is preferably used in the field of transportation equipment represented by glass for automobiles, the energy field represented by glass substrates for solar cells, and the like. According to the method of the present invention, after processing a material into a desired shape, a reinforcing portion having a desired shape can be collectively formed at a desired position inside the material by laser beam irradiation. There is no need to provide a reinforcing part in advance before processing the material, and it is also necessary to scan the condensing point as in the conventional method of forming the reinforcing part by irradiating a laser beam. First, the material manufacturing throughput is improved. The strength (orientation and characteristics) required depending on the use of the material is usually different. However, according to the present invention, a reinforcing part having a desired shape can be easily formed at a desired position inside the material. According to such required strength characteristics, the reinforcement portion having the most suitable position and shape can be formed. Furthermore, according to the present invention, since the reinforcing portion is formed by the light-induced change of the material due to the laser beam irradiation, the material does not change in appearance. This is a preferable characteristic as a transparent material excellent in strength.
[0057]
【Example】
Hereinafter, the present invention will be further described by examples. However, these examples are for illustrative purposes in order to facilitate understanding of the present invention, and the present invention is not limited to such examples.
Example 1
FIG. 5A is a schematic diagram showing one form of a laser processing apparatus using the method of the present invention. The laser processing apparatus of FIG. 5A has a pulsed laser beam 21 emitted from a laser light source (not shown) (wavelength 800 nm emitted from a solid-state laser-excited titanium-sapphire laser, pulse width 100 femtoseconds, and energy of one pulse. 180 μJ, pulse laser beam with a repetition frequency of 1 kHz) is opposite to the dispersion generated by all the optical components constituting the optical system and the glass material by the dispersion correction mechanism 23 configured by a grating pair having a dispersion generating function. Is given so that the pulse width at the focal point does not change from the desired pulse width at the time of launch. After the pulse laser beam 21 corrected by the dispersion correction mechanism 23 is widened by the beam expander 30, a phase type diffractive optical element 33 is used as a wavefront control element, and a plurality of regions of the wavefront of the laser beam are made independent. Control the phase individually. Thereafter, a laser beam is condensed on the condensing functional element using the apochromatic lens 25 for correcting chromatic aberration, and the material 11 (the transmittance T of the pulse laser beam is 99% or more and the refractive index is 1.46). A condensing shape 10 having a three-dimensional shape is formed inside (quartz glass). The three-dimensional condensing shape 10 is continuously formed as an aggregate of a plurality of condensing points. Then, a heterogeneous layer having the same shape as the condensing shape by a change due to light excitation and having a refractive index difference (with respect to the refractive index with respect to the laser pulse beam) of the material 11 is about 1%.
[0058]
FIG. 5B is a schematic diagram showing another embodiment of a laser processing apparatus using the method of the present invention. In the apparatus of FIG. 5B, phase control is performed using a cylindrical lens 26 as a wavefront control element. If the condensing shape 27 is a relatively simple shape, such a mechanism is sufficient. Thereby, a heterogeneous layer having the same shape as the light collecting shape is collectively formed by a change due to light excitation.
FIG. 5C is a schematic diagram showing still another embodiment of a laser processing apparatus using the method of the present invention. In the apparatus of FIG. 5C, the wavefront of the beam is controlled by the high-order curved mirror 28 instead of the diffractive optical element 33 and the cylindrical lens 26. Thereby, a heterogeneous layer having the same shape as the light collecting shape is collectively formed by a change due to light excitation.
[0059]
Example 2
FIG. 6 is a schematic view showing another embodiment of a laser processing apparatus using the method of the present invention. In the apparatus of FIG. 6, after the pulse laser beam 21 is separated into a plurality of beams by the beam splitter 22, the divergence angle and the emission direction of each beam are individually adjusted individually by the microlens array 29. In the apparatus of FIG. 6, the phase control and the light collection function are integrated into the microlens array 29. Such function integration greatly simplifies the apparatus. The three-dimensional condensing shape 10 is continuously formed in the material 11 as a set of a plurality of condensing points. In the apparatus of FIG. 6, a more complicated shape can be obtained by increasing the number of beam divisions. If the same pulse laser beam and quartz glass as in Example 1 are used, a heterogeneous layer having the same shape as the condensing shape is collectively formed by a change due to light excitation.
[0060]
Example 3
FIG. 7A is a schematic diagram showing another embodiment of a laser processing apparatus using the method of the present invention. In a form in which the functions of the laser processing apparatus shown in FIG. 6 are further consolidated, the pulse diameter of the pulse laser beam 21 is expanded by the beam expander 30, the phase is controlled by the microlens array 31, and a desired 3 is formed inside the material 11. The light is condensed on the condensing shape 10 in a dimensional positional relationship. The beam expander 30 can be omitted, but the microlens array 31 may be an optical system that meets the manufacturing cost in consideration of the small size of each microlens.
[0061]
FIG. 7B shows a conceptual diagram of a method for producing a photonic crystal using the apparatus of FIG. 7A. A photonic crystal is a material in which a high refractive index region having a periodic structure of the wavelength of light is formed in a medium made of a transparent material, and light is controlled by the structure. A photonic crystal is realized by periodically forming a heterogeneous phase having a higher refractive index than that of a medium. Although the period depends on the characteristics to be obtained, it is generally known that the period is about half of the wavelength. Therefore, considering the use of light having a wavelength of 1.5 μm, periodicity of 1 μm level is required. Therefore, as shown in FIG. 7B, the condensing points 32 of the laser beam are narrowed to a diameter of 1 μm or less by each microlens of the microlens array 31, and the condensing points 32 are separated from each other by about 1 μm. A photonic crystal can be realized by periodically arranging the inside of the substrate 11. When a defect that breaks the period is introduced into a periodically formed photonic crystal in order to form a circuit part of an optical waveguide having a photonic band gap as a waveguide principle, the part corresponding to the defect What is necessary is just to prevent a laser beam from condensing. Here, a wavelength of 800 nm, a pulse width of 100 femtoseconds, a repetition frequency of 250 kHz, and a spatial power density of 10 oscillated from a solid-state laser-pumped titanium-sapphire laser.¹⁶W / cm^Three, And a compound semiconductor glass having a transmittance T of 96% of the pulse laser beam, a heterogeneous phase having a refractive index of 2.5 with respect to a refractive index of 1.5 is obtained. A high refractive region having a refractive index difference of 67% with respect to other portions can be formed. In this way, by independently performing phase control on a plurality of regions of the wavefront of the pulse laser beam, it is possible to form a photonic crystal collectively by a change due to light excitation.
[0062]
Example 4
FIG. 8 is a schematic diagram showing another embodiment of a laser processing apparatus using the method of the present invention. In the apparatus shown in FIG. 8, the functions are further integrated as compared with the apparatus shown in FIG. 7A, and the amplitude control and condensing functions are all concentrated in the amplitude type diffractive optical element 45. The three-dimensional condensing shape 10 is continuously formed in the material 11 as a set of a plurality of condensing points. If the same pulse laser beam and quartz glass as in Example 1 are used, a heterogeneous layer having the same shape as the condensing shape is collectively formed by a change due to light excitation.
[0063]
Example 5
9A and 9B are schematic views showing another embodiment of a laser processing apparatus using the method of the present invention. In the apparatus of FIG. 9A, the beam diameter of the laser beam 21 emitted from the femtosecond pulse laser is expanded by the beam expander 30, and then condensed by the condenser lens 25 that performs phase control. An amplitude type diffractive optical element 46 for adjusting a beam divergence angle and an emission angle is disposed between the condensing lens 25 and the condensing shape 10. Control to shape. In the apparatus shown in FIG. 9B, the beam divergence angle and the emission angle are adjusted using a high-order curved surface lens 35 that performs phase control instead of the diffractive optical element 46. The three-dimensional condensing shape 10 is continuously formed in the material 11 as a set of a plurality of condensing points. If the same pulse laser beam and quartz glass as in Example 1 are used, a heterogeneous layer having the same shape as the condensing shape is collectively formed by a change due to light excitation.
[0064]
Example 6
In the example shown in FIG. 5A, a diffractive optical element, a microlens array, a micromirror array, or a high-order curved lens that collects light so that the heterogeneous phase has the basic structure of the optical component shown in FIG. By repeating the formation of a desired pattern at the position, a three-dimensional optical waveguide having a complicated three-dimensional configuration can be easily manufactured. 10A to 10C show an example of a procedure for forming a linear circuit portion of a three-dimensional optical waveguide having such a complicated three-dimensional configuration. Here, a pulse laser beam having a wavelength of 800 nm, a pulse width of 100 femtoseconds, a pulse energy of 180 μJ, and a repetition frequency of 1 kHz oscillated from a solid-state laser-pumped titanium-sapphire laser is used, and the diameter of the beam upon incidence of the material is 1 mm. , The collection volume of the material is 9000 μm^Three, The spatial power density of the focused part is 2 × 10¹⁷W / cm^ThreeThe laser power density I at the surface where the laser is incident on the material₀2.3 × 10¹¹W / cm²For example, as a glass material, the spatial power density I of the laser necessary to form a heterogeneous phase at a site to be condensed in the material is used._th10¹⁵W / cm^ThreeIf quartz glass having a laser beam transmittance T of 99% or more is used, a heterogeneous phase (refractive index 1.48) having a refractive index difference of about 1% with respect to the refractive index 1.46 of the material is obtained as a result of irradiation. It is done.
[0065]
Therefore, it is possible to independently control the phase of each of the plurality of regions of the wavefront of the pulse laser beam and collectively form a linear circuit portion of the optical waveguide by a change caused by optical excitation. As shown in FIG. 10A, a directional coupler structure 36 is first formed on the surface A in the material 11, and then a Y-branch waveguide structure 37 is formed on the surface B as shown in FIG. 10B. As shown in FIG. 10C, by forming the ring resonator structure 38 on the surface C, a three-dimensional optical waveguide having a complicated three-dimensional configuration can be manufactured.
[0066]
Example 7
FIGS. 11A and 11B show another example of a procedure for forming a linear circuit portion of a three-dimensional optical waveguide. As shown in FIG. 11A, the apparatus shown in FIG. 5B is used to independently control the phase of each of the plurality of wavefronts of the pulsed laser beam. After forming the linear heterogeneous phase 39, the cylindrical lens 26 is removed from the apparatus shown in FIG. 5B so that the laser beam can be focused in the form of dots, and as shown in FIG. By scanning the dots and forming the heterogeneous phase 40, a linear circuit portion of the three-dimensional optical waveguide is formed. In Example 7, a laser beam at the time of material incidence is obtained by using a pulsed laser beam with a wavelength of 800 nm, a pulse width of 100 femtoseconds, an energy of 90 μJ and a repetition frequency of 1 kHz oscillated from a solid-state laser-excited titanium-sapphire laser. Diameter of 2mm, material collection volume of 90000μm^ThreeThe power density I of the laser beam on the surface where the laser beam is incident on the material₀3 × 10^TenW / cm²The spatial power density of the laser beam at the portion where the laser beam is focused in the material is 1 × 10¹⁶W / cm^ThreeIn the case of focusing irradiation with a focusing magnification of 40, for example, as a glass material, the spatial power density I of the laser beam necessary for forming a heterogeneous phase at the site of focusing in the material._th10¹⁴W / cm^ThreeThus, if a borosilicate glass BK7 having a transmittance T of the pulse laser beam of 98% or more is used, a heterogeneous phase having a refractive index difference of about 1% with respect to the refractive index of the material 1.52 is obtained as a result of irradiation. It is possible to form a linear circuit portion of the optical waveguide.
[0067]
In the case of an optical waveguide in which the influence of fluctuation or the like does not need to be considered, the method of the present invention or the conventional laser beam can be obtained by combining the method of the present invention and the method of scanning the condensing point of the conventional laser beam. Such a three-dimensional optical waveguide can be manufactured in fewer parts and in a shorter time than in the case where each of the methods for scanning the focal point is used alone.
[0068]
Reference example
FIG. 12A shows a reinforcing portion formed by forming a linear heterogeneous phase 42 in a 50 μm pitch network inside a soda lime silicate glass having a laser beam transmittance T of 96% by focused irradiation of a femtosecond laser. It is the formed plate glass 41. The size of the plate glass is (50 mm × 6.5 mm, thickness 1 mm), and a laser beam is condensed by a condenser lens at a depth of 500 μm from the incident surface of the glass material, and a spot of about 25 μm is condensed. .
The laser beam uses a femtosecond laser beam with a pulse width of 100 femtoseconds, a repetition period of 1 kHz, and a wavelength of 800 nm oscillated from an Nd-YAG laser-excited Ti sapphire laser. The output at was about 65 mW. The position where the femtosecond laser beam was focused was fixed, and the glass material was moved linearly at a speed of 3 mm / sec using an automatic stage to repeatedly form heterogeneous layers.
In a four-point bending test with a distance between fulcrums of 30 mm, a distance between load points of 10 mm, and a load speed of 0.5 mm / min, the four-point bending strength was improved about 1.5 times compared to before the formation of the heterogeneous phase.
[0069]
Example 8
In the present invention, in order to form a linear heterogeneous phase similar to FIG. 12A, as shown in FIG. 12B, 10 condensing points 43 having a diameter of 5 μm are arranged at intervals of 50 μm between the respective condensing shapes. A condensing shape is created at once by the configuration of Example 1, and the glass material is scanned in a direction 44 perpendicular to the arrangement direction of the condensing points. Specifically, the pulse width is 100 femtoseconds, the repetition frequency is 1 kHz, the wavelength is 800 nm, and the spatial power density is 8 × 10 so that the power of the laser beam at each condensing point 43 is 65 mW.¹⁷W / cm^ThreeThen, a heterogeneous phase can be formed by irradiating the glass material in a direction 44 perpendicular to the arrangement direction of the condensing points at a relative speed of 3 mm / sec with respect to the condensing points. When the heterogeneous phase is formed in this example, ten heterogeneous phases forming the reinforcing portion can be formed in parallel at the same time, so when it is not necessary to consider the influence of fluctuation or the like, compared with the conventional method The time taken to form the heterogeneous phase can be shortened to 1/10, and the production throughput can be greatly improved.
[0070]
【The invention's effect】
According to the method of the present invention, a heterogeneous phase can be collectively formed at a plurality of desired positions inside the material. This makes it possible to collectively form two-dimensional or three-dimensional heterogeneous phases, and compared to the conventional method of scanning the focal point of the laser beam, the positional accuracy and shape accuracy of the heterogeneous phase formed Is expensive.
In addition, since the laser beam of multiple pulses is irradiated to the focused part inside the material, the influence of the laser beam intensity and pointing fluctuation is reduced, and the position accuracy and shape accuracy of the formed heterogeneous phase are reduced. high.
[0071]
According to the method of the present invention, a structure having a heterogeneous phase inside can be provided with high production throughput.
Since the structure having a heterogeneous phase inside provided by the present invention has a high positional accuracy and shape accuracy of the heterogeneous phase and a smooth interface, the optical filter, the multiplexing / demultiplexing element, the polarizing element, the sharp bend It is suitable as an optical component such as an ultra-compact coupling / branching device having a waveguide portion, an all-optical switch, an optical arithmetic element, or an optical bistable element, and particularly suitable as an optical waveguide or a photonic crystal.
The present invention can also produce and provide a material having a reinforcing portion inside the material at a high production throughput.
[Brief description of the drawings]
FIG. 1A is a conceptual diagram of a straight-line high refractive index region produced by a conventional method of scanning a condensing point, and FIGS. 1B and 1C show the amount of eccentricity and the amount of fluctuation in outer diameter. It is a graph. FIG. 1D is a conceptual diagram of a high-refractive index region having a linear shape formed by the method of the present invention, and FIGS. 1E and 1F are graphs showing the amount of eccentricity and the amount of fluctuation in outer diameter.
2A and 2B are schematic views showing one embodiment of a laser processing apparatus using the method of the present invention.
FIG. 3 is a diagram for explaining spatial power density, and shows a relationship between a condensing function element and a condensing shape of a laser beam.
4A to 4D are diagrams showing the main structure of an optical component that can be manufactured by the method of the present invention.
FIGS. 5A to 5C are schematic views showing another embodiment of a laser processing apparatus using the method of the present invention. FIGS.
FIG. 6 is a schematic view showing another embodiment of a laser processing apparatus using the method of the present invention.
FIG. 7A is a schematic view showing another embodiment of a laser processing apparatus using the method of the present invention. FIG. 7B is a conceptual diagram of a method for producing a photonic crystal using the apparatus shown in FIG. 7A.
FIG. 8 is a schematic view showing an optical system of another embodiment of a laser processing apparatus using the method of the present invention.
9A and 9B are schematic views showing another embodiment of a laser processing apparatus using the method of the present invention.
FIGS. 10A to 10C are perspective perspective views showing a procedure for producing a circuit portion of a three-dimensional waveguide by the method of the present invention. FIGS.
FIGS. 11A and 11B are perspective perspective views showing a procedure for producing a circuit portion of a three-dimensional optical waveguide by combining the method of the present invention and a conventional method of scanning a condensing point of a laser beam. FIGS.
FIG. 12A is a perspective perspective view of an example of a glass material in which a reinforcing portion with a heterogeneous phase is provided. FIG. 12B is a conceptual diagram showing the arrangement of condensing points of the laser beam and the scanning direction with respect to the glass material when the heterogeneous phase shown in FIG. 12A is formed in the glass material using the method of the present invention.
[Explanation of symbols]
1, 3, 14: Pulsed laser beam
2: Correction mechanism
4: Wavefront of laser beam before control
5: Wavefront control element
6: Wave front of laser beam after control
Light flux corresponding to 7: 6
8: Condensing functional element
9: Each luminous flux collected
10, 12, 27: Condensing shape
11: Material
13: Concentrated micro volume
15: Circuit portion of optical waveguide
15a, 15b: optical coupling part
15c: Y branch part
16: Gap of circuit part of optical waveguide
17, 36: Directional coupler structure
18, 37: Y-branch waveguide structure
19: Mach-Zehnder interferometer structure
20, 38: Ring resonator structure
21: Pulsed laser beam
22: Beam splitter
23: Dispersion correction mechanism
25: Lens
26: Cylindrical lens
28: High-order curved mirror
29, 31: Microlens array
30: Beam expander
32, 43: Focusing point
33, 45, 46: Diffractive optical element
35: High-order curved lens
39, 40: heterogeneous phase
41: Glass material
42: Heterogeneous phase
44: Scanning direction of condensing point with respect to glass material

Claims (19)

The plurality of regions of the wavefront of the pulsed laser beam are independently controlled in phase and / or amplitude, thereby focusing the pulsed laser beam at a plurality of desired positions inside the material, so that the pulse inside the material A method of forming a heterogeneous phase in a material, wherein a heterogeneous phase is collectively formed at a plurality of desired positions inside the material by causing a light-induced change in a portion where the laser beam is condensed. The method for forming a heterogeneous phase inside a material according to claim 1, wherein the plurality of heterogeneous phases formed inside the material are in a two-dimensional positional relationship with each other inside the material. The method for forming a heterogeneous phase inside a material according to claim 1, wherein the plurality of heterogeneous phases formed inside the material are in a three-dimensional positional relationship with each other inside the material. The method for forming a heterogeneous phase in a material according to claim 2 or 3, wherein the plurality of heterogeneous phases are continuously present in the material and form a two-dimensional shape or a three-dimensional shape. A pulsed laser beam having a spatial power density of 10 ¹⁰ W / cm ³ to 10 ²⁴ W / cm ³ represented by the following formula is condensed at a desired position in the material, and the desired position in the material The method for forming a heterogeneous phase in the material according to any one of claims 1 to 4, wherein a heterogeneous phase is formed in the material.
Spatial power density (W / cm ³ ) = energy (J) applied to a specific minute volume ÷ irradiation time (seconds) ÷ the minute volume (cm ³ ) The pulse laser beam is an ultrashort pulse laser having a pulse width of 10 femto (10 × 10 ^-15 ) seconds or more and 10 pico (10 × 10 ^-12 ) seconds or less. A method for forming a heterogeneous phase inside the material. In the material, the transmittance T of the pulse laser beam from the surface on which the pulse laser beam is incident to the portion where the pulse laser beam is condensed is related to the condensing magnification M by the following formula (1) and The method for forming a heterogeneous phase inside a material according to any one of claims 1 to 6, wherein the material satisfies (2).
T ≧ 100 / M ² (1)
T ≧ (I _th × 2 × 10 ⁻⁴ ) / (I ₀ × M ² ) (2)
M: (π / 4) ^1/2 × (diameter of pulsed laser beam at material incidence) / (third root of focused volume of material)
I _th : Spatial power density (W / cm ³ ) of the pulse laser beam necessary for forming a heterogeneous phase at the site where the pulse laser beam in the material is focused
I ₀ : Power density (W / cm ² ) of the pulse laser beam on the surface where the pulse laser beam is incident on the material The said material is a material which the said transmittance | permeability T satisfy | fills said Formula (1) and (2) with respect to a pulse laser beam with a wavelength of 0.1-11 micrometers, and forms a heterogeneous phase inside the material of Claim 7 how to. The method for forming a heterogeneous phase inside a material according to any one of claims 1 to 8, wherein the material is glass. The heterogeneous phase formed in the material is a phase in which a refractive index with respect to light having a wavelength of 0.1 to 2 μm differs by 0.1% or more with respect to a refractive index in other portions of the material. A method for forming a heterogeneous phase inside the material according to any one of 1 to 9. The method for forming a heterogeneous phase in the material according to claim 1, wherein the heterogeneous phase formed in the material forms a reinforcing portion of the material. The phase and / or amplitude of the pulse laser beam is controlled by at least one selected from the group consisting of a diffractive optical element, a microlens array, a high-order curved mirror, a cylindrical lens, and a high-order curved lens. A method for forming a heterogeneous phase inside a material according to any one of claims 1 to 11. 13. The method for forming a heterogeneous phase in a material according to claim 1, wherein chromatic aberration correction of the pulse laser beam is performed in the focusing of the pulse laser beam. 14. The inside of the material according to claim 1, wherein a change in a pulse time width of the pulsed laser beam generated when the pulsed laser beam is focused is corrected in advance before entering the material. To form a heterogeneous phase. The method for forming a heterogeneous phase inside a material according to any one of claims 1 to 14, wherein a focusing point of a pulsed laser beam focused at a desired position inside the material is further moved relative to the material. . A step of forming a heterogeneous phase at a plurality of desired positions inside the material by the method according to any one of claims 1 to 15, and condensing a pulsed laser beam at a desired one position inside the material, thereby Forming a heterogeneous phase due to light-induced change in the material by moving a condensing point of a laser beam relative to the material, and forming a heterogeneous phase in the material . The structure which has a heterogeneous phase inside produced by the method in any one of Claims 1 thru | or 16. An optical component comprising the structure according to claim 17, wherein the structure forms an optical functional structure. The optical component according to claim 18, wherein the optical functional structure includes at least one selected from the group consisting of a directional coupler structure, a Y-branch waveguide structure, a Mach-Zehnder interferometer structure, and a ring resonator structure.

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