JP7067736B2 - Processing method of fine periodic structure using pulse laser and glass body - Google Patents

Description

The present invention relates to a technique for processing a fine periodic structure in which a region having a relatively high refractive index and a region having a relatively low refractive index alternately exist in a glass body by using a pulse laser.

Conventionally, a polarizing element used for an optical isolator, a diffraction grating used as a lens of an optical system, a reflector and a filter used for a spectroscope, and an optical attenuator alternate between a region having a high refractive index and a region having a low refractive index. A glass having a periodic structure existing in the above has been proposed.

However, in the conventional device, vacuum vapor deposition, sputtering, lithography, or the like is used in order to form a submicron-order fine periodic structure suitable for the integration of optical circuits. In this case, there is a problem that the manufacturing process becomes complicated and the apparatus becomes large-scale, which causes an increase in the cost of the optical element.

Therefore, the present inventors have proposed the processing method described in Patent Document 1 below. In this processing method, a glass that transmits laser light is irradiated with a single focused pulsed laser beam having an amount of energy that causes a photoinduced refractive index change, so that the refractive index is relative to the focused position. It forms a fine periodic structure in which high regions and relatively low regions are alternately present.

Japanese Unexamined Patent Publication No. 2004-310009

The processing method described in Patent Document 1 is for, for example, a glass composed of only a network-forming oxide such as SiO ₂ and GeO ₂ , or a glass composed of the above-mentioned network-forming oxide and an intermediate oxide such as Al ₂ O ₃ . However, it was difficult to form the fine periodic structure for glass containing network-modified oxides such as Na ₂ O and Ca O. This probably disappears even if the fine periodic structure is temporarily formed because the vicinity of the condensing part of the laser melts to generate a viscous flow in the case of glass containing a network-modified oxide. It is thought that it will end up.

In view of the above circumstances, it should be solved in the present specification that even glass containing a network-modified oxide forms a fine periodic structure due to a photoinduced refractive index change generated when a pulsed laser is irradiated. It is a technical issue.

The solution to the above problems is achieved by the processing method of the fine periodic structure according to the present invention. That is, in this processing method, a first pulse laser having a predetermined repetition frequency is irradiated toward the glass body, and a second pulse laser having a lower repetition frequency than the first pulse laser is applied to the peripheral region of the focal point of the first pulse laser. By controlling the temperature distribution of the region melted by the irradiation of the first pulse laser by irradiating toward the first region, the network-forming oxide contained in the glass body becomes relatively dense in the melt region. A composition modification step of partially modifying the composition of the glass body by forming a second region in which the network-forming oxide is relatively sparse, and a photoinduced refractive index change with respect to the first region. By irradiating a single focused third-pulse laser with an amount of energy that causes It is characterized by having a fine periodic structure forming step for forming the fine periodic structure existing in the above.

The present inventors have proposed a joining method using a pulse laser in Japanese Patent Application Laid-Open No. 2016-165738. In this method, when irradiating a laser toward or near the abutting portion of two members and melting the abutting portion to join the two members, two types of pulse lasers having different frequencies are repeatedly used. By irradiating the abutting portion and its surrounding region to control the temperature distribution in the molten region, a specific element or a compound containing the element is allowed to flow in the molten region, and the melt-solidified portion straddles the two members. This allows for a strong bond between the two members. As a result of focusing on the movement of an element or an elemental compound by temperature control, the present inventors have found that the movement of a network-forming compound contained in a glass body can be controlled depending on the temperature control. I arrived.

The present invention has been made based on the above findings. First, the glass is irradiated with the first pulse laser, and the second pulse laser having a lower repetition frequency than the first pulse laser is applied to the peripheral region of the focal point of the first pulse laser. By irradiating and controlling the temperature distribution of the region melted by the irradiation of the first pulse laser, the first region in which the network-forming oxide contained in the glass body becomes relatively dense and the network formation are formed in the molten region. It forms a second region where the oxide is relatively sparse. At this point, in the first region in the molten region, the network-forming oxide can be denser than that of the glass body before laser irradiation. Therefore, for example, when the glass body contains a network-modified oxide, this network-modified oxide can be formed. The content ratio of can be relatively lowered. Therefore, by irradiating this first region with a single focused pulsed laser having an energy amount that causes a light-induced refractive index change, the first region can be divided into a region having a relatively high refractive index. It is possible to form a fine periodic structure in which relatively low regions are alternately present at a pitch of 1 μm or less.

Further, in the method for processing a fine periodic structure according to the present invention, when the glass body contains a network-forming oxide and a network-modified oxide, the network-modified in the first region in the composition modification step. The irradiation conditions of the first and second pulse lasers may be adjusted so that the oxide content ratio is 15 mol% or less.

As described above, the present inventors form a fine periodic structure on glass containing a network-modified oxide (for example, Na ₂ O) by utilizing the photoinduced refractive index change generated when a pulse laser is irradiated. For glass with a network-modified oxide content of 15 mol% or less, the above-mentioned fine periodic structure is formed with high probability by setting the pulse width and pulse energy of the pulse laser in an appropriate range. It turned out that it could be done. Therefore, in the composition modification step, by adjusting the irradiation conditions of the first pulse laser and the second pulse laser so that the content ratio of the network-modified oxide in the first region is 15 mol% or less, the network-modified oxide is Even if the content ratio of the glass body is larger than 15 mol%, the content ratio of the network-modified oxide in a part of the glass body is reduced to 15 mol% or less in the composition modification step, and a fine periodic structure is formed in the region. It becomes possible to do.

Further, in the method for processing a fine periodic structure according to the present invention, both the first pulse laser and the second pulse laser may be femtosecond lasers. Alternatively, the third pulse laser may be a femtosecond laser. Alternatively, the first to third pulse lasers may be femtosecond lasers.

With a first pulse laser having a pulse width on the order of femtoseconds, energy can be concentrated only in the condensing region, so that only the truly necessary part can be melted, and the processing efficiency is improved. Further, within the range of practical output, the extent to which the second pulse laser does not melt the peripheral region of the focal point of the first pulse laser and the extent to which the temperature distribution of the melting region generated by the first pulse laser can be affected. A femtosecond laser is suitable when considering heating.

Further, the solution to the above problems is also achieved by the glass body according to the present invention. That is, this glass body is a glass body having a melt-solidified portion formed inside, and the melt-solidified portion has a first region in which the network-forming oxide contained in the glass body is relatively dense and a mesh. A second region in which the formed oxide is relatively sparse is formed, and a region having a relatively high refractive index and a region having a relatively low refractive index are alternately present in the first region at a pitch of 1 μm or less. It is characterized by the formation of a fine periodic structure.

As described above, in the glass body according to the present invention, for example, by the above-mentioned processing method, a melt-solidified portion is formed inside, and the network-forming oxide contained in the glass body becomes relatively dense in the melt-solidified portion. A first region and a second region where the network-forming oxide is relatively sparse are formed, and in the first region, a region having a relatively high refractive index and a region having a relatively low refractive index have a pitch of 1 μm or less. I tried to form a fine periodic structure that exists alternately in. In this way, by forming a first region in which the network-forming oxide is relatively dense inside the glass body (melt-solidified portion), for example, when the glass body contains a network-modified oxide, the first The content ratio of the network-modified oxide contained in the region can be made lower than that of the glass body (content ratio of the network-modified compound). Therefore, by irradiating the first region with, for example, one focused pulsed laser having an energy amount that causes a light-induced refractive index change, the first region can be divided into a region having a relatively high refractive index. It is possible to obtain a glass body formed by forming a fine periodic structure in which relatively low regions are alternately present at a pitch of 1 μm or less.

As described above, according to the present invention, it is possible to form a fine periodic structure even for glass containing a network-modified oxide by the photo-induced refractive index change generated when a pulse laser is irradiated. Become.

It is a flowchart which shows the flow of the processing method of the fine periodic structure which concerns on 1st Embodiment of this invention. It is a figure for demonstrating the whole structure of the 1st laser irradiation apparatus used in the composition modification process shown in FIG. It is a main part perspective view for demonstrating the irradiation mode of the 1st and 2nd pulse lasers in a composition modification process. FIG. 3 is a plan view of a main part of the glass body shown in FIG. 3 as viewed from the irradiation direction of each pulse laser. It is a side view of the main part which looked at the glass body shown in FIG. 3 from the direction orthogonal to the irradiation direction of each pulse laser. It is a side view of the main part for demonstrating the state of the molten region at the time of irradiating each pulse laser in the aspect shown in FIG. A plan view (a) and a side sectional view (b) showing a three-dimensional distribution of a predetermined element (elemental compound) in a melt-solidified portion of a glass body obtained by irradiating each pulse laser in the embodiment shown in FIG. Is. It is a figure for demonstrating the whole structure of the 2nd laser irradiation apparatus used in the microperiodic structure forming process shown in FIG. It is (a) the front sectional view in the light irradiation direction, (b) the side sectional view in the light irradiation direction, (c) the plan sectional view in the light irradiation direction of the fine periodic structure formed in the refractive index change region. (A) Cross-sectional view of the fine periodic structure when irradiated with a third pulse laser whose polarization magnetic field direction is horizontal, and (b) Fine periodic structure when irradiated with a third pulse laser whose polarization magnetic field direction is perpendicular. It is a cross-sectional view.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

As shown in FIG. 1, a method for processing a fine periodic structure according to an embodiment of the present invention includes a composition reforming step S1 for partially modifying the composition of a glass body and fine particles in the glass body after the composition modification. A fine periodic structure forming step S2 for forming a periodic structure is provided. The details of each step will be described below.

(S1) Composition Modification Step FIG. 2 shows the overall configuration of the first laser irradiation device 10 used in the composition modification step S1. The first laser irradiation device 10 includes a first laser oscillator 12 capable of oscillating the first pulse laser 11, a second laser oscillator 14 capable of oscillating the second pulse laser 13, and first and second laser oscillators 12. The first and second pulse lasers 11 and 13 oscillated from the 14 are arranged on the path of the optical system 15 and the optical system 15 for condensing and incident on the glass body 1 described later, and the second pulse laser. A spatial optical phase modulator 16 that performs phase modulation of 13 and a table 17 on which the glass body 1 is placed are mainly provided.

Here, the glass body 1 to be irradiated by each of the pulse lasers 11 and 13 can have an arbitrary composition, for example, glass composed of a network-forming oxide and a network-modified oxide, or intermediate with the network-forming oxide. It is formed of a glass composed of an oxide, or a glass composed of a network-forming oxide, a network-modified oxide, and an intermediate oxide. Further, the composition ratio is not particularly limited. As an example, SiO ₂ : 65 (55 to 75) mol%, NaO ₂ : 15 (5 to 20) mol%, Al ₂ O ₃ : 10 (0 to 20) mol%, B ₂ O ₃ : 5 (1 to 1 to). 15) Glass having a composition of mol%, K ₂ O + Li ₂ O + CaO + BaO + MgO: 5 (15 to 30) mol% can be mentioned.

Hereinafter, details of each component of the first laser irradiation device 10 will be described.

The optical system 15 has a plurality of mirrors 18 and a lens 19. Further, in the present embodiment, as shown in FIG. 2, the optical system 15 includes a beam splitter 20 for combining a first pulse laser 11 and a second pulse laser 13 oscillated from different directions, and each mirror 18. Further includes an objective lens 21 that focuses both pulse lasers 11 and 13 transmitted via the lens 19 and the lens 19 inside the glass body 1.

Further, the spatial optical phase modulator 16 is configured to be able to modulate the spatial phase distribution of the second pulse laser 13 among the incoming first pulse laser 11 and the second pulse laser 13. Specifically, the second pulse laser 13 is branched by a phase hologram prepared in advance so that it can irradiate a predetermined phase (three-dimensional position) in the glass body 1 together with the first pulse laser 11. Will be done. In the present embodiment, as shown in FIG. 3, the second pulse laser 13 is divided into four and the second pulse laser 13 is irradiated with the peripheral region 11a1 of the focal point 11a of the first pulse laser 11. The three-dimensional position of the focal point 13a is set. Looking at this from the irradiation direction of each of the pulse lasers 11 and 13 (vertical direction in FIG. 3), as shown in FIG. 4, the four pulse lasers 11 are rotationally symmetric with respect to the focal point 11a of the first pulse laser 11. The position of the focal point 13a of the second pulse laser 13 of the book is set. Further, when this is viewed from the direction orthogonal to the irradiation direction of each of the pulse lasers 11 and 13 (the left-right direction in FIG. 3), as shown in FIG. 5, the focal point 13a of each second pulse laser 13 is the first. It is set at a position offset from the focal point 11a of the pulse laser 11 by a predetermined amount d in the irradiation direction, that is, on the upper surface side of the glass body 1.

The first pulse laser 11 and the second pulse laser 13 are focused and irradiated in a common glass body 1, but their repetition frequencies are set to different magnitudes from each other. Here, with respect to the first pulse laser 11, the amount of heating to the glass body 1 (focus 11a) per unit repetition time of the laser pulse is larger than the heat diffusion amount of the focal point 11a per unit repetition time. , The repetition frequency is set. Further, for the second pulse laser 13, the repetition frequency is set so that the heating amount to the peripheral region 11a1 per unit repetition time of the laser pulse is smaller than the heat diffusion amount of the peripheral region 11a1.

As an example, when the glass body 1 is made of alkaline glass, the threshold value of the repetition frequency is set to 50 kHz. That is, the repetition frequency of the first pulse laser 11 is set in a range of at least 50 kHz or more (for example, 50 kHz or more and 1000 kHz or less). Further, the repetition frequency of the second pulse laser 13 is set to at least 50 kHz or less (for example, 0.001 kHz or more and 10 kHz or less). Of course, this threshold value may be appropriately changed depending on the composition of the glass body 1 (particularly, if a network-modified oxide is contained, the content ratio thereof) and the outputs of the pulsed lasers 11 and 13 described later. desirable.

As other irradiation conditions, for example, when the glass body 1 is formed of alkaline glass, the wavelength of the first pulse laser 11 is set to 400 nm or more and 2000 nm or less, and the pulse width is 10 fs (femtoseconds) or more. And it is set to 10000 fs or less, and the output is set to 0.01 μJ or more and 10 μJ or less. The wavelength of the second pulse laser 13 is set to 400 nm or more and 2000 nm or less, the pulse width is set to 10 fs or more and 10000 fs or less, and the output is set to 0.01 μJ or more and 10 μJ or less. Further, the irradiation period of the first pulse laser 11 and the irradiation period of the second pulse laser 13 overlap in the entire period in the present embodiment, and the length thereof is set to, for example, 0.1 seconds or more and 10 seconds or less. To. During this period, the table 17 is fixed, and the positions of the focal points 11a and 13a of the first and second pulse lasers 11 and 13 do not change during the irradiation period.

Hereinafter, an example of the case where the composition reforming step S1 is carried out using the first laser irradiation device 10 having the above configuration will be described mainly with reference to FIGS. 6 and 7.

First, the first pulse laser 11 and the second pulse laser 13 in which the irradiation conditions such as the repetition frequency are appropriately set as described above are oscillated from the respective laser oscillators 12 and 14. Then, after the oscillated pulse lasers 11 and 13 are combined by the beam splitter 20, the phase distribution of the second pulse laser 13 is modulated by the spatial optical phase modulator 16 and passed through the objective lens 21. As a result, the first pulse laser 11 is irradiated toward a predetermined position in the glass body 1, and the plurality of second pulse lasers 13 are irradiated toward the peripheral region 11a1 of the focal point 11a of the first pulse laser 11 (FIG. 3 to 5).

At this time, in the irradiation region 11b of the first pulse laser 11, heating and melting occur due to the polyphoton absorption phenomenon. Therefore, by continuing the irradiation of the first pulse laser 11, the molten region 2 expands around the irradiation region 11b (see FIG. 6). Further, since the repetition frequency of the first pulse laser 11 is set in a range exceeding the threshold value of the repetition frequency that can store heat as described above, the heating amount per unit repetition time at the focal point 11a always determines the heat diffusion amount. It will be in a state of exceeding. Therefore, the temperature gradient in the irradiation region 11b and its vicinity becomes comparatively gentle.

On the other hand, in the irradiation region 13b of the second pulse laser 13, heating occurs in the same manner as in the irradiation region 11b of the first pulse laser 11, but the repetition frequency is set to be less than the threshold value of the heat storage repetitive frequency. Therefore, the amount of heat diffusion per unit repetition time in the peripheral region 11a1 exceeds the amount of heating. Therefore, although a steep temperature gradient occurs in the irradiation region 13b, heat melting does not occur.

Therefore, as shown in the figure, by setting the focal points 11a and 13a (irradiation regions 11b and 13b) at positions where the temperature gradients formed by the irradiation of the pulsed lasers 11 and 13 interfere with each other, the temperature gradient becomes predetermined. It shows a three-dimensional distribution, and a predetermined flow of the molten liquid in the melting region 2 is induced according to the distribution. In the present embodiment, the focal point 13a of the second pulse laser 13 is set at a position offset by a predetermined amount d from the focal point 11a of the first pulsed laser 11 to the front side in the irradiation direction (see FIG. 5). For example, between the irradiation region 11b of the first pulse laser 11 and the irradiation region 13b of the second pulse laser 13, a flow F1 is generated from the back side of the fusion region 2 in the irradiation direction toward the front side in the irradiation direction. As a result of such a flow F1, a predetermined elemental compound, for example, a network-forming oxide such as SiO ₂ is formed in the molten region 2 on the front side (above the focal point 11a) in the irradiation direction of the molten region 2. A relatively large number of molten portions 2a are generated. Along with this, outside the irradiation region 13b of the second pulse laser 13 (on the side opposite to the focal point 11a), a flow F2 is generated from the front side of the fusion region 2 in the irradiation direction toward the back side in the irradiation direction. The network-forming oxide contained in the melt in this flow F2 is relatively small. As described above, as a result of cyclical flows F1 and F2 including the movement of specific elemental compounds in the molten region 2, a predetermined elemental compound, here, a region in which the network-forming oxide is relatively dense. Areas that are relatively sparse are gradually formed.

FIG. 7 is a plan view of (a) a main part and (b) a cross-sectional view of a main part of the glass body 1'after the above-mentioned laser irradiation. That is, in the present embodiment, the melt-coagulated portion 3 formed inside the glass body 1'after laser irradiation has a substantially egg shape as shown in FIG. 7 (b), and the first pulse laser 11 The side where the focal point 13a of the second pulse laser 13 is offset with respect to the focal point 11a is relatively large in diameter. Further, as shown in FIG. 7A, the large-diameter side of the melt-solidified portion 3 has a shape influenced by the irradiation mode (position and number of focal points 13a) of the second pulse laser 13, which is close to a rectangle. It has a shape.

Further, FIGS. 7A and 7B show the relative content ratios of predetermined elemental compounds (here, network-forming oxides such as SiO ₂ ) in the melt-solidified portion 3 in different shades of color. As shown in FIG. 7B, a first region 3a in which the network-forming oxide is relatively dense is formed in a layer in the melt-solidified portion 3. In the present embodiment, the first region 3a is formed on the side offset from the focal point 13a of the second pulsed laser 13 with respect to the focal point 11a of the first pulsed laser 11. On the other hand, a second region 3b in which the network-forming oxide is relatively sparse is formed on the side opposite to the first region 3a, that is, the side opposite to the side where the focal point 13a is offset.

Here, when the glass body 1 before irradiating each of the pulse lasers 11 and 13 is formed of a glass having a composition containing a network-forming oxide and a network-modifying oxide, the network-forming oxide is relatively present. In the dense first region 3a, the network-modified oxide is relatively sparse, and in the second region 3b, where the network-forming oxide is relatively sparse, the network-modified oxide is relatively dense. Further, when compared with the content ratio of the mesh-modified oxide in the glass body 1 before the laser irradiation, the content ratio of the mesh-modified oxide in the first region 3a of the glass body 1'after the laser irradiation is the glass before the laser irradiation. The content ratio of the network-modified oxide in the body 1 is lower than that of the network-modified oxide, and the content ratio of the network-modified oxide in the second region 3b is higher than the content ratio of the network-modified oxide in the glass body 1.

By irradiating the first pulse laser 11 and the second pulse laser 13 toward the glass body 1 in this way, the inside of the glass body 1'is centered on the irradiation region 11b of the first pulse laser 11. The melt-solidified portion 3 is formed, and the melt-solidified portion 3 is formed with a first region 3a and a second region 3b having a composition different from that of the original glass body 1. From the above, the composition of the glass body 1'is partially modified.

(S2) Fine Periodic Structure Forming Step FIG. 8 shows the overall configuration of the second laser irradiation device 30 used in the fine periodical structure forming step S2. The second laser irradiation device 30 is a glass body 1'after the composition of the third laser oscillator 32 capable of oscillating the third pulse laser 31 and the third pulse laser 31 oscillated from the third laser oscillator 32. It is provided with an optical system 33 for condensing and incident light inside, a linear polarizing plate 34 arranged on the path of the optical system 33, and a table 35 on which the glass body 1'is placed.

The optical system 33 further includes a plurality of mirrors 36, and a lens 37 that condenses the third pulse laser 31 transmitted via each mirror 36 and the linear polarizing plate 34 into the inside of the glass body 1'. As a result, the optical system 33 having the above configuration is configured so that the third pulse laser 31 can be focused and irradiated on the first region 3a of the melt solidification portion 3 formed inside the glass body 1'.

Here, it is desirable that the power density of the third pulse laser 31 is an amount of energy that can cause a photo-induced refractive index change in the irradiation region of the glass body 1', and it depends on the composition of the glass body 1'and the like. For example, it is set to be 10 ⁸ W / cm ² or more. For example, when the glass body 1'is alkaline glass, the power density of the third pulse laser 31 is set to be 10 ¹⁰ W / cm ² or more.

As other irradiation conditions, for example, when the glass body 1'is formed of alkaline glass, the repetition frequency of the third pulse laser 31 is set to 1 kHz or more and 1000 MHz or less, and the wavelength is 100 nm or more and 2000 nm or less. The pulse width is set to 1 fs (femtoseconds) or more and 1000 fs or less, and the output is set to 0.1 μJ or more and 20 μJ or less. Further, the irradiation period of the first pulse laser 11 is set to 0.1 seconds or more and 6000 seconds or less. During this period, the table 35 may be fixed, or may be configured to be able to move three-dimensionally while the irradiation of the third pulse laser 31 is being performed or the irradiation is stopped.

Hereinafter, an example of carrying out the fine periodic structure forming step S2 using the second laser irradiation device 30 having the above configuration will be described mainly with reference to FIGS. 8 to 10.

In this step, the third pulse laser 31 in which irradiation conditions such as power density are appropriately set as described above is oscillated from the third laser oscillator 32. Then, the oscillated third pulse laser 31 is passed through the linear polarizing plate 34, the polarization state of the third pulse laser 31 is adjusted to a predetermined direction, and then the lens 37 is passed. As a result, the third pulse laser 31 is irradiated toward a predetermined position in the glass body 1', specifically, the first region 3a of the melt solidification portion 3 (see FIGS. 7 and 8).

By this irradiation, the first region 3a of the melt-solidified portion 3 is given an amount of energy that can cause a photo-induced refractive index change, so that the third pulse laser 31 of the first region 3a is used. A photoinduced index change occurs in the irradiated area. As a result, the refractive index change region 4 having a predetermined shape is formed. In the present embodiment, for example, as shown in FIGS. 9A to 9C, a spherical refractive index change region 4 is formed. The size of the refractive index change region 4 depends on the irradiation conditions of the third pulse laser 31, but is, for example, in the range of 1 μm to 1 mm.

Further, in this case, inside the refractive index change region 4, a region having a relatively high refractive index (high refractive index region 5a) and a region having a relatively low refractive index (low refractive index region 5b) at a pitch of 1 μm or less. ) And the fine periodic structure 5 are formed alternately. 9 (a) to 9 (c) are cross-sectional views showing a fine periodic structure 5 formed in the refractive index change region 4. In FIG. 9A, reference numeral P represents the pitch of the high refractive index region 5a, and reference numeral L represents the width dimension of the high refractive index region 5a.

FIG. 9A shows the form of the fine periodic structure 5 formed when the third pulse laser 31 whose magnetic field direction is horizontally polarized is irradiated perpendicularly to the paper surface. Of the fine periodic structures 5 formed in the spherical refractive index change region 4 (its diameter is indicated by D), the surface connecting the high refractive index regions 5a (here referred to as the main surface) is in the polarization direction of the magnetic field. It is formed in parallel in a sliced state. FIG. 9B shows the form of the fine periodic structure 5 formed when the third pulse laser 31 is irradiated from the right side to the left side of the paper surface. FIG. 9C shows the form of the fine periodic structure 5 formed when the third pulse laser 31 is irradiated from the lower side to the upper side of the paper surface.

Further, the relationship between the formation direction of the main surface and the polarization of the third pulse laser 31 is shown in FIGS. 10 (a) and 10 (b). FIG. 10A shows the form of the fine periodic structure 5 formed when the third pulse laser 31 whose magnetic field direction is horizontally polarized is irradiated perpendicularly to the paper surface, and FIG. 10B shows the magnetic field direction. Shows the form of the fine periodic structure 5 formed when the paper surface is vertically irradiated with the vertically polarized third pulse laser 31. As described above, the direction of the main surface composed of the region having a relatively high refractive index (high refractive index region 5a) is the same as the direction of the polarizing magnetic field.

By irradiating the inside of the glass body 1'with the third pulse laser 31 as described above, the refractive index change region 4 (see FIG. 9) is formed in the glass body 1'. Further, at this time, by forming the refractive index change region 4 in the first region 3a (see FIG. 7 and the like) in which the content ratio of the mesh-modified oxide is relatively small, the above-mentioned above-mentioned refractive index change region 4 is formed. As described above, it is possible to form a fine periodic structure 5 in which high refractive index regions 5a and low refractive index regions 5b alternately exist at a pitch of 1 μm or less, in other words, the refractive index changes periodically on the order of submicron.

Although one embodiment of the present invention has been described above, the processing method of the fine periodic structure and the glass body on which the fine periodic structure is formed can naturally take any form within the scope of the present invention. Is.

For example, with respect to the first region 3a and the second region 3b formed in the melt solidification portion 3 of the glass body 1', the shapes and sizes thereof appropriately control the temperature distribution in the melt region 2 (see FIG. 5). The temperature distribution can be controlled by appropriately adjusting the irradiation conditions of the first and second pulse lasers 11 and 13.

Although not shown, the periodic direction of the fine periodic structure 5 can be set to any direction by setting the polarization magnetic field direction of the third pulse laser 31 to be irradiated. Similarly, although not shown, a plurality of fine periodic structures 5 can be formed in the first region 3a. Alternatively, as long as it is formed in the first region 3a, it is also possible to form the fine periodic structure 5 into a shape other than a spherical shape (for example, a curved string having a circular cross section). These can be formed, for example, by appropriately adjusting the irradiation conditions of the third pulse laser 31, or by appropriately adjusting the three-dimensional movement of the glass body 1'and the irradiation and stopping of the third pulse laser 31.

The glass body 1'according to the above description is, for example, a control element for the polarization direction of an optical signal used for optical communication, an optical element having a diffraction effect, a reflector filter for reflecting an optical signal of a specific wavelength, an optical attenuator, or the like. It can be applied to various applications including the optical element of.

1,1'Glass body 2 Melted region 3 Melted solidified part 3a First region 3b Second region 4 Refractive index change region 5 Fine periodic structure 5a High refractive index region 5b Low refractive index region 10 First laser irradiation device 11 First pulse Laser 11a Focus 11b Irradiation area 12 First laser oscillator 13 Second pulse laser 13a Focus 13b Irradiation area 14 Second laser oscillator 15 Optical system 16 Spatial optical phase modulator 17 Table 20 Beam splitter 21 Objective lens 30 Second laser irradiation device 31 Third pulse laser 32 Third laser oscillator 33 Optical system 34 Linear polarizing plate 35 Table 36 Mirror 37 Lens

Claims (4)

A first pulse laser having a predetermined repetition frequency is irradiated toward a glass body containing a network-forming oxide and a network-modified oxide of 30 mol% or less, and the repetition frequency is lower than that of the first pulse laser. By irradiating the two-pulse laser toward the peripheral region of the focal point of the first pulse laser and controlling the temperature distribution of the region melted by the irradiation of the first pulse laser.
In the molten region, a first region in which the network-forming oxide contained in the glass body is relatively dense and a second region in which the network-forming oxide is relatively sparse are formed, and the first region is formed . A composition reforming step of partially modifying the composition of the glass body so that the content ratio of the network-modified oxide in one region is 15 mol% or less .
By irradiating the first region with a single focused third pulse laser having an amount of energy that causes a light-induced refractive index change.
A microperiodic structure comprising a microperiodic structure forming step in which a region having a relatively high refractive index and a region having a relatively low refractive index alternately exist at a pitch of 1 μm or less in the first region. Processing method. The method for processing a fine periodic structure according to claim 1 , wherein both the first pulse laser and the second pulse laser are femtosecond lasers. The method for processing a fine periodic structure according to claim 1 or 2 , wherein the third pulse laser is a femtosecond laser. A glass body having a melt-solidified portion formed therein and containing a network-forming oxide and a network-modified oxide of 30 mL or less .
In the melt-solidified portion, a first region in which the network-forming oxide contained in the glass body is relatively dense and a second region in which the network-forming oxide is relatively sparse are formed , and the said in the first region. The fine period in which the content ratio of the network-modified oxide is 15 mol% or less , and the region having a relatively high refractive index and the region having a relatively low refractive index alternately exist at a pitch of 1 μm or less in the first region. The glass body on which the structure is formed.

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