JP2006243667A - Optical element and apparatus using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize a spatial phase modulating element which is usable for various light sources, especially, a high-intensity laser light and a short-pulse laser light, and further to enable simultaneous control over intensity and phase modulation by the spatial phase modulating element which has been difficult in the conventional art. <P>SOLUTION: The optical modulator 10 comprises a plurality of light transmission structures 2 and a liquid supply means 3 of supplying liquid to the light transmission structures 2, and supplies at least two kinds of liquid differing in refractive index into the light transmission structures 2 by the liquid supply means 3 to spatially modulate phases of transmitting lights. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to an optical element capable of forming a laser wavefront having a spatial phase distribution by transmitting or reflecting laser light, and a laser processing apparatus and a laser manipulation apparatus to which the optical element is applied.
The optical element can be used as a spatial light modulator by controlling the phase of light, and further, as a wavefront aberration correction, condensing distribution correction, or a holographic processing mask for laser light, It can also be used in the fields of optical measurement, recording, display, and optical communication.
Further, it is possible to function as an optical compensation element by correcting a slight phase distribution of light, and similarly, it can be used in the field of optical computation, optical measurement, and the like.
An element having a high function as a holographic element can be realized by simultaneously controlling the phase and intensity of light.

Conventionally, the spatial phase modulation of light has been performed by a method using changes in physical properties of thin films and liquid crystal materials arranged in a matrix or a method of changing the distance of a transmissive thin film. These spatial phase modulations are usually performed by controlling an electric field or a magnetic field on the transparent electrode or the magnetic thin film. (For details, see “Basics of Optical Information Processing” Yatakai et al. (Maruzen, issued August 31, 1998) p. 53-)
Japanese Patent No. 3258029 (a phase modulation fine structure for a super-integrated spatial light modulator) is one that changes the phase of light by deformation of a viscous material. In this patent publication, the shape of the dielectric material is changed by an electric signal, thereby modulating the spatial phase of light transmitted therethrough.

As described above, the conventional optical element has the following problems because the phase of light is changed using a light-transmitting oxide thin film, a liquid crystal polymer, or the like.
(1) Damage occurs with high-intensity laser light.
(2) Alteration occurs due to repeated laser light irradiation, resulting in a change in transmittance.
(3) Especially in the short wavelength ultraviolet region, the transmission material is limited.
(4) It is difficult to increase the phase modulation in the thin film material.
(5) The usable wavelength range is narrow.
(6) The configuration becomes complicated.
(7) The material selection range is narrow.

The damage of the material by the laser beam is affected by the high temperature and chemical reaction due to the light absorption of the material and the heat propagation of the material. In the case of a solid material, even when a small amount of light is absorbed, irradiation with high intensity laser light causes direct material alteration due to absorption or alteration due to high temperature. As a result, when high-intensity laser light is irradiated, the optical characteristics of the substance change instantaneously or over time, and when the laser light intensity is high, the material is removed and the function as a spatial modulator is not achieved.
Japanese Patent No. 3258029

  The problem to be solved by the present invention is to realize a spatial phase modulation element that can be used for various light sources, particularly high-intensity laser light and short-pulse laser light, in view of the above-mentioned problems of the prior art. is there. Furthermore, it is possible to simultaneously control intensity and phase modulation by a spatial phase modulation element, which has been difficult in the past.

The solution to the above problem is basically to introduce a liquid material having a different refractive index into the transparent cell of the optical element and perform phase modulation by changing the refractive index of the liquid material. By using a liquid material, it is possible to perform spatial phase modulation that can be easily used even with a high-intensity or short-wavelength laser.
The “liquid” used here includes a sol-like liquid or fluid viscous material as long as it has fluidity. The same applies to “Claims”.

By changing the refractive index of the liquid material in the transparent cell, the phase of the transmitted light can be changed.
When the average refractive index of the liquid material at a certain wavelength λ is n (λ) and the distance (transmission optical path length) of the transparent cell containing the liquid material is L, the phase change amount in the liquid material is as follows: It is expressed in
Phase change amount = 2π × n (λ) × L / λ
The refractive index of the liquid material can usually be selected from about 1.1 to about 1.6, and the phase for each structure (cell) can be changed by changing the refractive index of the liquid material to be inserted at a constant distance. Can be changed.
Holographic light reproduction can be achieved by spatially arranging or changing the structures having a plurality of phases. For example, it is possible to form a pattern at a condensing point by condensing light whose phase is spatially changed. In addition, by changing the phase on a plurality of lines, it has a function as a diffraction grating and can divide light as diffracted light. (For details on hologram reproduction and phase modulation, see p. 27- of the above-mentioned publication "Basics of Optical Information Processing".)

Since the liquid material has no intermolecular bond, heat conduction between the molecules is small, and a material that absorbs less irradiation laser light can easily suppress the increase in temperature. In addition, a low-molecular liquid material has high intramolecular bond dissociation energy due to light absorption, and thus hardly changes in characteristics due to irradiation laser light. Moreover, it is easy to select a material that absorbs less in the ultraviolet region. Further, since it is a liquid material, it is possible to supply a new liquid material by flowing it, and it is possible to sequentially use the new liquid material that has not caused laser damage.
Further, in a solid material, phase modulation is often performed with a thin film. In that case, it is often difficult to increase the film thickness in the process, and it is usually about several tens of microns. In the case of a liquid material, it is easy to increase the transmission distance by increasing the thickness of the cell, and the optical characteristics do not change when the thickness is changed.

In addition, materials that cause phase modulation through transmission in the ultraviolet region are limited to a few inorganic oxide materials, but in the case of liquid materials, there is a wide selection range of materials that are transparent in the ultraviolet region and damage caused by laser light. It is known that there are many materials whose threshold values are lower than those of inorganic materials.
Furthermore, when these thin films or bulk transparent materials are used for spatial phase modulation, a method of changing the thickness spatially is required. In order to change the thickness and refractive index spatially, a very complicated construction method and management are required, such as sequentially applying a photolithography method using a large number of masks. On the other hand, in the present invention, spatial modulation can be realized simply by drilling the liquid cell and changing the refractive index of the flowing liquid material, and it can be manufactured at a low cost by a simple process.

[Solution 1] (corresponding to claim 1)
Solution 1 taken in order to solve the above problems comprises a plurality of light transmission structures and first liquid supply means for supplying liquid to the light transmission structures, and has at least two kinds of different refractive indexes. An optical element that spatially modulates the phase of transmitted light by supplying liquid into the light transmitting structure by the first liquid supply unit.
[Operation]
Liquids having different refractive indexes are spatially and selectively arranged by a plurality of light transmission structures (transparent cells), and at that time, the optical path length of the transparent cells is made constant so that phase modulation is performed only by the refractive index of the liquid. It is possible. At this time, it is desirable that the temperature and pressure of the cell be kept constant. However, the change in the refractive index due to the pressure of the normal liquid is about 0.0001 / atmospheric pressure, and the change in temperature is about 0.001 / degree, so usually precise management is not required.
Liquids having different refractive indexes are allowed to flow through the transparent cell, and phase modulation is performed by changing the refractive index of the liquid. By using a liquid, it is possible to use many materials even for a high-intensity laser for the above reasons.

[Embodiment 1] (corresponding to claim 2)
Embodiment 1 is that the optical element of Solution 1 includes a liquid mixing unit that adjusts at least two kinds of liquids having different refractive indexes by mixing liquids having different refractive indexes.
[Operation]
Since at least two kinds of liquids having different refractive indexes are adjusted by mixing liquids having different refractive indexes, the refractive index can be easily modulated.

[Embodiment 2] (corresponding to claim 3)
In Embodiment 2, the optical element according to Solution 1 or Embodiment 1 described above, when the wavelength of transmitted light is λ, the maximum refractive index of liquids having different refractive indexes is nmax, and the minimum refractive index is nmin, light transmission is performed. The light transmission distance of the structure is an integral multiple of λ / (nmax−nmin).
[Operation]
The optical distance of transmitted light due to the difference in the refractive index of the liquid is set to a maximum 2π phase difference, and phase modulation from 0 to 2π is performed according to the mixing ratio of the liquid.

[Solution 2] (corresponding to claim 4)
Solution means 2 taken to solve the above-mentioned problem is that in the optical element of solution means 1, embodiment 1 or embodiment 2, in addition to the first liquid supply means, a light-absorbing liquid is used as a light-absorbing liquid. Comprising a second liquid supply means for supplying to the permeable structure;
The second liquid supply means supplies the light-absorbing liquid into the light transmission structure at a predetermined mixing ratio, thereby spatially modulating the intensity of transmitted light according to the phase. It is.

[Operation]
In addition to liquids having different refractive indexes, by mixing both using liquids having light absorption properties, not only spatial phase modulation but also intensity modulation can be performed. If the liquid has absorptivity for light of a certain wavelength, the absorption coefficient is α and the transmission distance is L.
Transmittance T = exp (−αL)
Thus, the light transmittance can be controlled by using liquids having different absorption coefficients α. It is possible to select a liquid that has an absorptivity with respect to the wavelength of transmitted light, and by adding it, the refractive index and the absorptance are adjusted simultaneously.
Thereby, the change in phase and transmittance in transmitted light can be controlled simultaneously by the mixing ratio of different liquids. In addition to the phase change in transmitted light in Solution 1, Embodiment 1 and Embodiment 2 above, The spatial strength can be adjusted.

[Embodiment 3] (corresponding to claim 5)
Embodiment 3 is that two or more types of liquids having different refractive indexes are soluble liquids in the optical elements according to any one of the above-described solving means 1 and 2 and embodiments 1 and 2.
[Operation]
By selecting a soluble liquid having a different refractive index, the liquid can be easily mixed in the mixing section, the uniformity of the refractive index can be increased, and the occurrence of a liquid interface or the like can be prevented.

[Embodiment 4] (corresponding to claim 6)
In Embodiment 4, in the optical element according to any one of Solution 1 or 2 or Embodiments 1 and 2, two or more kinds of liquids having different refractive indexes are the same solvent or a soluble solvent, and depending on the concentration of the solute. It is to change the refractive index.
[Operation]
Using a solution as the liquid to be mixed, the refractive index is changed depending on the concentration of the solute. Thereby, the adjustment of the refractive index is easy, and the selection range of the solution is wide.

[Solution 3] (Corresponding to Claim 7)
Solution means 3 taken to solve the above-described problem includes a first light-transmitting structure in which a plurality of light-transmitting structures for modulating the phase of transmitted light are stacked, and a liquid having a predetermined refractive index. First liquid supply means for selectively supplying to the light transmission structure;
A plurality of second light transmission structures disposed in the light transmission direction of the first light transmission structure and modulating the intensity of the transmitted light, and two or more types of liquids having different absorption rates are used as the plurality of second light. Second liquid supply means for supplying to the permeable structure,
The liquid having the predetermined refractive index and the liquid having two or more different absorptances are supplied to each of the first and second light transmission structures by the first and second liquid supply means, thereby transmitting the liquid. An optical element that spatially modulates the phase and intensity of light.

[Operation]
Since the phase of the transmitted light is modulated by the first light transmitting structure and the intensity of the transmitted light is modulated by the second light transmitting structure, the spatial phase of the transmitted light and the intensity are also modulated, as in the above solution means 2. Can be modulated.
With the development of so-called MEMS (micromachine system) technology, fine three-dimensional processing technology has been realized, and liquid flow paths (first and second light transmission structures) can also be three-dimensionally formed. It is possible to arrange several layers of cell structures (first and second light transmission structures) in the transmission direction. By laminating and arranging the liquid flow paths and introducing the light absorbing material into at least one layer thereof, it is possible to simultaneously control the phase and the light intensity of the transmitted light.
By making the phase in the light absorption layer constant, it is possible to perform phase modulation only in the phase modulation layer. Also, in this case, independent control is possible in which the transmission intensity is adjusted by changing the thickness of the light absorption layer and the phase is corrected by the phase modulation layer.

[Embodiment 5] (corresponding to claim 8)
Embodiment 5 is that the optical element of any one of the above-described solving means 1 to 3 or embodiments 1 to 4 is provided with a light shielding member that shields transmitted light that passes through at least a part of the liquid supply means.
[Operation]
By disposing a light shielding member such as a mask that prevents transmission of light to the flow path, the transmitted light passes only through the region where phase modulation is performed.

[Embodiment 6] (corresponding to claim 9)
Embodiment 6 is the optical element according to any one of Solution 1 to 3 or Embodiments 1 to 5, further including a reflective layer that reflects the light transmitted through the plurality of light transmission structures, and the liquid supply unit includes the reflective layer. It is arranged on the back side.
[Operation]
In order to make the phase modulation element reflective, a reflective layer for transmitting light is arranged. At that time, liquid supply means (flow path) is arranged on the back side of the reflective layer so that liquid is supplied from the reflective layer side.

[Embodiment 7] (corresponding to claim 10)
Embodiment 7 is that the optical path lengths of the plurality of light transmission structures are different in the optical element of any one of Solution 1 to 3 or Embodiments 1 to 6.
[Operation]
The light transmission structure itself also changes the phase of the transmitted light, and phase modulation is performed by introducing a liquid whose refractive index is adjusted.
As a result, when the phase modulation width does not necessarily require 2π phase modulation, or when performing phase modulation of light whose initial phase is known to some extent, it can be performed by using only a small amount of liquid.

[Solution 4] (corresponding to claim 11)
Solution means 4 taken to solve the above-mentioned problem comprises the optical element according to any one of the above solution means 1 to 3 or embodiments 1 to 7 as a spatial phase modulation element, and laser light is emitted by the spatial phase modulation element. This is a laser processing apparatus that irradiates space selectively.
[Operation]
In the projection type laser processing, processing using laser light that has passed through a photomask is performed. At that time, a large part of the light is shielded by a mask, which may result in processing with low energy utilization efficiency. By using a so-called diffraction element or hologram element to perform spatial phase modulation of the laser beam, it is possible to create various shapes on the focal plane of the condenser lens or to split the laser beam, for example. Therefore, there is an advantage that the energy use efficiency is higher than that of the mask projection method. However, it is often difficult to use a normal phase modulation element with a high intensity laser or an ultraviolet laser.
On the other hand, by using the optical elements of the above-described solving means 1 to 3 or embodiments 1 to 7 as a spatial phase modulation element in a laser processing apparatus, phase modulation of a high intensity laser becomes possible. Holographic processing becomes possible.

[Solution 5] (Corresponding to Claim 12)
Solution 5 taken in order to solve the above-described problem includes the optical element according to any one of Solution 1 to 3 or Embodiments 1 to 7 as a spatial phase modulation element, and laser light is emitted by the spatial phase modulation element. This is a laser manipulation device that controls space selectively.
[Operation]
By utilizing the optical elements of the above-mentioned solving means 1 to 3 or embodiments 1 to 7 as a spatial phase modulation element in a laser manipulation device, it becomes possible to control laser light with a high peak power in the same manner as the above-described solving means 4. It is possible to adjust the beam splitting, the minute condensing diameter, or the irradiation position.

The effects of the present invention are summarized for each main claim as follows.
(1) The invention according to claim 1 Since the liquid is used, there is a material (liquid) having a high transmittance in a wide wavelength region, a wide selection range of the transparent material in the ultraviolet region, and a selection range of the refractive index. Is also wide. In addition, the phase can be changed greatly depending on the length of the flow path (the optical path length of the transparent cell), and the phase modulation element can be manufactured only by drilling. Furthermore, by flowing the liquid through the flow path (transparent cell), a new liquid can be introduced even when the liquid deteriorates, and an element without deterioration can be realized.
(2) Invention of Claim 2 Since the refractive index of the liquid is adjusted by mixing the liquid, the refractive index can be easily adjusted, and the refractive index can be adjusted continuously (in infinite gradation). In addition, various refractive indexes can be adjusted.

(3) Invention according to claim 3 The optical distance of transmitted light due to the difference in the refractive index of the liquid is set to a maximum 2π phase difference, and phase modulation of 0 to 2π is performed by the mixing ratio of the liquid. Since there is no need to consider phase modulation, the phase can be easily calculated.
(4) Invention according to Claim 4 By mixing liquids having different refractive indexes and light-absorbing liquids, in addition to phase modulation of transmitted light, it is possible to simultaneously modulate spatial intensity. It is easy to create a two-dimensional hologram image, and it is possible to reduce the noise of the hologram image and simplify the design of the hologram pattern.
In addition, it is possible to realize a hologram element that is highly accurate and can be easily calculated.

(5) The invention according to claim 5 By selecting a soluble liquid, it is easy to mix the liquid in the mixing section, so that the uniformity of the refractive index is increased and the occurrence of a liquid interface or the like can be prevented. In addition, various liquids can be used, and inexpensive materials can be selected.
(6) Invention of Claim 6 Since the refractive index is changed depending on the concentration of the solute using a solution as the liquid to be mixed, the refractive index can be easily adjusted, and the selection range of the solution can be widened. Moreover, since various solutes can be used, inexpensive materials can be used.

(7) Invention of Claim 7 Since spatial phase modulation and intensity modulation of transmitted light can be controlled simultaneously and can be controlled independently of each other, spatial light modulation, which has been considered difficult in the past, becomes possible. Creation of a typical hologram image is facilitated, and noise reduction of the hologram image and simplification of the design of the hologram pattern are possible.
Further, similarly to the invention according to claim 4, it is possible to realize a hologram element that is highly accurate and easy to calculate by calculation.
(8) The invention according to claim 8 Since the transmitted light passes only through the region where the phase modulation is performed, the noise of the hologram image can be reduced, and the change of the wavefront due to the light diffraction in the flow path is suppressed. Is possible.

(9) The invention according to claim 9 By using the phase modulation element as a reflection type and disposing the flow path on the back side of the reflection layer, the phase modulation can be doubled as compared with the transmission type, and the flow path section. It is possible to reduce the influence due to light transmission in and to simplify the structure.
(10) The invention according to claim 10 The phase modulation width is not necessarily 2π by performing phase modulation with the liquid having a refractive index adjusted and the transmission optical path length (thickness) of the light transmission structure (cell). Is not necessary, or when phase modulation of light whose initial phase is known to some extent, it is only necessary to use a small amount of liquid, so high-precision phase modulation is possible, and processing of the light transmission structure is possible. It becomes easy. Accordingly, it is possible to function as a phase compensation element for laser light.

(11) Invention according to claim 11 By using the optical element as a spatial phase modulation element in a laser processing apparatus, phase modulation of a high-intensity laser becomes possible, and holographic processing with a high-intensity laser Therefore, it is possible to perform processing that is significantly more efficient than mask projection, for example, high-speed processing by splitting into multiple beams, high-precision processing by beam interference, or arbitrary shape processing that changes the pattern. Become.
In addition, by changing the intensity and phase of transmitted light at the same time, it is easy to form a three-dimensional intensity distribution of light and easily realize internal modification processing, three-dimensional shape processing, or three-dimensional exposure (modeling). can do.
(12) Invention of claim 12 Claims 1 to 10 By using the optical element as a spatial phase modulation element in a laser manipulation device, it becomes possible to control high peak power laser light. It is possible to realize particle control such as movement, capture or movement of a plurality of particles, continuous movement by changing an irradiation pattern, or three-dimensional movement.

  Realizes spatial phase modulation elements that can be used for various light sources, especially high-intensity laser light and short-pulse laser light, and simultaneously controls intensity and phase modulation using spatial phase modulation elements, which was difficult in the past. This was achieved with a relatively simple structure at low cost by introducing liquids having different refractive indexes into the transparent cell of the optical element and performing phase modulation by changing the refractive index of the liquid.

Example 1 (corresponding to claims 1 to 3) of the present invention will be described with reference to FIGS. FIGS. 1-1 and 2 are schematic views of optical elements.
The optical element 10 includes a large number of cells 2, 2... That transmit light in the transparent substrate 1, for example, formed in a matrix, and these cells 2, 2. It is arranged so that liquid can be introduced. At this time, the fine flow paths 3, 3... Can be arranged in a three-dimensional manner. For example, an introduction port 4 and a discharge port 5 are provided for each cell 2, 2,. As the material of the transparent substrate 1, for example, a transparent polymer material such as quartz or acrylic is suitable. When visible or near infrared light is incident, a polymer material such as glass or polycarbonate can be used. .
In this optical element 10, light is incident from a direction perpendicular to the paper surface in FIG. 1-1 (a), and light is incident from the left direction of the paper surface in (b).
The processing of these three-dimensional cells 2, 2,... Can be realized by techniques such as processing by photolithography and dry etching, adhesion method, laser three-dimensional modeling, direct processing by laser, or internal processing. At present, these processes can be realized with nano-order accuracy, particularly in the depth direction.

Thus, liquids having different refractive indexes are introduced into the three-dimensional cells processed with high accuracy for each cell. As the liquid supply means, liquid is supplied to and discharged from the cell by connecting a flow path from the liquid tank via a valve to supply the liquid, and sucking the liquid with a pump or the like and discharging it to the discharge tank. Is possible. Then, it is desirable to adjust the flow rate by adjusting the flow rate of the valve or the valve diameter. In addition to discharging to the discharge tank, it is possible to repeatedly introduce the liquid by making the flow path a circulation type. At this time, it is possible to remove impurities and dust by providing a filter or the like in the middle.
As the liquid, a liquid that is transmissive to the irradiation laser beam can be used. For example, by using an aqueous solution of sodium salt, salt, etc., refractive index modulation can be performed over a wide wavelength range corresponding to a wide transmission region of water. Can be realized. Thereby, for example, spatial modulation of 193 nm vacuum ultraviolet light, which has been difficult in the past, is also possible. In addition, many solutions and liquids such as alcohols such as ethanol and isopropyl alcohol, silicone oil, and immersion oil used in microscopes can be used, and these can be mixed to change the refractive index.

The liquid can be selected by connecting different liquids individually to the respective flow paths, so that liquids having different refractive indexes can be selectively flowed to the flow paths. In order to flow the same liquid to different cells, It is possible to select the liquid for each cell by opening and closing a liquid selection valve or the like from the supply tank. By preparing a plurality of the selection valves, one of a large number of liquids can be selected and introduced into the flow path.
By making light incident on the transparent substrate 1, it is possible to generate transmitted light that spatially generates a phase distribution. At this time, the height and width of the cells 2, 2... Can be arbitrarily selected.
Since each of these cells 2, 2... Can flow a liquid, it is possible to change the phase modulation of each cell sequentially or as necessary, as a phase modulator that changes over time. Can fulfill the function.

In this case, the cells do not need to have a matrix shape, and the flow path may have a linear shape such as cells 12, 12,... Shown in FIG. At this time, a plurality of types of liquids (those having different refractive indexes) can be flowed through the flow path 13, and each flow path 13 is switched to a different type such as a liquid 14 or a liquid 15 by valves 16, 17, etc. It can also be used. It is also possible to circulate and use the liquid discharger 18 to circulate the liquid.
As described above, since a liquid is used as a material for changing the phase of transmitted light, there is a highly transparent material (liquid) in a wide wavelength region, and there is a wide selection range of a transparent material in the ultraviolet region. There is a wide selection range of refractive index. In addition, the phase can be changed greatly depending on the length of the flow path (the optical path length of the transparent cell), and the phase modulation element can be manufactured only by drilling. Furthermore, by flowing the liquid through the flow path (transparent cell), a new liquid can be introduced even when the liquid deteriorates, and an element without deterioration can be realized.

Next, in the optical element 30 shown in FIG. 2, the refractive index of the liquid introduced into each cell can be easily adjusted by mixing two kinds of liquids.
When the liquid is introduced from the flow path 23 into the plurality of cells 22, 22..., A mixing process of the liquid 24 and the liquid 25 is provided. This can be performed, for example, by adjusting the amount of each liquid by the cock 26 and the cock 27 and then mixing in the branched flow path. Such mixing does not need to be performed inside the device, and a mixing mechanism can be provided outside. The liquid mixed by adjusting the amount in this way can be selected while selecting the introduction position by, for example, the moving mechanism 29 that changes the position of the introduction hole of the liquid. Further, by selecting the introduction position, the liquid (material) having the same refractive index can be simultaneously introduced into the plurality of cells 22, 22. By mixing and introducing liquids in this way, it is possible to easily adjust the refractive index, not only to adjust the refractive index continuously (infinite gradation), but also to adjust various refractive indexes. It becomes.

Next, an optical element capable of continuously modulating the phase difference of transmitted light to 2π by mixing two kinds of liquids having different refractive indexes will be described.
The light transmission distance of the cell is changed in accordance with the maximum refractive index and the minimum refractive index in two types of liquids having different refractive indexes. For example, when a mixture of oils having a refractive index of 1.4 and 1.5 is used, the light transmission distance of the cell is an integral multiple of 4 microns when the wavelength of the irradiation laser light is 400 nm. At this time, the phase change on the low refractive index side is 14 * 2π and on the high refractive index side is 15 * 2π = 14 * 2π + 2π, and the difference is exactly 2π. Since the refractive index of the mixed liquid of these two types of liquids can take an intermediate value, phase modulation within 2π can be performed by changing the mixing ratio of the liquids.
Thus, since the optical distance of the transmitted light due to the difference in the refractive index of the liquid is set to a maximum 2π phase difference, the phase modulation of 0 to 2π is performed according to the mixing ratio of the liquid. There is no need to consider, and the calculation of the phase is easy.

Example 2 (corresponding to claims 4 to 6) of the present invention will be described with reference to FIG. FIG. 3 is a top view and a side view of the optical element.
In the conventional phase modulation element, since the refractive index is controlled in a single material, it is difficult to perform intensity modulation at the same time, and it is difficult to reproduce a three-dimensional hologram image. It was difficult to design.
The optical element 40 of the second embodiment can modulate intensity as well as spatial phase modulation by using a mixture of three types of liquids having different refractive indexes and light absorption rates.
As shown in FIG. 3, a plurality of cells 32 and 33 are formed in the transparent substrate 31. These cells 32, 33 can be arranged three-dimensionally. Here, for example, the cells 32, 32... Are arranged two-dimensionally in the first layer and the cells 33, 33. is doing. Such an arrangement of cells can be realized by stacking cells having substantially the same structure, and has an advantage of being easily processed by superimposing planes.
In the top view of FIG. 3A, light enters from a direction perpendicular to the paper surface, and in the side view of FIG. 3B, light enters from the upper side of the paper surface.

At this time, the cells 32 and 33 are provided with liquid (solution) flow paths 34 and 35 having different refractive indexes, respectively, and have the same refractive index as the liquid in the liquid flow path 34. An absorptive liquid flow path 36 in which the absorbent material is dissolved is also disposed. At this time, the intensity and phase of transmitted light can be modulated by adjusting the amount of liquid (solution) introduced into each flow path 34, 35, 36. The transmitted light intensity can be modulated by the ratio of the introduction amount from the flow path 34 and the flow path 36, and the transmitted light intensity can be modulated by the sum of the introduction amount of the flow path 34 and the flow path 36 and the ratio of the introduction amount of the flow path 35. The phase can be modulated.
The introduction of liquid into each cell can be realized by three-dimensionally arranging the connection ports to each cell, and two-dimensionally processed introduction channels with valves are bonded together or arranged in layers. This can be achieved. The piping to this flow path does not need to be a structure such as glass, and can be realized by bonding a fine plastic tube or a fine tube.

With this configuration, it is possible to simultaneously modulate the phase and intensity of transmitted light for each cell. In addition, by stacking a plurality of cells as described above, it is possible to control each of them independently such as only the intensity or only the phase. Furthermore, by adopting a multilayer arrangement and introducing different liquids, respectively. The intensity or phase can be precisely controlled.
In the above description, a plurality of cells are stacked. However, even in the case of a single layer, it is possible to simultaneously modulate the phase and intensity of transmitted light by changing the type of liquid mixture and the mixing ratio.
As described above, by mixing liquids having different refractive indexes and light-absorbing liquids, in addition to phase modulation of transmitted light, spatial intensity can be modulated at the same time, so a three-dimensional hologram It is easy to create an image, and the noise reduction of the hologram image and the design of the hologram pattern can be easily performed. In addition, it is possible to realize a hologram element that is highly accurate and can be easily calculated.

Next, the liquid introduced into the cell of the optical element will be described. The liquid can be used as a material whose refractive index continuously changes by using two or more kinds of soluble materials. This can be easily realized using, for example, two types of alcohol. Alcohols can be mixed with each other, and the mixed liquid has an intermediate value between the two liquids. Therefore, the refractive index of the alcohol can be continuously changed according to the mixing ratio.
As described above, since the liquid can be easily mixed in the mixing portion by selecting the soluble liquid, the uniformity of the refractive index can be increased and the occurrence of a liquid interface or the like can be prevented. In addition, various liquids can be used, and inexpensive materials can be selected.

Moreover, as another liquid, it can use as a material from which a refractive index changes continuously by using the liquid of two or more types of the same solvents. This can be easily realized using, for example, two types of saline solutions having different concentrations. Since the liquid mixture has an intermediate value between the two kinds of liquids, the refractive index can be continuously changed according to the concentration. Similarly, the refractive index change can be realized by the mixing ratio even in the case of an aqueous solution of other salts.
Thus, since the refractive index is changed depending on the concentration of the solute using the solution as the liquid to be mixed, the refractive index can be easily adjusted and the selection range of the solution can be widened. Moreover, since various solutes can be used, inexpensive materials can be used.

A third embodiment (corresponding to claims 7 and 8) of the present invention will be described with reference to FIGS. FIG. 4 is a side view of the optical element, and light enters from the upper side of the drawing. FIG. 5 is a top view of the optical element.
The optical element 50 of the third embodiment performs phase modulation and intensity modulation together using a plurality of types of liquids, and can modulate the phase and intensity of transmitted light independently.
This optical element 50 is formed with three-dimensional cells 42, 43, and 44 in the transparent substrate 41 in the same manner as shown in FIG. 3, and the phase modulation of transmitted light selects the cells, For example, by introducing a liquid into the cell 43 and the cell 44, it is realized by stacking the cells. With such a configuration, it is possible to easily add phases.
In this optical element 50, in addition to the above-described phase modulation control, a cell 45 for introducing a light-absorbing liquid is separately arranged. For each cell into which the light-absorbing liquid is introduced, for example, a liquid (solution) having a changed concentration of the light-absorbing material is introduced through the flow path 46. At this time, the cell 45 does not need to have the same height as the cells 42 to 44 for phase modulation, and the light transmission length can be set independently. By disposing such a light-absorbing liquid cell 45, not only the phase of transmitted light but also the intensity can be modulated independently at the same time.

As described above, since spatial phase modulation and intensity modulation of transmitted light can be controlled simultaneously and independently, spatial light modulation, which has been difficult in the past, can be realized, and a three-dimensional hologram image can be obtained. This makes it easy to reduce the noise of the hologram image and to design the hologram pattern.
Further, similarly to the second embodiment, it is possible to realize a hologram element that is highly accurate and can be easily calculated.

The optical element 60 in the optical element 50 shown in FIG. 4 or the like shields the influence between parts other than the cell (particularly the flow path part) by shielding the part between the cells. .
As shown in FIG. 5, for example, a light-shielding photomask 54 is disposed at a location where a flow path is formed. The light-shielding photomask 54 can be easily formed by etching metal deposited on the transparent substrate 51. As a result, it is possible to remove light that normally passes through the flow paths 53 that are stacked or arranged in a complicated manner, and it is possible to perform phase modulation that is more controlled only by the cells 52.
In this way, since the transmitted light passes only through the region where phase modulation is performed, noise in the hologram image can be reduced, and a change in wavefront due to light diffraction in the flow path can be suppressed.
Needless to say, the light shielding member such as the light shielding photomask 54 is not limited to the optical element of the third embodiment, and can be similarly arranged in all the optical elements of the first and second embodiments.

Example 4 (corresponding to claim 9) of the present invention will be described with reference to FIG. FIG. 6 is a perspective view of the optical element, and light is incident from above in the drawing.
The optical element 70 of the fourth embodiment is provided with a reflective layer and is of a reflective type so as to suppress the influence of transmitted light from the flow path portion and increase phase modulation.
As shown in FIG. 6, the cells 62 formed in the transparent substrate 61 are arranged in a matrix, for example, so as to communicate with the flow path via the liquid inlet 63 and the outlet 64. On the back surface of the cell 62 (lower side in FIG. 6), a reflection layer 65 coated with a reflection mirror for incident laser light is disposed. The reflective layer 65 can be realized by depositing a multilayer film or a metal material on a transparent substrate by sputtering, or contacting a bulk substrate. The incident light at this time is reflected by the reflective layer 65, and becomes a reflective spatial phase modulator by modulating the refractive index of the cell 62.

With this configuration, it is possible to reduce the influence of light transmission through the flow path, which is a problem when using cells arranged two-dimensionally. In a transmissive optical element in which cells are arranged in a matrix type, the amount of light transmitted through the flow channel is affected by the area of the flow channel other than the cell. Thus, by making the diameter of the flow path considerably small, the cell phase modulation error due to the flow path can be greatly reduced compared to the transmission type.
As described above, the phase modulation element is made a reflection type, and the flow path is arranged on the back side of the reflection layer, so that the phase modulation can be doubled compared to the transmission type, and the light is transmitted through the flow path. In addition, the structure can be simplified.
Although the optical elements (see FIGS. 1-1 to 5) of the first to third embodiments are described as transmissive types, these optical elements are also reflective by disposing a reflective layer. Needless to say, it can be configured as an optical element. At this time, since the optical path is doubled, the amount of change is doubled. Therefore, it is possible to modulate twice as much as the transmission type.

Embodiment 5 (corresponding to claim 10) of the present invention will be described with reference to FIG. FIG. 7 is a front sectional view of the optical element.
The optical element 80 of the fifth embodiment is capable of high-accuracy phase modulation by slight phase change, and uses phase-modulated cells instead of cells having the same thickness.
As shown in FIG. 7, the optical element 80 is formed with a large number of cells that transmit light in a transparent substrate 71, and the laser light is incident from the upper side of the figure and reflected by the reflective film 74. It is configured to be used. At this time, the phase change amount is adjusted by changing the thicknesses of the cell 72 and the cell 73, and the phase is spatially modulated on the same principle as described in the first embodiment by flowing the liquid into the cell. . By adjusting the cell thickness (transmission optical path length) in advance, for example, a large phase modulation can be performed with a slight change in refractive index, or a precise phase control can be performed.
In this way, by performing phase modulation using the liquid having the refractive index adjusted and the transmission optical path length (thickness) of the cell, the phase modulation width does not necessarily require 2π phase modulation, or the initial phase is known to some extent. In the case of phase modulation of the light, it is only necessary to use a small amount of liquid, so that high-accuracy phase modulation is possible and cell processing is facilitated. Accordingly, it is possible to function as a phase compensation element for laser light.

As Example 6 (corresponding to claims 11 and 12) of the present invention, various examples when the optical element of the present invention is specifically applied will be described with reference to FIGS.
First, a laser processing apparatus to which the optical element of the present invention is applied as a phase modulation element will be described with reference to FIG.
In this laser processing apparatus 90, as shown in FIG. 8A, the laser light emitted from the laser 81 is phase-modulated by, for example, a transmissive spatial phase modulation element 82 and condensed by a lens 83. Then, the processed sample 84 is irradiated. At this time, the positions of the phase modulation element 82 and the processed sample 84 are arranged at the position of the focal length f of the lens 83. The phase modulation element 82 is adjusted by the liquid control device 85 to achieve a desired modulation.

At this time, the phase modulation element 82 has a phase distribution as indicated by 86 in FIG. Here, white has a phase of 0 and black has a phase of 2π, and gray has an intermediate phase.
The refractive index modulation cell of this phase modulation element can be realized by introducing individual liquids into, for example, 64 × 64 cells. For example, a necessary number of cells shown in FIG. 6 are prepared and spatially selective. This can be realized by introducing liquids having different refractive indexes.
When such a phase-modulated image is used in the laser processing apparatus shown in FIG. 8A, an intensity distribution of the letter A indicated by 87 in FIG. 8B is formed on the surface of the processed sample 84 by image reproduction, It can be processed into this shape. This is merely an example, and various shapes can be produced by hologram reproduction by performing phase modulation in this way.
As described above, by applying the optical elements of Examples 1 to 5 to the laser processing apparatus, phase modulation of the high-intensity laser becomes possible, and holographic processing with the high-intensity laser becomes possible. Compared with mask projection, it is possible to perform highly efficient processing, for example, high-speed processing by splitting into multiple beams, high-precision processing by beam interference, or arbitrary shape processing that changes the pattern.
In addition, by changing the intensity and phase of transmitted light at the same time, it is easy to form a three-dimensional intensity distribution of light and easily realize internal modification processing, three-dimensional shape processing, or three-dimensional exposure (modeling). can do.

Further, a phase modulation element which is an optical element of the present invention will be described with reference to FIG.
FIG. 9A shows a liquid refractive index distribution cell structure, in which a refractive index distribution is spatially produced by the number of cells and the refractive index. FIG. 9B shows the intensity distribution when this structure is irradiated with a circular laser beam. In this way, it becomes possible to convert a circular laser beam into a linear beam by arranging the liquid. In this way, it is possible to change the shape of the beam corresponding to the refractive index distribution of the liquid or to correct the aberration of the phase laser beam.
This shape can be obtained by calculation. For example, three-dimensional laser processing and intensity adjustment can be performed by changing the refractive index distribution for each pulse and changing the width of the laser light.

Further, the phase modulation element which is the optical element of the present invention can be used like a diffraction grating as shown in FIG. 10, for example. When incident laser light 91 is irradiated to the phase modulation element in which the liquid cells 89 are arranged in a line in the transparent substrate 88, the laser light 91 is diffracted according to the pitch of the liquid cells 89, and the zero-order light 92 and the primary It will be branched like light 93. Here, by changing the refractive index of the liquid cell 89, the intensity of the primary light and the secondary light can be adjusted. In this case, each cell can use the same liquid. Further, at this time, the diffracted light can be made zero by making the refractive index of the cell the same as the refractive index of the substrate.
As described above, by separating the light using the diffraction grating, it is possible to process a number of points and control the irradiation position.

Next, the cell structure of the spatial modulation element formed by a plurality of ring-shaped channels will be described with reference to FIG.
As described in the above embodiments, the spatial modulation element cell structure does not necessarily have to be arranged in a matrix. For example, as shown in FIG. A plurality of adjusted ring-shaped flow paths (cells) 96, 97, 98,... Are formed. Here, by changing the refractive index of each flow path, and then condensing with, for example, a lens or the like, the condensing position can be slightly changed. In addition, it is possible to adjust a complicated intensity pattern by the initial flow path (cell) shape and refractive index.
At this time, for example, by adjusting the transmission phase with a liquid having a refractive index slightly different from that of the transparent substrate 95, it is also possible to fulfill a function as a correction optical element such as adjusting a phase change due to a processing error.

Next, a case where the spatial modulation element is used as a laser manipulation device will be described.
For example, the condensing position of the laser light is changed by the spatial modulation element 100 shown in FIG. In the laser manipulation method, a material (particle) can be trapped and moved at a condensing position of the laser beam. By applying such a spatial modulation element 100 to a laser manipulation device, a laser with a high peak power can be obtained. Since light can be controlled, particle control such as movement of large particles, capture or movement of a plurality of particles, continuous movement due to irradiation pattern change, or three-dimensional movement can be realized.

These are the schematic diagrams of the optical element provided with the matrix-shaped cell in Example 1 of this invention, (a) is a top view, (b) is side sectional drawing. These are the schematic top views of an optical element provided with the cell of a linear shape in Example 1. FIG. FIG. 3 is a schematic top view of an optical element including a linear cell in Example 1 as well. These are the schematic diagrams of the optical element which arranged the cell three-dimensionally in Example 2 of this invention, (a) is a top view, (b) is front sectional drawing. These are the typical front sectional views of the optical element which arranged the cell three-dimensionally in Example 3 of the present invention. These are the schematic top views of the optical element provided with the light shielding film in Example 3. FIG. These are the typical perspective views of the reflective optical element in Example 4 of this invention. These are typical front sectional drawing of the optical element from which the thickness of a cell in Example 5 of this invention differs. These are the schematic diagrams which show the application example of the optical element of this invention, (a) is a schematic diagram of a laser processing apparatus, (b) is explanatory drawing of an optical element. These are explanatory drawings of a phase modulation element which is an optical element of the present invention, in which (a) shows a refractive index distribution cell structure of a liquid, and (b) shows an intensity distribution of laser light. These are explanatory drawings at the time of using the phase modulation element which is an optical element of the present invention as a diffraction grating. These are the schematic diagrams of an optical element provided with the ring-shaped cell applied to a laser manipulation apparatus etc., (a) is a top view, (b) is side sectional drawing.

Explanation of symbols

1, 31, 41, 51, 61, 71 ... Transparent substrate 2, 12, 22, 32, 33, 42 to 45, 52, 62, 72, 73 ... Cell (light transmission structure)
3, 13, 23, 34 to 36, 46, 53, 63 ... flow path (liquid supply means)
4, 64 ... Inlet port 5 ... Discharge port 10, 20, 30, 40, 50, 60, 70, 80, 100 ... Optical element (phase modulation element)
18, 28 ... Liquid discharge part 14, 15, 24, 25 ... Liquid 16, 17, 26, 27 ... Valve, cock 29 ... Movement mechanism 54 ... Photomask for light shielding, light shielding member 65, 74 ... Reflective layer 88,95 ... Transparent substrate 89, 96 to 98 ... Cell (flow path, light transmission structure)
91-93 ... Laser light

Claims (13)

A plurality of light transmission structures;
Comprising a first liquid supply means for supplying a liquid to the light transmission structure,
An optical element characterized in that the phase of transmitted light is spatially modulated by supplying at least two kinds of liquids having different refractive indexes into the light transmission structure by the first liquid supply means. .   The optical element according to claim 1, further comprising a liquid mixing unit that adjusts at least two kinds of liquids having different refractive indexes by mixing liquids having different refractive indexes.   When the wavelength of transmitted light is λ, the maximum refractive index of liquids having different refractive indexes is nmax, and the minimum refractive index is nmin, the light transmission distance of the light transmission structure is an integral multiple of λ / (nmax−nmin). The optical element according to claim 1, wherein: In addition to the first liquid supply means, a second liquid supply means for supplying a light-absorbing liquid to the light transmission structure is provided.
The second liquid supply means supplies the light-absorbing liquid into the light transmission structure at a predetermined mixing ratio, thereby spatially modulating the intensity of transmitted light according to the phase. The optical element according to claim 1, wherein:   The optical element according to any one of claims 1 to 4, wherein the two or more types of liquids having different refractive indexes are mutually soluble liquids.   5. The optical element according to claim 1, wherein the two or more types of liquids having different refractive indexes are the same solvent or a soluble solvent, and the refractive index is changed depending on the concentration of the solute. . A first light transmission structure in which a plurality of light transmission structures for modulating the phase of transmitted light are stacked;
First liquid supply means for selectively supplying a liquid having a predetermined refractive index to the first light transmission structure;
A plurality of second light transmission structures disposed in the light transmission direction of the first light transmission structure for modulating the intensity of the transmitted light;
A second liquid supply means for supplying two or more kinds of liquids having different absorption rates to the plurality of second light transmission structures,
By supplying the liquid having a predetermined refractive index and two or more kinds of liquids having different absorptances to the first and second light transmission structures by the first and second liquid supply units, An optical element characterized by spatially modulating the phase and intensity of transmitted light.   8. The optical element according to claim 1, further comprising a light shielding member that shields transmitted light that passes through at least a part of the liquid supply means.   The reflective layer which reflects the transmitted light of the said several light transmissive structure is provided, The said liquid supply means is arrange | positioned at the back side of this reflective layer, The claim 1 characterized by the above-mentioned. Optical elements.   The optical element according to claim 1, wherein the transmission light path lengths of the plurality of light transmission structures are different.   11. A laser processing apparatus comprising the optical element according to claim 1 as a spatial phase modulation element, wherein laser light is spatially selectively irradiated by the spatial phase modulation element.   11. A laser manipulation apparatus comprising the optical element according to claim 1 as a spatial phase modulation element, wherein laser light is spatially controlled by the spatial phase modulation element. Multiple cells,
Comprising a flow path for supplying liquid to the cell,
An optical element characterized by spatially modulating the phase of transmitted light by supplying at least two kinds of liquids having different refractive indexes into the cell through the flow path.