JP5410043B2 - Light control device and light control method - Google Patents

Description

  The present invention relates to a light control device and a light control method.

  The spatial light modulator can present a hologram that modulates the intensity or phase of input light in each of a plurality of two-dimensionally arranged pixels, and can output light modulated by this hologram. As such a spatial light modulator, an intensity modulation type capable of modulating only the intensity, a phase modulation type capable of modulating only the phase, and both intensity and phase can be modulated. Some are of the intensity phase modulation type. The light whose intensity or phase is modulated and output in each pixel of the spatial light modulator is condensed by a condensing optical system provided at the subsequent stage of the spatial light modulator, and the object existing at the condensing position Can be processed.

  The intensity-modulated spatial light modulator adjusts the transmittance of input light for each pixel and cannot use the light that has not been transmitted, so that the light utilization efficiency is poor. An intensity phase modulation type spatial light modulator cannot easily control intensity modulation and phase modulation in each pixel independently of each other, and is difficult to handle.

  On the other hand, the phase modulation type spatial light modulator adjusts the phase change of the input light for each pixel and can output almost all light, so that the light use efficiency is high. In addition, the phase modulation type spatial light modulator has a high degree of freedom in the phase distribution in the beam cross section of the output light and a high degree of freedom in the condensing position of the output light by the condensing optical system by presenting a computer generated hologram. . Applications of light control using such a phase modulation type spatial light modulator include processing of the surface and inside of a workpiece, generation of Laguerre Gaussian mode light, and the like.

By the way, it is known that the intensity of output light that is phase-modulated for each pixel in a phase modulation spatial light modulator can be modulated (see Non-Patent Document 1). This can adjust the intensity of the primary light, which is the light that should be used through the condensing optical system in the subsequent stage, but at this time, unnecessary light is condensed as zero-order light. The 0th-order light is light that is not generally used and should be shielded by the shielding member so that the object is not irradiated.
Joseph P. Kirk and Alan L. Jones, “Phase-only complex-value spatialfilter”, Journal of the optical society of America, Vol. 61, No. 8, 1971

  In applications of light control using a phase modulation type spatial light modulator, the diffracted light of a predetermined order to be used (in many cases, the first-order diffracted light) has various aspects regarding the condensing position and the number of condensing points. May change. Accordingly, the diffracted light of the predetermined order (or a part thereof) may be shielded by the shielding member that shields the 0th-order light. Further, if the 0th-order light is not completely shielded, the diffracted light of the predetermined order may interfere with the 0th-order light. In any of these cases, even if the diffracted light of the predetermined order when output from the phase modulation type spatial light modulator is desired, the diffracted light of the predetermined order when entering the target object. Will be different from what is desired. In particular, when the phase and the intensity of the diffracted light are modulated using the method of Non-Patent Document 1, the 0th-order light becomes extremely strong, and this problem is great.

  The present invention has been made to solve the above-described problems, and provides a light control device and a light control method that can easily make a desired order of diffracted light when entering a target object. The purpose is to provide.

  The light control device according to the present invention includes: (1) a laser light source that outputs laser light; and (2) a laser light output from the laser light source, and the phase of the laser light at each of a plurality of pixels that are two-dimensionally arranged. A phase-modulating spatial light modulator that outputs a laser beam that has been phase-modulated by this hologram, and (3) a condensing optical system provided at the subsequent stage of the spatial light modulator, And (4) a control unit that causes the spatial light modulator to present a hologram.

  In the light control device according to the present invention, the control unit collects the diffracted light of a predetermined order output from the spatial light modulator by the condensing optical system by the laser light input to the spatial light modulator on which the hologram is presented. The position where the light is emitted is defined as position A, the position where the diffracted light of other orders output from the spatial light modulator is collected by the condensing optical system is defined as position B, and the 0th order light output from the spatial light modulator. When the position where the light is condensed by the condensing optical system is defined as the position C, the spatial light modulator presents a hologram so that the distance between the position A and the position B is determined from the distance between the position A and the position C. And the intensity of the diffracted light of other orders is made larger than the intensity of the 0th order light, and the intensity of the diffracted light of the predetermined order is adjusted.

  Further, the light control method according to the present invention uses the laser light source, the spatial light modulator, the condensing optical system and the control unit as described above, and the laser to the spatial light modulator on which the hologram is presented by the control unit. A position where the diffracted light of a predetermined order output from the spatial light modulator by light input is condensed by the condensing optical system is defined as position A, and the diffracted light of other orders output from the spatial light modulator is condensing optics. When the position where the light is collected by the system is position B, and the position where the zero-order light output from the spatial light modulator is collected by the condensing optical system is position C, a hologram is presented to the spatial light modulator. By doing so, the distance between the position A and the position B is made longer than the distance between the position A and the position C, the intensity of the diffracted light of other orders is made larger than the intensity of the 0th order light, and a predetermined order of The intensity of diffracted light is adjusted.

  In the light control device according to the present invention or the light control method according to the present invention, a predetermined hologram is presented on the spatial light modulator, whereby a condensing position A of diffracted light of a predetermined order and a condensing position of zero-order light. The distance between the condensing position A of the diffracted light of the predetermined order and the condensing position B of the diffracted light of the other orders is longer than the distance between C and C. The intensity of the diffracted light of other orders is greater than the intensity of the 0th order light. Further, the intensity of the diffracted light of a predetermined order is adjusted. The adjustment of the intensity of the diffracted light of the predetermined order includes not only the case where the total intensity of the diffracted light of the predetermined order is temporally modulated but also the case where the beam cross section of the diffracted light of the predetermined order has an intensity distribution. . Therefore, it is easy to effectively block unnecessary light (other orders of diffracted light and zeroth order light) without affecting the diffracted light of a predetermined order.

  The control unit of the light control device according to the present invention includes a hologram for outputting a predetermined order of diffracted light and other orders of diffracted light from the spatial light modulator, and a predetermined order of diffracted light output from the spatial light modulator. It is preferable to superimpose a hologram for condensing the light at a predetermined position by a condensing optical system and present it on the spatial light modulator. In the light control method according to the present invention, the control unit outputs a hologram for outputting the diffracted light of a predetermined order and other orders from the spatial light modulator, and the predetermined order output from the spatial light modulator. It is preferable to superimpose a diffracted light beam on a predetermined position by a condensing optical system and present it on a spatial light modulator.

The control unit of the light control device according to the present invention outputs the diffracted light of a predetermined order output from the spatial light modulator from the spatial light modulator as the number of positions where the light is condensed by the condensing optical system increases. a hologram to increase the intensity of the diffracted light of a predetermined order Ru is presented on the spatial light modulator. Further, in the light control method according to the present invention, the greater the number of positions where the predetermined order of the diffracted light output from the spatial light modulator is collected by the condensing optical system, the greater the number of positions from the spatial light modulator. a hologram to increase the intensity of the diffracted light of a predetermined order is output Ru is presented on the spatial light modulator.

  The control unit of the light control device according to the present invention causes the spatial light modulator to present a hologram that outputs diffracted light of a predetermined order having an intensity distribution or a phase distribution in a beam cross section when output from the spatial light modulator. Is preferred. In the light control method according to the present invention, the control unit causes the spatial light modulator to generate a hologram that outputs diffracted light of a predetermined order having an intensity distribution or a phase distribution in the beam cross section when output from the spatial light modulator. It is preferable to present it.

  The control unit of the light control device according to the present invention preferably causes the spatial light modulator to present a hologram that outputs Laguerre Gaussian mode light as diffracted light of a predetermined order output from the spatial light modulator. In the light control method according to the present invention, it is preferable that the control unit presents the spatial light modulator to display a hologram that outputs Laguerre Gaussian mode light as diffracted light of a predetermined order output from the spatial light modulator. .

  According to the present invention, diffracted light of a predetermined order when entering a target can be easily made desired.

  The best mode for carrying out the present invention will be described below in detail with reference to the accompanying drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted.

  FIG. 1 is a configuration diagram of a light control device 1 according to the present embodiment. The light control device 1 shown in this figure is a device for processing a processing object 90 by condensing and irradiating a processing region 91 in the processing object 90 with a laser light source 10, a spatial filter. 11, a collimating lens 12, a mirror 13, a mirror 14, a spatial light modulator 20, a driving unit 21, a control unit 22, a condensing optical system 30, and a shielding member 40.

  The laser light source 10 outputs laser light to be applied to the processing region 91 of the processing object 90, and is preferably a pulse laser light source such as a femtosecond laser light source or an Nd: YAG laser light source. The laser light output from the laser light source 10 passes through the spatial filter 11, is collimated by the collimating lens 12, is reflected by the mirror 13 and the mirror 14, and is input to the spatial light modulator 20.

  The spatial light modulator 20 is a phase modulation type, and receives a laser beam output from the laser light source 10 and presents a hologram that modulates the phase of the laser beam in each of a plurality of two-dimensionally arranged pixels. Then, the laser light after the phase modulation is output. The phase hologram presented in the spatial light modulator 20 is preferably a hologram (CGH: Computer Generated Hologram) obtained by numerical calculation.

  The spatial light modulator 20 may be a reflection type or a transmission type. The reflective spatial light modulator 20 may be any of LCOS (Liquid Crystal on Silicon) type, MEMS (Micro Electro Mechanical Systems) type, and optical address type. The transmissive spatial light modulator 20 may be an LCD (Liquid Crystal Display) or the like. In FIG. 1, a reflection type is shown as the spatial light modulator 20.

  The drive unit 21 sets a phase modulation amount in each of a plurality of pixels arranged two-dimensionally in the spatial light modulator 20, and sends a signal for setting the phase modulation amount for each pixel to the spatial light modulator 20. give. The drive unit 21 causes the spatial light modulator 20 to present a hologram by setting the phase modulation amount in each of the plurality of pixels of the spatial light modulator 20 that are two-dimensionally arranged.

  The condensing optical system 30 is provided at the subsequent stage of the spatial light modulator 20 and inputs laser light that is phase-modulated for each pixel in the spatial light modulator 20 and output. In particular, the condensing optical system 30 includes a lens that Fourier transforms the laser light output from the spatial light modulator 20. The Fourier transform image is formed on the back focal plane of the Fourier transform lens.

  The control unit 22 is configured by a computer, for example, and controls the operation of the drive unit 21 to write a hologram from the drive unit 21 to the spatial light modulator 20. At this time, the control unit 22 can also cause the spatial light modulator 20 to present a hologram for condensing the laser light output from the spatial light modulator 20 at a plurality of condensing positions by the condensing optical system 30.

  In particular, in the present embodiment, the control unit 22 collects the diffracted light of a predetermined order output from the spatial light modulator 20 by the condensing optical system 30 by the laser light input to the spatial light modulator 20 on which the hologram is presented. The position where the light is emitted is defined as position A, and the position where the diffracted light of another order output from the spatial light modulator 20 is condensed by the condensing optical system 30 is defined as position B, and is output from the spatial light modulator 20. When the position where the zero-order light is collected by the condensing optical system 30 is a position C, the spatial light modulator 20 presents a hologram, so that the position A and the position A can be determined from the distance between the position A and the position C. The distance to the position B is increased, the intensity of the diffracted light of other orders is made larger than the intensity of the 0th order light, and the intensity of the diffracted light of the predetermined order is adjusted. The adjustment of the intensity of the diffracted light of the predetermined order includes not only the case where the total intensity of the diffracted light of the predetermined order is temporally modulated but also the case where the intensity distribution is given to the beam cross section of the diffracted light of the predetermined order.

  For example, the diffracted light of a predetermined order is + 1st order diffracted light, and the other orders of diffracted light are −1st order diffracted light. In the following description, the diffracted light of a predetermined order will be described as + 1st order diffracted light, and the other orders of diffracted light will be described as −1st order diffracted light.

  The control unit 22 condenses the diffracted light of the predetermined order (+ 1st order diffracted light) output from the spatial light modulator 20 on which the hologram is presented by the condensing optical system 30 and selects the condensing position as the processing region 91. Therefore, the processing object 90 is processed. Note that the processing region 91 where the converging position of the + 1st order diffracted light is arranged includes not only the surface of the processing target 90 but also the inside of the processing target 90.

  The shielding member 40 shields the −1st order diffracted light so as not to place the condensing position of other orders of diffracted light (−1st order diffracted light) on the workpiece 90. In addition, it is also preferable that the shielding member 40 shields the 0th-order light so that the focusing position of the 0th-order light is not disposed on the workpiece 90.

  FIG. 2 is a diagram illustrating a condensing position and the like on the workpiece 90 by the light control device 1 according to the present embodiment. A processing region 91 in the processing target 90 is a region where the first-order diffracted light output from the spatial light modulator 20 on which the hologram is presented can be condensed by the condensing optical system 30. In addition, the region 92 in the workpiece 90 is a region in which the first-order diffracted light output from the spatial light modulator 20 on which the hologram is presented can be condensed by the condensing optical system 30. The processing region 91 and the region 92 are in a symmetric relationship with the zero-order light collection position 30 as the center.

  In such a case, the distance between the condensing position of the + 1st order diffracted light and the condensing position of the −1st order diffracted light is longer than the distance between the condensing position of the + 1st order diffracted light and the condensing position of the 0th order light. Become. Further, by devising the hologram presented in the spatial light modulator 20, the intensity of the −1st order diffracted light can be made larger than the intensity of the 0th order light, and the intensity of the + 1st order diffracted light can be adjusted.

  Next, the hologram presented in the spatial light modulator 20 will be described in more detail. The hologram presented in the spatial light modulator 20 collects the hologram for outputting the + 1st order diffracted light and the −1st order diffracted light from the spatial light modulator 20 and the + 1st order diffracted light output from the spatial light modulator 20. A hologram for condensing light at a predetermined position by the system 30 is superimposed.

A hologram (phase modulation distribution for each pixel) for outputting the + 1st order diffracted light and the −1st order diffracted light from the spatial light modulator 20 is represented by φ _braze in the following formula (1) or the following (2). Dog grating. Here, n represents a pixel position in a two-dimensionally arranged pixel structure in the spatial light modulator 20. N represents the number of pixels per period of the blazed grating. mod (n, N) is an operator for obtaining a remainder when n is divided by N. k is a parameter that determines the intensity ratio between the + 1st order diffracted light and the −1st order diffracted light. k may be a constant value over time or may change over time. Further, k may be a spatially constant value or may have a spatial distribution.

  FIG. 3 is a diagram for explaining the shape and diffraction of the blazed grating represented by the expression (1). FIG. 4 is a diagram for explaining the shape and diffraction of the blazed grating represented by equation (2). These figures show the phase modulation distribution for one period of the blazed grating, and schematically show the theoretical intensity of each of the + 1st order diffracted light and the −1st order diffracted light with the thickness of the arrow when the light is vertically incident. ing. Each figure (a) shows the phase modulation distribution when the k value is 0, each figure (b) shows the phase modulation distribution when the k value is more than 0 and less than 1, and each figure (c) Indicates a phase modulation distribution when the k value is 1.

  FIG. 5 shows the intensities and k values of the + 1st order diffracted light, the −1st order diffracted light, and the 0th order light generated by the spatial light modulator 20 on which the blazed grating represented by the formula (1) or (2) is presented. It is a graph which shows the relationship. This figure shows the result of actual measurement using an LCOS type spatial light modulator 20. The k value is 0 at the center of the horizontal axis. The left side from the center shows the intensity of each light when the blazed grating represented by the equation (1) is presented to the spatial light modulator 20. Further, the right side from the center shows the intensity of each light when the blazed grating represented by the equation (2) is presented to the spatial light modulator 20.

  As can be seen from FIGS. 3 to 5, when the k value is 0, the intensities of the + 1st order diffracted light and the −1st order diffracted light are the same. When the blazed grating represented by the above equation (1) is used, the intensity of the −1st order diffracted light increases as the k value increases, and when the k value is 1, only the −1st order diffracted light is generated. To do. On the other hand, when the blazed grating represented by the above equation (2) is used, the intensity of the + 1st order diffracted light increases as the k value increases, and when the k value is 1, only the + 1st order diffracted light is generated. To do. Thus, by presenting the blazed grating represented by the formula (1) or (2) to the spatial light modulator 20, it is possible to generate the + 1st order diffracted light and the −1st order diffracted light, and the 0th order. Generation of light can be suppressed. Further, by adjusting the k value, the intensity ratio of each of the + 1st order diffracted light and the −1st order diffracted light can be adjusted.

The hologram φ _result presented in the spatial light modulator 20 _collects the hologram φ _braze for outputting the + 1st order diffracted light and the −1st order diffracted light as described above and the + 1st order diffracted light at a predetermined position by the condensing optical system 30. A hologram φ _phase for light emission is superimposed. The latter hologram φ _phase has a predetermined phase in the beam cross section of the + 1st order diffracted light output from the spatial light modulator 20 so that the + 1st order diffracted light can be condensed at a predetermined position by the condensing optical system 30. The distribution is given and is created by an iterative Fourier transformation algorithm (IFTA).

  FIG. 6 is a flowchart of IFTA. At the time of IFTA, a target arrangement (target pattern) of condensing points on the object to be processed, an intensity distribution (incident light pattern) in a beam cross section of light input to the spatial light modulator 20, and a random phase pattern are prepared in advance. Is done. Then, FFT (Fourier transform) and IFFT (inverse Fourier transform) are alternately repeated.

In the first FFT, a complex pattern whose amplitude is an incident light pattern and whose phase is a random phase pattern is Fourier transformed. In the subsequent IFFT, the complex pattern in which the amplitude is replaced with the target pattern among the results obtained by the first FFT is subjected to inverse Fourier transform. In the subsequent second FFT, the complex pattern in which the amplitude is replaced with the incident light pattern among the results obtained in the first IFFT is Fourier-transformed. In the subsequent second IFFT, the complex pattern in which the amplitude is replaced with the target pattern among the results obtained in the second FFT is subjected to inverse Fourier transform. Thereafter, FFT and IFFT are alternately repeated in the same manner. It is determined whether or not the result obtained by each IFFT is a desired value. If the result obtained by IFFT is a desired value, the processing is terminated, and the phase distribution at that time is the hologram φ _phase As obtained. Alternatively, when the number of repetitions reaches a specified number, the process may be terminated, and the phase distribution at that time may be obtained as the hologram φ _phase .

A hologram phi _braze for outputting the + 1st-order diffracted light and -1-order diffracted light as described above, + 1 by the condensing optical system 30 the diffracted light and hologram phi _phase for condensing at a predetermined position is superimposed, The superimposed hologram φ _result (= φ _phase + φ _braze ) is presented to the spatial light modulator 20.

  Next, a case where laser marking is performed on the surface of the object to be processed will be described. Laser marking is for marking a serial number or the like on the surface of a plastic bottle, glass, metal, silicon, or the like with a laser beam. For example, laser marking is said to be less environmentally polluted than conventional marking of ink on a PET bottle, and is attracting attention.

  FIG. 7 is a diagram showing an example of a 4-digit serial number stamp by laser marking. However, in actual laser marking, laser light is focused and applied to a plurality of discrete points. FIG. 8 is a diagram showing a state of laser marking in the comparative example. FIG. 9 is a diagram showing a state of laser marking by the light control device or the light control method according to the present embodiment.

  In both of the comparative example (FIG. 8) and the present embodiment (FIG. 9), the + 1st order diffracted light output from the spatial light modulator 20 is condensed at a plurality of positions by the condensing optical system 30, and a 4-digit serial number is obtained. The number “1234” is engraved. In the comparative example (FIG. 8), the intensity of the zero-order light output from the spatial light modulation 20 is strong, and the condensing position of the zero-order light is close to the condensing position of the + 1st-order diffracted light. Therefore, in the comparative example, if unnecessary zero-order light is shielded by the shielding member 40, a part of the + 1st order diffracted light may be shielded by the shielding member 40, and +1 next time when entering the workpiece. The folding light may differ from the desired one.

On the other hand, in the present embodiment (FIG. 9), since the hologram φ _result as described above is presented in the spatial light modulation 20, the intensity of the zero-order light output from the spatial light modulation 20 is weak. Thus, the intensity of the −1st order diffracted light output from the spatial light modulation 20 is strong, and the condensing position of the −1st order diffracted light is far from the condensing position of the + 1st order diffracted light. Therefore, in this embodiment, it is easy to shield unnecessary −1st order diffracted light with the shielding member 40, and + 1st order diffracted light when entering the workpiece can be easily made desired.

By the way, when the number of characters to be engraved is limited as in the case where the serial number is engraved on the workpiece, for example, 10 numbers from 0 to 9 are selected and the 4-digit serial number is engraved. In this case, a hologram for reproducing each of ten numbers from 0 to 9 is created in advance as a hologram φ _{phase, and} a hologram for converging + 1st order diffracted light in each of the four marking regions is generated as a hologram φ. _{It is preferable} that these ten types of holograms φ _phase and four types of holograms φ _braze are stored by the control unit 22 in _{advance as braze} . Then, depending on the number and position to be imprinted, any hologram φ _phase is selected from the 10 types of holograms φ _phase, and any hologram φ _braze is selected from the 4 types of holograms φ _braze , The selected hologram φ _phase and hologram φ _braze are superimposed on each other to obtain a hologram φ _result presented to the spatial light modulator 20.

At this time, the number of converging points of the + 1st order diffracted light generated by the hologram φ _{phase and} condensed by the condensing optical system 30 varies depending on the characters to be stamped. Therefore, if the intensity of the + 1st order diffracted light is constant regardless of characters, the intensity of the + 1st order diffracted light at each condensing position becomes weaker as the number of condensing points of the + 1st order diffracted light increases. In addition, if the intensity of the laser beam input to the spatial light modulator 20 is non-uniform in intensity, even if the number of converging points of the + 1st order diffracted light is constant, the + 1st order light generation range in the spatial light modulator 20 is obtained. Depending on, the intensity at each condensing position of the + 1st order diffracted light becomes non-uniform. Furthermore, the diffraction efficiency varies depending on the spatial frequency of the blazed grating of the hologram φ _braze , and the intensity of the + 1st order diffracted light varies.

In order to _cope with such a laser surface processing problem, in the present embodiment, the hologram φ _braze is created by _{setting the} k value to an appropriate value in the blazed grating represented by the above formula (1) or (2). , + 1st order diffracted light at each condensing position can be made uniform in intensity. That is, the greater the number of converging points of the + 1st order diffracted light, the lower the intensity of the laser light input to the spatial light modulator 20, and the higher the spatial frequency of the blazed grating, the greater the intensity of the + 1st order diffracted light. The spatial light modulator 20 presents a hologram φ _braze that can be _enlarged (that is, a hologram φ _braze having a small k value in the above equation (1) or a hologram φ _braze having a large k value in the above equation (2)). Just do it.

  Next, the case where the inside of the workpiece is laser processed will be described. So far, the case where the surface of the workpiece is laser processed has been mainly described, but the light control device 1 and the light control method according to the present embodiment are also effective when the inside of the workpiece is laser processed. .

  Laser internal processing uses a pulsed laser light source such as a femtosecond laser, and the multi-photon absorption is generated by injecting a laser beam of extremely high intensity into a processing target that normally transmits laser light, thereby generating a multi-photon absorption. Process inside. In the laser internal processing, a crack region is formed, a refractive index is changed, and a modified region is formed on an object to be processed.

  In such laser internal processing, the processing object itself becomes an aberration object. Therefore, when using a high NA objective lens or processing at a deep position inside the processing object, aberration is required. As a result, problems such as inability to perform processing and deterioration of the processing shape occur. If the phase modulation type spatial light modulator 20 is used, these aberration problems can be solved, and multi-point simultaneous processing is possible, so that the processing throughput can be improved.

  However, in the case of laser internal processing, the same problem as in the case of laser surface processing (laser marking) described above exists. For example, it is assumed that there is one converging point of the + 1st order diffracted light inside the processing object until a certain point in time, and after that point, there are two converging points of the + 1st order diffracted light inside the processing object. If it has changed, the intensity at each condensing position of the + 1st order diffracted light is reduced by a factor of two.

In order to deal with such a problem of laser internal processing, in the present embodiment, the hologram φ _braze is created by _{setting the} k value to an appropriate value in the blazed grating represented by the above formula (1) or (2). , + 1st order diffracted light at each condensing position can be made uniform in intensity. That is, the larger the number of converging points of the + 1st order diffracted light, the greater the intensity of the + 1st order diffracted light, that is, the hologram φ _braze (that is, the hologram φ _braze having a small k value in the above equation (1), or ( The hologram φ _braze ) having a large k value in equation (2) may be presented to the spatial light modulator 20. Thereby, even if the number of condensing points changes, the intensity | strength in each condensing position of + 1st order diffracted light can be equalize | homogenized.

  For example, assume a case where a Y-branch optical waveguide as shown in FIG. 10 is formed. The workpiece 90 in this case is glass, and Y-branch-shaped optical waveguides 93 to 95 are formed by laser light irradiation. In the comparative example not using the spatial light modulator, as shown in FIG. 11, an optical waveguide 93 and an optical waveguide 94 are sequentially formed (FIG. 11A), and thereafter an optical waveguide 95 is formed. In this comparative example, since processing is performed point by point, a long processing time is required.

  In the present embodiment, while the workpiece 90 is moved, initially, the branched optical waveguides 94 and 95 are formed simultaneously with the number of converging points of the + 1st order diffracted light being 2, and the converging of the + 1st order diffracted light is performed from the middle. Since the optical waveguide 93 before branching is formed with a score of 1, high-speed formation is possible. At this time, the condensing point of the −1st order diffracted light is positioned on the shielding member 40, and the intensity of the + 1st order diffracted light is adjusted by adjusting the k value, so that the condensing point before and after the branching is adjusted at each condensing point. To equalize the light intensity. By doing so, the Y-branch optical waveguide can be manufactured at high speed and with high accuracy.

  FIGS. 13 to 15 are tables summarizing the light intensity at each condensing point in each of the one-point processing and the two-point processing. In the example shown in FIG. 13, the intensity of the + 1st order diffracted light is not adjusted at all. In this case, the light at each condensing point of the + 1st order diffracted light at the time of 2-point processing as compared to at the time of 1-point processing. The strength is reduced to about a half. In the example shown in FIG. 14, the intensity of both the + 1st order diffracted light and the 0th order light is adjusted. In this case, each of the + 1st order diffracted light is condensed at one-point processing and two-point processing. Although the light intensity at the point is about the same, the intensity of the 0th-order light is large at the time of one-point processing. Further, the example shown in FIG. 15 relates to the present embodiment, which is a case where the + 1st order diffracted light and the −1st order diffracted light are mainly generated and the generation of the 0th order light is suppressed. The one-point processing and the two-point processing have the same light intensity at each condensing point of the + 1st order diffracted light, and the 0th-order light intensity is small.

  In this way, in this embodiment, the intensity of the 0th-order light is small, and it is only necessary to prevent the −1st-order diffracted light from being focused on the object to be processed. ) Is easy to shield.

  Next, in the light control apparatus 1 according to the present embodiment, a hologram that outputs + first-order diffracted light having an intensity distribution or a phase distribution in the beam cross section when output from the spatial light modulator 20 is presented to the spatial light modulator 20. The case where it is made to explain is demonstrated. Here, the + 1st order diffracted light having intensity distribution or phase distribution in the beam cross section is Laguerre Gaussian mode light or Hermitian Gaussian light. In particular, Laguerre Gaussian mode light is expected to be used in various ways, and a technique for generating it has been studied.

  Laguerre Gaussian mode light has a specific phase distribution in each of the circumferential direction and the radial direction in the beam cross section, and the mode is defined by the declination index and the radial index. The declination index is an index defining the phase distribution in the circumferential direction, and the radial index is an index defining the phase distribution in the radial direction.

Such Laguerre Gaussian mode light can be generated by causing the _phase modulation spatial light modulator 20 to present an appropriate hologram φ _phase . The spatial light modulator 20 may be presented with a hologram φ _phase having a phase modulation distribution corresponding to the declination index and radial index of the Laguerre Gaussian mode light to be generated.

  However, in actuality, even if an attempt is made to generate Laguerre Gaussian mode light having a specific declination index and radial exponent, not only Laguerre Gaussian mode light having a desired declination exponent and radial exponent, Laguerre Gaussian mode light having the same exponent but different radial exponents and Laguerre Gaussian mode light having the same radial exponent but different declination exponents may be output from the spatial light modulator 20 in some cases.

FIG. 16 shows the relationship between the mode purity and the ratio a (= R ₀ / w ₀ ) between the pattern diameter R ₀ of the hologram φ _phase presented in the spatial light modulator 20 and the beam diameter w ₀ of the incident light. It is a graph. In FIG. 5A, the declination index is 1, and the radial index is 1, 2, 3, and 5. In FIG. 5A, the radial index is 1, and the declination index is 1, 2, 3, and 5. As can be seen from this figure, there is an optimum value for the diameter R ₀ of the pattern of the hologram φ _phase presented in the spatial light modulator 20 with respect to the beam diameter w ₀ of the incident light. The mode purity is only about 0.8.

  If Laguerre Gaussian mode light having a specific declination index and radial index with higher purity can be generated, the trapping power is further increased in the optical trap. Further, when the quantum characteristics of Laguerre Gaussian mode light are used for quantum information processing, the purity of Laguerre Gaussian mode light is essentially important in realizing its function.

Therefore, in the present embodiment, in order to generate Laguerre Gaussian mode light with high mode purity, the hologram φ _result presented to the spatial light modulator 20 outputs the + 1st order diffracted light and the −1st order diffracted light as described above. a hologram phi _braze for a hologram phi _phase for condensing at a predetermined position + 1-order diffracted light by the condensing optical system 30, is to have been superimposed. The hologram φ _phase has a phase distribution corresponding to the desired declination index and radial index. Further, in the hologram φ _braze , _either of the above formulas (1) and (2) is used depending on the position, and the k value has a spatial distribution and is output from the spatial light modulator 20. An intensity distribution is given to the beam cross section of the + 1st order diffracted light.

  For example, in order to generate Laguerre Gaussian mode light having a radial index of 5 and a declination index of 5 with high purity, the intensity distribution in the beam section is set as shown in FIG. It is necessary that the phase distribution at is set as shown in FIG. In FIG. 18, the phase modulation amount (0 to 2π) is shown in shades.

The intensity of the laser beam input to the spatial light modulator 20 in the beam cross section has, for example, a Gaussian distribution or is uniform. And intensity distribution in the beam cross section of light input to such spatial light modulator 20, in accordance with the intensity distribution and the Laguerre-Gaussian mode of the beam cross-section having a desired mode shown in FIG. 17, k in the hologram phi _braze Set the spatial distribution of values. At this time, in the hologram φ _braze , the k value is set by using either of the above formulas (1) and (2) depending on the position.

FIG. 19 is a diagram illustrating a hologram φ _braze for generating + _1st order diffracted light having the intensity distribution of FIG. 17 when uniform intensity laser light is input to the spatial light modulator 20. When uniform intensity laser light is input to the spatial light modulator 20 on which such a hologram φ _braze is presented, the intensity distribution in the beam cross section of the + 1st order diffracted light output from the spatial light modulator 20 is shown in FIG. It comes to be.

A hologram φ _result in which the hologram φ _phase corresponding to the phase distribution shown in FIG. 18 and the hologram φ _braze shown in FIG. 19 are superimposed is presented to the spatial light modulator 20. FIG. 20 is a diagram showing the hologram φ _result . When uniform intensity laser light is input to the spatial light modulator 20 on which the hologram φ _result is presented, the + 1st order diffracted light output from the spatial light modulator 20 has a radial index of 5 and a declination index. 5 is high-purity Laguerre Gaussian mode light.

FIG. 21 is a diagram illustrating an intensity distribution of Laguerre Gaussian mode light generated by the light control device 1 according to the present embodiment. This figure shows the intensity distribution of the light output from the spatial light modulator 20 on which the hologram φ _result shown in FIG. 20 is presented. On the left side of the figure, high-purity Laguerre Gaussian mode light having a radial index of 5 and a declination index of 5 is recognized. In addition, zero-order light is recognized in a region surrounded by a right circle in the drawing.

Note that, when the above equations (1) and (2) are used, high-intensity + 1st order diffracted light can be generated, but the hologram φ _braze becomes complicated. _If the size of the hologram φ _braze is not sufficiently fine with respect to the desired hologram φ _phase , a phase shift may occur. In such a case, only one of the above formulas (1) and (2) may be used.

  The above formulas (1) and (2) are one-dimensional blazed gratings, and it may be necessary to actually use a two-dimensional complex blazed grating. In such a case, a blazed grating that diffracts into + 1st order light and −1st order light may be created using an iterative Fourier method (for example, IFTA). At this time, using the fact that the square of the gradation ratio of two or more reproduction points in the target pattern becomes the actual intensity ratio of the reproduction light, the desired + 1st order light and the unnecessary −1st order of the target pattern are used. Adjust the light gradation to create a blazed grating.

It is a lineblock diagram of light control device 1 concerning this embodiment. It is a figure which shows the condensing position etc. in the process target object 90 by the light control apparatus 1 which concerns on this embodiment. It is a figure explaining the shape and diffraction of a blazed grating represented by (1) Formula. It is a figure explaining the shape and diffraction of a blazed grating represented by (2) Formula. The relationship between the k value and the intensity of each of the + 1st order diffracted light, the −1st order diffracted light, and the 0th order light generated by the spatial light modulator 20 in which the blazed grating represented by the formula (1) or (2) is presented. It is a graph to show. It is a flowchart of IFTA. It is a figure which shows an example of the marking of the 4-digit serial number by laser marking. It is a figure which shows the mode of the laser marking of a comparative example. It is a figure which shows the mode of the laser marking by the light control apparatus or light control method which concerns on this embodiment. It is a top view of a Y branch optical waveguide. It is a figure explaining the formation method of the Y branch optical waveguide of a comparative example. It is a figure explaining the formation method of the Y branch optical waveguide of this embodiment. It is the table | surface which put together the light intensity in each condensing point in the case of 1 point processing and 2 point processing. It is the table | surface which put together the light intensity in each condensing point in the case of 1 point processing and 2 point processing. It is the table | surface which put together the light intensity in each condensing point in the case of 1 point processing and 2 point processing. 6 is a graph showing the relationship between the mode purity and the ratio a (= R ₀ / w ₀ ) between the pattern diameter R ₀ of the hologram φ _phase presented in the spatial light modulator 20 and the beam diameter w _{0 of} incident light. It is a figure which shows intensity distribution in the beam cross section of the Laguerre Gaussian mode light whose radial index is 5 and whose declination index is 5. It is a figure which shows the phase distribution in the beam cross section of the Laguerre Gaussian mode light whose radius index is 5 and whose declination index is 5. FIG. 18 is a diagram illustrating a hologram φ _braze for generating + _1st order diffracted light having the intensity distribution of FIG. 17 when uniform intensity laser light is input to the spatial light modulator 20. It is a figure which shows the hologram (phi) _result on which the hologram (phi) _phase and the hologram (phi) _braze were superimposed. It is a figure which shows intensity distribution of the Laguerre Gaussian mode light produced | generated by the light control apparatus 1 which concerns on this embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Light control apparatus, 10 ... Laser light source, 11 ... Spatial filter, 12 ... Collimating lens, 13, 14 ... Mirror, 20 ... Spatial light modulator, 21 ... Drive part, 22 ... Control part, 30 ... Condensing optics 40, shielding member.

Claims (8)

A laser light source for outputting laser light;
The laser light output from the laser light source is input, a hologram that modulates the phase of the laser light is presented in each of a plurality of two-dimensionally arranged pixels, and the laser light that has been phase-modulated by this hologram is output. A phase modulation spatial light modulator;
A condensing optical system provided at a subsequent stage of the spatial light modulator;
A control unit for causing the spatial light modulator to present a hologram;
With
The control unit is
A position where a predetermined order of diffracted light output from the spatial light modulator by the laser light input to the spatial light modulator on which the hologram is presented is condensed by the condensing optical system is defined as position A, and the spatial light The position where the diffracted light of another order output from the modulator is condensed by the condensing optical system is defined as position B, and the zero-order light output from the spatial light modulator is condensed by the condensing optical system. When the position to be performed is position C, by causing the spatial light modulator to present a hologram, the distance between position A and position B is made longer than the distance between position A and position C, and Increasing the intensity of the diffracted light of the other order than the intensity of 0th order light, adjusting the intensity of the diffracted light of the predetermined order ,
The intensity of the diffracted light of the predetermined order output from the spatial light modulator increases as the number of positions where the diffracted light of the predetermined order output from the spatial light modulator is collected by the condensing optical system increases. The spatial light modulator to present a hologram that increases
A light control device characterized by that.   The control unit outputs the hologram for outputting the diffracted light of the predetermined order and the other orders of diffracted light from the spatial light modulator, and the diffracted light of the predetermined order output from the spatial light modulator. The light control apparatus according to claim 1, wherein a hologram for condensing light at a predetermined position by a condensing optical system is superimposed and presented to the spatial light modulator.   The control unit causes the spatial light modulator to present a hologram that outputs the diffracted light of a predetermined order having an intensity distribution or a phase distribution in a beam cross section when output from the spatial light modulator. The light control device according to claim 1. Wherein the control unit, according to claim 3, wherein is present a hologram for outputting a Laguerre-Gaussian mode light as the predetermined order diffracted light output from the spatial light modulator to said spatial light modulator, characterized in that Light control device. A laser light source for outputting laser light;
The laser light output from the laser light source is input, a hologram that modulates the phase of the laser light is presented in each of a plurality of two-dimensionally arranged pixels, and the laser light that has been phase-modulated by this hologram is output. A phase modulation spatial light modulator;
A condensing optical system provided at a subsequent stage of the spatial light modulator;
A control unit for causing the spatial light modulator to present a hologram;
Using,
By the control unit,
A position where a predetermined order of diffracted light output from the spatial light modulator by the laser light input to the spatial light modulator on which the hologram is presented is condensed by the condensing optical system is defined as position A, and the spatial light The position where the diffracted light of another order output from the modulator is condensed by the condensing optical system is defined as position B, and the zero-order light output from the spatial light modulator is condensed by the condensing optical system. When the position to be performed is position C, by causing the spatial light modulator to present a hologram, the distance between position A and position B is made longer than the distance between position A and position C, and Increasing the intensity of the diffracted light of the other order than the intensity of 0th order light, adjusting the intensity of the diffracted light of the predetermined order ,
The intensity of the diffracted light of the predetermined order output from the spatial light modulator increases as the number of positions where the diffracted light of the predetermined order output from the spatial light modulator is collected by the condensing optical system increases. The spatial light modulator to present a hologram that increases
The light control method characterized by the above-mentioned. The control unit outputs the hologram for outputting the diffracted light of the predetermined order and the other orders of diffracted light from the spatial light modulator, and the diffracted light of the predetermined order output from the spatial light modulator. The light control method according to claim 5 , wherein a hologram for condensing light at a predetermined position by a condensing optical system is superimposed and presented on the spatial light modulator. The control unit causes the spatial light modulator to present a hologram for outputting the diffracted light of the predetermined order having an intensity distribution or a phase distribution in a beam cross section when output from the spatial light modulator. The light control method according to claim 5 . By the control unit, according to claim 7, wherein to present a hologram for outputting a Laguerre-Gaussian mode light as the predetermined order diffracted light output from the spatial light modulator to said spatial light modulator, it is characterized by Light control method.