JP6324452B2 - Pulsed light generator - Google Patents

Description

  The present specification discloses a pulsed light generator that generates pulsed laser light and outputs pulsed wavelength converted light obtained by wavelength-converting the generated pulsed laser light.

  When the wavelength of the laser beam generated by the laser beam generator is different from the required wavelength, the laser beam generated by the laser beam generator is input to the wavelength conversion element, and the wavelength is converted by the wavelength converter. A technique for outputting the converted light is used.

  The intensity of the laser beam output from the laser beam generator is very strong. For example, a technique has been developed in which the duration of the laser beam is shortened to form a pulse, and the temporal concentration of energy is increased to increase the laser beam intensity.

  However, due to the problems existing in the wavelength conversion element, the problem that the intensity of the required wavelength cannot be increased even if the intensity of the pulse laser beam is increased is becoming apparent. Problems that did not become obstacles with the intensity of conventional laser light are reaching the intensity level of the laser light that becomes an obstacle.

The most widely used wavelength conversion element at present is LiNbO ₃ (abbreviated as LN). LN has high wavelength conversion efficiency. However, when a strong laser beam is input to the LN, there is a problem that the LN is damaged. As a result of increasing the intensity by pulsing the laser light, the LN is damaged when the intensity of the pulse laser light input to the LN reaches several hundred MW / cm ² or more. Therefore, utilization of LiB ₃ O ₅ (abbreviated as LBO), which is more resistant to damage, is assumed.

The present inventors are at the forefront of research to increase the peak intensity of pulsed laser light, and have succeeded in developing a high-intensity pulsed laser light generating apparatus having a peak intensity of 50 GW / cm ² or more. At such a high strength, even LBO that is resistant to damage cannot be damaged.

  As described in Non-Patent Document 1, it has been known that a wavelength conversion capability exists in a quartz plate.

Masakatsu OKADA, Kuniharu TAKIZAWA and Shogo IEIRI, SECOND HARMONIC GENERATION BY PERIODIC LAMINAR STRUCTURE OF NONLINEAR OPTICAL CRYSTAL, Vol. 18, No. 3, OPTICS COMMUNATIONS, August 1976

In the present specification, a technique is disclosed that enables wavelength conversion without damage even for high-intensity pulsed laser light having an intensity of 50 GW / cm ² or more, which damages even LBO that is resistant to damage. In addition, the awareness of the problem that a wavelength conversion element that can be used in a high-intensity region is necessary so that even LBO, which is resistant to damage, is damaged, and the peak intensity is 50 GW / cm ² or more ahead of others. The present inventors who have succeeded in generating intense pulsed laser light have been able to recognize it, and the recognition of the problem itself is novel.

As a result of investigating a material capable of converting the wavelength without being damaged even by a high-intensity pulsed laser beam having an intensity of 50 GW / cm ² or more, the crystal plate was reached. As disclosed in Non-Patent Document 1, it has been known that a wavelength conversion capability exists in a quartz plate. This time the results of the new survey, the quartz plate is strongly destruction strength is, without having to destroy the order of 50GW / cm ^2, up to several hundred GW / cm ² was found to not be destroyed.

However, it is recognized that the wavelength conversion efficiency by the quartz plate is very low, and it has been recognized that it cannot replace LN and LBO.
Actually, even if the quartz plate is simply thickened, the wavelength conversion efficiency is low, and it cannot be a substitute for LN or LBO. Non-Patent Document 1 discloses a technique of laminating quartz plates in order to increase wavelength conversion efficiency. In this technique, a plurality of quartz plates are stacked so that the crystal axis directions of adjacent quartz plates are reversed. According to this technique, the wavelength conversion efficiency increases. Even with such a device, the wavelength conversion efficiency of the quartz plate is still low, and the technology for wavelength conversion using the quartz plate has not been put into practical use. It has been recognized that it cannot replace LN and LBO. The technology of Non-Patent Document 1 has not been put into practical use even after 40 years have passed since the announcement.

  The present inventors reviewed the technique of Non-Patent Document 1 and considered the reason why the wavelength conversion efficiency is low. As a result of the examination, it was confirmed that the wavelength conversion efficiency depends on the light intensity input to the wavelength conversion crystal in addition to the physical properties of the crystal itself. Since the wavelength conversion phenomenon is a nonlinear phenomenon, the light intensity input to the wavelength conversion crystal affects the wavelength conversion efficiency.

Intensity of wavelength converted light = Laser light intensity before wavelength conversion × wavelength conversion efficiency.
The laser beam available at the time when the technology of Non-Patent Document 1 was studied was about 10 MW (the pulse width was about 10 ns and the pulse energy was about 100 mJ). The intensity when this is condensed to an area of 1 mm ² is about 1 GW / cm ² . That is, the maximum intensity of laser light available at that time was about 1 GW / cm ² . After that, technological development to increase the energy density per unit area by reducing the condensing area of the laser light progressed, and technological development to increase the energy density per unit time by shortening the pulse width of the pulsed laser light The inventors have succeeded in generating high-intensity pulsed laser light of 50 GW / cm ² or more. Obviously, the former is low strength and the latter is high strength.

The intensity of the wavelength-converted light available at the time when the technology of Non-Patent Document 1 was studied was
“Conventional wavelength-converted light intensity = light intensity before wavelength conversion (low intensity) × wavelength conversion efficiency (at low intensity)”
On the other hand, the intensity of wavelength-converted light that can be obtained by the present technology is as follows.
"Wavelength converted light intensity by this technology = Light intensity before wavelength conversion (high intensity) x Wavelength conversion efficiency (at high intensity)"

  When comparing the wavelength conversion efficiency (at low intensity) and the wavelength conversion efficiency (at high intensity), it was found that the order of the former and the latter was different, and the latter was much higher.

As a result of this research, when the pulse laser light intensity before wavelength conversion becomes high intensity of 50 GW / cm ² or more, the wavelength conversion efficiency by the quartz plate greatly increases, and the wavelength conversion of LN and LBO at the conventional light intensity level. It has been found that the efficiency approaches the conversion efficiency level that can be fully put to practical use. Utilizing the characteristics of the quartz plate that has a high destructive strength, it is possible to obtain a sufficiently high-intensity wavelength-converted light without being damaged by a high-intensity pulsed laser beam having an intensity of 50 GW / cm ² or more. Confirmed that it would be possible.

The pulsed light generator disclosed in the present specification includes a pulsed laser light generator and a wavelength conversion element that outputs pulsed light that has been converted by the pulsed laser light generated by the pulsed laser light generator. . The pulse laser beam generated by the pulse laser beam generator has a high intensity, and the intensity of the pulse laser beam input to the wavelength conversion element is 50 GW / cm ² or more. The wavelength conversion element is characterized in that a plurality of quartz plates are laminated so that the crystal axis directions of adjacent quartz plates are reversed.

When the energy per pulse of the pulse laser beam is 2 mJ or more and the pulse width is 10 ps to 1 ns, the intensity of the pulse laser beam input to the wavelength conversion element is 50 GW / cm ² or more. Even a quartz that is resistant to damage may be damaged when it exceeds 400 GW / cm ² . The technique described in this specification is extremely effective when the intensity of the pulse laser beam input to the wavelength conversion element is 50 to 400 GW / cm ² .

  Regarding the orientation of the crystal plate, as in Non-Patent Document 1, the surfaces including the x-axis of the crystal crystal may be in contact with each other, and the x-axis directions of the adjacent crystal plates may be reversed. Instead of this, the surfaces orthogonal to the x-axis of the quartz crystal may be in contact with each other, and the adjacent quartz plates may be stacked so that the x-axis direction is opposite. The latter increases the intensity of wavelength-converted light.

The thickness of the quartz plate corresponds to the wavelength before wavelength conversion, and needs to be thick if the wavelength before wavelength conversion is long, and thin if the wavelength before wavelength conversion is short. In addition, when wavelength conversion elements are arranged in series and light before wavelength conversion (referred to as primary light for convenience) is input to the first-stage wavelength conversion element, the first-stage wavelength conversion element emits light after wavelength conversion ( For convenience, secondary light) and light before wavelength conversion are output and input to the second-stage wavelength conversion element. From the second-stage wavelength conversion element, light obtained by wavelength conversion of the secondary light or light obtained by wavelength conversion of the secondary light and the primary light (referred to as tertiary light for convenience), secondary light, and primary light are output.
It is necessary to increase the thickness of the quartz plate in the first-stage wavelength conversion element that converts to secondary light, and to reduce the thickness of the quartz plate in the second-stage wavelength conversion element that converts to secondary light.

A laminated body of a crystal film group of the first film thickness and a laminated body of a crystal film group of the second film thickness are laminated, the first film thickness is thicker than the second film thickness, and the pulse laser beam is on the first film thickness side. Is used, and a device that outputs tertiary pulsed light is obtained using a wavelength conversion element that outputs pulsed light from the second film thickness side.
In addition to the laminated body of the first film thickness and the laminated body of the second film thickness, the laminated body of the quartz film group of the third film thickness, the laminated body of the quartz film group of the fourth film thickness, and the like are further laminated. Also good. There are no particular restrictions on the number of stacked layers.

The quartz plate is transparent, and there is a possibility that a mistake that breaks the relationship between the intended crystal axes during the stacking operation may occur. Each quartz plate has a substantially rectangular shape (that is, it is indistinguishable if it is rotated 180 in the plane, but it can be distinguished if it has other rotation angles. Rotate in the plane like a circle) It is not a shape that cannot be recognized as being rotated, nor a shape that is indistinguishable when rotated 90 ° in a plane like a substantially square.), In the same position in a posture in which the x, y, and z axes are aligned. If marking is made, mistakes are less likely to occur. If there is this marking, the marking positions of adjacent quartz plates are different, and if they are laminated according to the rule that they are aligned every other piece, the intended crystal axis relationship can be obtained.
The approximate rectangle here is a shape in which the vicinity of one vertex of the rectangle is notched, a shape in which one of the four sides forming the rectangle is inclined, or a curve in which one of the four sides is asymmetric. The shape etc. which are formed in are included.
The marking here refers to a mark for identifying the front and back surfaces and the rotation angle of the quartz plate, and refers to a mark made by processing or printing applied to the quartz plate, or a mark based on the shape of the quartz plate. For example, the top left corner of the crystal plate cut along a plane orthogonal to the x axis extends toward the front, the y axis extends upward, and the z axis extends to the left. When a corner is cut out, the posture is reproduced by placing the cutout in the upper left. If the front and back of the quartz plate are reversed and the x-axis faces the back side, the notch is located at the lower left or upper right, and not at the upper left. If the notch is located on the lower left, it is found that the x direction and the y direction are reversed and the z direction is not reversed. Note that the quartz plate may be washed. The marking is preferably not erased by washing.

  According to the technique described in the present specification, it is possible to perform wavelength conversion by taking advantage of the pulse laser beam generating apparatus that has been strengthened. High intensity wavelength-converted light can be realized.

The figure which shows the whole structure of the pulsed light generator which generate | occur | produces a pulse-shaped wavelength conversion light. The figure which shows the relationship between the wavelength before wavelength conversion, and the thickness per sheet of the quartz plate which converts it into a 2nd harmonic. The figure which shows the relationship between the number of quartz plates and the energy of the light after wavelength conversion. The figure which shows the relationship between the energy of the light before wavelength conversion, and the energy of the light after wavelength conversion. The figure which shows the relationship between the intensity | strength of the light before wavelength conversion, and wavelength conversion efficiency. The figure which shows Example 1 of the wavelength conversion element which laminated | stacked the crystal plate. The figure which shows Example 2 of the wavelength conversion element which laminated | stacked the crystal plate. The figure which shows Example 3 of the wavelength conversion element which laminated | stacked the crystal plate. The figure which shows Example 1 of the structure maintained in the state which laminated | stacked the crystal plate. The figure which shows Example 2 of the structure kept in the state which laminated | stacked the crystal plate. The figure which shows Example 3 of the structure maintained in the state which laminated | stacked the crystal plate. The example of a shape when the laminated surface of a crystal plate is planarly shown is shown.

The features of the embodiments described below are listed first.
(Feature 1) Each crystal plate has a wide surface orthogonal to the x-axis, and a surface orthogonal to the y-axis and a surface orthogonal to the z-axis constitute the side surface of the crystal plate.
(Feature 2) Each crystal plate has a wide surface including the y-axis and the z-axis.
(Feature 3) Comparing adjacent quartz plates, the directions of the x-axis and y-axis are opposite, and the directions of the z-axis are aligned.
(Feature 4) Comparing adjacent quartz plates, the directions of the x-axis and the z-axis are opposite, and the directions of the y-axis are aligned.
(Characteristic 5) Each crystal plate is rectangular, and one vertex of four corners is cut out.
(Characteristic 6) The number of quartz plates per crystal plate is adjusted to a thickness with high efficiency for converting to a double wave (light having a double frequency).
(Feature 7) Two colors of light having different frequencies (frequency ω1, ω2) are input to the crystal plate. The number of quartz plates per one plate is adjusted to a thickness with high efficiency for conversion to light having a frequency of ω1 + ω2.
(Feature 8) Using a mirror having different reflectivities for light before wavelength conversion and light after wavelength conversion, the light is separated into light before wavelength conversion and light after wavelength conversion.

FIG. 1 shows the overall configuration of a pulsed light generator that generates pulsed wavelength-converted light. Reference numeral 2 is a so-called microchip laser beam generator, which generates a pulsed laser beam 10. The microchip laser light generator 2 includes a semiconductor laser device 2a, a reflective film 2b, a light emitting crystal 2c, a passive Q switch 2d, and a reflective mirror 2e. The reflective film 2b is formed on the end face of the light emitting crystal 2c, and the reflective film 2b and the reflective mirror 2e form a resonant optical system. The pulsed excitation laser light generated by the semiconductor laser device 2a is input to the light emitting crystal 2c to excite the light emitting crystal 2c. The excited light emitting crystal 2c generates laser light. The light-emitting crystal 2c and the passive Q switch 2d are disposed inside the resonant optical systems 2b and 2e, and the intensity of the laser light output from the light-emitting crystal 2c is increased. When the intensity of the laser beam reaches a predetermined value, the transmittance of the passive Q switch 2d increases, and the pulse laser beam 10 is emitted from the reflecting mirror 2e constituting the resonance system. In the microchip laser beam generator 2, the resonance length is extremely short, and the duration (referred to as pulse width) of one pulse of the pulse laser beam 10 is extremely short. The pulse width is 10 ps to 1 ns. Although not limited thereto, Nd: YAG or Nd: YVO ₄ can be used for the light emitting crystal (laser medium), and Cr: YAG can be used for the passive Q switch.
In FIG. 1, the semiconductor laser device 2a and the light emitting crystal 2c, the light emitting crystal 2c and the passive Q switch 2d, and the passive Q switch 2d and the reflecting mirror 2e are shown in direct contact with each other. May be. Further, a fiber may be disposed between the semiconductor laser device 2a and the light emitting crystal 2c, and the excitation laser light may be introduced into the light emitting crystal 2c through the fiber.

Reference numeral 4 denotes a condensing lens, which condenses the pulsed laser light 10 on the incident surface of the wavelength conversion element 6. The pulse laser beam 10 is close to a Gaussian beam, and the value of M ² is close to 1. That is, the minimum beam waist obtained by condensing with the condensing lens 4 is very small. Since the pulse width of the pulse laser beam 10 is short and the light beam can be condensed so as to reduce the minimum beam waist, the intensity per unit area of the pulse laser beam on the incident surface of the wavelength conversion element 6 reaches 50 GW / cm ² .

When high-intensity light reaching 50 GW / cm ² is input to LN or LBO, LN and LBO are damaged. In this embodiment, the wavelength conversion element 6 is formed of a quartz plate. The quartz plate is resistant to damage, and is not damaged even when high-intensity pulsed laser light reaching 50 GW / cm ² is input. The wavelength conversion element 6 outputs pulsed light 12 after wavelength conversion. The wavelength conversion element 6 also outputs a pulse laser beam 10 before wavelength conversion. Reference numeral 8 is a mirror that transmits the pulsed laser light 10 before wavelength conversion and reflects the wavelength-converted light 12, and separates the wavelength-converted light 12 and the pulsed laser light 10 before wavelength conversion.

FIG. 2 shows the relationship between the wavelength (horizontal axis) of light before wavelength conversion and the thickness (vertical axis) of a quartz plate that converts the light into half-wavelength light (frequency is doubled). For example, a 21 μm quartz plate converts light having a wavelength of 1064 nm into light having a wavelength of 532 nm.
FIG. 3 shows the relationship between the number of quartz plates (horizontal axis) and the energy of pulsed light after wavelength conversion (vertical axis, energy per pulse, the same applies hereinafter). The energy of the input pulsed laser beam was 2.3 mJ. As the number of sheets increases, the energy of light after wavelength conversion increases. As will be described later, the wavelength conversion efficiency is low, and it remains at about 1% even if the number of sheets is increased. In that range, the energy of light after conversion increases as the number of quartz plates increases. In this embodiment, the wavelength conversion element 6 is formed by laminating 12 crystal plates.

FIG. 4 shows the relationship between the energy (horizontal axis) of the pulsed laser light input to the wavelength conversion element 6 and the energy (vertical axis) of the pulsed light subjected to wavelength conversion.
FIG. 5 is obtained by converting the horizontal axis of FIG. 4 into the intensity per unit area of the pulsed laser light before wavelength conversion, and converting the vertical axis of FIG. 4 into wavelength conversion efficiency. Obviously, the conversion efficiency increases as the intensity of the pulsed laser beam increases. The conversion efficiency in the conventional pulsed laser beam intensity (1 GW / cm ² ) before wavelength conversion described in paragraph 0013 is about 0.0001%, and is located at the origin in FIG.
The intensity of pulsed light after wavelength conversion is proportional to light intensity before wavelength conversion × wavelength conversion efficiency. If the pulse laser beam intensity before wavelength conversion increases, not only the first term but also the second term will increase. As a result, when the intensity of the pulsed laser beam before wavelength conversion reaches 50 GW / cm ² , it becomes possible to obtain wavelength-converted light having the required intensity even for a crystal having low wavelength conversion efficiency. For example, it becomes possible to convert a 1064 nm laser beam into a 532 nm green beam and provide it to a medical instrument using the green beam. Further, it can be converted into 193 nm light used by the semiconductor processing apparatus.

FIG. 6 shows the details of the wavelength conversion element 6, and it can be seen that 12 crystal plates 6 a to 6 l are laminated. The lower left figure in FIG. 6 shows the postures of the odd-numbered quartz plates from the left, and the lower right diagram shows the postures of the even-numbered quartz plates from the left. Each quartz plate has a substantially rectangular shape, and the quartz crystal has a wide plane orthogonal to the x-axis (that is, the plane including the y-axis and z-axis), and the planes are stacked in contact with each other. As shown in the figure on the lower left, each crystal plate is notched at the apex angle located at the upper left when the x-axis faces forward, the y-axis faces upward, and the z-axis faces left. A is formed. A defect shown in a triangular notch A is provided at one corner of a rectangle. In this specification, this is also called a substantially rectangular shape. When the notch A of the crystal plate is positioned at the lower left, as shown in the lower right figure, the x-axis faces the back side, the y-axis faces the lower side, and the z-axis faces the left. When the odd-numbered crystal plates are stacked with the notch A positioned at the upper left and the even-numbered crystal plates positioned with the notch A positioned at the lower left, between the adjacent crystal plates, the x-axis and the y-axis Is reversed, and a uniform relationship is obtained for the z-axis. Between the odd-numbered quartz plates or between the even-numbered quartz plates, all the directions of the x-axis, the y-axis, and the z-axis are aligned.
In FIG. 6, the size of the notch A is enlarged and displayed. The cutout A may be reduced in size as long as the marking function is exhibited.
The substantially rectangular shape referred to in this specification is not limited to FIG. As shown in FIG. 12 (a), one of the four sides constituting the rectangle may be inclined, and as shown in FIG. 12 (b), one of the four sides constituting the rectangle. The sides may be asymmetrical curves.

  When the adjacent quartz plates are laminated so that the x-axis is inverted, as shown in FIG. 3, the wavelength conversion efficiency increases when the number of laminated quartz plates is increased. If the thickness of one quartz plate is set to the thickness shown in FIG. 2 with respect to the frequency ω1 of the light before wavelength conversion, the wavelength conversion phenomenon is obtained by the quartz plate, and light having a frequency of 2 × ω1 is obtained. From the wavelength conversion element 6, light after wavelength conversion (frequency 2 × ω1) and light before wavelength conversion (frequency ω1) are output.

Crystals are not damaged even if the light intensity before wavelength conversion is strong. Even if the strength of 50 W / cm ² or more that would damage LN or LBO is input, it will not be damaged. When a quartz plate is used, it is possible to input a light intensity of about 400 GW / cm ² .

  FIG. 7 illustrates the wavelength conversion element 6 of the second embodiment. When light having a frequency ω1 and light having a frequency ω2 are input to the wavelength conversion element, light having a frequency ω1 + ω2 is obtained. By adjusting the thickness of the unit crystal plate, it is possible to obtain a relationship in which the phenomenon of converting the light of ω1 and ω2 into the light of ω1 + ω2 is obtained.

FIG. 8 illustrates the wavelength conversion element 6 of the third embodiment. The left side (the side on which light before wavelength conversion is input) is formed of the laminate of FIG. The right side (the side that outputs the light after wavelength conversion) is formed of the laminate of FIG. Both laminated bodies are laminated and integrated.
When light having a frequency of ω1 is input to the left laminate, light having ω1 and 2 × ω1 is obtained as described in FIG. 6, and is input to the right laminate. In the laminate on the right side, as described with reference to FIG. 7, the phenomenon of converting light of ω1, 2 × ω1 into light of ω1 + 2 × ω1 = 3 × ω1 is obtained. From the wavelength conversion element of FIG. 8, ω1 (light before wavelength conversion), 2 × ω1 (light that is wavelength-converted by the left laminate and wavelength-converted by the right laminate) and 3 × ω1 (right laminate) ) Is output.
The thickness of the unit crystal plate constituting the laminate on the right side of FIG. 8 is converted to the double wave shown in FIG. 6, and the phenomenon of converting 2 × ω1 light into 4 × ω1 light is dominant. It can also be obtained. In this case, ω1 (light before wavelength conversion), 2 × ω1 (light that was wavelength-converted by the left laminate, and wavelength that was not wavelength-converted by the right laminate) and 4 × ω1 (wavelength-converted by the right laminate) Light) is output.

  There is no particular restriction on the number of stages in which the laminated body is continuous, and it can be converted into higher-order light. The laser light of 1064 nm can be converted into green light of 532 nm, or can be converted into ultraviolet light of 266 nm or 177 nm.

FIG. 9 shows an example of a jig for maintaining a stacked state of a plurality of quartz plates, and for the sake of clarity of illustration, three sets of bolts and nuts are not shown. Alternatively, the quartz plates may be optically contacted with each other by pressure.
As shown in FIG. 10, the stacked body 6 may be accommodated in a cylindrical container 14.
Or as shown in FIG. 11, you may apply | coat an adhesive along the boundary line of the quartz plates exposed to the side surface of the laminated body 6, and you may make it harden | cure. There is an adhesive that does not enter the contact surface between the quartz plates and solidifies in a state of covering the boundary line, and the laminate 6 in FIG. 11 can be realized by using the adhesive.
6 to 11, the illustration of the notch A is omitted.

In addition, this invention is not limited to the said Example, A various deformation | transformation is possible based on the meaning of this invention, and these are not excluded from the scope of the present invention.
For example, each surface of the quartz plate may be activated and then bonded at a low temperature to be integrated at the molecular level. Alternatively, adjacent quartz plates may be laminated so that the x-axis and z-axis are reversed and the y-axis is aligned. From the viewpoint of conversion efficiency, the relationship in which the x-axis between adjacent quartz plates is inverted is important, and the relationship between the y-axis and the z-axis does not significantly affect the conversion efficiency. Further, although the condensing lens 4 is used in the configuration of FIG. 1, the pulse laser beam generator 2 and the wavelength conversion element 6 can be stacked. The beam diameter of the pulsed laser light input to the wavelength conversion element 6 can be narrowed down by the excitation light irradiation device in the pulsed laser light generator 2, and the condenser lens 4 can be omitted.

  The technical elements described in this specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology illustrated in the present specification or the drawings achieves a plurality of objects at the same time, and has technical utility by achieving one of the objects.

2: Pulse laser light generator 4: Condensing lens 6: Wavelength conversion element 8: Mirror 10 that transmits light before wavelength conversion and reflects light after wavelength conversion 10: Pulse laser light 12 before wavelength conversion: Wavelength conversion Back pulse 14: container

Claims (5)

It has a pulse laser beam generator and a wavelength conversion element that outputs the pulse laser beam that has been converted by inputting the pulse laser beam generated by the pulse laser beam generator,
The energy per pulse of the pulse laser beam is 2 mJ or more, the pulse width is 10 ps to 1 ns, and the intensity of the pulse laser beam input to the wavelength conversion element is 50 GW / cm ² or more,
The wavelength conversion element, it a quartz plate of several sheets double, in which faces thereof perpendicular to the x-axis of the crystal plate are stacked in relation to the x-axis direction of the adjacent crystal plate are opposite with opposite A pulsed light device. 2. The pulse light generator according to claim 1, wherein, in adjacent quartz plates, one of the y-axis and the z-axis is opposite and the other axis is aligned . The side surfaces of adjacent quartz plates are bonded to each other with an adhesive that does not penetrate into the contact surfaces between the quartz plates and is solidified in a state of covering the boundary line between the side surfaces. The pulsed light device described. A stack of crystal plate groups of the first film thickness and a stack of crystal plate groups of the second film thickness are stacked,
The first film thickness is thicker than the second film thickness,
The pulsed light generator according to any one of claims 1 to 3, wherein the pulsed laser light is input to the first film thickness side and the pulsed light is output from the second film thickness side.   Each quartz plate has a substantially rectangular shape, and is marked at the same position in a posture in which the x-axis, y-axis, and z-axis are aligned. The marking positions of adjacent quartz plates are different, and every other plate is aligned. The pulsed light generator according to any one of claims 1 to 4, wherein the pulsed light generators are stacked in accordance with a rule that they are provided.