JP2009192275A - Method for evaluating laser irradiation resistance of organic optical crystal and evaluated organic optical crystal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To establish a method for preliminarily easily and simply evaluating the laser irradiation resistance of an organic optical crystal in a non-destructive manner in order to irradiate the organic optical crystal with a laser beam to continuously use it, and the organic optical crystal having laser irradiation resistance evaluated by the evaluation method. <P>SOLUTION: The evaluation method for determining the presence of the laser irradiation resistance of the organic optical crystal by the diffractive analyzing process before the organic optical crystal is irradiated with the laser beam. Further, the organic optical crystal having laser irradiation resistance evaluated by the evaluation method is easily and simply provided to a wide field in a non-destructive manner. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for evaluating laser irradiation resistance when an organic optical crystal is irradiated with laser light, an organic optical crystal evaluated by the evaluation method, and an application thereof.

  As organic optical crystals, stilbazolium derivatives, and DAST (4-dimethylamino-N-methyl-4-stilbazolium tosylate) crystals which are stilbazolium derivatives, DASC (4-dimethylamino-N-methyl-4-stilbazolium-) p-chlorobenzenesulfonate) crystal, MC-PTS (merocyanine-p-toluenesulfonic acid) crystal, MMONS (3-methyl-methoxy-4′-nitrostilbene) crystal, DAD ((−) 4- (4′-dimethyl) Aminophenyl) -3- (2′-hydroxypropylamino) cyclobutene-3,4-dione) crystals and LAP (L-arginine phosphate mono-hydrate) crystals, pNA (4-nitroaniline), MNA (2-methyl) -Nitroaniline) and other organic crystals Are, has high nonlinearity as compared with inorganic optical crystal, the wavelength conversion element for threshold is high photodamage, application to optical elements is expected.

  Among these organic optical crystals, DAST crystal, DASC crystal, and MC-PTS crystal, which are stilbazolium cation derivatives, are used as organic nonlinear optical crystals by utilizing the nonlinear optical effect and electro-optical effect, Expected to be applied to terahertz wave detection elements, high-sensitivity electric field sensors, etc., various research and development have been conducted.

  So far, in order to provide a uniform crystal free of defects in a DAST crystal, a crystal having uniform electro-optical characteristics over the entire crystal (Patent Document 1), a magnetic field when depositing a solute from a supersaturated solution. When applied to a magnetic field application method (Patent Document 2) for growing a crystal structure with a high density orientation by acting on a terahertz wave generator, the crystal does not attenuate the terahertz wave output. There has been proposed a crystal (Patent Document 3) in which no defect exists.

  In general, a frequency region (0.1 to 100 THz) including a submillimeter wave to a far infrared region is collectively referred to as a terahertz electromagnetic wave region, and is located at a boundary between a light wave and a radio wave. This terahertz wave is not only used in the information and communication field as an electromagnetic wave, but also has properties such as energy that is 1/1 million of X-rays, is safe for the human body, penetrates paper and plastic materials, and does not penetrate metal. Because of its nature, it reacts sensitively to the difference in the water content of drugs and compounds that need to be inspected easily and without contact with non-contact, non-destructive materials, analysis tools for biomolecules and various compounds, malignant tumors Its application is wide-ranging, such as early detection of defects, defect inspection of internal structure of semiconductor LSI, and physical property evaluation of wafers.

  The terahertz wave generator generates two electromagnetic waves having different wavelengths in a two-wavelength parametric oscillator by a laser irradiated from a laser irradiator, and the two electromagnetic waves are incident on a difference frequency generating element through a condenser lens, A configuration in which an electromagnetic wave (terahertz wave) corresponding to a difference frequency between the two electromagnetic waves is generated from a difference frequency generating element is generally used, and the organic nonlinear optical crystal is used as the difference frequency generating element.

Although the organic nonlinear optical crystal is irradiated with the laser irradiated from the laser irradiator, the inside of the crystal may be damaged at this time, and the quality of the crystal such as laser resistance becomes a problem. Furthermore, individual differences due to the crystals occur in the damage generation pattern depending on the crystal growth method, growth conditions, and the like.
This means that the terahertz wave generator has a problem that it cannot be determined whether it is a laser-resistant crystal unless it uses an organic nonlinear optical crystal used as a difference frequency generating element. . In other words, it has become necessary to reliably confirm the quality of the crystal such as laser resistance before laser irradiation, but until now, no study has been made on the method for evaluating the laser resistance of organic optical crystals.

On the other hand, with the recent development of the biotechnology field, there is an increasing need to develop a technique capable of analyzing the crystal structure of biopolymers quickly and easily. In the crystal structure analysis of biopolymers, the accuracy of analysis depends on the quality of the crystal used, and in the case of structure analysis, generally, the crystal from which high resolution data can be obtained is considered to be of good quality, and there are problems associated with structure analysis. In order to reduce the amount of data and the time required, preliminary evaluation of crystal quality is indispensable in order to determine which crystal is used for analysis. Therefore, a method (Patent Document 4) for quickly and easily evaluating the quality of a crystal used for crystal structure analysis of a biopolymer has also been proposed.
However, here, the quality of the crystal used for the analysis of the crystal structure of the biopolymer is evaluated quickly and simply, and nothing is shown to evaluate the laser irradiation resistance of the organic optical crystal.
JP 2004-107104 A JP 2004-205531 A JP 2007-232936 A Japanese Patent Laid-Open No. 2005-3489

  An object of the present invention is to establish a method for evaluating the laser irradiation resistance of an organic optical crystal in a non-destructive manner prior to laser irradiation in order to continuously use the organic optical crystal by irradiating a laser beam. It is an object of the present invention to provide an organic optical crystal having laser irradiation resistance evaluated by the evaluation method and its application.

  As a result of intensive studies to solve the above problems, the present inventors have developed a method for evaluating the presence or absence of laser irradiation resistance of an organic optical crystal by a diffraction analysis step before irradiating the organic optical crystal with a laser. It came to invent. In addition, the present inventors have invented an organic optical crystal whose laser irradiation resistance has been evaluated by the method for evaluating laser irradiation resistance of the organic optical crystal and its application.

Furthermore, the present inventors have conducted a diffraction analysis process for comparing the diffraction analysis data of the standard crystal sample having laser irradiation resistance with the diffraction analysis data of the crystal sample to be evaluated before irradiating the organic optical crystal with laser. The inventors have invented a method for evaluating the laser irradiation resistance of an organic optical crystal, which evaluates the presence or absence of the laser irradiation resistance of the organic optical crystal.
Also, compare the temperature factor obtained from the diffraction analysis data of the standard crystal sample with laser irradiation resistance before irradiating the organic optical crystal with the laser to the temperature factor obtained from the diffraction analysis data of the crystal sample to be evaluated. As a result, the inventors have invented a method for evaluating the laser irradiation resistance of an organic optical crystal, which evaluates the presence or absence of the laser irradiation resistance of the organic optical crystal.

That is, the present invention
[1] In the method for evaluating the laser irradiation resistance of an organic optical crystal, the organic optical crystal is evaluated for presence or absence of laser irradiation resistance by a diffraction analysis step before irradiating the organic optical crystal with laser. Evaluation method of laser irradiation resistance of optical crystal.
[2] The diffraction analysis step evaluates the presence or absence of laser irradiation resistance of the crystal by comparing with diffraction analysis data of a standard crystal sample having laser irradiation resistance. Evaluation method of laser irradiation resistance of organic optical crystal.
[3] The method for evaluating tolerance to laser irradiation of an organic optical crystal according to [1] or [2], wherein the diffraction analysis step includes a step of measuring a temperature factor.
[4] The method for evaluating resistance to laser irradiation of an organic optical crystal according to any one of [1] to [3], wherein the organic optical crystal is a crystal made of a stilbazolium derivative.
[5] The organic optical crystal is at least one crystal selected from any one of DAST, DASC and MC-PTS crystals which are stilbazolium cation derivatives. [1] to [4] The evaluation method of the laser irradiation tolerance of the organic optical crystal in any one of.
[6] An organic optical crystal whose laser irradiation resistance has been evaluated by the laser irradiation resistance evaluation method described in any one of [1] to [5].
[7] An electro-optical element comprising the organic optical crystal according to [6] as a constituent material.
[8] The electro-optic element is for terahertz wave generation, terahertz wave detection, high-sensitivity electric field sensor, high-speed optical modulator, electric field probe, electro-optic sampling, two-dimensional electric field mapping, or spatial electric field detection. The electro-optic element according to any one of [7].

  In accordance with the present invention, the laser irradiation tolerance is preliminarily determined in a simple and non-destructive manner through a simple diffraction analysis process that compares the diffraction analysis data of a standard crystal sample with laser irradiation resistance before irradiating the organic optical crystal with laser. As a result, it was possible to judge the quality of organic optical crystals such as laser irradiation resistance before use, and to evaluate organic optical crystals with laser irradiation resistance evaluated by the evaluation method. Crystals can be provided non-destructively and easily.

The present invention is described in detail below.
The organic optical crystal that can be evaluated in the method for evaluating the laser irradiation resistance of the organic optical crystal of the present invention includes a stilbazolium derivative crystal represented by the following formula 1. The stilbazolium derivatives, -X, -Y and Z ^- combined in various derivatives have been configured. MMONS (3-methyl-methoxy-4′-nitrostilbene) crystal, DAD ((−) 4- (4′-dimethylaminophenyl) -3- (2′-hydroxypropylamino) cyclobutene-3,4-dione ) Crystals and various organic crystals such as LAP (L-arginine phosphate mono-hydrate) crystals, pNA (4-nitroaniline), MNA (2-methyl-nitroaniline) crystals.

Among them, it can be evaluated using a crystal composed of a stilbazolium derivative represented by the following formula 1 useful as an organic nonlinear optical crystal.
* Includes substances that contain at least one deuterium (D) in the derivative molecule.

  In particular, among the stilbazolium derivative crystals, DAST (4-dimethylamino-N-methyl-4-stilbazolium tosylate) crystal in which X = 9, Y = i, and Z = b, X = 9, Y DASC (4-dimethylamino-N-methyl-4-stilbazolium-p-chlorobenzenesulfonate) crystal in which Z = c, MC-PTS (merocyanine- in which X = 1, Y = i, Z = b) It is most preferable to evaluate a single crystal of (p-toluenesulfonic acid) in that a useful organic nonlinear optical crystal used for a wide range of applications can be evaluated.

  In the evaluation method of the laser irradiation resistance of the organic optical crystal of the present invention, any laser that can generate a terahertz wave when irradiated with the organic optical crystal is used as a laser for generating a terahertz wave. It doesn't matter. For example, laser light sources include Nd; YAG lasers with wavelengths of 1475 nm and 1493 nm and a pulse width of 15 ns / pulse, and Nd; YAG / SHG lasers with a wavelength of 532 nm and a pulse width of 10 ns / pulse. .

  In the evaluation method of the laser irradiation resistance of the organic optical crystal of the present invention, the diffraction analysis step used in the evaluation method performed before irradiating the organic optical crystal with the laser is an X-ray structure known as a diffraction analysis of the crystal structure. Any of analysis, neutron structure analysis, and electron beam structure analysis may be used as long as the average structure of crystal structure and lattice vibration can be analyzed.

  The inventors of the present invention performed neutron structural analysis on DAST crystal among organic optical crystals and evaluated the crystal quality. As a result, they found that hydrogen atom information based on neutron structural analysis differs depending on various crystals. In particular, the hydrogen atom position in the DAST crystal was specified as a regular structure, and the thermal vibration of each atom could be obtained as an anisotropic temperature factor.

DAST has four methyl groups, but the hydrogen atom of the methyl group at the C2 site has been incongruent (disordered), so the remaining three hydrogen groups of methyl groups are H1, H16, and H17 (see Formula 2). The temperature factor data was obtained by neutron structure analysis. Here, in DAST chemical structural formula 2, the hydrogen atom of the upper left methyl group is H1, the hydrogen atom of the rightmost methyl group is H16, and the hydrogen atom of the intermediate methyl group is H17.

The atoms in the crystal are not stationary but actually move by thermal vibration. Therefore, the crystal structure factor F (hkl) obtained by diffraction analysis using a specific radiation source (neutron, X-ray, electron beam) includes the effect of thermal vibration in the crystal. Structural factors including thermal vibration are
It can be expressed. Here, T represents thermal vibration.
When thermal vibration can be regarded as isotropic, T = exp (−8π ² Usin ² θ / λ ² ) (1.2)
U is called an isotropic temperature factor. However, in general, the thermal vibration differs for each direction, so it is expressed as follows using six variables.
T = exp {−2π ² (U ₁₁ h ² a ^{* 2} + U ₂₂ k ² b ^{* 2} + U ₃₃ l ² c ^{* 2} +2 U ₁₂ hka ^* b ^* +2 U ₁₃ hla ^* c ^* +2 U ₂₃ klb ^* c ^* )} (1.3)
Here, Uij is called an anisotropic temperature factor. For convenience of calculation, a temperature factor defined as follows may be used.
T = exp (-Bsin2θ / λ2)
_{= Exp {- (B 11 h} 2 + B 22 k 2 + B 33 l 2 + 2B 12 hk + 2B 23 kl + 2B 31 lh)} ··· (1.4)
From the comparison of the equations (1.3) and (1.4), the isotropic temperature factor and the anisotropic temperature factor are U = B / (8π ² ) (1.5)
U _ij = B _ij / (2π ² a _i ^* a _j ^* ) (i, j = 1,2,3) (1.6)
Connect with each other. Here, a ₁ ^* , a ₂ ^* , and a ₃ ^* indicate reciprocal lattice constants a ^* , b ^* , and c ^* , respectively.
Therefore, in the present invention, the value of either an isotropic temperature factor or an anisotropic temperature factor is used as a temperature factor obtained by diffraction analysis using a specific radiation source (neutron, X-ray, electron beam). It can be handled as an index of crystal durability.

  The neutron structure analyzer generates secondary particles such as neutrons by colliding the protons accelerated to almost the speed of light with the nucleus of the target crystal, and using these particles, the structure and structure of atoms and molecules It is a device that can analyze sequences. By using the neutrons generated at the high-intensity proton accelerator facility and detecting the diffracted neutron beam with the neutron detector, the neutron angle applied to the crystal is changed, and the collected diffraction data is analyzed to analyze the hydrogen atoms. The crystal structure including the position can be determined.

  The present inventors repeated laser irradiation with laser light used for generating terahertz waves on a crystal sample for which temperature factor data was obtained until the crystal was damaged by laser irradiation, investigated the peak power density at which the damage occurred, When compared with temperature factor data by structural analysis, it was possible to distinguish between crystals that were resistant to laser irradiation and crystals that were not resistant to laser irradiation, that is, crystals that were damaged.

This is due to the diffraction analysis process that compares the diffraction analysis data of the standard crystal sample that is resistant to laser irradiation with the diffraction analysis data of the crystal sample to be evaluated before irradiating the organic optical crystal with laser. An evaluation method for laser irradiation resistance of an organic optical crystal for evaluating the crystal irradiation resistance of a crystal can be found.
Also, compare the temperature factor obtained from the diffraction analysis data of the standard crystal sample with laser irradiation resistance before irradiating the organic optical crystal with the laser to the temperature factor obtained from the diffraction analysis data of the crystal sample to be evaluated. By this step, an evaluation method for the laser irradiation resistance of the organic optical crystal for evaluating the presence or absence of the laser irradiation resistance of the organic optical crystal can be found.

In this specification, a crystal with laser irradiation resistance is a THz wave output obtained when laser irradiation under a certain condition is performed, and each output value is divided using the maximum THz wave output observed at the same measurement. The value calculated in this way is a crystal that does not decay for 20 seconds or more and 0.5 or less continuously within 5 minutes from the start of irradiation.
In addition, a crystal with no laser irradiation resistance is calculated by dividing each output value using the maximum THz wave output observed during the same measurement in the THz wave output obtained when laser irradiation is performed under a certain condition. The value obtained is a crystal that decays continuously to 20 seconds or more and 0.5 or less within 5 minutes from the start of irradiation.
Here, the measurement time required for once splitting the region of 0.1 THz to 10 THz is 5 minutes, and the laser irradiation time is set to 5 minutes in order to evaluate a crystal capable of one or more measurements from the viewpoint of practicality. .

  Furthermore, the present inventors have a correlation between the temperature factor data obtained by the neutron structure analysis and the temperature factor obtained by the X-ray structure diffraction analysis, and the like by analyzing the DAST crystal by the X-ray structure analysis. The average arrangement of the methyl groups having anisotropy is analyzed, and the X-ray diffraction analysis results distinguish between crystals that are resistant to laser irradiation and crystals that are not resistant to laser irradiation, that is, crystals that are damaged. I was able to.

  Usually, from crystal structure analysis using X-rays, neutron beams, electron beams, etc., an amount equivalent to the mean square displacement from the average position of atoms called temperature factor is obtained, and by analyzing this for the whole molecule It is possible to know dynamic states throughout the molecule such as rigid body vibrations and internal molecular motion. Until now, quality evaluation of organic optical crystals has not been studied from the viewpoint of laser resistance, and thus laser resistance evaluation using a temperature factor by this crystal structure analysis has not been performed.

  In the method of analyzing molecular motion using the temperature factor of atoms obtained by crystal structure analysis, a rigid body vibration analysis method is used. This method analyzes rigid vibrations of the whole molecule or a part from the anisotropic temperature factor of each atom. Thereby, the parameters of the rotation and translation of the molecule can be obtained.

  The anisotropic temperature factor referred to here is an atomic vibration expressed using components in the x, y, and z directions that are coordinate axes, mathematically displayed as a tensor, and visualized as an ellipsoid. it can. By performing neutron structural analysis, the anisotropic temperature factor in hydrogen atoms can be obtained with high accuracy. On the other hand, the isotropic temperature factor is an amount corresponding to the magnitude of vibration that is an average of components in the x, y, and z directions and has no directionality, and a specific radiation source (neutron, It can be obtained by conducting a structural analysis using X-rays or electron beams.

  In the present invention, there is a correlation between the anisotropic temperature factor and the isotropic temperature factor of the DAST crystal, and there is also a correlation between the temperature factor and the damage relationship of the crystal. And a crystal having no laser irradiation resistance, that is, a crystal having damage to the crystal, has been obtained, and a method for evaluating the laser irradiation resistance of an organic optical crystal has been established.

  In the present invention, the measurement conditions in the X-ray diffraction method are not particularly limited. For example, an easy-to-handle X-ray having a wavelength that satisfies the measurable Bragg condition in the target DAST crystal and an intensity that can be measured is selected. For example, CuKα rays or the like can be used at an arbitrary intensity. By X-ray structural analysis, the DAST crystal structure was found to be space group Cc. Lattice constants a [Å] = 10.365, b [Å] = 11.322, c [Å] = 17.893, β [dcg.] = 92.24, V [Å3] = 2098.2, and Z = 4.

  As a method of calculating the temperature factor from the relationship between the diffraction angle measured by the X-ray diffraction method and the width of the diffraction line, and a method of calculating the temperature factor from the structural analysis based on the diffraction data measured by the neutron diffraction method Although not limited, the Wilson Plot method can be mentioned.

  The present invention uses, as a constituent material, an organic optical crystal whose laser irradiation resistance has been evaluated by any of the laser irradiation resistance evaluation methods described above, and an organic optical crystal whose laser irradiation resistance has been evaluated. The present invention also relates to an electro-optical element including the same. Furthermore, the electro-optic element is for terahertz wave generation, terahertz wave detection, high-sensitivity electric field sensor, high-speed optical modulator, electric field probe, electro-optic sampling, two-dimensional electric field mapping, or spatial electric field detection. The present invention also relates to an organic optical element that can be used for the above.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. This will be described below using a DAST crystal that is a typical example of the organic optical single crystal of the present invention.

[Reference Example 1]
A production example of a DAST single crystal is shown.
N-10, D-neu-2 crystal growth method (preparation of seed crystal)
A DAST single crystal was obtained by growing a seed crystal. The DAST seed crystal was prepared by adding 400 g of methanol to 10.4 g of commercially available DAST powder (purity: 99.0% or more, manufactured by Daiichi Chemicals Co., Ltd.) to prepare a DAST solution. Next, this solution was heated to 55.0 ° C. while being stirred, and maintained at 55.0 ° C. for 10 hours to completely dissolve the DAST powder. Thereafter, 40 mL of the prepared solution was dispensed to prepare a seed crystal solution. The prepared seed crystal solution was heated again to 55.0 ° C., maintained at 55.0 ° C. for 10 hours, and then lowered to 23.3 ° C. to precipitate seed crystals.
(Single crystal growth)
For growth of the DAST single crystal, 400 g of methanol was added to 17.7 g of DAST powder to prepare a DAST growth solution. Next, this solution was heated to 55.0 ° C. while being stirred, and maintained at 55.0 ° C. for 10 hours to completely dissolve the DAST powder. Thereafter, 280 mL of the prepared solution was dispensed to obtain a crystal growth solution. The adjusted crystal growth solution was again heated to 55.0 ° C. and maintained at 55.0 ° C. for 10 hours. Next, the solution was lowered to 44.8 ° C. while being stirred, and then maintained for 30 minutes, and seed crystals attached to the support were introduced. After introducing the seed crystal, the temperature was quickly lowered to 43.3 ° C., and the crystal was grown for 40 days while the solution temperature was lowered at a rate of 0.1 ° C./day.

N-11 crystal growth method (preparation of seed crystal)
In each step described in the seed crystal manufacturing method, a seed crystal was deposited by applying a magnetic field of 5 T (Tesla) so that the [100] direction was parallel to the magnetic field direction.
(Single crystal growth)
Using the magnetic field applied seed crystal produced by the above method, it was grown by the same method as the single crystal growth method described above.

  The N-10, D-neu-2 and N-11 crystals obtained above were washed and then used for neutron structure analysis of the examples.

The size of each DAST single crystal obtained in Reference Example 1 is as follows.

[Example 1]
(Neutron structure analyzer, experimental conditions)
The neutron diffraction measurement was performed using BIX-3 in JRR-3 owned by Japan Atomic Energy Agency. While changing the crystal orientation manually, 120, 60 and 60 1.5 ° vibration photographs were measured for all three orientations. The exposure time per sheet was 10 minutes, and the measurement time was 30 hours. Based on the obtained data, structural analysis was performed using SHELXL.

  The crystal structure parameters obtained by neutron structural analysis are the space group Cc. Lattice constants a [Å] = 10.306, b [Å] = 111.273, c [Å] = 17.799, β [dcg.] = 92.34, V [Å3] = 2066.16, and Z = 4. Thereafter, the hydrogen atom position in the DAST crystal was specified as a regular structure, and the thermal vibration of each atom was determined as an anisotropic temperature factor.

  The THz output was detected by a pyroelectric element (DTGS (deuterium triglycine sulfate)).

  For the DAST single crystal LotN-10 and LotN-11, the average value of the temperature factor in each methyl group hydrogen atom before laser irradiation was determined. The results were as shown in Table 2.

Next, the wavelength λ ₁ = 1475 nm, λ ₂ = 1493 nm, the pulse width 15 ns / pulse, the repetition frequency 50 Hz, and the initial beam at the site where the transmission of the DAST single crystal is good with respect to N-10 and N-11. Laser light with a power density set to 480 MW / cm ² was irradiated.

  As shown in FIG. 1, N-11 having a small temperature factor with respect to N-10 was not observed to attenuate THz output for 1200 seconds (20 minutes) even by irradiation with the laser beam. On the other hand, for N-10, attenuation of 50% THz output was observed between 241 seconds and 242 seconds.

  Table 3 shows the average value of the temperature factor of each methyl group hydrogen atom before and after laser irradiation for the DAST single crystal LotN-10.

As shown in Table 3, the temperature factor after laser irradiation of N-10, in which the THz output was attenuated by 50%, was increased between 241 seconds and 242 seconds as compared with before irradiation.
From the above, it was observed that there is a correlation between the laser irradiation resistance and the temperature factor in each crystal solid, and in the DAST crystal that does not have the laser irradiation resistance, the temperature factor increases before and after the laser irradiation.

[Example 2]
For the same crystalline solid of D-neu-2, in which the attenuation of THz output was not observed for 1200 seconds (20 minutes) under the laser irradiation conditions of Example 1 for 1200 seconds (20 minutes), the wavelength of the laser light to be irradiated was λ ₁ = 1475 nm, λ ₂ = 1493 nm, pulse width 15 ns / pulse, repetition frequency 50 Hz, initial beam power density was increased to 1.5 GW / cm ² , laser irradiation was performed again, and the subsequent temperature factor was measured.

  As shown in FIG. 2, the D-neu-2 crystal maintains the THz output for 1800 seconds (30 minutes) despite the second laser irradiation and irradiation with the power-up laser light. did.

Table 4 shows the measured values of the temperature factor after irradiation with the laser that was powered up.

  The temperature factor of D-neu-2 after laser irradiation was smaller than the temperature factor of N-10 even though the irradiated laser was powered up.

Based on Examples 1 and 2, “In the THz wave output obtained when laser irradiation is performed for 5 minutes, the value calculated by dividing each output value by the maximum THz wave output observed at the time of measurement is continuous. If the laser irradiation resistance is evaluated by setting the laser irradiation resistance as a specified value for laser resistance evaluation of “not decay to 50% or less for 20 seconds or longer”, the laser irradiation resistance of the DAST crystal is the beam for LotD-neu-2 or N-11. A power density of 480 MW / cm ² can be secured for a maximum of 20 minutes, D-neu-2 has a durability of 30 minutes at a power density of 1.5 GW / cm ² , and has sufficient laser resistance compared to LotN-10 Can be evaluated. This indicates that, in general, dense crystals with good crystal quality have a smaller temperature factor based on thermal vibration than crystals with poor crystal quality, and DAST has the same tendency.
That is, a crystal (LotD-neu-2 or N-11) having a beam power density of 480 MW / cm ^{2 for a} maximum of 20 minutes and a durability of 30 minutes at a power density of 1.5 GW / cm ² can be used as a resistant crystal (standard crystal). When the crystal that could not satisfy the specified value at 480 MW / cm ² was evaluated as a damaged crystal, the temperature factor was damaged crystal> resistant crystal (standard crystal sample).

      This means that the temperature factor of the DAST crystal can be obtained by the diffraction analysis process, and the presence or absence of the laser irradiation resistance of the DAST crystal can be evaluated according to the temperature factor. That is, a temperature crystal of a target crystal sample whose resistance to laser irradiation is used is determined as a standard crystal sample, the temperature factor of the DAST crystal is obtained in advance by a neutron diffraction analysis process, and it is not known whether the laser irradiation resistance is present or not. Is obtained in the diffraction analysis step, and if it is larger than the temperature factor of the standard crystal sample, it can be evaluated as a damaged crystal.

      In particular, the measurement results show that there is a correlation similar to the above between the temperature factor based on the X-ray diffraction analysis of the DAST crystal known as the diffraction analysis of the crystal structure and the temperature factor based on the neutron diffraction analysis. all right. That is, when the temperature factor based on the X-ray diffraction analysis of the DAST crystal was determined, it was the same as the temperature factor of the DAST crystal in the neutron diffraction analysis process.

      X-ray diffraction analysis can be easily analyzed unlike neutron structural analysis. Therefore, the temperature factor data and the resistant crystal with resistance to laser irradiation are used as standard crystal samples, and the temperature factor of the DAST crystal is determined in advance by the neutron diffraction analysis process. The temperature factor of the target crystal sample for which it is not known whether or not it is currently resistant to laser irradiation is obtained in the diffraction analysis process, and if it is greater than the temperature factor of the standard crystal sample, it can be evaluated as a damaged crystal. is there.

  The temperature factor and the specified value can be appropriately set experimentally in view of desired performance (output value, irradiation time, etc.) relating to laser resistance. At this time, it is possible to select and set a specific methyl group in a similar manner by selecting and defining a specific methyl group or using an average value of each methyl group. From the above, it was found that the laser resistance of DAST can be evaluated by measuring the temperature factor.

According to the present invention, since the organic optical crystal is continuously used by irradiating the laser light, it is possible to evaluate the laser irradiation resistance of the organic optical crystal in advance in a non-destructive manner, and the evaluation method is used. In addition, organic optical crystals having resistance to laser irradiation can be used in a wide range of fields.

Damage test result of the crystal of the present invention (peak power density 480 MW / cm ² ) Damage test result of the crystal of the present invention (power density 1.5 GW / cm ² )

Claims (8)

  In the method for evaluating the laser irradiation resistance of an organic optical crystal, the organic optical crystal is characterized by evaluating whether the organic optical crystal has laser irradiation resistance by a diffraction analysis step before irradiating the organic optical crystal with a laser. Evaluation method of laser irradiation resistance.   2. The organic optical crystal according to claim 1, wherein the diffraction analysis step evaluates the presence or absence of laser irradiation resistance of the crystal by comparing with diffraction analysis data of a standard crystal sample having laser irradiation resistance. Evaluation method of laser irradiation resistance.   The said diffraction analysis process includes the process of measuring a temperature factor, The evaluation method of the laser irradiation tolerance of the organic optical crystal of Claim 1 or Claim 2 characterized by the above-mentioned.   The method for evaluating resistance to laser irradiation of an organic optical crystal according to any one of claims 1 to 3, wherein the organic optical crystal is a crystal made of a stilbazolium derivative.   The organic optical crystal is at least one crystal selected from any one of DAST, DASC, and MC-PTS crystals that are stilbazolium cation derivatives. Evaluation method of laser irradiation resistance of organic optical crystals.   An organic optical crystal whose laser irradiation resistance is evaluated by the method for evaluating laser irradiation resistance according to claim 1.   An electro-optical element comprising the organic optical crystal according to claim 6 as a constituent material.   The electro-optic element is for terahertz wave generation, terahertz wave detection, high-sensitivity electric field sensor, high-speed optical modulator, electric field probe, electro-optic sampling, two-dimensional electric field mapping, or spatial electric field detection. The electro-optical element according to claim 7.