Iodate melamine second-order nonlinear optical crystal material as well as preparation and application thereof

Abstract

The invention relates to an iodic acid melamine second-order nonlinear optical crystal material and preparation and application thereof, the chemical formula of the crystal material is (C3N6H7) (IO3), the molecular weight is 302.05, the crystal material belongs to a monoclinic system, the space group is Cc, the cell parameters are # imgabs 0 # alpha = 90 degrees, beta = 96.24-96.44 degrees, gamma = 90 degrees, Z = 4, and the cell volume is # imgabs 1 #. Under 1064nm laser irradiation, the frequency doubling intensity of the powder is about 3.5 times that of a KH2PO4 crystal, and phase matching can be realized. In addition, the crystal material has a short ultraviolet absorption cut-off edge (269nm), and has important application value in the photoelectric conversion fields of photoetching, spectral analysis, environmental monitoring, laser frequency conversion and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of nonlinear optical crystal materials, and relates to a melamine iodate second-order nonlinear optical crystal material and a preparation method and application thereof. Background Art

[0002] Nonlinear optical (NLO) crystals are widely used in optoelectronic fields such as lithography, spectral analysis, environmental monitoring and laser frequency conversion. With the progress of society and the expansion of application fields, the performance requirements of NLO crystal materials are getting higher and higher. Therefore, exploring new NLO materials with better performance has become one of the important tasks and challenges faced by modern scientific researchers. In recent years, researchers have found that organic π-conjugated cationic groups (such as [CN 3 H 6 ] + , [C 5 H 6 ON] + , [C 3 N 6 H 7 ] + ) usually show good NLO performance, for example, (C 5 H 6 ON)(H 2 PO 4 ), C(NH 2 ) 3 SO 3 F and (C 3 N 6 H 7 )(C 3 N 6 H 6 )HgCl 3 However, these organic π-conjugated cation groups usually have highly symmetrical structures, which makes it difficult for the crystal materials constructed by them to crystallize in non-centrosymmetric space groups. At the same time, it is difficult for existing second-order nonlinear optical crystal materials to have a strong frequency doubling effect, a moderate refractive index, and a short ultraviolet absorption cutoff edge. Therefore, the development of NLO materials containing organic π-conjugated cation groups remains a major challenge. Summary of the invention

[0003] The purpose of the present invention is to provide a melamine iodate second-order nonlinear optical crystal material and its preparation and application, which exhibits a strong frequency doubling response (3.5×KDP), a moderate birefringence (0.146@546nm) and a short ultraviolet absorption cutoff edge (269nm).

[0004] The purpose of the present invention can be achieved by the following technical solutions:

[0005] In the first aspect, the present invention provides a second-order nonlinear optical crystal material of iodate melamine, the chemical formula of which is (C 3 N 6 H 7 )(IO 3 ), molecular weight is 302.05, belongs to monoclinic system, space group is Cc, unit cell parameters are α=90°,β=96.24~96.44°,γ=90°,Z=4,the unit cell volume is

[0006] Further, the chemical formula of the crystalline material is (C 3 N 6 H 7 )(IO 3 ), which belongs to the monoclinic system, the space group is Cc, and the unit cell parameters are α=90°,β=96.29~96.39°,γ=90°,Z=4. Further preferably, the unit cell parameters are α=90°,β=96.33~96.34°,γ=90°,Z=4. Most preferably, the unit cell parameters are α=90°, β=96.336°, γ=90°, Z=4.

[0007] The crystal structure of iodinated melamine of the present invention is as follows Figure 1 Each asymmetric unit contains a [C 3 N 6 H 7 ] + Group and a [IO 3 ] - Group. Planar π conjugation [C 3 N 6 H 7 ] + Group and [IO 3 ] - The groups are connected to each other through intermolecular hydrogen bonds to form a two-dimensional honeycomb [(C 3 N 6 H 7 )(IO 3 )] ∞ Layer. Layer and layer through [IO 3 ] - The group is π-conjugated with the plane [C 3 N 6 H 7 ] + The groups are connected by hydrogen bonds to form a three-dimensional structure.

[0008] In a second aspect, the present invention provides a method for preparing a melamine iodate second-order nonlinear optical crystal material, comprising the following steps:

[0009] (1) mixing a melamine source, an iodine source and water to form an initial mixed raw material;

[0010] (2) The initial mixed raw materials in step (1) are crystallized under hydrothermal conditions to obtain the target product.

[0011] Furthermore, the melamine source is melamine.

[0012] Furthermore, the iodine source is selected from at least one of iodine pentoxide and iodic acid.

[0013] Furthermore, the added amounts of melamine source and iodine source satisfy: the molar ratio of melamine to iodine element is 1:(0.1-10), preferably, the molar ratio of melamine to iodine element is 1:(0.5-5).

[0014] Furthermore, the amount of water added satisfies: in the initial mixed raw material, the molar concentration of iodine element is 0.1-2 mol / L, preferably, the molar concentration of iodine element is 0.5-1.5 mol / L.

[0015] Furthermore, the temperature of the hydrothermal condition is 100-150° C., and the crystallization time is not less than 24 hours.

[0016] In a third aspect, the present invention provides an application of a melamine iodate second-order nonlinear optical crystal material in a laser frequency converter, a frequency doubling generator, an optical parametric oscillator, an optical parametric amplifier and a photoelectric rectifier.

[0017] Furthermore, the iodate melamine second-order nonlinear optical crystal material is used for a laser frequency converter and outputs 532nm green light under 1064nm laser irradiation. Specifically, (C 3 N 6 H 7 )(IO 3 ) crystal is a second-order nonlinear optical crystal material. It can output a strong 532nm green laser under 1064nm laser irradiation. Its powder frequency doubling intensity is about KH 2 PO 4 The ultraviolet absorption cutoff edge of the crystal material is 269nm, and the birefringence is 0.146@546nm.

[0018] Compared with the prior art, the present invention has the following advantages:

[0019] (1) This application provides a new nonlinear optical crystal (C3 N 6 H 7 )(IO 3 ), under 1064nm laser irradiation, its frequency doubling effect is 3.5 times that of KDP crystal, which can achieve phase matching. In addition, the crystal material has a high transmittance in the 269-1500nm spectral range, and the ultraviolet absorption cutoff wavelength is 269nm. Therefore, the crystal has broad application prospects in the field of nonlinear optics.

[0020] (2) The present invention adopts a mild hydrothermal method, and a high-purity sample can be quickly obtained by hydrothermal crystallization at a temperature of 100 to 150° C. The method is simple and easy to implement, and the reaction conditions are mild, which is conducive to large-scale industrial production.

[0021] (3) The iodinated melamine crystal material of the present invention can be applied to a laser frequency converter, which can convert a laser beam into a double frequency harmonic output. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the crystal structure of melamine iodate;

[0023] Figure 2 The X-ray diffraction pattern of sample 1# obtained by fitting the crystal structure analyzed by single crystal X-ray diffraction is compared with the pattern obtained by X-ray diffraction test after sample 1# is ground into powder;

[0024] Figure 3 is the UV-Vis-NIR diffuse reflectance spectrum of sample 1#;

[0025] Figure 4 is the infrared spectrum of sample 1#;

[0026] Figure 5 It is the second harmonic signal diagram of sample 1# and KDP sample with size ranging from 200 to 280 μm;

[0027] Figure 6 This is the second harmonic phase matching diagram of sample 1# at a wavelength of 1064nm. DETAILED DESCRIPTION

[0028] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0029] In the following examples, unless otherwise specified, raw materials or processing techniques are conventional commercially available raw materials or conventional processing techniques in the art.

[0030] Embodiment 1:

[0031] Preparation of samples 1# to 8#

[0032] Melamine source, iodine source and water are mixed into raw materials in a certain proportion, sealed in a hydrothermal reactor lined with polytetrafluoroethylene, heated to the crystallization temperature, kept constant for a period of time, and then the temperature of the reaction system is slowly lowered to room temperature, filtered and washed, and transparent rod-shaped crystals (C 3 N 6 H 7 )(IO 3 ).

[0033] The relationship between the type and ratio of raw materials in the initial mixture, the volatilization temperature, the volatilization time and the sample number is shown in Table 1.

[0034] Table 1 Correspondence between samples, raw materials and synthesis conditions

[0035]

[0036] Crystal structure analysis of samples 1# to 8#

[0037] Single crystal X-ray diffraction and powder X-ray diffraction methods were used to perform structural analysis and phase analysis on samples 1#~8#, respectively.

[0038] The single crystal X-ray diffraction test was carried out on a D8 VENTURE CMOS X-type single crystal X-ray diffractometer from Bruker, Germany. The data collection temperature was 298.15K, and the diffraction light source was graphite monochromatized Mo Kα rays. The scanning mode was ω; the data were processed for absorption correction using the Multi-Scan method. The structure analysis was completed using the Olex2 program package; the positions of heavy atoms were determined using the direct method, and the coordinates of the remaining atoms were obtained using the difference Fourier synthesis method; the F-based 2 The full-matrix least-squares method was used to refine the coordinates of all atoms and the anisotropic thermal parameters.

[0039] Single crystal X-ray diffraction results show that samples 1# to 8# have the same chemical formula and crystal structure. The chemical formula is (C 3 N 6 H 7 )(IO 3 ), belongs to the monoclinic system, its space group is Cc, and the unit cell parameters are α=90°,β=96.24~96.44°,γ=90°,Z=4,the unit cell volume is

[0040] Sample 1# is a typical example, and its crystallographic parameters are α=90°,β=96.336°,γ=90°,Z=4. Its crystal structure is as follows Figure 1 shown.

[0041] The powder X-ray diffraction test was carried out on a Bruker D8 powder X-ray diffractometer from Bruker, Germany. The test conditions were a fixed target monochromatic light source Cu Kα, a wavelength The voltage and current are 40 kV / 20 A, the slits DivSlit / RecSlit / SctSlit are 2.00 deg / 0.3 mm / 2.00 deg respectively, the scanning range is 5 to 70°, and the scanning step is 0.02°.

[0042] The powder X-ray diffraction test results show that in the X-ray diffraction spectra of samples 1# to 8#, the peak positions of each sample are the same, but the peak intensities are slightly different.

[0043] Take sample 1# as a typical example. Figure 2 As shown in the figure, according to the crystal structure analyzed by single crystal X-ray diffraction, the peak position of the fitted X-ray diffraction pattern is consistent with that of the X-ray diffraction pattern measured after sample 1# was ground into powder, and the peak intensity is slightly different. This shows that the obtained sample has a high purity.

[0044] UV-Vis-NIR diffuse reflectance spectroscopy test

[0045] The diffuse reflectance spectrum test of sample 1# was conducted on a Cary 5000 UV-Vis-NIR spectrophotometer from Agilent Technologies, USA. Figure 3 As shown, the compound has no absorption in the range of 269nm to 1500nm. The compound has a short ultraviolet absorption cutoff edge and an optical band gap of 4.61eV.

[0046] Infrared spectrum test

[0047] The infrared spectrum test of sample 1# was conducted on a Nicolet iS10 Fourier infrared spectrometer from Thermo Fisher Scientific Inc., USA. The results are as follows Figure 4 As shown, [IO 3 ] - The characteristic peaks of anionic groups are at 1056, 981, 756 and 535 cm -1 For [C 3 N 6 H 7 ] + Among the characteristic peaks of the group, 1188, 1117 and 1600~3300cm -1 The characteristic peaks in the range correspond to NH 2 Bending and stretching vibrations of the group, 1522 and 1396 cm -1The stretching vibration of CN bond is at 710 and 603 cm -1 The peak at is the bending vibration of the melamine ring. These results show that the crystalline material contains [C 3 N 6 H 7 ] + Group and [IO 3 ] - Group.

[0048] Powder frequency doubling test experiment and results

[0049] The frequency doubling test experiment of sample 1# is as follows: a laser with a wavelength of 1064nm generated by a Q-switched Nd:YAG solid laser is used as the fundamental frequency light to irradiate the tested crystal powder, a photomultiplier tube is used to detect the generated second harmonic, and an oscilloscope is used to display the harmonic intensity. The crystal sample and the control sample KDP crystal are ground separately, and crystals of different particle sizes are sieved out with a standard sieve. The particle size ranges are less than 26, 26-50, 50-74, 74-105, 105-150, 150-200, and 200-280μm. Observe the trend of the frequency doubling signal intensity changing with the particle size to determine whether phase matching can be achieved. Under the same test conditions, the second harmonic intensity generated by the sample and the KDP sample is compared to obtain the relative size of the sample frequency doubling effect.

[0050] The test results show that the compound iodic acid melamine crystal has a large frequency doubling effect. Under 1064nm wavelength laser irradiation, the frequency doubling signal intensity is 3.5 times that of the control sample KDP crystal (such as Figure 5 ), phase matching can be achieved (such as Figure 6 ).

[0051] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A melamine iodate second-order nonlinear optical crystal material, characterized in that: The chemical formula is (C3N6H7)(IO3), the molecular weight is 302.05, it belongs to the monoclinic system, the space group is Cc, and the unit cell parameters are α=90°,β=96.24~96.44°,γ=90°,Z=4,the unit cell volume is 2. The iodinated melamine second-order nonlinear optical crystal material according to claim 1, characterized in that: The unit cell parameters of the crystal material are α=90°, β=96.29~96.39°, γ=90°, Z=4.

3. The method for preparing a melamine iodate second-order nonlinear optical crystal material according to claim 1 or 2, characterized in that: The following steps are involved: (1) mixing a melamine source, an iodine source and water to form an initial mixed raw material; (2) The initial mixed raw materials in step (1) are crystallized under hydrothermal conditions to obtain the target product.

4. The method for preparing a melamine iodate second-order nonlinear optical crystal material according to claim 3, characterized in that: The melamine source is melamine.

5. The method for preparing a melamine iodate second-order nonlinear optical crystal material according to claim 3, characterized in that: The iodine source is selected from at least one of iodine pentoxide and iodic acid.

6. The method for preparing a melamine iodate second-order nonlinear optical crystal material according to claim 3, characterized in that: The added amounts of melamine source and iodine source satisfy the following requirement: the molar ratio of melamine to iodine element is 1:(0.1-10).

7. The method for preparing a melamine iodate second-order nonlinear optical crystal material according to claim 3, characterized in that: The amount of water added satisfies: the molar concentration of iodine element in the initial mixed raw material is 0.1-2 mol / L.

8. The method for preparing a melamine iodate second-order nonlinear optical crystal material according to claim 3, characterized in that: The temperature of the hydrothermal condition is 100-150°C, and the crystallization time is not less than 24 hours.

9. Application of the iodinated melamine second-order nonlinear optical crystal material as claimed in claim 1 or 2 in laser frequency converters, frequency doubling generators, optical parametric oscillators, optical parametric amplifiers and photoelectric rectifiers.

10. The use of the iodinated melamine second-order nonlinear optical crystal material according to claim 9, characterized in that: The iodate melamine second-order nonlinear optical crystal material is used for a laser frequency converter and outputs 532nm green light under 1064nm laser irradiation.

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