A melamine iodate second-order nonlinear optical crystal material and its preparation and application

Abstract

The present invention relates to a melamine iodate second-order nonlinear optical crystal material and its preparation and application. The crystal material has a chemical formula of (C3N6H7)(IO3), a molecular weight of 302.05, belongs to the monoclinic system, has a space group of Cc, unit cell parameters of α=90°, β=96.24-96.44°, γ=90°, Z=4, and a unit cell volume of 1000 nm. The melamine iodate crystal material of the present invention has excellent optical properties. Under 1064 nm laser irradiation, the powder frequency harmonic intensity is approximately 3.5 times that of KH2PO4 crystal, and phase matching can be achieved. In addition, the crystal material has a short ultraviolet absorption cutoff edge (269 nm) and has important application value in photoelectric conversion fields such as lithography, spectral analysis, environmental monitoring, and laser frequency conversion.

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 becoming increasingly higher. Therefore, exploring new NLO materials with better performance has become one of the important tasks and challenges facing modern scientific researchers. In recent years, researchers have found that organic π-conjugated cationic groups (such as [CN3H6] + , [C5H6ON] + , [C3N6H7] + ) usually exhibit good NLO properties, such as crystals such as (C5H6ON)(H2PO4), C(NH2)3SO3F and (C3N6H7)(C3N6H6)HgCl3. 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, existing second-order nonlinear optical crystal materials are difficult 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 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 (C3N6H7)(IO3), the molecular weight of which is 302.05, the crystal system of which is monoclinic, the space group of which is Cc, and the unit cell parameters of which are α=90°,β=96.24~96.44°,γ=90°,Z=4,unit cell volume is

[0006] Furthermore, the chemical formula of the crystalline material is (C3N6H7)(IO3), 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 iodate melamine of the present invention is as follows Figure 1 Each asymmetric unit contains a [C3N6H7] + group and a [IO3] - Group. Planar π conjugated [C3N6H7] + Group and [IO3] - The groups are connected to each other through intermolecular hydrogen bonds to form a two-dimensional honeycomb [(C3N6H7)(IO3)] ∞ Layer. Layer by layer through [IO3] - Group is π-conjugated with the plane [C3N6H7] + 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 the melamine source and the iodine source satisfy: the molar ratio of melamine to iodine is 1:(0.1-10), preferably, the molar ratio of melamine to iodine 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 in a laser frequency converter and outputs 532nm green light under 1064nm laser irradiation. Specifically, the (C3N6H7)(IO3) crystal, as a second-order nonlinear optical crystal material, can output a strong 532nm green laser under 1064nm laser irradiation. Its powder frequency-harmonic intensity is approximately 3.5 times that of KH2PO4 (KDP) crystal, and it can achieve phase matching. In addition, the crystal material has an ultraviolet absorption cutoff edge of 269nm and a birefringence of 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 (C3N6H7)(IO3) that, under 1064nm laser irradiation, exhibits a frequency-doubled effect 3.5 times that of a KDP crystal, enabling phase matching. Furthermore, the crystal material exhibits high transmittance within the 269-1500nm spectral range and an ultraviolet absorption cutoff wavelength of 269nm. Therefore, the crystal has broad application prospects in the field of nonlinear optics.

[0020] (2) The present invention uses a mild hydrothermal method to rapidly obtain high-purity samples through hydrothermal crystallization at a temperature of 100-150°C. This method is simple and easy to implement, with mild reaction conditions, which is conducive to large-scale industrial production.

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

[0022] Figure 1 This 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# was ground into powder;

[0024] Figure 3 is the UV-visible-near-infrared diffuse reflectance spectrum of sample 1#;

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

[0026] Figure 5 This 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 with reference to 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] Example 1:

[0031] Preparation of samples 1# to 8#

[0032] Melamine source, iodine source and water are mixed in a certain proportion to form raw materials, sealed in a polytetrafluoroethylene-lined hydrothermal reactor, 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. After filtering and washing, transparent rod-shaped crystals (C3N6H7)(IO3) can be obtained.

[0033] The relationship between the types and ratios of raw materials in the initial mixture, volatilization temperature, volatilization time and sample numbers 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# to 8#, respectively.

[0038] Single crystal X-ray diffraction measurements were performed on a Bruker D8 VENTURE CMOS X-type single crystal X-ray diffractometer. The data collection temperature was 298.15 K, 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 was solved using the Olex2 program package; the positions of heavy atoms were determined by direct method, and the coordinates of the remaining atoms were obtained by difference Fourier synthesis method; the F-based 2The coordinates of all atoms and anisotropic thermal parameters were refined using the full-matrix least-squares method.

[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 (C3N6H7)(IO3), 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,unit cell volume is

[0040] Taking sample 1# as a typical example, 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 of 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, the X-ray diffraction pattern obtained by fitting the crystal structure determined by single crystal X-ray diffraction is consistent with the X-ray diffraction pattern measured after grinding sample 1# into powder. The peak positions are consistent, with slightly different peak intensities. This indicates that the obtained sample has a high purity.

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

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

[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. Figure 4 As shown, [IO3] - The characteristic peaks of anionic groups are at 1056, 981, 756 and 535 cm -1 For [C3N6H7] + Among the characteristic peaks of the group, 1188, 1117 and 1600~3300cm -1 The characteristic peaks in the range of 1522 and 1396 cm correspond to the bending and stretching vibrations of the NH2 group. -1 The stretching vibration of C-N bond is at 710 and 603 cm -1 The peak at is the bending vibration of the melamine ring. These results indicate that the crystal material contains [C3N6H7] + Group and [IO3] - group.

[0048] Powder frequency doubling test experiment and results

[0049] The SHG test experiment for sample 1# was conducted as follows: a Q-switched Nd:YAG solid-state laser with a wavelength of 1064 nm was used as the fundamental frequency to illuminate the crystal powder under test. The generated second harmonic was detected using a photomultiplier tube, and the harmonic intensity was displayed on an oscilloscope. The crystal sample and a control KDP crystal were ground separately and sieved using a standard sieve to produce crystals of varying particle sizes: less than 26 μm, 26–50 μm, 50–74 μm, 74–105 μm, 105–150 μm, 150–200 μm, and 200–280 μm. The SHG signal intensity was observed as a function of particle size to determine whether phase matching was achieved. Under the same test conditions, the SHG intensity of the sample was compared with that of the KDP sample to determine the relative magnitude of the SHG effect.

[0050] The test results show that the compound iodate 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 intended to facilitate understanding and use of the invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the above-described embodiments. 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 crystal system, the space group is Cc, and the unit cell parameters are α=90°,β=96.24~96.44°,γ=90°,Z=4,unit cell volume is 2. The iodate-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 the melamine source and the iodine source satisfy the following conditions: 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 following conditions: the molar concentration of iodine in the initial mixed raw materials is 0.1 to 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. Use of the iodate-melamine second-order nonlinear optical crystal material according to claim 1 or 2 in a laser frequency converter, a frequency doubling generator, an optical parametric oscillator, an optical parametric amplifier and a photoelectric rectifier.

10. The use of the iodate-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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