Application of methylene diboronic acid second-order nonlinear optical crystal material in nonlinear optical field

Abstract

The invention relates to an application of a methylene diboronic acid second-order nonlinear optical crystal material in the field of nonlinear optics, the chemical formula of the crystal material is CH6B2O4, the molecular weight is 103.68, the crystal material belongs to a tetragonal crystal system, the space group is I41md, the cell parameters are # imgabs0 # alpha = beta = gamma = 90 degrees, Z = 4, and the crystal material has the structural formula shown in the description. The methylene diboronic acid crystal material disclosed by the invention has excellent optical performance, the frequency doubling intensity of powder is about 0.3 time of that of monopotassium phosphate crystal under 1064nm laser irradiation, and phase matching can be realized. Besides, the preparation method of the single crystal of the second-order nonlinear optical material is simple and convenient, the ultraviolet absorption cut-off edge of the single crystal is smaller than 190nm, and due to the advantages, the single crystal has important application potential in the fields of laser frequency conversion, optical information processing, holographic storage, optical communication and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of nonlinear optical crystal materials, and relates to the application of a methylene diboric acid second-order nonlinear optical crystal material in the field of nonlinear optics. Background Art

[0002] Nonlinear optical (NLO) crystals are important optoelectronic information functional materials and are an important material basis for optoelectronic technology, especially laser technology. Ultraviolet NLO crystals can use their frequency conversion properties to convert lasers in the visible light band into ultraviolet band lasers, and have important application value in the fields of medicine, communications, scientific research, etc. At present, the exploration of the development of new ultraviolet NLO materials is mainly focused on borate systems, such as β-BaB2O4 (β-BBO) and NH4B4O6F crystals. However, the dangling bonds of the [BO3] unit cannot bring a wide deep ultraviolet transmittance range, and the anisotropy of the [BO4] unit is very small, which limits the birefringence of the crystal. Therefore, the development of new borate crystals that can balance the optical band gap and birefringence still faces great challenges.

[0003] Although the molecular formula of CH6B2O4 is known (CAS No.: 13251-32-6), its crystal structure has not been determined, and its linear optical and nonlinear optical properties and applications in the field of nonlinear optics have not been reported. The existing CH6B2O4 synthesis method is to use C 13 H 26 After B2O4 is hydrolyzed under acidic conditions, the mother liquor is post-treated to obtain the target product (Hijazi AbuAli, et al. Organometallics. 2001, 20(18), 3962-3965), but there is no report on the preparation method of single crystals. Summary of the invention

[0004] The purpose of the present invention is to provide a methylene diboric acid second-order nonlinear optical crystal material for application in the field of nonlinear optics. The crystal exhibits a moderate frequency response (0.3×KH2PO4(KDP)), a moderate birefringence (0.074@546nm) and a short ultraviolet cutoff edge (<190nm).

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] The invention discloses an application of a methylene diboric acid second-order nonlinear optical crystal material in the field of nonlinear optics. The chemical formula of the crystal material is CH6B2O4, the molecular weight is 103.68, the crystal material belongs to the tetragonal system, the space group is I41md, and the unit cell parameters are α=β=γ=90°, Z=4, the unit cell volume is

[0007] Furthermore, the chemical formula of the crystalline material is CH6B2O4, the molecular weight is 103.68, it belongs to the tetragonal system, its space group is I41md, and the unit cell parameters are α=β=γ=90°, Z=4. Further preferably, the unit cell parameters are α=β=γ=90°, Z=4. Most preferably, the unit cell parameters are α=β=γ=90°, Z=4.

[0008] The crystal structure of methylene diboronic acid of the present invention is as follows Figure 1 As shown. Two [CBO2] triangular planar units form a [CH2(B(OH)2)2] group by sharing carbon atoms. Each [CH2(B(OH)2)2] group forms a three-dimensional structure with four adjacent [CH2(B(OH)2)2] groups through hydrogen bonds.

[0009] Furthermore, the optical crystal material is composed of [CH2(B(OH)2)2] groups connected to each other through hydrogen bonds to form a three-dimensional framework structure.

[0010] Furthermore, the preparation process of the crystal material is specifically as follows:

[0011] C 13 H 26 B2O4 and water are mixed, and acid is added to form an initial mixed raw material, which is then heated and refluxed until the solution becomes clear and transparent. After cooling, the solvent is naturally evaporated to obtain colorless and transparent millimeter-sized crystals, which are the target compound.

[0012] Furthermore, the heating reflux temperature is 115-125° C. and the time is 4-6 hours.

[0013] Furthermore, the temperature of the natural evaporation solvent is 25-35°C and the time is not less than 1 week.

[0014] Furthermore, the acid is hydrochloric acid, and its mass fraction is 36-38%.

[0015] Furthermore, C 13 H 26 The ratio of the added amounts of B2O4, acid and water is 20mmol:(20~30)mL:(100~150)mL.

[0016] More preferably, C 13 H 26 The ratio of added amounts of B2O4, acid and water is 20mmol:25mL:125mL.

[0017] Furthermore, the crystal material is used in laser frequency converters, frequency doubling generators, optical parametric oscillators, optical parametric amplifiers and photoelectric rectifiers.

[0018] Furthermore, when the crystal material is used in a laser frequency converter, it can achieve frequency-doubled output under 1064nm laser irradiation.

[0019] Specifically, under 1064nm laser irradiation, the crystal can output 532nm green light, its powder frequency doubling intensity is about 0.3 times that of KDP crystal, and phase matching can be achieved.

[0020] The present invention synthesizes deep ultraviolet-transmitting second-order nonlinear optical crystal material methylene diboric acid by solution volatilization based on ester hydrolysis reaction. The crystal material has excellent linear and nonlinear optical properties, including moderate frequency response (0.3×KDP), moderate birefringence (0.074@546nm) and short ultraviolet absorption cutoff edge (<190nm).

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] (1) The present application provides a second-order nonlinear optical crystal methylene diboric acid, which has a large frequency doubling effect, which is about 0.3 times the frequency doubling intensity of KDP crystal under 1064nm laser irradiation, and can achieve phase matching. In addition, the ultraviolet absorption cutoff wavelength of the crystal material is less than 190nm, and has a wide optical band gap. Therefore, the crystal material has broad application prospects in the field of nonlinear optics.

[0023] (2) The present application provides a method for preparing methylene diboric acid single crystals. After the hydrolysis reaction of the ester, a solution volatilization method is used to successfully obtain colorless and transparent methylene diboric acid crystals. The method is simple in process and mild in conditions, and can grow millimeter-level single crystals with high optical quality and high purity, which is conducive to large-scale industrial production.

[0024] (3) The methylene diboric acid crystal material provided by 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

[0025] Figure 1 It is a schematic diagram of the crystal structure of methylene diboronic acid;

[0026] Figure 2 This is a photo of millimeter-scale crystals of methylene diboronic acid;

[0027] Figure 3The following are comparisons of X-ray diffraction patterns; (a) is the simulated X-ray diffraction pattern of sample 1# based on the crystal structure analyzed from single crystal X-ray diffraction data; (b) is the pattern obtained by X-ray diffraction test after sample 1# is ground into powder;

[0028] Figure 4 is the UV-visible light transmission spectrum of sample 1#;

[0029] Figure 5 is the infrared spectrum of sample 1#;

[0030] Figure 6 This is the birefringence test chart of sample 1#;

[0031] Figure 7 It is the second harmonic signal diagram of sample 1# and KDP sample with size ranging from 200 to 280 μm;

[0032] Figure 8 This is the second harmonic phase matching diagram of sample 1# in the 1064nm band. DETAILED DESCRIPTION

[0033] 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.

[0034] 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.

[0035] Embodiment 1:

[0036] Preparation of samples 1# to 8#

[0037] C 13 H 26 B2O4, water and acid (using hydrochloric acid with a mass fraction of about 37%) are mixed into raw materials in a certain proportion, placed in a three-necked flask, and heated and stirred in a condensation reflux device to obtain a clear and transparent solution. After cooling, transfer to a beaker and slowly evaporate at room temperature to obtain colorless and transparent methylene diboric acid crystals.

[0038] The relationship between the type and ratio of raw materials in the initial mixture, heating temperature, heating time, volatilization temperature, volatilization time and sample number is shown in Table 1.

[0039] Table 1 Correspondence between samples, raw materials and synthesis conditions

[0040]

[0041] Crystal structure analysis of samples 1# to 8#

[0042] 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.

[0043] The single crystal X-ray diffraction test was carried out on a D8 VENTURE CMOS X-ray single crystal 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.

[0044] The single crystal X-ray diffraction results show that samples 1# to 8# have the same chemical formula and crystal structure, the chemical formula is CH6B2O4, the molecular weight is 103.68, it belongs to the tetragonal system, its space group is I41md, and the unit cell parameters are α=β=γ=90°, Z=4.

[0045] Take sample 1# as a typical example, its crystal structure data is α=β=γ=90°,Z=4,the crystal structure is as follows Figure 1 shown.

[0046] The powder X-ray diffraction test was carried out on a Bruker D8 X-ray powder 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 10-70°, and the scanning step is 0.02°.

[0047] The powder X-ray diffraction test results show that in the XRD spectra of samples 1# to 8#, the peak positions of each sample are basically the same.

[0048] Take sample 1# as a typical example. Figure 3 As shown, according to the crystal structure obtained by single crystal X-ray diffraction analysis, the fitted X-ray diffraction pattern is consistent with the X-ray diffraction pattern measured after sample 1# is ground into powder in terms of peak position and peak intensity, indicating that the obtained sample has a very high purity.

[0049] UV-Visible light transmission spectrum test

[0050] The UV-visible light transmission spectrum test of sample 1# was conducted on a Cary 5000 UV-visible-near infrared spectrophotometer from Agilent Technologies, USA. Figure 4 As shown, the compound has no absorption in the range of 190 to 800 nm. The compound has a short ultraviolet absorption cutoff edge (<190 nm) and an optical band gap greater than 6.52 eV. The wide optical band gap is conducive to the generation of second harmonic ultraviolet light by the fundamental frequency light through the crystal.

[0051] Infrared spectrum test

[0052] 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 5 As shown, 1150, 1286, 1370, 3180cm in the infrared spectrum -1 The characteristic absorption peak at proves the existence of the unit [CH2(B(OH)2)2].

[0053] Birefringence test

[0054] The birefringence test of sample 1# was conducted on an Axioscope A1 polarizing microscope equipped with a Berek compensator from Zeiss, Germany, with a light source wavelength of 546nm. The birefringence can be calculated using the formula:

[0055] ΔR=Δn×T (3)

[0056] ΔR represents the optical path difference, Δn represents the birefringence, and T is the thickness of the crystal. The test results are as follows Figure 6 As shown, the crystal optical path difference is 3.166 μm, the crystal thickness is 42.784 μm, and the birefringence measurement value is calculated to be 0.074.

[0057] Frequency doubling test experiment and results

[0058] 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 spectrometer is used to detect the generated second harmonics, 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, with the particle size ranges of 50-74, 74-105, 105-150, 150-200, and 200-280μm, respectively. 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, compare the second harmonic intensity generated by the sample and the KDP sample to obtain the relative size of the sample frequency doubling effect.

[0059] The test results show that the methylene diboric acid crystal has a large frequency doubling effect. Under 1064nm wavelength laser irradiation, the frequency doubling signal intensity is 0.3 times that of the control sample KDP crystal (such as Figure 7 ), phase matching can be achieved (such as Figure 8 ).

[0060] 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. An application of a methylene diboric acid second-order nonlinear optical crystal material in the field of nonlinear optics, characterized in that: The chemical formula of the crystalline material is CH6B2O4, the molecular weight is 103.68, it belongs to the tetragonal system, its space group is I41md, and the unit cell parameters are α=β=γ=90°, Z=4, the unit cell volume is 2. The use of a methylene diboric acid second-order nonlinear optical crystal material according to claim 1, characterized in that: The preparation process of the crystal material is specifically as follows: C 13 H 26 B2O4 and water are mixed, and acid is added to form an initial mixed raw material, which is then heated and refluxed until the solution becomes clear and transparent. After cooling, the solvent is naturally evaporated to obtain colorless and transparent millimeter-sized crystals, which are the target compound.

3. The use of a methylene diboric acid second-order nonlinear optical crystal material according to claim 2, characterized in that: The heating reflux temperature is 115-125°C and the time is 4-6 hours.

4. The use of a methylene diboric acid second-order nonlinear optical crystal material according to claim 2, characterized in that: The temperature of the naturally volatile solvent is 25-35°C and the time is not less than 1 week.

5. The use of a methylene diboric acid second-order nonlinear optical crystal material according to claim 2, characterized in that: The acid is hydrochloric acid, and its mass fraction is 36-38%.

6. The use of a methylene diboric acid second-order nonlinear optical crystal material according to claim 2, characterized in that: C 13 H 26 The ratio of the added amounts of B2O4, acid and water is 20mmol:(20-30)mL:(100-150)mL.

7. The use of a methylene diboric acid second-order nonlinear optical crystal material according to claim 6, characterized in that: C 13 H 26 The ratio of added amounts of B2O4, acid and water is 20mmol:25mL:125mL.

8. The use of a methylene diboric acid second-order nonlinear optical crystal material according to claim 1, characterized in that: The crystal material is used in laser frequency converters, frequency doubling generators, optical parametric oscillators, optical parametric amplifiers and photoelectric rectifiers.

9. The use of a methylene diboric acid second-order nonlinear optical crystal material according to claim 1, characterized in that: When the crystal material is used in a laser frequency converter, frequency doubling output can be achieved under 1064nm laser irradiation.

10. The use of a methylene diboric acid second-order nonlinear optical crystal material according to claim 1, characterized in that: The optical crystal material is composed of [CH2(B(OH)2)2] groups connected to each other through hydrogen bonds to form a three-dimensional framework structure.

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