A lithium 2-hydroxyethanesulfonate second-order nonlinear optical crystal, its preparation and application

Abstract

This invention relates to a second-order nonlinear optical crystal of lithium 2-hydroxyethanesulfonate, its preparation, and its applications. The crystal material has the chemical formula Li[SO3(CH2)2OH], a molecular weight of 132.06, belongs to the monoclinic crystal system, has a space group of Cc, and has the following cell parameters: a = 6.70~6.90 Å, b = 8.53~8.73 Å, c = 8.55~8.75 Å, α = γ = 90°, β = 92.04~92.24°, Z = 4, and a cell volume of V = 503.04~513.04 Å. 3 The lithium 2-hydroxyethanesulfonate crystal of this invention possesses excellent optical properties. In terms of nonlinear optical properties, its powder frequency doubling effect is significant: under 1064 nm laser irradiation, its intensity is approximately three times that of KH₂PO₄ (KDP); under 532 nm laser irradiation, its intensity is approximately 0.45 times that of β-BaB₂O₄ (BBO), and phase matching can be achieved at all of these wavelengths. Furthermore, the crystal has a moderate birefringence (0.06@546 nm) and a short ultraviolet absorption cutoff edge (<190 nm), and is easy to grow. These characteristics enable the crystal to effectively extend the wavelength range of coherent light sources through techniques such as second harmonic generation and optical parametric amplification, showing significant application prospects in fields such as laser frequency conversion and optoelectronic information storage.

Description

Technical Field

[0001] This invention belongs to the field of nonlinear optical crystal materials technology, and relates to a second-order nonlinear optical crystal of lithium 2-hydroxyethanesulfonate and its preparation and application. Background Technology

[0002] Coherent deep ultraviolet (DUV, λ < 200 nm) light sources have wide and crucial applications in many fields, including laser frequency conversion, high-precision ranging, space communication, biomedicine, and national defense. Currently, the second harmonic generation (SHG) effect based on nonlinear optical (NLO) crystals is one of the most effective ways to generate coherent DUV radiation. Among the many NLO materials used as building blocks, [the text abruptly ends here, likely due to an incomplete sentence or missing information]. and Non-π conjugated units, represented by [specific unit name], have attracted much attention due to their excellent deep-ultraviolet (DUL) transmittance resulting from their wide bandgap. However, these units typically suffer from polarizability anisotropy and weak hyperpolarizability, leading to insufficient macroscopic second-order nonlinear optical response and limiting their practical applications. To overcome this bottleneck, an effective strategy is to introduce heteroatoms or organic groups into these non-π conjugated units to construct heterotetrahedral structures, thereby enhancing structural anisotropy. However, this modification method easily causes an unfavorable redshift in the optical bandgap, weakening its width and thus impairing the material's transmittance in the DUL region. Therefore, achieving a strong second-harmonic response while maintaining a wide optical bandgap has become a core challenge in the field of DUL Vibration Non-Low-Earth Optical (NLO) materials. Against this backdrop, developing novel NLO crystals that combine deep-ultraviolet transmittance with efficient frequency doubling performance is particularly important. Summary of the Invention

[0003] The purpose of this invention is to provide a second-order nonlinear optical crystal of lithium 2-hydroxyethanesulfonate, its preparation, and its applications. The unique advantage of this crystal lies in its sulfur-containing heterocoordinated tetrahedrons. The functional group serves as the core building block, and also interacts with alkali metals. The synergistic effect ensures that the crystal has deep ultraviolet transmission capability and greatly enhances the macroscopic second-order nonlinear optical effect of the material, exhibiting moderate birefringence (0.06 @ 546 nm) and strong frequency doubling effect (3 × KDP @ 1064 nm, 0.45 × BBO @ 532 nm).

[0004] The objective of this invention can be achieved through the following technical solutions:

[0005] In one aspect, the present invention provides a second-order nonlinear optical crystal of lithium 2-hydroxyethanesulfonate, with the chemical formula Li[SO3(CH2)2OH], a molecular weight of 132.06, belonging to the monoclinic crystal system, with space group Cc, cell parameters a = 6.70~6.90 Å, b = 8.53~8.73 Å, c = 8.55~8.75 Å, α = γ = 90°, β = 92.04~92.24°, Z = 4, and cell volume V = 503.04~513.04 Å. 3 .

[0006] Further, the unit cell parameters of the optical crystal are a = 6.75~6.85 Å, b = 8.58~8.68 Å, c = 8.60~8.70 Å, α = γ = 90°, β = 92.09~92.19°, and Z = 4. More preferably, the unit cell parameters are a = 6.80~6.81 Å, b = 8.63~8.64 Å, c = 8.65~8.66 Å, α = γ = 90°, β = 92.14~92.15°, and Z = 4. Most preferably, the cell parameters are a = 6.808(4) Å, b = 8.630(5) Å, c = 8.652(5) Å, α = γ = 90°, β = 92.143°(2), Z = 4.

[0007] The crystal structure of lithium 2-hydroxyethanesulfonate of the present invention is as follows: Figure 1 As shown. The optical functional unit of the crystal material is The central S atom is coordinated with three O atoms and one CH2CH2OH moiety. In this structure... The bond lengths are 1.452(2)~1.469(18) Å. The bond length is 1.779(2) Å. Through with Tetrahedrons Bonds connect to each other, forming a three-dimensional crystal framework. The group greatly enhances the nonlinear optical properties of lithium 2-hydroxyethanesulfonate.

[0008] In a second aspect, the present invention provides a method for preparing a second-order nonlinear optical crystal of lithium 2-hydroxyethanesulfonate, wherein a lithium source, a sulfur source and water are mixed and stirred continuously to obtain a clear and transparent solution, which is then left to stand in a low-temperature environment, and the colorless and transparent sheet-like target crystal is obtained by natural evaporation of the solvent.

[0009] Furthermore, the addition amounts of lithium source and sulfur source satisfy the following: the molar ratio of Li element to S element is (1~10): (1~10).

[0010] Furthermore, the lithium source is at least one selected from lithium carbonate, lithium chloride, and lithium nitrate. Preferably, the Li source is lithium chloride.

[0011] Furthermore, the sulfur source is at least one selected from sodium 2-hydroxyethanesulfonate and 2-hydroxyethanesulfonic acid. Preferably, the sulfur source is sodium 2-hydroxyethanesulfonate.

[0012] Furthermore, the solvent evaporation temperature is 0~10℃. .

[0013] Furthermore, the solvent evaporation time should be no less than one week.

[0014] In a third aspect, the present invention provides an application of a second-order nonlinear optical crystal, lithium 2-hydroxyethanesulfonate, in laser frequency converters, optical parametric oscillators, optical parametric amplifiers, and photoelectric rectifiers.

[0015] Furthermore, when lithium 2-hydroxyethanesulfonate second-order nonlinear optical crystal material is used in laser frequency converters, it can output 532 nm and 266 nm lasers under 1064 nm and 532 nm laser irradiation.

[0016] This invention utilizes a substitution strategy to achieve sulfur-containing heterocoordinated tetrahedra. The functional group serves as the core building block, and also interacts with alkali metals. The synergistic effect ensures that the crystal has deep ultraviolet transmission capability, while also greatly enhancing the macroscopic second-order nonlinear optical effect of the material, exhibiting a large birefringence (0.06 @ 546 nm) and a strong frequency doubling effect (3 × KDP @ 1064 nm, 0.45 × BBO @ 532 nm).

[0017] Compared with the prior art, the present invention has the following advantages:

[0018] (1) This application provides a novel second-order nonlinear optical crystal, Li[SO3(CH2)2OH], which exhibits a large frequency doubling effect. Under 1064 nm laser irradiation, its frequency doubling intensity is approximately three times that of a KDP crystal, and under 532 nm laser irradiation, it is approximately 0.45 times that of a BBO crystal, enabling phase matching. Furthermore, this crystal material possesses high transmittance in the 190–800 nm spectral range, with an ultraviolet absorption cutoff wavelength less than 190 nm. Therefore, this crystal material has broad application prospects in the field of ultraviolet nonlinear optics.

[0019] (2) This application provides a method for preparing the nonlinear optical crystal Li[SO3(CH2)2OH], which uses a solution evaporation method to grow colorless, plate-like Li[SO3(CH2)2OH] crystals. The method is simple, the conditions are mild, and it is easy to grow millimeter-scale single crystals.

[0020] (3) The lithium 2-hydroxyethanesulfonate crystal material of the present invention can be applied to laser frequency converters and can be used to output laser beams in second harmonic mode. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the crystal structure of lithium 2-hydroxyethanesulfonate;

[0022] Figure 2 The X-ray diffraction pattern of sample 1-1# obtained by fitting the crystal structure resolved by single-crystal X-ray diffraction is compared with the X-ray diffraction pattern obtained by grinding sample 1-1# into powder.

[0023] Figure 3 This is the ultraviolet-visible light transmission spectrum of sample 1#;

[0024] Figure 4 This is the infrared spectrum of sample 1#;

[0025] Figure 5 This is the thermogravimetric analysis chromatogram of sample 1#;

[0026] Figure 6 The diagram shows the second harmonic signal of sample 1# and KDP sample with dimensions in the range of 150~200 μm.

[0027] Figure 7 The diagram shows the second harmonic signal of sample 1# and BBO sample with dimensions in the range of 150~200 μm.

[0028] Figure 8 This is the second harmonic phase matching diagram of sample 1# at a wavelength of 1064 nm.

[0029] Figure 9 This is the second harmonic phase matching diagram of sample 1# at a wavelength of 532 nm.

[0030] Figure 10 This is a birefringence test result of sample 1# at a wavelength of 546 nm. Detailed Implementation

[0031] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0032] In the following embodiments, unless otherwise specified, the raw materials or processing techniques are conventional commercially available raw materials or conventional processing techniques in the art.

[0033] Example 1:

[0034] Preparation of samples 1#~8#

[0035] Lithium source, sulfur source and water are mixed in a certain proportion to form raw materials, which are placed in a polytetrafluoroethylene liner. After continuous stirring to obtain a clear and transparent solution, the solution is left to stand in a low temperature environment and the solvent is allowed to evaporate naturally to obtain colorless and transparent flaky Li[SO3(CH2)2OH] crystals.

[0036] The relationship between the types and proportions of raw materials, volatilization temperature, volatilization time and sample number in the initial mixture is shown in Table 1.

[0037] Table 1. Correspondence between samples and raw materials and synthesis conditions.

[0038]

[0039] Crystal structure analysis of samples 1#~8#

[0040] The structural analysis and phase analysis of samples 1# to 8# were performed using single-crystal X-ray diffraction and powder X-ray diffraction techniques, respectively.

[0041] Single-crystal X-ray diffraction measurements were performed on a Bruker D8 VENTURE CMOS X-ray single-crystal diffractometer (Germany). Data collection was conducted at 100 K, using graphite-monochromatic Mo Kα rays (λ = 0.71073 Å) as the diffraction source, with an ω scanning mode. Data were processed using the Multi-Scan method for absorption correction. Structural analysis was performed using the Olex2 package; the positions of heavy atoms were determined using a direct method, and the coordinates of the remaining atoms were obtained using difference Fourier synthesis. The results were then analyzed using an F-based method. 2 The full matrix least squares method is used to refine the coordinates and anisotropic thermal parameters of all atoms.

[0042] Single-crystal X-ray diffraction results showed that samples 1#~8# had the same chemical and crystal structures, with the chemical formula Li[SO3(CH2)2OH], a molecular weight of 132.06, belonging to the monoclinic crystal system, with space group Cc, and cell parameters a = 6.70~6.90 Å, b = 8.53~8.73 Å, c = 8.55~8.75 Å, α = γ = 90°, β = 92.04~92.24°, and Z = 4.

[0043] Taking sample 1# as a typical example, its crystal structure data are a = 6.808(4) Å, b = 8.630(5) Å, c = 8.652(5) Å, α = γ = 90°, β = 92.143°(2), Z = 4. The crystal structure of Li[SO3(CH2)2OH] is as follows: Figure 1 As shown.

[0044] Powder X-ray diffraction tests were performed on a Bruker D8 X-ray powder diffractometer from Bruker GmbH, Germany. The test conditions were: fixed target, monochromatic Cu-Kα light source, wavelength 1.540598 Å, voltage and current 40 kV / 20 A, slit widths (DivSlit / RecSlit / SctSlit) of 2.00 deg / 0.3 mm / 2.00 deg, and scanning range... Scan step size .

[0045] The powder X-ray diffraction test results show that the peak positions of samples 1# to 8# are basically the same, while the peak intensities are slightly different.

[0046] Taking sample 1# as a typical example, such as Figure 2 As shown, the peak positions of the fitted X-ray diffraction pattern obtained from the single-crystal X-ray diffraction analysis are consistent with those of the X-ray diffraction pattern obtained after grinding sample #1 into powder. This indicates that the obtained sample has high purity.

[0047] Ultraviolet-Visible Light Transmission Spectroscopy Test

[0048] The UV-Vis transmittance spectrum of sample 1# was measured using an Agilent Technologies Cary 5000 UV-Vis-NIR spectrophotometer. The results are as follows: Figure 3 As shown, the ultraviolet absorption cutoff edge of this compound is less than 190 nm.

[0049] Infrared spectroscopy test

[0050] The infrared spectroscopy of sample 1# was performed using a Nicolet iS10 Fourier transform infrared spectrometer from Thermo Fisher Scientific, Inc., USA. The results are as follows: Figure 4 As shown, in the infrared spectrum ( , , , , The characteristic absorption peaks of the crystal confirmed that... The presence of functional groups.

[0051] Thermogravimetric test

[0052] Thermogravimetric analysis (TGA) of sample #1 was performed on a Netzsch STA 409PC thermogravimetric analyzer from Netzsch GmbH, Germany. The results are as follows: Figure 5 As shown, the thermal decomposition temperature of this compound is 274°C. .

[0053] Frequency doubling test experiment and results

[0054] The frequency doubling test experiment for sample #1 is as follows: A Q-switched Nd:YAG solid-state laser with a wavelength of 1064 nm was used as the fundamental frequency light to irradiate the test crystal powder. The generated second harmonic intensity was detected by an Ocean Optics Maya2000 Pro spectrometer. The crystal sample, standard sample KDP, and standard sample BBO crystals were ground separately and sieved with standard sieves to separate crystals of different particle sizes, with particle size ranges of 26~50, 50~74, 74~105, 105~150, and 150~200 μm, respectively. The variation of the frequency doubling signal with particle size was observed to determine whether phase matching could be achieved. Under the same test conditions, the second harmonic intensity generated by the sample, standard sample KDP, and standard sample BBO crystals was compared to obtain the relative magnitude of the sample's frequency doubling effect. Using the same test method, the test crystal powder was irradiated with a fundamental frequency light with a wavelength of 532 nm, and the generated second harmonic intensity was detected by an Ocean Optics Maya2000 Pro spectrometer. Observe the variation of the harmonic signal with 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 standard sample BBO to obtain the relative magnitude of the harmonic effect of the sample.

[0055] Test results show that the Li[SO3(CH2)2OH] crystal exhibits a significant powder frequency doubling effect; under 1064 nm laser irradiation, the frequency doubling signal intensity is three times that of the KDP crystal (e.g., Figure 6 This crystalline material can achieve phase matching under 1064 nm laser irradiation (e.g., Figure 7 Under 532 nm laser irradiation, the frequency doubling signal intensity is 0.45 times that of the BBO crystal (e.g., Figure 8 This crystalline material can achieve phase matching under 532 nm laser irradiation (e.g., Figure 9 ).

[0056] Crystal birefringence test

[0057] The birefringence properties of crystal sample 1# were measured using a ZEISS AXIO Scope 5 polarizing microscope equipped with a Berek compensator. The light source wavelength was 546 nm. The birefringence was calculated using the following formula:

[0058]

[0059] In the formula For optical path difference, It is birefringent. For crystal thickness. Compensated positive and negative rotations provide a relative delay.

[0060] The results are as follows Figure 10 As shown, Figure 10 Image a shows a Li[SO3(CH2)2OH] crystal after complete extinction achieved using a Berek compensator. Optical path difference ( The thickness of the single crystal was measured to be 8.07 μm. The value is 134.54 μm. Figure 10 b). The crystal planes identified by single-crystal XRD analysis are... 001) ( Figure 10 c). Calculations were performed on Li[SO3(CH2)2OH] crystals. The refractive index difference of the crystal plane at 546 nm is 0.06.

[0061] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any 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 invention should be within the protection scope of the present invention.

Claims

1. A second-order nonlinear optical crystal of lithium 2-hydroxyethanesulfonate, characterized in that, Its chemical formula is Li[SO3(CH2)2OH], its molecular weight is 132.06, it belongs to the monoclinic crystal system, its space group is Cc, its unit cell parameters are a = 6.70~6.90 Å, b = 8.53~8.73 Å, c = 8.55~8.75 Å, α = γ = 90°, β = 92.04~92.24°, Z = 4, and its unit cell volume is V = 503.04~513.04 Å. 3 .

2. The second-order nonlinear optical crystal of lithium 2-hydroxyethanesulfonate according to claim 1, characterized in that, The unit cell parameters of the optical crystal are a = 6.75~6.85 Å, b = 7.58~7.68 Å, c = 8.60~8.70 Å, α = γ = 90°, β = 92.09~92.19°, and Z = 4.

3. The method for preparing a second-order nonlinear optical crystal of lithium 2-hydroxyethanesulfonate as described in claim 1 or 2, wherein: a lithium source, a sulfur source and water are mixed, and a clear and transparent solution is obtained by continuous stirring. The solution is then left to stand in a low-temperature environment, and a colorless and transparent sheet-like target crystal is obtained by natural evaporation of the solvent.

4. The method for preparing the second-order nonlinear optical crystal of lithium 2-hydroxyethanesulfonate according to claim 3, characterized in that, The addition amounts of lithium source and sulfur source satisfy the following: the molar ratio of Li element to S element is (1~10): (1~10).

5. The method for preparing the second-order nonlinear optical crystal of lithium 2-hydroxyethanesulfonate according to claim 3, characterized in that, The lithium source is at least one of lithium carbonate, lithium chloride, and lithium nitrate.

6. The method for preparing the second-order nonlinear optical crystal of lithium 2-hydroxyethanesulfonate according to claim 3, characterized in that, The sulfur source is at least one of sodium 2-hydroxyethanesulfonate and 2-hydroxyethanesulfonic acid.

7. The method for preparing the second-order nonlinear optical crystal of lithium 2-hydroxyethanesulfonate according to claim 3, characterized in that, The solvent evaporates at a temperature of 0~15°C. .

8. The method for preparing the second-order nonlinear optical crystal of lithium 2-hydroxyethanesulfonate according to claim 3, characterized in that, The solvent should be allowed to evaporate for at least one week.

9. The application of a second-order nonlinear optical crystal of lithium 2-hydroxyethanesulfonate as described in claim 1 or 2 in laser frequency converters, optical parametric oscillators, optical parametric amplifiers, and photoelectric rectifiers.

10. The application of the second-order nonlinear optical crystal of lithium 2-hydroxyethanesulfonate according to claim 9, characterized in that, When lithium 2-hydroxyethanesulfonate, a second-order nonlinear optical crystal material, is used in a laser frequency converter, it can output 532 nm and 266 nm lasers under 1064 nm and 532 nm laser irradiation, respectively.

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