Potassium hydroxyborate nonlinear optical crystal, its preparation method and applications

Abstract

This invention relates to a potassium hydroxyborate nonlinear optical crystal, its preparation method, and its applications. The crystal has the chemical formula K₂B₅O₈(OH), a molecular weight of 277.26, belongs to the orthorhombic crystal system, and has a space group of [missing information]. Pca 21, with unit cell parameters a=8.5523(8)Å, b=7.3326(7)Å, c=12.9739(10)Å, α=β=γ=90°, V=813.60(13)Å. 3 A nonlinear optical crystal composed of potassium hydroxyborate can be obtained using a mild hydrothermal (solvothermal) method through programmed or natural cooling. The frequency doubling effect of this crystal powder is approximately twice that of KDP (KH₂PO₄), and its ultraviolet cutoff edge is below 200 nm, making it suitable as a deep-ultraviolet nonlinear optical crystal. The crystal growth process offers advantages such as simple operation, low raw material toxicity, short growth cycle, low cost, and stable physicochemical properties. It has been widely applied in the fabrication of nonlinear optical devices such as frequency doubling generators, up- or down-frequency converters, or optical parametric oscillators.

Description

Technical Field

[0001] This invention relates to potassium hydroxyborate nonlinear optical crystals, their preparation methods, and applications, as well as nonlinear optical devices fabricated using these crystals. This invention belongs to the fields of inorganic chemistry, materials science, and optics. Background Technology

[0002] Ultraviolet / deep ultraviolet (UV / DUV) laser devices, with nonlinear optical materials as their core components, are an important part of precision machining, the semiconductor industry, and information storage, making UV / DUV optical materials of paramount scientific research value. Particularly in the deep ultraviolet range, there are stringent requirements for potential nonlinear optical crystals: they must have a wide transmission range (<200nm), a large frequency doubling factor, a suitable birefringence, a high damage threshold, ease of growth, and good chemical stability.

[0003] Experimental work on nonlinear optics was first reported by Franken et al. in 1961, who reported the generation of second harmonic generation (SHG) in quartz. Currently, SHG-modified lasers are used in various applications such as laser pointers, optical signal processing, optical storage, and photonic devices. These applications utilize this technology to generate shorter wavelength light from the input of a neodymium solid-state laser pumped by an infrared diode.

[0004] Nonlinear optical properties were first observed in inorganic materials, and now they are components of most optical devices. For example, lithium niobate (LiNbO3) is being used in electro-optic modulators; similarly, many other applications include optical modulation, frequency shifting, optical switching, and information processing. Therefore, based on current research and development, nonlinear optical materials are not only important now but are also considered key contributors to future industrial and technological applications.

[0005] With advancements in research, more and more borate crystal structures have been resolved. Currently, ultraviolet nonlinear optical crystals with significant application prospects internationally are all borates, such as β-BBO, LBO, CsB3O5(CBO), and CsLiB6O. 10(CLBO), etc. Among them, LBO and β-BBO crystals are mainly used for third harmonic (355nm) Nd:YAG lasers, while β-BBO and CLBO crystals can be used for fourth harmonic (266nm). Nonlinear optical crystal materials in these wavelength regions can basically meet the requirements. In addition, my country was the first to grow KBe2BO3F2 (KBBF) crystals and invented the prism coupling technology for KBBF crystals, making KBBF crystals the only crystals in the world that can achieve direct sixth harmonic (177.3nm) output at short wavelengths. However, KBBF crystals have obvious layered characteristics, and currently only single crystals with a thickness of a few millimeters can be obtained, which seriously limits the wider application of the crystals. In addition, KBBF crystal raw materials contain the highly toxic substance Be, requiring strict safety protection measures during material preparation. Therefore, efforts are being made to develop new nonlinear optical crystals with better performance and shorter matching wavelengths that are more practical.

[0006] As research progresses, the development of novel nonlinear optical crystals not only aims for superior performance but also for low synthesis costs and difficulty. In terms of synthesis strategy, alkali metal cations are introduced into the boron-oxygen framework to enhance performance. The anions, based on boron-oxygen functional units, have a larger band gap and a higher laser damage threshold, which is beneficial for obtaining strong nonlinear optical effects; the BO bond facilitates broadband light transmission. Alkali metal ions are chosen as cations because they do not undergo d0 electron transitions in the ultraviolet region, which is conducive to ultraviolet transmission.

[0007] The problem to be solved by the potassium hydroxyborate nonlinear optical crystal synthesized in this invention is to provide an inorganic deep ultraviolet potassium hydroxyborate nonlinear optical crystal with a wide transmission band, a large second-order nonlinear optical coefficient, easy preparation and good stability, as well as its preparation method and uses. Summary of the Invention

[0008] The purpose of this invention is to provide a potassium hydroxyborate K₂B₅O₈(OH) nonlinear optical crystal to fill the spectral gaps in the emission wavelengths of various lasers. This crystal has the molecular formula K₂B₅O₈(OH), a molecular weight of 277.26, belongs to the orthorhombic crystal system, has the space group Pca₂₁, and its cell parameters are as follows: α=β=γ=90°,

[0009] Another object of the present invention is to provide a simple method for preparing potassium hydroxyborate (K2B5O8(OH)) nonlinear optical crystals using a hydrothermal method;

[0010] Another object of the present invention is to provide performance analysis of potassium hydroxyborate (K2B5O8(OH)) nonlinear optical crystal;

[0011] Another object of the present invention is to provide the use of potassium hydroxyborate (K2B5O8(OH)) in nonlinear optical devices.

[0012] The present invention discloses a potassium hydroxyborate nonlinear optical crystal with the molecular formula K₂B₅O₈(OH), a molecular weight of 277.26, belonging to the orthorhombic crystal system, space group Pca₂₁, and unit cell parameters of [missing information]. α=β=γ=90°,

[0013] The method for preparing the potassium hydroxyborate nonlinear optical crystal employs a hydrothermal method, and the specific operation is carried out according to the following steps:

[0014] a. Add KBO2 and H3BO3 or KBF4 and H3BO3 to the polytetrafluoroethylene liner of a 23 mL high-pressure reactor at a molar ratio of 1:1.5, tighten the lid, and mix thoroughly.

[0015] b. Place the polytetrafluoroethylene liner from step a into a clean, uncontaminated high-pressure reactor of the appropriate volume, and tighten the reactor piston.

[0016] c. Place the high-pressure reactor from step b in a constant temperature chamber, raise the temperature to 220°C at a rate of 50-73°C / h, keep it at the constant temperature for 3 days, and then cool it down to room temperature at a rate of 1°C / h or by natural cooling.

[0017] d. Open the high-pressure reactor, take out the sample, and determine the transparent K2B5O8(OH) nonlinear optical crystal by X-ray single crystal diffraction.

[0018] The potassium hydroxyborate nonlinear optical crystal is used in the fabrication of frequency multiplier generators, up or down frequency converters, or optical parametric oscillators.

[0019] The potassium hydroxyborate nonlinear optical crystal of this invention has an ultraviolet cutoff edge below 200 nm, a nonlinear optical effect approximately twice that of KDP, and a space group of Pca21. This crystal is simple to prepare, has a short growth cycle, and uses starting materials with low toxicity and minimal harm to the human body.

[0020] The method used in this invention is a hydrothermal method, in which the starting materials are mixed in proportion and then reacted under high temperature and high pressure in a sealed reactor within a temperature range. The transparent potassium hydroxyborate nonlinear optical crystal can be obtained by programmed cooling or constant temperature.

[0021] The potassium hydroxyborate nonlinear optical crystal of the present invention is prepared by hydrothermal method according to the following chemical reaction formula:

[0022] (1)2KBO2+3H3BO3→K2B5O8(OH)+4H2O;

[0023] (2)2KBF4+3H3BO3→K2B5O8(OH)+8HF↑.

[0024] The potassium hydroxyborate nonlinear optical crystal, its preparation method, and its applications described in this invention have advantages such as crystal transparency, simple operation, and low cost. It can be used to prepare frequency multipliers, up- or down-frequency converters, or optical parametric oscillators.

[0025] The nonlinear device fabricated from the potassium hydroxyborate nonlinear optical crystal includes the ability to generate at least one coherent beam with a frequency different from the incident light by transmitting at least one incident fundamental wave light.

[0026] The potassium hydroxyborate nonlinear optical crystal has no special requirements for optical processing precision. Attached Figure Description

[0027] Figure 1 The X-ray diffraction pattern of this invention;

[0028] Figure 2 This is a structural diagram of the K2B5O8(OH) crystal of the present invention;

[0029] Figure 3 The working principle diagram of the nonlinear optical device fabricated for this invention includes (1) a laser, (2) a full-focus lens, (3) a K2B5O8(OH) nonlinear optical crystal, (4) a beam splitter, (5) a filter, and ω is the frequency of the refracted light, which is equal to or twice the frequency of the incident light. Detailed Implementation

[0030] The present invention will now be described in detail with reference to the accompanying drawings and embodiments:

[0031] Example 1

[0032] The specific steps for preparing crystals using the chemical reaction 2KBO₂ + 3H₃BO₃ → K₂B₅O₈(OH) + 4H₂O are as follows:

[0033] a. Add KBO2 and H3BO3 to the polytetrafluoroethylene liner of a 23mL high-pressure reactor at a molar ratio of 1:1.5, tighten the lid, and mix thoroughly.

[0034] b. Place the polytetrafluoroethylene liner from step a into a clean, uncontaminated high-pressure reactor of the appropriate volume, and tighten the reactor piston.

[0035] c. Place the high-pressure reactor from step b in a constant temperature chamber, raise the temperature to 220°C at a rate of 50°C / h, keep it at the constant temperature for 3 days, and then lower it to room temperature at a rate of 1°C / h.

[0036] e. Open the high-pressure reactor, remove the sample, and determine the size of the relatively transparent sample as 0.12 × 0.09 × 0.08 mm using X-ray single-crystal diffraction. 3 K2B5O8(OH) nonlinear optical crystal.

[0037] Example 2

[0038] The specific steps for preparing crystals using the chemical reaction 2KBO₂ + 3H₃BO₃ → K₂B₅O₈(OH) + 4H₂O are as follows:

[0039] a. Add KBO2 and H3BO3 to the polytetrafluoroethylene liner of a 23mL high-pressure reactor at a molar ratio of 1:1.5, tighten the lid, and mix thoroughly.

[0040] b. Place the polytetrafluoroethylene liner from step a into a clean and uncontaminated high-pressure reactor of the appropriate volume, and tighten the reactor piston.

[0041] c. Place the high-pressure reactor from step b in a constant temperature chamber, raise the temperature to 220°C at a rate of 55°C / h, keep it at the constant temperature for 3 days, and then lower it to room temperature at a rate of 1°C / h.

[0042] e. Open the high-pressure reactor, remove the sample, and determine the size of the relatively transparent sample as 0.15 × 0.07 × 0.10 mm using X-ray single-crystal diffraction. 3 K2B5O8(OH) nonlinear optical crystal.

[0043] Example 3

[0044] The specific steps for preparing crystals using the chemical reaction 2KBO₂ + 3H₃BO₃ → K₂B₅O₈(OH) + 4H₂O are as follows:

[0045] a. Add KBO2 and H3BO3 to the polytetrafluoroethylene liner of a 23mL high-pressure reactor at a molar ratio of 1:1.5, tighten the lid, and mix thoroughly.

[0046] b. Tighten the polytetrafluoroethylene liner cap from step a, place it into a clean and uncontaminated high-pressure reactor of the appropriate volume, and tighten the reactor piston.

[0047] c. Place the high-pressure reactor from step b in a constant temperature chamber, raise the temperature to 220°C at a rate of 62°C / h, keep it at the constant temperature for 3 days, and then lower the temperature to room temperature at a rate of 1°C / h.

[0048] e. Open the high-pressure reactor, remove the sample, and determine the size of the relatively transparent sample as 0.17 × 0.05 × 0.06 mm using X-ray single-crystal diffraction. 3 K2B5O8(OH) nonlinear optical crystal.

[0049] Example 4

[0050] The specific steps for preparing crystals using the chemical reaction 2KBO₂ + 3H₃BO₃ → K₂B₅O₈(OH) + 4H₂O are as follows:

[0051] a. Add KBO2 and H3BO3 to the polytetrafluoroethylene liner of a 23mL high-pressure reactor at a molar ratio of 1:1.5, tighten the lid, and mix thoroughly.

[0052] b. Place the polytetrafluoroethylene liner from step a into a clean, uncontaminated high-pressure reactor of the appropriate volume, and tighten the reactor piston.

[0053] c. Place the high-pressure reactor from step b in a constant temperature chamber, raise the temperature to 220°C at a rate of 70°C / h, keep it at the constant temperature for 3 days, and then lower it to room temperature at a rate of 1°C / h.

[0054] d. Open the high-pressure reactor, remove the sample, and determine the transparent size to be 0.11 × 0.07 × 0.13 mm using X-ray single-crystal diffraction. 3 K2B5O8(OH) nonlinear optical crystal.

[0055] Example 5

[0056] The specific steps for preparing crystals using the chemical reaction 2KBO₂ + 3H₃BO₃ → K₂B₅O₈(OH) + 4H₂O are as follows:

[0057] a. Add KBO2 and H3BO3 to the polytetrafluoroethylene liner of a 23mL high-pressure reactor at a molar ratio of 1:1.5, tighten the lid, and mix thoroughly.

[0058] b. Place the polytetrafluoroethylene liner from step a into a clean, uncontaminated high-pressure reactor of the appropriate volume, and tighten the reactor piston.

[0059] c. Place the high-pressure reactor from step b in a constant temperature chamber, raise the temperature to 220°C at a rate of 73°C / h, keep it at the constant temperature for 3 days, and then lower it to room temperature at a rate of 1°C / h.

[0060] d. Open the high-pressure reactor, remove the sample, and determine the transparent size to be 0.18 × 0.09 × 0.10 mm using X-ray single-crystal diffraction. 3K2B5O8(OH) nonlinear optical crystal.

[0061] Example 6

[0062] The specific steps for preparing crystals using the chemical reaction 2KBF4 + 3H3BO3 → K2B5O8(OH) + 8HF↑ are as follows:

[0063] a. Add KBF4:H3BO3 to the polytetrafluoroethylene liner of a 23mL high-pressure reactor at a molar ratio of 1:1.5, tighten the lid, and mix thoroughly.

[0064] b. Place the polytetrafluoroethylene liner from step a into a clean, uncontaminated high-pressure reactor of the appropriate volume, and tighten the reactor piston.

[0065] c. Place the high-pressure reactor from step b in a constant temperature chamber, raise the temperature to 220°C at a rate of 50°C / h, maintain the temperature for 3 days, and then allow it to cool naturally to room temperature.

[0066] d. Open the high-pressure reactor, remove the sample, and determine the transparent size to be 0.11 × 0.09 × 0.08 mm using X-ray single-crystal diffraction. 3 K2B5O8(OH) nonlinear optical crystal.

[0067] Example 7

[0068] The specific steps for preparing crystals using the chemical reaction 2KBF4 + 3H3BO3 → K2B5O8(OH) + 8HF↑ are as follows:

[0069] a. Add KBF4 and H3BO3 to the polytetrafluoroethylene liner of a 23mL high-pressure reactor at a molar ratio of 1:1.5, tighten the lid, and mix thoroughly.

[0070] b. Place the polytetrafluoroethylene liner from step a into a clean, uncontaminated high-pressure reactor of the appropriate volume, and tighten the reactor piston.

[0071] c. Place the high-pressure reactor from step b in a constant temperature chamber, raise the temperature to 220°C at a rate of 55°C / h, keep it at the constant temperature for 3 days, and then lower it to room temperature at a rate of 1°C / h.

[0072] d. Open the high-pressure reactor, remove the sample, and determine the transparent size to be 0.14 × 0.06 × 0.09 mm using X-ray single-crystal diffraction. 3 K2B5O8(OH) nonlinear optical crystal.

[0073] Example 8

[0074] The specific steps for preparing crystals using the chemical reaction 2KBF4 + 3H3BO3 → K2B5O8(OH) + 8HF↑ are as follows:

[0075] a. Add KBF4 and H3BO3 to the polytetrafluoroethylene liner of a 23mL high-pressure reactor at a molar ratio of 1:1.5, tighten the lid, and mix thoroughly.

[0076] b. Place the polytetrafluoroethylene liner from step a into a clean, uncontaminated high-pressure reactor of the appropriate volume, and tighten the reactor piston.

[0077] c. Place the high-pressure reactor from step b in a constant temperature chamber, raise the temperature to 220°C at a rate of 62°C / h, maintain the temperature for 3 days, and then allow it to cool naturally to room temperature.

[0078] d. Open the high-pressure reactor, remove the sample, and determine the transparent size to be 0.13 × 0.07 × 0.09 mm using X-ray single-crystal diffraction. 3 K2B5O8(OH) nonlinear optical crystal.

[0079] Example 9

[0080] The specific steps for preparing crystals using the chemical reaction 2KBF4 + 3H3BO3 → K2B5O8(OH) + 8HF↑ are as follows:

[0081] a. Add KBF4 and H3BO3 to the polytetrafluoroethylene liner of a 23mL high-pressure reactor at a molar ratio of 1:1.5, tighten the lid, and mix thoroughly.

[0082] b. Place the polytetrafluoroethylene liner from step a into a clean, uncontaminated high-pressure reactor of the appropriate volume, and tighten the reactor piston.

[0083] c. Place the high-pressure reactor from step b in a constant temperature chamber, raise the temperature to 220°C at a rate of 70°C / h, keep it at the constant temperature for 3 days, and then cool it down to room temperature at a rate of 1°C / h or by natural cooling.

[0084] d. Open the high-pressure reactor, remove the sample, and determine the transparent size to be 0.16 × 0.08 × 0.16 mm using X-ray single-crystal diffraction. 3 K2B5O8(OH) nonlinear optical crystal.

[0085] Example 10

[0086] The specific steps for preparing crystals using the chemical reaction 2KBF4 + 3H3BO3 → K2B5O8(OH) + 8HF↑ are as follows:

[0087] a. Add KBF4:H3BO3 to the polytetrafluoroethylene liner of a 23mL high-pressure reactor at a molar ratio of 1:1.5, tighten the lid, and mix thoroughly.

[0088] b. Tighten the polytetrafluoroethylene liner cap containing the mixed reagents from step a, and place it into a clean and uncontaminated high-pressure reactor of the appropriate volume. Tighten the reactor piston.

[0089] c. Place the high-pressure reactor from step b in a constant temperature chamber, raise the temperature to 220°C at a rate of 73°C / h, keep it at the constant temperature for 3 days, and then lower it to room temperature at a rate of 1°C / h.

[0090] e. Open the high-pressure reactor, remove the sample, and determine the size of the relatively transparent sample as 0.13 × 0.07 × 0.05 mm using X-ray single-crystal diffraction. 3 K2B5O8(OH) nonlinear optical crystal.

[0091] Example 11

[0092] Take any one of the K2B5O8(OH) nonlinear optical crystals obtained in Examples 1-10, and apply it according to the attached... Figure 3 As shown, when placed at position 3, at room temperature, using the 1064nm output of a Q-switched Nd:YAG laser as the light source, a significant 532nm frequency-doubled green light output was observed, with an output intensity approximately twice that of KDP under the same conditions.

[0093] Figure 3 As shown, an infrared beam with a wavelength of 1064nm emitted by a Q-switched Nd:YAG laser 1 is incident on a K2B5O8(OH) nonlinear optical crystal 3 through a full-focus lens 2, producing green frequency-doubled light with a wavelength of 532nm. The outgoing beam 4 contains infrared light with a wavelength of 1064nm and green light with a wavelength of 532nm. After being filtered by a filter 5, the frequency-doubled light with a wavelength of 532nm is obtained.

Claims

1. A potassium hydroxyborate nonlinear optical crystal, characterized in that... The crystal has the molecular formula K₂B₅O₈(OH)₂, a molecular weight of 277.26, belongs to the orthorhombic crystal system, and has a space group of [missing information]. Pca 21, with unit cell parameters a = 8.5523(8) Å, b = 7.3326(7) Å, c = 12.9739(10) Å, α = β = γ = 90°, V = 813.60(13) Å. 3 .

2. The method for preparing potassium hydroxyborate nonlinear optical crystal according to claim 1, characterized in that... The crystals were prepared using a hydrothermal method, and the specific procedures are as follows: a. Add KBO2 and H3BO3 or KBF4 and H3BO3 to the polytetrafluoroethylene liner of a 23 mL high-pressure reactor at a molar ratio of 1:1.5, tighten the lid, and mix thoroughly. b. Place the polytetrafluoroethylene liner from step a into a clean, uncontaminated high-pressure reactor of the appropriate volume, and tighten the reactor piston. c. Place the high-pressure reactor from step b in a constant temperature chamber, raise the temperature to 220°C at a rate of 50-73°C / h, keep it at the constant temperature for 3 days, and then cool it down to room temperature at a rate of 1°C / h or by natural cooling. d. Open the high-pressure reactor, take out the sample, and determine the transparent K2B5O8(OH) nonlinear optical crystal by X-ray single crystal diffraction.

3. The use of the potassium hydroxyborate nonlinear optical crystal according to claim 1 in the preparation of frequency doubling generators, up or down frequency converters, or optical parametric oscillators.

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