CN104611769B - A kind of mid-infrared nonlinear optical crystal material RbIO2F2 and its preparation method and application - Google Patents

Abstract

The invention discloses an intermediate infrared nonlinear optical crystal material having the chemical formula of RbIO2F2. The crystallographic space group of the material is Pca21 and the cell parameters are as follows: a=8.567(4) angstroms, b=6.151(3) angstroms, c=8.652(4) angstroms, alpha=beta=gamma=90 degrees, and z=4. The invention also provides a hydrothermal preparation method of the crystal material. The intermediate infrared nonlinear optical crystal material prepared has a quite strong phase-matching second harmonic generation (SHG); the result of a Kurtz powder SHG test indicates that the powder SHG of the crystal material is four times that of potassium dihydrogen phosphate (KDP); the laser-damagedthreshold of the crystal material is at least 700MW/cm<2>, which is more than 23 times the laser-damagedthreshold of the existing commercial intermediate infrared nonlinear optical crystal material AgGaS2; the crystal material has a relatively wide transmission range within the visible region and the intermediate infrared region, and the complete transmission waveband is 0.29-12 microns; the crystal material contains no crystal water, and is stable in air and good in thermal stability; in addition, a single crystal material can be prepared by use of a simple solvent evaporation method.

Description

A kind of mid-infrared nonlinear optical crystal material RbIO2F2 and its preparation method and application

technical field

The invention relates to the field of inorganic chemistry, in particular to a mid-infrared nonlinear optical crystal material and its preparation method and application.

Background technique

Nonlinear optical effects originate from the interaction between laser and medium. When the laser propagates in a medium with non-zero second-order polarizability, nonlinear optical effects such as frequency doubling, sum frequency, difference frequency, and optical parametric amplification will occur. Using the second-order nonlinear optical effect of crystals, nonlinear optical devices such as second harmonic generators, frequency converters, and optical parametric oscillators can be made. In many fields, such as laser technology, atmospheric monitoring, national defense and military, etc., All have important application value. Inorganic nonlinear optical materials play a dominant role in the practical research of second-order nonlinear optical materials. According to the light transmission band and scope of application, inorganic nonlinear optical crystal materials can be divided into nonlinear optical materials in the ultraviolet region, nonlinear optical materials in the visible region and nonlinear optical materials in the infrared region. At present, the inorganic nonlinear optical materials that have been put into practical use in the ultraviolet and visible light regions include BBO (β-barium metaborate), LBO (lithium borate), KDP (potassium dihydrogen phosphate), KTP (potassium titanyl phosphate), etc., which can basically Meet most practical requirements. But for infrared nonlinear optical materials, there is still a gap from practicality. The reason is that the existing infrared nonlinear optical materials, such as AgGaS ₂ , AgGaSe ₂ , etc., have a large second-order nonlinear optical coefficient and a wide transmission range in the infrared region, but the synthesis conditions are harsh and it is not easy Growing large single crystals with high optical quality, especially with a low damage threshold, cannot meet the practical requirements of nonlinear optical crystal materials. The frequency conversion of mid-infrared lasers is of great value in the fields of national economy and national defense, such as the realization of continuously adjustable molecular spectrum, and the realization of continuous laser spectrum in the 3-5 micron band. Therefore, the research on infrared inorganic nonlinear optical materials has become an important topic in the field of nonlinear optical materials research. In the book "Nonlinear Optical Crystal Materials Science" published by Science Press in 2003, it was clearly stated that "in the entire spectral band of nonlinear optics, nonlinear optical crystals in the infrared band are a weak link. Therefore, in this band Research on new frequency conversion crystals needs to be strengthened."

Contents of the invention

The problem to be solved by the present invention is to provide a mid-infrared nonlinear optical crystal material with strong nonlinear optical performance, high laser damage threshold, easy preparation and good stability, its preparation method and application.

Concrete technical scheme of the present invention is as follows:

A mid-infrared nonlinear optical crystal material, the chemical formula is RbIO ₂ F ₂ , the crystal space group is Pca21, and the unit cell parameters are α=β=γ=90°, Z=4.

The above-mentioned mid-infrared nonlinear optical crystal material is prepared by a hydrothermal reaction method: _RbIO is dissolved in HF aqueous solution, and after the liquid is completely volatilized, it is suction-filtered and dried to obtain the mid-infrared nonlinear optical crystal material; the molar amount of the HF The number is more than twice the number of moles of RbIO ₃ .

The preparation method of the above-mentioned mid-infrared nonlinear optical crystal material specifically includes the following steps: adding RbIO to a reaction kettle filled with a 40% HF aqueous solution, sealing it and reacting at 230 degrees Celsius for 24 hours, and then sealing and cooling for ₃ A colorless and transparent filtrate was obtained; the reaction kettle was opened, and the colorless and transparent filtrate was volatilized at room temperature to obtain a colorless block crystal, which was filtered by suction and dried to obtain a mid-infrared nonlinear optical crystal material.

Preferably:

RbIO ₃ : 40% aqueous HF solution with a mass fraction of 1 mmol: 1 ml.

Described reactor, its liner is polytetrafluoroethylene.

The application of the mid-infrared nonlinear optical crystal material in the field of optics.

The invention uses _RbIO3 and HF solution as initial reactants, and prepares mid-infrared nonlinear optical crystal material by hydrothermal reaction method. Experiments show that the frequency doubling effect of the mid-infrared nonlinear optical crystal material powder in the present invention is 4 times that of KDP; phase matching can be realized; the total transmission range is 0.29-12 microns; the laser damage threshold of the crystal is 700MW/cm ² ; Thermal weight loss temperature is 400 ℃.

The inorganic mid-infrared nonlinear optical material RbIO ₂ F ₂ disclosed in the present invention uses [IO ₂ F ₂ ] ^2- as an anion group, and the cation is an alkali metal ion Rb ⁺ . The anionic group of this compound is a distorted [IO ₂ F ₂ ] tetrahedral configuration, and the group forms a non-centrosymmetric arrangement in the crystal, which is conducive to the geometric superposition of the microscopic second-order nonlinear optical effect, showing macroscopic nonlinear optical effects. The space group of this crystal material is Pca21, and the unit cell parameters are α=β=γ=90°, Z=4. This compound does not contain crystal water, and the light transmission range in the mid-infrared region can reach 12 microns; the measured value of the absorption edge in the ultraviolet-visible region can reach 0.29 microns. It has a strong nonlinear optical effect and a high laser damage threshold. In short, it has excellent comprehensive properties and can be used as a nonlinear optical crystal material.

Compared with the prior art, this inorganic mid-infrared nonlinear optical crystal material prepared by the present invention has the following advantages:

1. It has a strong frequency-doubling effect (SHG) capable of phase matching. The Kurtz powder frequency-doubling test results show that its powder frequency-doubling effect is 4 times that of potassium dihydrogen phosphate (KDP);

2. The laser damage threshold reaches at least 700MW/cm ² , which is more than 23 times the laser damage threshold of the current commercial mid-infrared nonlinear optical crystal material AgGaS ₂ .

3. The powder of this compound has a wide transmission range in the visible light region and mid-infrared light region, and the complete transmission band is 0.29-12 microns;

4. Does not contain crystal water, is stable to air, and has good thermal stability, and the thermal weight loss temperature reaches 400 degrees Celsius;

5. A simple solvent evaporation method can be used to prepare single crystal materials.

6. The mid-infrared nonlinear optical crystal material provided by the present invention has a strong second-order nonlinear optical effect that can be phase-matched, has a wide light transmission window in the visible light region and infrared light region, and has a high laser damage threshold and Thermal stability, simple synthetic method, short reaction time, mild experimental conditions, high product purity, can be widely used in the field of optics.

Description of drawings

Fig. 1 is the unit cell packing figure of RbIO ₂ F ₂ crystal of the present invention;

Figure 2 is the distorted [IO ₂ F ₂ ] tetrahedral configuration in RbIO ₂ F ₂ of the present invention;

Fig. 3 is the ultraviolet-visible-near-infrared absorption spectrum of RbIO ₂ F ₂ powder of the present invention;

Fig. 4 is the Fourier transform attenuated total reflection infrared spectrum of RbIO ₂ F ₂ powder of the present invention;

Fig. 5 is the thermogravimetric spectrum of RbIO ₂ F ₂ powder of the present invention;

Fig. 6 is the frequency doubling effect phase matching spectrum of the RbIO ₂ F ₂ powder of the present invention.

detailed description

The technical solutions of the present invention will be further described below in conjunction with specific embodiments.

Example 1:

3 millimoles of RbIO ₃ are filled with 3 milliliters of mass fraction of 40% HF aqueous solution in the polytetrafluoroethylene-lined reactor, sealed, reacted at 230 degrees Celsius for 24 hours, then sealed and cooled for 3 days, obtained The transparent filtrate was allowed to slowly volatilize at room temperature to obtain colorless massive crystals, which were filtered by suction and dried to obtain a mid-infrared nonlinear optical crystal material.

Example 2:

3 millimoles of RbIO ₃ were added into a reactor containing 10 milliliters of HF aqueous solution with a mass fraction of 30%, reacted at 230 degrees Celsius for 24 hours after sealing, then sealed and cooled for 10 days, and the reaction solution was placed at room temperature to volatilize freely. After the liquid evaporates completely, a colorless massive crystal is obtained, which is filtered by suction and dried to obtain a mid-infrared nonlinear optical crystal material.

Example 3:

₃ millimoles of RbIO Adding 30 milliliters of mass fraction is 50% in the reaction kettle of HF aqueous solution, reacted at 230 degrees Celsius for 24 hours after sealing, then sealed and cooled for 10 days to obtain a colorless and transparent filtrate; open the reaction kettle, The colorless transparent filtrate was volatilized at room temperature to obtain colorless massive crystals, which were filtered by suction and dried to obtain mid-infrared nonlinear optical crystal materials.

In the above embodiments, it is necessary to satisfy that the number of moles of HF is more than twice the number of moles of RbIO ₃ . At room temperature, _RbIO3 reacts slowly with HF aqueous solution, and can accelerate the reaction process and crystal formation under high temperature and high pressure. Preferably, it is best to react at 230 degrees Celsius for 24 hours after sealing; when the volume of HF aqueous solution is too large, volatilization will increase. time, preferably, 1 mmol RbIO ₃ is added per mL of HF aqueous solution (40%).

Performance Testing

The infrared nonlinear optical crystal material prepared in Example 1 is detected as follows:

(1) Powder frequency doubling effect experiment:

The frequency doubling performance of infrared nonlinear optical crystal materials is obtained by the Kurtz-Perry powder frequency doubling test method. The specific operation steps are as follows:

Grind the mid-infrared nonlinear optical crystal material prepared in Example 1 into a powder with a particle size of about 100 to 125 microns, then install it in a sample cell with glass windows on both sides, then place the sample cell on the laser optical path, and use Nd: The YAG pulsed laser is used as the light source to generate fundamental frequency light with a wavelength of 1064 nanometers into the sample cell. The KDP single crystal powder with a particle size of about 100-125 microns is used as the standard sample, and the signal is displayed on the oscilloscope through the photomultiplier tube. The Kurtz powder frequency doubling test results show that the powder frequency doubling effect of the mid-infrared nonlinear optical crystal material prepared in Example 1 is 4 times that of KDP.

(2) Whether the frequency doubling effect of RbIO ₂ F ₂ can be phase matched test:

The mid-infrared nonlinear optical crystal material prepared in Example 1 was ground and sieved into powders of different particle size ranges (20-40, 40-60, 60-80, 80-100, 100-125, 125-150, 150-200, 200- 300, 300 ~ 400 and 400 ~ 500 microns), and then installed in the sample cell with glass windows on both sides, and then put the sample cell on the laser optical path, using Nd:YAG pulsed laser as the light source to generate fundamental frequency light with a wavelength of 1064 nm Enter the sample cell, the signal is displayed on the oscilloscope through the photomultiplier tube, and the intensity of the frequency-doubling signal of different particle sizes is tested. After drawing, analyze and judge whether the frequency-doubling effect of the compound can be phase-matched.

Figure 1 and Figure 2 are the unit cell packing diagram and [IO ₂ F ₂ ] tetrahedral configuration diagram of RbIO ₂ F ₂ crystal, respectively. The structure of RbIO ₂ F ₂ is simple, I, O, and F atoms form a distorted tetrahedral structure, and the length of the I—O bond formed by O atoms and I atoms is The length of the I—F bond formed by the F atom and the I atom is and All [IO ₂ F ₂ ] tetrahedral groups form a noncentrosymmetric arrangement in the crystal.

Figure 3 is the ultraviolet-visible spectrum diagram of the powder material. It can be seen from Figure 3 that its ultraviolet absorption edge is at 0.29 microns, and the calculated band gap is 4.2 electron volts.

Fig. 4 is the Fourier transform attenuated total reflection infrared spectrogram of the mid-infrared nonlinear optical crystal material prepared in Example 1. As can be seen from the infrared spectrogram, the material does not have any absorption between 4000 wavenumbers and 810 wavenumbers, which shows that the The material has no absorption between 4000 wavenumber and 810 wavenumber. Based on the results of the ultraviolet-visible spectrum and the infrared spectrum, it can be deduced that the material has a wide light transmission range, and the light transmission range is from 0.29 microns to 12 microns. The thermal analysis of the material and the test results of powder frequency doubling phase matching are shown in Figure 5 and Figure 6. It can be seen from Figure 5 that the material begins to lose weight above 400 degrees Celsius and has good thermal stability. It can be seen from Figure 6 It is found that the frequency doubling effect of this material can be phase-matched.

Claims (7)

1. a kind of mid-infrared non-linear optical crystal material it is characterised in that: its chemical formula be rbio₂f₂, crystal space group is Pca21, cell parameter is:α=β=γ=90 °, z=4.

2. mid-infrared non-linear optical crystal material according to claim 1 it is characterised in that: its powder SHG effect is 4 times of potassium dihydrogen phosphate；It is 0.29-12 micron that full impregnated crosses scope.

3. mid-infrared non-linear optical crystal material according to claim 1 and 2 it is characterised in that: the laser of its crystal Damage threshold is at least 700mw/cm², thermal weight loss temperature be 400 DEG C.

4. the mid-infrared non-linear optical crystal material described in any one of claim 1-3 preparation method it is characterised in that: tool Body comprises the following steps: by rbio₃Adding fills in the reactor of hf aqueous solution that mass fraction is 40%, wherein, described hf Molal quantity be rbio₃More than the twice of molal quantity；React under 230 degrees Celsius after sealing 24 hours, then seal cooling 3 My god, obtain water white transparency filtrate；Open reactor, water white transparency filtrate is put and volatilizees at room temperature, obtain colourless block crystalline substance Body, sucking filtration, it is dried, that is, obtain mid-infrared non-linear optical crystal material.

5. mid-infrared non-linear optical crystal material according to claim 4 preparation method it is characterised in that: rbio₃: Mass fraction is 40% hf aqueous solution=1 mM: 1 milliliter.

6. mid-infrared non-linear optical crystal material according to claim 4 preparation method it is characterised in that: described Reactor, its liner is politef.

7. the mid-infrared non-linear optical crystal material described in any one of claim 1-3 is in the application of optical field.