Application of millimeter-scale ammonium cadmium iodide monohydrate second-order nonlinear optical crystal

Abstract

The invention relates to an application of a millimeter-scale ammonium cadmium iodide monohydrate second-order nonlinear optical crystal. The optical crystal is used for outputting 532nm green light under 1064nm laser irradiation. Compared with the prior art, the millimeter-level second-order nonlinear optical crystal NH4CdI3. H2O provided by the invention can output 532nm green light under the irradiation of 1064nm laser, the powder frequency-doubled effect of the millimeter-level second-order nonlinear optical crystal NH4CdI3. H2O is 2.5 times that of KH2PO4 under the irradiation of 1064nm laser, phase matching can be realized, the band gap of the millimeter-level second-order nonlinear optical crystal NH4CdI3. H2O is 3.8 eV, and the millimeter-level second-order nonlinear optical crystal NH4CdI3. H2O belongs to a wide-band-gap crystal. The optical crystal can be applied to the fields of laser frequency conversion, photoelectric modulation or laser signal holographic storage 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 millimeter-level ammonium cadmium iodide monohydrate second-order nonlinear optical crystal. Background Art

[0002] Nonlinear optical (NLO) crystals are extremely important optoelectronic functional materials and are widely used in solid-state lasers, photoelectron spectroscopy, lithography, laser imaging and other fields. Therefore, the development of NLO crystal materials is of great significance. At present, nonlinear optical crystals used in the infrared band, such as AgGaS2, although they have a large second harmonic generation (SHG) coefficient and a wide infrared transparent window, have a narrow band gap (less than 3eV), resulting in a low laser damage threshold (LDT) and cannot meet the needs of technical applications. In contrast, halides have been regarded as promising infrared NLO materials in recent years due to their wide band gap. Exploring d-based 10 New infrared crystals with high damage threshold in transition metal halide system have become an important research direction in this field.

[0003] NH4CdI3·H2O is a known compound, and its structure was first reported in 1993 in Zeitschrift für Kristallographie-New Crystal Structures (208(2), 376-377). However, to date, there has been no systematic study of the linear and nonlinear optical properties of this crystal, nor has there been any report on its application in the field of nonlinear optics. In addition, the reported method for preparing NH4CdI3·H2O crystals is the aqueous solution volatilization method. The NH4CdI3·H2O crystals obtained by this method are small in size and cannot meet the crystal size requirements for testing their optical properties. Summary of the invention

[0004] The purpose of the present invention is to provide an application of a millimeter-scale ammonium cadmium iodide monohydrate second-order nonlinear optical crystal. The obtained ammonium cadmium iodide monohydrate second-order nonlinear optical crystal can output 532nm green light under 1064nm laser irradiation, and its powder frequency doubling effect under 1064nm laser irradiation is 2.5 times that of KH2PO4 (KDP), and phase matching can be achieved, and its band gap is 3.8eV.

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

[0006] The invention discloses an application of a millimeter-scale ammonium cadmium iodide monohydrate second-order nonlinear optical crystal, wherein the optical crystal is used to output 532nm green light under 1064nm laser irradiation.

[0007] Furthermore, the optical crystal is used in laser frequency conversion, photoelectric modulation or holographic storage of laser signals.

[0008] Furthermore, the optical crystal is used in the field of infrared second-order nonlinear optics.

[0009] Furthermore, the chemical formula of the optical crystal is NH4CdI3·H2O, the molecular weight is 529.16, it belongs to the orthorhombic system, its space group is Pmc21, and the unit cell parameters are α=β=γ=90°, Z=4.

[0010] Furthermore, the optical crystal is prepared by the following method: an initial mixed raw material formed by cadmium iodide, ammonium iodide and water is sealed in a hydrothermal reactor, heated and then subjected to constant temperature treatment, cooled, filtered, and washed to obtain NH4CdI3·H2O crystals, which are the target product.

[0011] Furthermore, the ratio of the added amounts of cadmium iodide, ammonium iodide and water is 1 mmol: (1-2) mmol: (3-5) mL.

[0012] Furthermore, the temperature of the constant temperature treatment is 40-60° C., and the time is 48-96 hours.

[0013] Furthermore, the rate of the heating process is 5°C / h.

[0014] Furthermore, the cooling rate during the cooling process is 0.5-1°C / h.

[0015] Furthermore, the length of the NH4CdI3·H2O crystal is 2.2-2.6 mm.

[0016] Compared with the prior art, the present invention has the following advantages:

[0017] (1) The present invention provides a method for preparing millimeter-sized NH4CdI3·H2O crystals. A mild hydrothermal method is used. Through hydrothermal crystallization at a temperature of 40 to 60°C, a high-purity crystalline sample can be obtained with a high yield, and the length of the prepared crystal can reach 2.4 mm. This synthesis method is simple and suitable for large-scale industrial production. In a sealed hydrothermal reactor, the reaction conditions can simulate the natural formation environment of the bottom rock minerals, which is conducive to the dissolution and mixing of insoluble raw materials, and accelerates the chemical reaction and crystallization rate. Through this heterogeneous reaction, millimeter-sized NH4CdI3·H2O crystals can be prepared.

[0018] (2) The present invention provides a new inorganic second-order nonlinear optical crystal material NH4CdI3·H2O, which outputs 532nm laser under 1064nm laser irradiation. The crystal material has a large frequency doubling effect, which is about 2.5 times the frequency doubling intensity of KDP crystal under 1064nm laser irradiation, and can achieve phase matching;

[0019] (3) The optical band gap of the inorganic compound NH4CdI3·H2O provided in the present application is 3.8 eV, which enables the crystal to have a higher laser damage threshold and thus has broad application prospects in the field of laser frequency conversion. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a millimeter-scale crystal photo of the compound NH4CdI3·H2O;

[0021] Figure 2 It is the comparison of X-ray diffraction patterns;

[0022] Figure 3 is the UV-visible transmission spectrum of sample 1#;

[0023] Figure 4 is the infrared spectrum of sample 1#;

[0024] Figure 5 This is the thermogravimetric analysis spectrum of sample 1#;

[0025] Figure 6 It is the second harmonic signal diagram of sample 1# and KDP sample with size ranging from 105 to 150 μm;

[0026] Figure 7 This is the second harmonic phase matching diagram of sample 1# at a wavelength of 1064nm. DETAILED DESCRIPTION

[0027] 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.

[0028] 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.

[0029] Embodiment 1:

[0030] Hydrothermal Synthesis of Millimeter-Scale Crystals

[0031] Cadmium iodide, ammonium iodide and water are mixed in a certain proportion to form a starting material, sealed in a hydrothermal reactor with a polytetrafluoroethylene liner, 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 at a certain rate, filtered and washed, and transparent NH4CdI3·H2O block crystals can be obtained (taking sample 1# as an example, its length is about 2.4mm, such as Figure 1 shown).

[0032] The relationship between the type and ratio of raw materials in the initial mixture, crystallization temperature, crystallization time and sample number is shown in Table 1.

[0033] Table 1 Correspondence between samples, raw materials and synthesis conditions

[0034]

[0035]

[0036] X-ray diffraction pattern comparison

[0037] 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 5 to 70°, and the scanning step is 0.02°.

[0038] The powder X-ray diffraction test results show that in the XRD spectra of samples 1# to 5#, the positions of the diffraction peaks of each sample are basically the same, and the peak intensities are slightly different. Sample 1# is a typical representative. Figure 2 The peak position of the X-ray diffraction spectrum obtained by grinding sample 1# into powder and then conducting an X-ray diffraction test is completely consistent with that obtained by simulating the X-ray diffraction analysis of its single crystal, indicating that the obtained sample has a high purity.

[0039] UV transmittance spectrum test

[0040] The transmission spectrum test of sample 1# was conducted on a Cary 5000 UV-Vis-NIR spectrophotometer from Agilent Technologies, USA. Figure 3 As shown, the optical band gap of this compound is 3.8 eV.

[0041] Infrared spectrum test

[0042] 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 4As shown, the infrared spectrum test results are consistent with the structure of the compound.

[0043] Thermogravimetric testing

[0044] The thermogravimetric test of sample 1# was conducted on a Netzsch STA 409PC thermogravimetric analyzer manufactured by Netzsch Equipment Manufacturing Co., Ltd., Germany. The results are shown in the figure below. Figure 5 As shown, the thermal decomposition temperature of this compound is 90°C.

[0045] Frequency doubling test experiment and results

[0046] 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. The particle size ranges are less than 26, 26-50, 50-74, 74-105, 105-150, 150-200, and 200-280μm. 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.

[0047] The test results show that the compound NH4CdI3·H2O crystal has a large frequency doubling effect. Under 1064nm wavelength laser irradiation, the frequency doubling signal intensity is 2.5 times that of the control sample KDP crystal (such as Figure 6 ), phase matching can be achieved (such as Figure 7 ).

[0048] 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 millimeter-scale ammonium cadmium iodide monohydrate second-order nonlinear optical crystal, characterized in that: The optical crystal is used to output 532nm green light under 1064nm laser irradiation.

2. The use of a millimeter-scale ammonium cadmium iodide monohydrate second-order nonlinear optical crystal according to claim 1, characterized in that: The optical crystal is used in laser frequency conversion, photoelectric modulation or laser signal holographic storage.

3. The use of a millimeter-scale ammonium cadmium iodide monohydrate second-order nonlinear optical crystal according to claim 1, characterized in that: The optical crystal is used in the field of infrared second-order nonlinear optics.

4. Use of a millimeter-scale ammonium cadmium iodide monohydrate second-order nonlinear optical crystal according to any one of claims 1 to 3, characterized in that: The optical crystal is prepared by the following method: sealing an initial mixed raw material formed by cadmium iodide, ammonium iodide and water in a hydrothermal reaction kettle, heating it up and then subjecting it to constant temperature treatment, cooling it, filtering it, and washing it to obtain NH4CdI3·H2O crystals, which are the target product.

5. The use of a millimeter-scale ammonium cadmium iodide monohydrate second-order nonlinear optical crystal according to claim 4, characterized in that: The ratio of the added amounts of cadmium iodide, ammonium iodide and water is 1 mmol: (1-2) mmol: (3-5) mL.

6. The use of a millimeter-scale ammonium cadmium iodide monohydrate second-order nonlinear optical crystal according to claim 4, characterized in that: The temperature of the constant temperature treatment is 40-60°C and the time is 48-96h.

7. The use of a millimeter-scale ammonium cadmium iodide monohydrate second-order nonlinear optical crystal according to claim 4, characterized in that: The heating rate was 5°C / h.

8. The use of a millimeter-scale ammonium cadmium iodide monohydrate second-order nonlinear optical crystal according to claim 4, characterized in that: The cooling rate during the cooling process is 0.5 to 1°C / h.

9. The use of a millimeter-scale ammonium cadmium iodide monohydrate second-order nonlinear optical crystal according to claim 4, characterized in that: The length of the NH4CdI3·H2O crystal is 2.2-2.6 mm.

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