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

Abstract

The application relates to application of a millimeter-level cadmium ammonium iodide monohydrate second-order nonlinear optical crystal, and 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 application can output 532nm green light under 1064nm laser irradiation, the powder frequency doubling effect thereof under 1064nm laser irradiation is 2.5 times that of KH2PO4, phase matching can be realized, the band gap is 3.8eV, and the optical crystal 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-scale 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 systems have become an important research direction in this field.

[0003] NH4CdI3·H2O is a known compound whose 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 have there been any reports 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 relatively 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. Under 1064nm laser irradiation, its powder frequency doubling effect is 2.5 times that of KH2PO4 (KDP), and phase matching can be achieved. 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 crystal 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: sealing an initial mixed raw material formed by cadmium iodide, ammonium iodide and water in a hydrothermal reactor, heating and then maintaining the temperature, cooling, filtering and washing 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 constant temperature treatment temperature is 40 to 60° C., and the time is 48 to 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 to 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. Using a mild hydrothermal method, high-purity crystalline samples can be obtained in high yield through hydrothermal crystallization at a temperature of 40 to 60°C, and the prepared crystals can reach a length of 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 substrate rock minerals, which is conducive to the dissolution and mixing of insoluble raw materials, accelerating chemical reactions and crystallization rates. Through this heterogeneous reaction, millimeter-sized NH4CdI3·H2O crystals can be prepared.

[0018] (2) The application provides a new inorganic second-order nonlinear optical crystal material NH4CdI3H2O which outputs 532nm laser under 1064nm laser irradiation. The crystal material has large frequency doubling effect, about 2.5 times of the frequency doubling intensity of KDP crystal under 1064nm laser irradiation, and can realize phase matching;

[0019] (3) The optical band gap of the inorganic compound NH4CdI3H2O provided in the application is 3.8eV, which makes the crystal have high laser damage threshold, and thus has wide application prospect in the field of laser frequency conversion. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 is a millimeter-level crystal photograph of the compound NH4CdI3H2O;

[0021] Figure 2 is an X-ray diffraction spectrum comparison;

[0022] Figure 3 is the ultraviolet-visible transmittance spectrum of sample 1#;

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

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

[0025] Figure 6 is the second harmonic signal diagram of sample 1# and KDP sample with the sample size in the range of 105-150μm;

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

[0027] The application will be described in detail below in combination with the drawings and specific examples. The examples are implemented on the premise of the technical scheme of the application, and detailed implementation and specific operation process are given, but the protection scope of the application is not limited to the examples below.

[0028] In the following examples, if no special raw material or processing technology is indicated, it means that the raw material or processing technology is a conventional commercially available raw material or conventional processing technology in the art.

[0029] Example 1:

[0030] Hydrothermal synthesis of millimeter-level crystal

[0031] Cadmium iodide, ammonium iodide and water are mixed in a certain proportion to form the starting raw materials, sealed in a hydrothermal reactor with a polytetrafluoroethylene lining, 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. After filtering and washing, transparent NH4CdI3·H2O bulk crystals can be obtained (taking sample 1# as an example, its length is about 2.4mm, as shown in Figure 2). Figure 1 shown).

[0032] The relationship between the types and ratios of the raw materials in the initial mixture, the crystallization temperature, the crystallization time and the 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, but the peak intensities are slightly different. Taking sample 1# as a typical example, Figure 2 The peak positions of the X-ray diffraction pattern obtained by grinding sample 1# into powder and then conducting X-ray diffraction testing are completely consistent with those of the X-ray diffraction pattern obtained by analyzing and simulating its single crystal X-ray diffraction, indicating that the obtained sample has a high purity.

[0039] UV transmittance spectrum test

[0040] The transmission spectrum of sample 1# was tested on a Cary 5000 UV-visible-near infrared 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. 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 carried out on a Netzsch STA 409PC thermogravimetric analyzer manufactured by Netzsch Equipment Manufacturing Co., Ltd., Germany. Figure 5 As shown, the thermal decomposition temperature of this compound is 90°C.

[0045] Frequency doubling test experiment and results

[0046] The SHG test experiment for sample 1# was conducted as follows: a Q-switched Nd:YAG solid-state laser with a wavelength of 1064 nm was used as the fundamental frequency to illuminate the crystal powder under test. The generated second harmonics were detected using a spectrometer, and the harmonic intensity was displayed using an oscilloscope. The crystal sample and a control KDP crystal were ground separately and sieved using a standard sieve to produce crystals of varying particle sizes: less than 26 μm, 26–50 μm, 50–74 μm, 74–105 μm, 105–150 μm, 150–200 μm, and 200–280 μm. The SHG signal intensity was observed as a function of particle size to determine whether phase matching was achieved. Under the same test conditions, the SHG intensity generated by the sample was compared with that of the KDP sample to determine the relative magnitude of the SHG effect.

[0047] The test results show that the compound NH4CdI3·H2O crystal has a large frequency-doubled effect. Under 1064nm wavelength laser irradiation, the frequency-doubled 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 intended to facilitate understanding and use of the invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the above-described embodiments. 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. Application of a millimeter-scale ammonium cadmium iodide monohydrate second-order nonlinear optical crystal, characterized in that: The optical crystal is used to output 532 nm green light under 1064 nm laser irradiation; 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 and then maintaining the temperature, cooling, filtering and washing to obtain NH4CdI3·H2O crystals, which are the target product; The ratio of the added amounts of cadmium iodide, ammonium iodide and water is 1 mmol: (1-2) mmol: (3-5) mL; The temperature of the constant temperature treatment is 40~60℃ and the time is 48~96h; The rate of the heating process is 5 °C / h; The cooling rate during the cooling process is 0.5~1 ℃ / h; The length of the NH4CdI3·H2O crystal is 2.2-2.6 mm.

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.

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