Tantalum phosphate nonlinear optical crystal and preparation method and application thereof

Abstract

The invention discloses a tantalum phosphate nonlinear optical crystal as well as a preparation method and application thereof. The chemical formula of the nonlinear optical crystal is Na11Ta8P7O43, the nonlinear optical crystal belongs to a monoclinic system, the space group is Cc, the nonlinear optical crystal is of a non-centrosymmetric structure, and the cell parameters are respectively # imgabs0 # beta = 92.304 (2) degrees and Z = 4. The tantalum phosphate nonlinear optical crystal belongs to a monoclinic system, the space group is Cc, and the tantalum phosphate nonlinear optical crystal has a good nonlinear optical effect, a short cut-off edge and a high indirect band gap.

Description

Technical Field

[0001] The present invention relates to the technical field of nonlinear optical crystals, and more specifically to a tantalum phosphate nonlinear optical crystal and a preparation method and application thereof. Background Art

[0002] Nonlinear optical crystals can expand the wavelength range of laser radiation through laser frequency doubling, sum frequency, difference frequency, optical parametric oscillation, etc. In the past few decades, nonlinear optical crystals with efficient second harmonic generation have aroused the interest and pursuit of scientists, and great efforts have been made to synthesize nonlinear optical crystals. Excellent and practical second-order nonlinear optical crystals should not only meet the non-centrosymmetric structure, but also have large nonlinear optical coefficients, phase matching, high laser damage threshold, wide optical transparent window, high transmittance, stable physical and chemical properties, easy to grow into large-sized transparent crystals, and easy to process. At present, most of the nonlinear optical crystals used in commercial applications are inorganic crystals, such as KH2PO4 (KDP), KTiOPO4 (KTP), LiNbO3, β-BaB2O4 (BBO), LiB3O5 (LBO), KBe2B2O6F2 (KBBF), etc. However, they all have some disadvantages, such as KBBF is toxic and difficult to grow, KTP crystals cannot completely cover the entire 3-5μm mid-infrared region, and LiNbO3 has a low laser damage threshold. Summary of the invention

[0003] Based on the above facts, the purpose of the present invention is to provide a tantalum phosphate nonlinear optical crystal and its preparation method and application. The tantalum phosphate nonlinear optical crystal belongs to the monoclinic system and has a space group of Cc, and has good nonlinear optical effect, short cutoff edge and high indirect band gap.

[0004] In order to achieve the above object, the present invention adopts the following technical solutions:

[0005] In one aspect, the present invention provides a tantalum phosphate nonlinear optical crystal, wherein the chemical formula of the nonlinear optical crystal is Na 11 Ta8P7 43 , belongs to the monoclinic system, the space group is Cc, it is a non-centrosymmetric structure, and the unit cell parameters are β=92.304(2)° and Z=4.

[0006] Furthermore, according to an ultraviolet-visible-near infrared diffuse reflection test, the nonlinear optical crystal has a reflectivity of 90-93% within a wavelength range of 400-2500 nm.

[0007] Furthermore, the indirect band gap of the nonlinear optical crystal is 5.55 eV.

[0008] The tantalum phosphate nonlinear optical crystal has a large nonlinear optical effect (1×KDP), which is verified by theoretical calculation (d 11 =-0.63pm / V,d 12 =0.78pm / V,d 13 =-0.08pm / V,d 31 =-0.07pm / V,d 32 =0.10pm / V and d 33 =0.03pm / V). Considering the theoretical indirect band gap of 5.55eV and the short ultraviolet cutoff edge, it can be seen that the tantalum phosphate nonlinear optical crystal has a relatively large laser damage threshold and can be used as a mid-infrared nonlinear optical crystal material for high-power lasers. In addition, the tantalum phosphate nonlinear optical crystal also has the advantages of stable physical and chemical properties, good mechanical properties, not easy to deliquesce, and easy to store.

[0009] In another aspect, the present invention provides a method for preparing the tantalum phosphate nonlinear optical crystal as described above, the preparation method comprising the following steps:

[0010] The crystal growth material is heated until it is completely melted, and stirred thoroughly to obtain a mixed melt;

[0011] When the temperature is lowered to 5°C above the saturation temperature of the mixed melt, a seed crystal rod is placed in the mixed melt, and the temperature is lowered to allow the crystal to grow, wherein the seed crystal rod is rotated while the temperature is lowered;

[0012] After the crystal growth is completed, the crystal is lifted from the liquid surface and then cooled to room temperature to obtain the tantalum phosphate nonlinear optical crystal.

[0013] Furthermore, the temperature of the crystal growth material is raised to 950° C., at which the crystal growth material is completely melted.

[0014] Furthermore, the crystal growth material is composed of tantalum phosphate Na 11 Ta8P7 43 It is obtained by mixing polycrystalline material with flux.

[0015] Furthermore, the crystal growth material is obtained by mixing NaH2PO4, Na2HPO4 and Ta2O5 in a Na:Ta:P molar ratio of 11:8:7 with a flux.

[0016] Furthermore, the Na 11 Ta8P7 43 The mass ratio of the total amount of polycrystalline material or NaH2PO4, Na2HPO4 and Ta2O5 to the flux is 1:2; and / or

[0017] The flux is selected from NaH2PO4, or a mixture of NaH2PO4 and Na2HPO4 in a mass ratio of 1:1.

[0018] Furthermore, the Na 11 Ta8P7 43 The preparation of polycrystalline material includes the following steps:

[0019] NaH2PO4, Na2HPO4 and Ta2O5 were weighed in a Na:Ta:P molar ratio of 11:8:7, mixed and ground thoroughly, and placed in a muffle furnace;

[0020] The temperature was raised to 200°C at a rate of 50°C / h and kept at this temperature for 12h; then the temperature was raised to 850°C at the same rate and kept at this temperature for 24h, during which the Na 11 Ta8P7 43 Polycrystalline material.

[0021] In the preparation method of the polycrystalline material, the purpose of first maintaining a constant temperature at 200° C. is to perform a pre-firing process so as to remove water from the raw materials and prepare for subsequent calcination; repeated grinding and mixing during the reaction process is conducive to more uniform mixing of the reaction raw materials and easy synthesis of pure polycrystalline powder.

[0022] Furthermore, the crystal growth temperature range is 900-850° C.; the cooling rate is 0.01-2° C. / h; the seed rod rotation parameter is 20-30 rd / min; and the crystal growth period is 20-30 days.

[0023] Furthermore, the crystal growth temperature range is 900-870° C., 900° C., 870° C., etc. At this time, the transmittance of the grown crystal in the visible light and near-infrared regions is very high, and a large-sized crystal can be obtained.

[0024] Preferably, the cooling rate includes but is not limited to 0.5-2°C / h, 0.5°C / h, 2°C / h, 0.02-0.5°C / d, etc. At this time, the transmittance of the grown crystal in the visible light and near infrared region is very high, and a large-sized crystal can be obtained.

[0025] Preferably, the rotation parameter of the seed rod is 20-26rd / min, 20rd / min, 26rd / min, etc. At this time, the transmittance of the grown crystal in the visible light and near-infrared region is very high, and a large-sized crystal can be obtained.

[0026] Preferably, the crystal growth period includes but is not limited to 20-25 days, 25-30 days, 20 days, 25 days, 30 days, etc.

[0027] Furthermore, the rate of cooling to room temperature includes but is not limited to 5-15°C / h.

[0028] Furthermore, the rate of cooling to room temperature is 10° C. / h. At this time, the transmittance of the grown crystal in the visible light and near infrared regions is very high, and a large-sized crystal can be obtained.

[0029] During the preparation of the tantalum phosphate nonlinear optical crystal, the crystal growth temperature is moderate and the viscosity of the mixed melt is low. The obtained tantalum phosphate crystal is block-shaped rather than layered, and it is relatively easy to further obtain a large-sized single crystal.

[0030] On the other hand, the present invention provides the use of the tantalum phosphate nonlinear optical crystal as described above in the preparation of mid-infrared laser nonlinear optical composite functional devices and piezoelectric devices.

[0031] The tantalum phosphate nonlinear optical crystal has a large nonlinear optical effect, a wide transmission range, and a high indirect band gap. Therefore, the crystal has a good application prospect in the preparation of mid-infrared laser nonlinear optical composite functional devices and piezoelectric devices.

[0032] Furthermore, the tantalum phosphate nonlinear optical crystal is used as a nonlinear optical crystal to make a laser frequency conversion device, which is a frequency doubling device, a sum frequency device and a difference frequency device. It is used to generate at least one output radiation device with a frequency different from the incident electromagnetic wave after passing through at least one nonlinear optical crystal containing at least one beam, wherein at least one nonlinear optical crystal is the tantalum phosphate nonlinear optical crystal.

[0033] Furthermore, the tantalum phosphate nonlinear optical crystal is used as a piezoelectric crystal to make a piezoelectric device, and the piezoelectric device is a piezoelectric oscillator, a filter, a piezoelectric transducer, a piezoelectric pressure sensor, an electroacoustic transducer or an ultrasonic sensor.

[0034] Furthermore, the tantalum phosphate nonlinear optical crystal is used as a ferroelectric crystal.

[0035] Furthermore, the tantalum phosphate nonlinear optical crystal is used as a pyroelectric crystal.

[0036] Furthermore, the tantalum phosphate nonlinear optical crystal is used as a laser matrix material.

[0037] The beneficial effects of the present invention are as follows:

[0038] The nonlinear optical effect of the tantalum phosphate nonlinear optical crystal provided in the present invention is about 1×KDP, and its cutoff edge is shorter than that of LiTaO3 and KTP, and its transmittance is very high in the visible light and near-infrared regions; in the preparation method of the tantalum phosphate nonlinear optical crystal provided in the present invention, a flux method is used for crystal growth, and high-quality large-size single crystals are easily obtained, and the conditions required for the growth method are easy to achieve, the operation is simple, and the raw materials are easy to obtain. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The specific implementation modes of the present invention are further described in detail below in conjunction with the accompanying drawings.

[0040] Figure 1 The powder X-ray diffraction spectrum (PXRD) of the tantalum phosphate compound prepared in Example 1 is shown.

[0041] Figure 2 A schematic diagram of the tantalum phosphate crystal structure prepared in Example 2 is shown.

[0042] Figure 3 The UV-visible-near infrared diffuse reflectance spectrum of the tantalum phosphate crystal powder prepared in Example 2 is shown.

[0043] Figure 4 The mid-infrared transmission spectrum of the tantalum phosphate crystal powder prepared in Example 2 is shown.

[0044] Figure 5 A schematic diagram of the optical path system of a tantalum phosphate crystal as a nonlinear optical device is shown. The infrared light with a wavelength of 1064 nm generated by laser a is converged by lens b and incident on crystal c. Then, it passes through prism d to obtain frequency-doubled light e and unconverted fundamental frequency light f. DETAILED DESCRIPTION

[0045] In order to more clearly illustrate the present invention, the present invention is further described below in conjunction with preferred embodiments and accompanying drawings. Similar components in the accompanying drawings are represented by the same reference numerals. It should be understood by those skilled in the art that the content specifically described below is illustrative rather than restrictive, and should not be used to limit the scope of protection of the present invention.

[0046] Example 1

[0047] Preparation of Tantalum Phosphate Compounds Na by Traditional Solid Phase Reaction 11 Ta8P7 43 , comprising the following steps:

[0048] NaH2PO4, Na2HPO4 and Ta2O5 were weighed according to the stoichiometric ratio (Na:Ta:P=11:8:7), mixed and fully ground, and placed in a muffle furnace; the temperature was raised to 200°C at a rate of 50°C / h and kept at this temperature for 12 hours to remove H2O; the temperature was then raised to 850°C at the same rate and kept at this temperature for 24 hours, during which time the polycrystalline material Na2O5 was repeatedly ground. 11 Ta8P7 43 The powder X-ray diffraction test (PXRD) was performed on it, and the results were as follows Figure 1 As shown in the figure, the results show that the XRD pattern of the polycrystalline powder obtained in the experiment is basically consistent with the theoretical XRD pattern, proving that the target tantalum phosphate compound Na 11 Ta8P7 43 of polycrystalline powder.

[0049] Example 2

[0050] Growth of Tantalum Phosphate Compounds Na by Flux Method 11 Ta8P7 43 Crystal, comprising the steps of:

[0051] NaH2PO4 was selected as flux, and the Na 11 Ta8P7 43 The polycrystalline powder (150.40 g) and flux NaH2PO4 (300.80 g) were mixed in a mortar, ground thoroughly, and added in batches. Melt in a platinum crucible to obtain a mixed melt; place the crucible containing the mixed melt in a crystal growth furnace, heat it to 950°C, and stir it at a constant temperature for 24 hours to melt the raw materials and mix them evenly; lower the platinum wire to extend it into the melt, and cool it to 900°C at a rate of 0.5°C / h, while ensuring that the seed crystal rod rotates at a speed of 20r / min; the growth cycle is 20 days, and after the crystal growth is completed, lift the seed crystal rod, lift the crystal from the liquid surface, and then cool it to room temperature at a rate of 10°C / h to obtain a colorless small single crystal. The obtained crystal was structurally analyzed, and the analysis results confirmed that it was the target tantalum phosphate Na 11 Ta8P7 43 .

[0052] The schematic diagram of the obtained crystal structure is shown in Figure 2 Its UV-visible-near infrared diffuse reflectance spectrum and mid-infrared transmission spectrum are shown in Figure 3 and Figure 4 shown.

[0053] Example 3

[0054] Growth of Tantalum Phosphate Compounds Na by Flux Method 11 Ta8P7 43Crystal, comprising the steps of:

[0055] Select NaH2PO4 as flux, weigh NaH2PO4 (171.18g), Na2HPO4 (32.78g) and Ta2O5 (102.10g), put them into a mortar, mix and grind them, and put them in batches. The mixed melt is melted in a platinum crucible to obtain a mixed melt; the crucible containing the mixed melt is placed in a crystal growth furnace, heated to 950°C, and stirred at a constant temperature for 24 hours; when the temperature is lowered to 5°C above the saturation temperature of the mixed melt, a platinum wire is inserted into the melt; the temperature is lowered to 900°C at a rate of 2°C / d, while the seed crystal rod is rotated at a speed of 20r / min to observe the growth of the crystal; the growth cycle is 20 days, after the crystal growth is completed, the seed crystal rod is lifted, the crystal is lifted off the liquid surface, and then the temperature is lowered to room temperature at a rate of 10°C / h to obtain transparent tantalum phosphate Na 11 Ta8P7 43 .

[0056] Example 4

[0057] Growth of Tantalum Phosphate Compounds Na by Flux Method 11 Ta8P7 43 Crystal, comprising the steps of:

[0058] NaH2PO4 and Na2HPO4 were selected as fluxes. 11 Ta8P7 43 The polycrystalline powder (150.40 g) and flux NaH2PO4 (150.40 g) were mixed and ground in a mortar, and then added in batches. Melt in a platinum crucible to obtain a mixed melt; place the crucible containing the mixed melt in a crystal growth furnace, heat it to 950°C, stir at a constant temperature for 24 hours, and cool it to 5°C above the saturation temperature of the mixed melt; slowly lower the preheated seed crystal into the crystal furnace so that it contacts the surface of the melt. After the seed crystal is introduced, start to cool it down to 870°C at a rate of 0.02-0.5°C / d, while ensuring that the seed crystal rod is rotated at a speed of 26r / min to observe the growth of the crystal; the growth cycle is 25-30 days. After the crystal growth is completed, lift the seed crystal rod, lift the crystal from the liquid surface, and then cool it to room temperature at a rate of 10°C / h to obtain transparent tantalum phosphate Na 11 Ta8P7 43 Crystal.

[0059] Example 5

[0060] The application of infrared laser nonlinear optical composite functional devices includes the following steps:

[0061] Tantalum phosphate Na 11Ta8P7 43 The crystal is cut in a directional manner to obtain a crystal device with a cross-sectional size of 4×4mm and a length of 6mm in the light-transmitting direction; the light-transmitting surfaces at both ends of the crystal device are precisely polished and coated. Figure 5 ), the infrared light with a wavelength of 1064nm generated by laser a is converged by lens b and incident on crystal c, and then passes through dispersion prism d to obtain doubled frequency light e (532nm) and unconverted fundamental frequency light f (1064nm). The nonlinear optical effect is about 1×KDP.

[0062] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not limitations on the implementation methods of the present invention. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is impossible to list all the implementation methods here. All obvious changes or modifications derived from the technical solution of the present invention are still within the protection scope of the present invention.

Claims

1. A tantalum phosphate nonlinear optical crystal, characterized in that: The chemical formula of the nonlinear optical crystal is Na 11 Ta8P7 43 , belongs to the monoclinic system, the space group is Cc, it is a non-centrosymmetric structure, and the unit cell parameters are β=92.304(2)° and Z=4.

2. The tantalum phosphate nonlinear optical crystal according to claim 1, characterized in that: According to an ultraviolet-visible-near infrared diffuse reflection test, the nonlinear optical crystal has a reflectivity of 90-93% within a wavelength range of 400-2500 nm.

3. The tantalum phosphate nonlinear optical crystal according to claim 1, characterized in that: The indirect band gap of the nonlinear optical crystal is 5.55 eV.

4. The method for preparing a tantalum phosphate nonlinear optical crystal according to any one of claims 1 to 3, characterized in that: The steps include: The crystal growth material is heated until it is completely melted, and stirred thoroughly to obtain a mixed melt; When the temperature is lowered to 5°C above the saturation temperature of the mixed melt, a seed crystal rod is placed in the mixed melt, and the temperature is lowered to allow the crystal to grow, wherein the seed crystal rod is rotated while the temperature is lowered; After the crystal growth is completed, the crystal is lifted from the liquid surface and then cooled to room temperature to obtain the tantalum phosphate nonlinear optical crystal.

5. The preparation method according to claim 4, characterized in that: The crystal growth material is composed of tantalum phosphate Na 11 Ta8P7 43 Obtained by mixing polycrystalline material with flux; or The crystal growth material is prepared by mixing NaH2PO4, Na2HPO4 and Ta2O5 in a Na:Ta:P molar ratio of 11:8:7 with a flux.

6. The preparation method according to claim 5, characterized in that: The Na 11 Ta8P7 43 The mass ratio of the total amount of polycrystalline material or NaH2PO4, Na2HPO4 and Ta2O5 to the flux is 1:2; and / or The flux is selected from NaH2PO4, or a mixture of NaH2PO4 and Na2HPO4 in a mass ratio of 1:

1.

7. The preparation method according to claim 5, characterized in that: The Na 11 Ta8P7 43 The preparation of polycrystalline material includes the following steps: NaH2PO4, Na2HPO4 and Ta2O5 were weighed in a Na:Ta:P molar ratio of 11:8:7, mixed and ground thoroughly, and placed in a muffle furnace; The temperature was raised to 200°C at a rate of 50°C / h and kept at this temperature for 12h; then the temperature was raised to 850°C at the same rate and kept at this temperature for 24h, during which the Na 11 Ta8P7 43 Polycrystalline material.

8. The preparation method according to claim 4, characterized in that: The crystal growth temperature range is 900-850° C.; the cooling rate is 0.01-2° C. / h; the seed crystal rod rotation parameter is 20-30 rd / min; and the crystal growth cycle is 20-30 days.

9. The preparation method according to claim 4, characterized in that: The cooling rate to room temperature is 5-15°C / h, preferably 10°C / h.

10. Use of the tantalum phosphate nonlinear optical crystal according to any one of claims 1 to 3 in the preparation of mid-infrared laser nonlinear optical composite functional devices and piezoelectric devices.

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