Lanthanum-niobium-tellurium compound, lanthanum-niobium-tellurium nonlinear optical crystal and preparation method and application thereof

Abstract

The invention discloses a lanthanum-niobium-tellurium compound, a lanthanum-niobium-tellurium nonlinear optical crystal and a preparation method and application of the lanthanum-niobium-tellurium nonlinear optical crystal. The chemical formula of the crystal is LaNbTe2O8, the crystal is of a non-centrosymmetric structure and belongs to an orthorhombic crystal system, the space group is Abm2, and the unit cell parameters are # imgabs0 # alpha = 90 degrees, beta = 90 degrees, gamma = 90 degrees, Z = 4 and # imgabs1 # # imgabs2. The nonlinear optical crystal has a high damage threshold, a large nonlinear optical effect and a wide transmission range, the frequency-doubled effect is equivalent to that of KTP, and the crystal is stable in physicochemical property, good in mechanical property and high in mechanical property. And cutting, polishing and storing are easy.

Description

Technical Field

[0001] The present invention relates to the field of artificial crystal technology, and more specifically, to a lanthanum niobium telluride compound and a lanthanum niobium telluride nonlinear optical crystal, and a preparation method and application thereof. Background Art

[0002] Solid-state lasers have the advantages of small size, easy use, long service life, good beam quality and narrow line width. Solid-state lasers using laser crystals can often only produce lasers with a single wavelength. For example, the common Nd:YAG laser can only produce infrared lasers with a laser wavelength of 1064nm. On this basis, the common method of obtaining lasers in other wavelength ranges is to use nonlinear optical effects to double or adjust the laser light source with a fixed wavelength. Nonlinear optical effects include frequency doubling effects, difference frequency, sum frequency and other frequency conversion effects. Crystal materials with the above effects are collectively referred to as nonlinear optical crystal materials.

[0003] With the continuous development of laser technology, there is a great demand for lasers of different wavelengths in the fields of national defense, medical treatment, communication engineering, lithography technology, laser processing, etc. Therefore, nonlinear optical crystals, as an important means of laser frequency regulation, have important research value.

[0004] Currently, the commonly used nonlinear optical crystal materials mainly include phosphates for visible and ultraviolet bands, including KDP (KH2PO4) and KTP (KTiOPO4), borates for visible, ultraviolet and deep ultraviolet bands, including BBO (β-BaB2O4), LBO (LiB3O5) crystals and KBBF (KBe2BO3F2), as well as sulfides, selenides and phosphides for mid- and far-infrared bands, including AGS (AgGaS2), AGSe (AgGaSe2) and ZGP (ZnGeP2).

[0005] For excellent second-order nonlinear optical crystal materials, their space group must be non-centrosymmetric, and they should have an appropriate refractive index to achieve phase matching, and they need to have a sufficiently large frequency doubling factor, a high laser damage threshold, and a sufficiently wide transmission range. In addition, they must have good physical and chemical stability. However, the currently known crystals all have certain shortcomings and are not satisfactory in practical applications. Therefore, the task of exploring new applicable nonlinear optical crystals is imminent. Summary of the invention

[0006] Based on the above facts, the purpose of the present invention is to provide a lanthanum niobium telluride compound and a lanthanum niobium telluride nonlinear optical crystal and a preparation method and application thereof.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] In one aspect, the present invention provides a lanthanum niobium tellurium compound, wherein the chemical formula of the lanthanum niobium tellurium compound is LaNbTe2O8.

[0009] The lanthanum niobium telluride compound of the present invention is a non-centrosymmetric compound having nonlinear optical properties.

[0010] In another aspect, the present invention provides a method for preparing the lanthanum niobium tellurium compound as described above, the preparation method comprising the following steps:

[0011] The La-containing compound, the Nb-containing compound and the Te-containing compound are mixed and ground in a molar ratio of 1:1:2, and calcined to obtain the lanthanum niobium tellurium compound.

[0012] Furthermore, the calcination temperature is 750° C. and the calcination time is more than 12 hours.

[0013] Furthermore, the La-containing compound is selected from La oxide, La hydroxide, La carbonate, La halide, La nitrate or La oxalate.

[0014] Furthermore, the Nb-containing compound is selected from Nb oxide, Nb hydroxide, Nb halide, Nb nitrate or Nb oxalate.

[0015] Furthermore, the Te-containing compound is selected from Te oxides, Te hydroxides, Te halides or Te nitrates.

[0016] In a third aspect, the present invention provides a lanthanum niobium telluride nonlinear optical crystal, wherein the chemical formula of the crystal is LaNbTe2O8, the crystal is a non-centrosymmetric structure, belongs to the orthorhombic crystal system, has a space group of Abm2, and a unit cell parameter of α=90°, β=90°, γ=90°, Z=4,

[0017] In a fourth aspect, the present invention provides a method for preparing the lanthanum niobium tellurium nonlinear optical crystal as described above, the preparation method comprising the following steps:

[0018] grinding the lanthanum niobium telluride compound, or

[0019] A mixture of a La-containing compound, a Nb-containing compound and a Te-containing compound in a molar ratio of 1:1:2,

[0020] obtaining a grinding material;

[0021] The ground material is melted and placed in a crystal growth furnace, heated to 780-820°C, stirred at a constant temperature for 20-48 hours, preferably 24 hours, and then cooled to 2-10°C above the melt saturation point, a seed crystal is introduced, and the seed crystal rod is rotated while cooling to grow the crystal. After the crystal growth is completed, the crystal is taken out and cooled to room temperature to obtain the nonlinear optical crystal.

[0022] Furthermore, the cooling rate after the seed crystal is introduced is 0.1-5°C / day, and the rotation speed of the seed crystal rod is preferably 15-30r / min.

[0023] Furthermore, during the process of cooling to room temperature, the cooling rate is below 100°C / h, preferably below 20°C / h, and more preferably 20°C / h.

[0024] Furthermore, the La-containing compound is selected from La oxide, La hydroxide, La carbonate, La halide, La nitrate or La oxalate.

[0025] Furthermore, the Nb-containing compound is selected from Nb oxide, Nb hydroxide, Nb halide, Nb nitrate or Nb oxalate.

[0026] Furthermore, the Te-containing compound is selected from Te oxide, Te hydroxide, Te halide or Te nitrate.

[0027] In a fifth aspect, the present invention provides another method for preparing the lanthanum niobium telluride nonlinear optical crystal as described above, the preparation method comprising the following steps:

[0028] The lanthanum niobium telluride compound, or

[0029] A mixture of a La-containing compound, a Nb-containing compound and a Te-containing compound in a molar ratio of 1:1:2

[0030] Mixing with a flux and then grinding to obtain a grind;

[0031] The grinding material is heated to melt, then cooled to completely solidify the melt, and the solidified material is cooled to room temperature to obtain the nonlinear optical crystal.

[0032] Furthermore, the heating rate of heating the abrasive to melt is 20°C / h, and the temperature after heating is 650-750°C.

[0033] Furthermore, the rate of cooling the temperature until the melt solidifies is 0.5-2°C / h, preferably 0.5°C / h.

[0034] Furthermore, the rate of cooling the solidified material to room temperature is 15-20°C / h, preferably 20°C / h.

[0035] Furthermore, the La-containing compound is selected from La oxide, La hydroxide, La carbonate, La halide, La nitrate or La oxalate.

[0036] Furthermore, the Nb-containing compound is selected from Nb oxide, Nb hydroxide, Nb halide, Nb nitrate or Nb oxalate.

[0037] Furthermore, the Te-containing compound is selected from Te oxides, Te hydroxides, Te halides or Te nitrates.

[0038] Furthermore, the molar ratio of the lanthanum niobium tellurium compound to the flux is 1:(4-8).

[0039] Furthermore, the molar ratio of the La-containing compound, the Nb-containing compound and the Te-containing compound to the flux is 1:1:2:(4-8).

[0040] In a sixth aspect, the present invention provides another method for preparing the lanthanum niobium telluride nonlinear optical crystal as described above, the preparation method comprising the following steps:

[0041] The lanthanum niobium telluride compound, or

[0042] A mixture of a La-containing compound, a Nb-containing compound and a Te-containing compound in a molar ratio of 1:1:2

[0043] mixing with a flux and then grinding to obtain a ground material;

[0044] The ground material is melted and placed in a crystal growth furnace, heated to 650-750°C, stirred at a constant temperature for 20-48 hours, preferably 24 hours, and then cooled to 2-10°C above the melt saturation point, a seed crystal is introduced, and the seed crystal rod is rotated while cooling to grow the crystal. After the crystal growth is completed, the crystal is taken out and cooled to room temperature to obtain the nonlinear optical crystal.

[0045] Furthermore, the cooling rate after the seed crystal is introduced is 0.1-5°C / day, and the rotation speed of the seed crystal rod is preferably 15-30r / min.

[0046] Furthermore, during the process of cooling to room temperature, the cooling rate is below 100°C / h, preferably below 20°C / h, and more preferably 20°C / h.

[0047] Furthermore, the La-containing compound is selected from La oxide, La hydroxide, La carbonate, La halide, La nitrate or La oxalate.

[0048] Furthermore, the Nb-containing compound is selected from Nb oxide, Nb hydroxide, Nb halide, Nb nitrate or Nb oxalate.

[0049] Furthermore, the Te-containing compound is selected from Te oxide, Te hydroxide, Te halide or Te nitrate.

[0050] Furthermore, the molar ratio of the lanthanum niobium tellurium compound to the flux is 1:(4-8).

[0051] Furthermore, the molar ratio of the La-containing compound, the Nb-containing compound and the Te-containing compound to the flux is 1:1:2:(4-8).

[0052] In a seventh aspect, the present invention provides the use of the nonlinear optical crystal as described above in the preparation of a nonlinear optical device.

[0053] The beneficial effects of the present invention are as follows:

[0054] The lanthanum niobium tellurium nonlinear optical crystal provided by the present invention has a non-centrosymmetric structure and belongs to the orthorhombic crystal system. The high-quality and large-sized crystal can be prepared by the flux method. The nonlinear optical crystal of the present invention has a high damage threshold, a large nonlinear optical effect, a wide transmission range, and a frequency doubling effect equivalent to KTP. The crystal has stable physical and chemical properties and is easy to cut, polish and store.

[0055] The lanthanum niobium tellurium nonlinear optical crystal provided by the invention has good application prospect in preparing laser nonlinear optical composite functional devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] The specific implementation modes of the present invention are further described in detail below in conjunction with the accompanying drawings.

[0057] Figure 1 The diffuse reflectance spectrum of the LaNbTe2O8 compound prepared in Example 1 is shown.

[0058] Figure 2 The UV-Vis-IR transmission spectrum of the LaNbTe2O8 compound prepared in Example 1 is shown.

[0059] Figure 3 The XRD spectrum of the LaNbTe2O8 compound prepared in Example 1 is shown.

[0060] Figure 4 A schematic structural diagram of the LaNbTe2O8 nonlinear optical crystal in the present invention is shown.

[0061] Figure 5The working principle diagram of the nonlinear optical device prepared by using the LaNbTe2O8 nonlinear optical crystal prepared in Example 3-4 is shown.

[0062] Figure 6 The figure shows the test result of the frequency doubling effect of the LaNbTe2O8 compound prepared in Example 1. DETAILED DESCRIPTION

[0063] 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.

[0064] Example 1

[0065] A method for preparing a LaNbTe2O8 compound comprises the following steps:

[0066] Preparation of LaNbTe2O8 compound by solid phase reaction method:

[0067] Put La2O3 (1.629 g, 0.005 mol), Nb2O5 (1.329 g, 0.005 mol), and TeO2 (3.192 g, 0.02 mol) in a mortar, grind and mix them, then put them into a platinum crucible, put them into a muffle furnace, heat them to 500°C at a rate of 50°C / h for pre-sintering, keep them warm for 24 hours, and then cool them. After cooling to room temperature, take out the sample, grind and mix it again, and then sinter it at 750°C in a muffle furnace for 24 hours to obtain LaNbTe2O8 compound.

[0068] The diffuse reflectance spectrum of the LaNbTe2O8 compound is as follows Figure 1 As shown, the UV-Vis-IR transmission spectrum is Figure 2 As shown, the XRD spectrum is Figure 3 shown.

[0069] According to the attached Figure 1 The ultraviolet cutoff edge of the nonlinear optical crystal of the present invention is about 300nm, which is better than KTP (350nm). Figure 2 And the wave number wavelength conversion formula: wave number = 1 / wavelength, the nonlinear optical crystal of the present invention has a wave number of 2000cm -1 Up to 4000cm -1The transmittance is high, and it is expected to have high transmittance in the mid-infrared band of 2.5-5μm, which is better than the infrared transmittance range of KTP (~4.5μm). The nonlinear coefficient of LaNbTe2O8 was theoretically calculated using the calculation program Crystal. The atomic orbitals of La, Te, B and O were directly imported from the pob-TZVP basis set, and the band structure was calculated using the hybrid function B3LYP. The calculation results are: the band gap size of LaNbTe2O8 is 4.246eV, which is higher than KTP (3.8eV); the maximum nonlinear coefficient d that LaNbTe2O8 can phase match 32 =3.83pm / V, equivalent to KTP (d 32 =3.7 pm / V). In summary, the nonlinear optical crystal of the present invention is a potential mid-infrared nonlinear material with excellent performance.

[0070] Example 2

[0071] The LaNbTe2O8 nonlinear optical crystal is prepared by a flux method, comprising the following steps:

[0072] Using TeO2 as flux, La2O3 (0.651 g, 0.002 mmol), Nb2O5 (0.531 g, 0.002 mol), TeO2 (1.915 g, 0.012 mol) were weighed and ground in a mortar, and then loaded into a Φ20mm×10mm platinum crucible; the temperature was raised to 700°C at a rate of 20°C / h until all the raw materials were melted, the temperature was lowered to 650°C at a rate of 2°C / h until the solution was completely solidified, and then the temperature was lowered to room temperature at a rate of 20°C / h. The obtained product was separated under a polarizing microscope to obtain colorless prismatic crystals LaNbTe2O8.

[0073] Example 3

[0074] The LaNbTe2O8 nonlinear optical crystal is prepared by a melt method, comprising the following steps:

[0075] Weigh 615.007 grams of the synthesized LaNbTe2O8 compound (1 mol), grind and mix in a mortar, melt in batches in a muffle furnace and load into a Φ70mm×70mm crucible; put the melted crucible into a vertical crystal growth furnace, heat it to 800°C, stir at a constant temperature for 24 hours, then cool it to 5°C above the saturation point, introduce a seed crystal and cool it at a rate of 0.5°C / day, start crystal growth at a rotation speed of 10r / min, 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 50°C / h to obtain a transparent LaNbTe2O8 nonlinear optical crystal.

[0076] Example 4

[0077] The LaNbTe2O8 nonlinear optical crystal is prepared by a flux method, comprising the following steps:

[0078] TeO2 was used as a flux, and the molar ratio of solute to flux was 1:4. 615.007 g of the synthesized LaNbTe2O8 compound (1 mol) and 975.594 g of TeO2 (6 mol) were weighed respectively, and after grinding and mixing in a mortar, they were melted in batches and loaded into a crucible of Φ100mm×80mm; the crucible after the melting was placed in a vertical crystal growth furnace, heated to 750°C, stirred at a constant temperature for 24 hours, and then cooled to 5°C above the saturation point, a seed crystal was introduced and the temperature was cooled at a rate of 0.5°C / day, and the crystal growth was started at a rotation speed of 10r / min. After the crystal growth was completed, the seed crystal rod was lifted to lift the crystal from the liquid surface, and then cooled to room temperature at a rate of 20°C / h to obtain a transparent LaNbTe2O8 nonlinear optical crystal.

[0079] In the above embodiment, the structure diagram of the prepared LaNbTe2O8 nonlinear optical crystal is as follows: Figure 4 shown.

[0080] The working principle diagram of the nonlinear optical device prepared by using the LaNbTe2O8 nonlinear optical crystal prepared in the above Examples 3-4 is as follows: Figure 5 shown. Figure 5 Among them, 1-laser, 2-lanthanum niobium telluride nonlinear optical crystal, 3-beam splitter prism.

[0081] The parameters of the LaNbTe2O8 nonlinear optical crystal obtained in the above embodiment were tested by a single crystal diffractometer. The results showed that the chemical formula of the crystal was LaNbTe2O8, the crystal had a non-centrosymmetric structure, belonged to the orthorhombic system, had a space group of Abm2, and had a unit cell parameter of α=90°, β=90°, γ=90°, Z=4,

[0082] Using Kurtz-Perry's powder frequency-doubler effect test method, LaNbTe2O8 compounds and KDP samples (50-100nm in size) of equal particle size were placed in standard plastic sample holders and covered with transparent glass. The wavelength of the incident light and Nd:YAG laser was 1064nm. The test results are shown in Figure 2. Figure 6 As shown, the test results show that the LaNbTe2O8 compound has nonlinear optical properties. Using the same method, the LaNbTe2O8 nonlinear optical crystal obtained in the above embodiment is tested to have nonlinear optical properties.

[0083] 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 lanthanum niobium tellurium compound, characterized in that: The chemical formula of the lanthanum niobium tellurium compound is LaNbTe2O8.

2. The method for preparing lanthanum niobium tellurium compound according to claim 1, characterized in that: The steps include: The La-containing compound, the Nb-containing compound and the Te-containing compound are mixed and ground in a molar ratio of 1:1:2, and calcined to obtain the lanthanum niobium tellurium compound; Preferably, the calcination temperature is 750°C and the time is more than 12 hours; Preferably, the La-containing compound is selected from La oxides, La hydroxides, La carbonates, La halides, La nitrates or La oxalates; Preferably, the Nb-containing compound is selected from Nb oxide, Nb hydroxide, Nb halide, Nb nitrate or Nb oxalate; Preferably, the Te-containing compound is selected from Te oxides, Te hydroxides, Te halides or Te nitrates.

3. A lanthanum niobium telluride nonlinear optical crystal, characterized in that: The chemical formula of the crystal is LaNbTe2O8. The crystal has a non-centrosymmetric structure and belongs to the orthorhombic system. The space group is Abm2 and the unit cell parameters are α=90o, β=90o, γ=90o, Z=4, 4. The method for preparing the lanthanum niobium telluride nonlinear optical crystal according to claim 3, characterized in that: The steps include: grinding the lanthanum niobium telluride compound, or A mixture of a La-containing compound, a Nb-containing compound and a Te-containing compound in a molar ratio of 1:1:2, obtaining a grinding material; The ground material is melted and placed in a crystal growth furnace, heated to 780-820°C, stirred at a constant temperature for 20-48 hours, preferably 24 hours, and then cooled to 2-10°C above the melt saturation point, a seed crystal is introduced, and the seed crystal rod is rotated while cooling to grow the crystal. After the crystal growth is completed, the crystal is taken out and cooled to room temperature to obtain the nonlinear optical crystal.

5. The preparation method according to claim 4, characterized in that: The cooling rate after the seed crystal is introduced is 0.1-5°C / day, and the rotation speed of the seed crystal rod is preferably 15-30r / min; Preferably, during the process of cooling to room temperature, the cooling rate is below 100°C / h, more preferably below 20°C / h.

6. The method for preparing the lanthanum niobium telluride nonlinear optical crystal according to claim 3, characterized in that: The steps include: The lanthanum niobium telluride compound, or A mixture of a La-containing compound, a Nb-containing compound and a Te-containing compound in a molar ratio of 1:1:2 Mixing with a flux and then grinding to obtain a grind; The grinding material is heated to melt, then cooled to completely solidify the melt, and the solidified material is cooled to room temperature to obtain the nonlinear optical crystal.

7. The preparation method according to claim 6, characterized in that: The heating rate of heating the abrasive material to melt is 15-25°C / h, preferably 20°C / h, and the temperature after heating is 650-750°C; Preferably, the rate of cooling until the melt solidifies is 0.5-2°C / h, preferably 0.5°C / h; Preferably, the rate of cooling the solidified material to room temperature is 15-20°C / h, preferably 20°C / h.

8. The method for preparing the lanthanum niobium telluride nonlinear optical crystal according to claim 3, characterized in that: The steps include: The lanthanum niobium telluride compound, or A mixture of a La-containing compound, a Nb-containing compound and a Te-containing compound in a molar ratio of 1:1:2 Mixing with a flux and then grinding to obtain a grind; The abrasive is melted and placed in a crystal growth furnace, heated to 650-750° C., stirred at a constant temperature for 20-48 hours, preferably 24 hours, and then cooled to 2-10° C. above the melt saturation point, a seed crystal is introduced, and the seed crystal rod is rotated while the temperature is reduced to grow the crystal, and after the crystal growth is completed, the crystal is taken out and cooled to room temperature to obtain the nonlinear optical crystal; Preferably, the cooling rate after the seed crystal is introduced is 0.1-5°C / day, and the rotation speed of the seed crystal rod is preferably 15-30r / min; Preferably, during the process of cooling to room temperature, the cooling rate is below 100° C. / h, preferably below 20° C. / h.

9. The preparation method according to any one of claims 4 to 8, characterized in that: The La-containing compound is selected from La oxide, La hydroxide, La carbonate, La halide, La nitrate or La oxalate; The Nb-containing compound is selected from Nb oxide, Nb hydroxide, Nb halide, Nb nitrate or Nb oxalate; The Te-containing compound is selected from Te oxides, Te hydroxides, Te halides or Te nitrates; Preferably, the molar ratio of the lanthanum niobium tellurium compound to the flux is 1:(4-8); Preferably, the molar ratio of the La-containing compound, the Nb-containing compound and the Te-containing compound to the flux is 1:1:2:(4-8).

10. Use of the nonlinear optical crystal according to claim 3 in the preparation of nonlinear optical devices.

Images