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

Abstract

The application discloses a lanthanum-niobium tellurium compound and a lanthanum-niobium tellurium nonlinear optical crystal as well as a preparation method and application thereof. The chemical formula of the crystal is LaNbTe2O8, the crystal is a non-centrosymmetric structure, belongs to an orthorhombic system, a space group is Abm2, cell parameters are alpha=90 degrees, beta=90 degrees, gamma=90 degrees, and Z=4. The nonlinear optical crystal has a high damage threshold, a large nonlinear optical effect, a wide transmission range, a frequency doubling effect equivalent to KTP, and stable physical and chemical properties of the crystal, and is easy to cut, polish, process and preserve.

Description

Technical Field

[0001] This invention relates to the field of artificial crystal technology. More specifically, it relates to a lanthanum-niobium-tellurium compound and a lanthanum-niobium-tellurium nonlinear optical crystal, as well as their preparation methods and applications. Background Technology

[0002] All-solid-state lasers offer advantages such as small size, ease of use, long lifespan, high beam quality, and narrow linewidth. However, solid-state lasers using laser crystals often only produce laser light of a single wavelength; for example, common Nd:YAG lasers can only produce infrared laser light with a wavelength of 1064 nm. Therefore, a common method for obtaining lasers in other wavelength ranges is to utilize nonlinear optical effects to double or adjust the laser source of a fixed wavelength. Nonlinear optical effects include frequency doubling, difference frequency, and sum frequency transformation effects. Crystal materials exhibiting these effects are collectively referred to as nonlinear optical crystal materials.

[0003] With the continuous development of laser technology, there is a significant demand for lasers of various wavelengths in various production and daily life fields such as national defense, medicine, communications engineering, photolithography technology, and laser processing. Therefore, nonlinear optical crystals, as an important means of laser frequency modulation, have significant research value.

[0004] Currently, commonly used nonlinear optical crystal materials mainly include phosphates for the visible and ultraviolet bands, such as KDP (KH2PO4) and KTP (KTiOPO4); borates for the visible, ultraviolet, and deep ultraviolet bands, such as BBO (β-BaB2O4), LBO (LiB3O5) crystals, and KBBF (KBe2BO3F2); and sulfides, selenides, and phosphides for the mid- and far-infrared bands, such as 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 possess an appropriate refractive index to achieve phase matching. They also need a sufficiently large frequency doubling factor, a high laser damage threshold, and a sufficiently wide transmission range, in addition to good physical and chemical stability. However, currently known crystals all have certain drawbacks and are not entirely satisfactory in practical applications. Therefore, the task of exploring new, applicable nonlinear optical crystals is urgent. Summary of the Invention

[0006] Based on the above facts, the purpose of this invention is to provide a lanthanum-niobium-tellurium compound and a lanthanum-niobium-tellurium nonlinear optical crystal, as well as their preparation methods and applications.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] On one hand, 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-tellurium compound in this invention is a non-centrosymmetric compound with nonlinear optical properties.

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

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

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

[0013] Furthermore, the La-containing compound is selected from La oxides, La hydroxides, La carbonates, La halides, La nitrates, or La oxalates.

[0014] Furthermore, the Nb-containing compound is selected from Nb oxides, Nb hydroxides, Nb halides, Nb nitrates, or Nb oxalates.

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

[0016] Thirdly, this invention provides a lanthanum-niobium-tellurium nonlinear optical crystal with the chemical formula LaNbTe2O8. The crystal has a non-centrosymmetric structure, belongs to the orthorhombic crystal system, has a space group of Abm2, and a unit cell parameter of [missing information]. α=90°, β=90°, γ=90°, Z=4,

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

[0018] Grinding the lanthanum-niobium-tellurium compound, or

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

[0020] Abrasive material is obtained;

[0021] The abrasive is melted and placed in a crystal growth furnace, heated to 780-820℃, and stirred at a constant temperature for 20-48 hours, preferably 24 hours. Then it is cooled to 2-10℃ above the melt saturation point, and a seed crystal is introduced. While cooling, the seed crystal rod is rotated 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 introducing the seed crystal is 0.1-5℃ / day, and the rotation speed of the seed crystal rod is preferably 15-30r / min.

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

[0024] Furthermore, the La-containing compound is selected from La oxides, La hydroxides, La carbonates, La halides, La nitrates, or La oxalates.

[0025] Furthermore, the Nb-containing compound is selected from Nb oxides, Nb hydroxides, Nb halides, Nb nitrates, or Nb oxalates.

[0026] Furthermore, the Te-containing compound is selected from oxides of Te, hydroxides of Te, halides of Te, or nitrates of Te.

[0027] Fifthly, the present invention provides another method for preparing the lanthanum-niobium-tellurium nonlinear optical crystal as described above, the method comprising the following steps:

[0028] The lanthanum-niobium-tellurium compound, or

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

[0030] After mixing with flux, the mixture is ground to obtain abrasive material;

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

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

[0033] Furthermore, the rate of cooling to solidification of the melt is 0.5-2℃ / h, preferably 0.5℃ / h.

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

[0035] Furthermore, the La-containing compound is selected from La oxides, La hydroxides, La carbonates, La halides, La nitrates, or La oxalates.

[0036] Furthermore, the Nb-containing compound is selected from Nb oxides, Nb hydroxides, Nb halides, Nb nitrates, or Nb oxalates.

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

[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-tellurium nonlinear optical crystal as described above, the method comprising the following steps:

[0041] The lanthanum-niobium-tellurium compound, or

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

[0043] After mixing with flux, the mixture is ground to obtain abrasive material;

[0044] The abrasive is melted and placed in a crystal growth furnace, heated to 650-750℃, and stirred at a constant temperature for 20-48 hours, preferably 24 hours. Then it is cooled to 2-10℃ above the melt saturation point, and a seed crystal is introduced. While cooling, the seed crystal rod is rotated 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 introducing the seed crystal is 0.1-5℃ / day, and the rotation speed of the seed crystal rod is preferably 15-30r / min.

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

[0047] Furthermore, the La-containing compound is selected from La oxides, La hydroxides, La carbonates, La halides, La nitrates, or La oxalates.

[0048] Furthermore, the Nb-containing compound is selected from Nb oxides, Nb hydroxides, Nb halides, Nb nitrates, or Nb oxalates.

[0049] Furthermore, the Te-containing compound is selected from oxides of Te, hydroxides of Te, halides of Te, or nitrates of Te.

[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 application of the nonlinear optical crystal described above in the fabrication of nonlinear optical devices.

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

[0054] The lanthanum-niobium-tellurium nonlinear optical crystal provided by this invention has a non-centrosymmetric structure and belongs to the orthorhombic crystal system. High-quality, large-size crystals can be prepared using a flux method. The nonlinear optical crystal of this invention possesses a high damage threshold, a large nonlinear optical effect, a wide transmission range, and a frequency doubling effect comparable to KTP. Furthermore, the crystal exhibits stable physicochemical properties and is easy to cut, polish, and store.

[0055] The lanthanum-niobium-tellurium nonlinear optical crystal provided by this invention has promising application prospects in the fabrication of laser nonlinear optical composite functional devices. Attached Figure Description

[0056] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

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

[0058] Figure 2 The ultraviolet-visible-infrared 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 diagram of the structure of the LaNbTe2O8 nonlinear optical crystal in this invention is shown.

[0061] Figure 5The diagram shows the working principle of the nonlinear optical device prepared using the LaNbTe2O8 nonlinear optical crystal obtained in Examples 3-4.

[0062] Figure 6 The diagram shows the frequency doubling effect test results of the LaNbTe2O8 compound prepared in Example 1. Detailed Implementation

[0063] To more clearly illustrate the present invention, the following description, in conjunction with preferred embodiments and accompanying drawings, further explains the invention. Similar components in the drawings are indicated by the same reference numerals. Those skilled in the art should understand that the specific description below is illustrative rather than restrictive and should not be construed as limiting the scope of protection of the present invention.

[0064] Example 1

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

[0066] LaNbTe2O8 compounds were prepared by solid-state reaction method:

[0067] La2O3 (1.629 g, 0.005 mol), Nb2O5 (1.329 g, 0.005 mol), and TeO2 (3.192 g, 0.02 mol) were placed in a mortar and ground until homogeneous. The mixture was then placed in a platinum crucible and placed in a muffle furnace. The temperature was increased to 500 °C at a rate of 50 °C / h for pre-calcination. After holding at this temperature for 24 h, the mixture was cooled. Once cooled to room temperature, the sample was removed, ground and mixed again, and then sintered in a muffle furnace at 750 °C for 24 h to obtain the LaNbTe2O8 compound.

[0068] The diffuse reflectance spectrum of this LaNbTe2O8 compound is as follows: Figure 1 As shown, the ultraviolet-visible-infrared transmission spectrum is as follows: Figure 2 As shown, the XRD pattern is as follows Figure 3 As shown.

[0069] According to the appendix Figure 1 The nonlinear optical crystal of this invention has an ultraviolet cutoff edge of approximately 300 nm, which is superior to KTP (350 nm). According to the appendix... Figure 2 And the wavenumber-wavelength conversion formula: wavenumber = 1 / wavelength. The nonlinear optical crystal described in this invention operates at a wavenumber of 2000 cm⁻¹. -1 Up to 4000cm -1High transmittance, with expected high transmittance in the mid-infrared band of 2.5-5 μm, superior to the infrared transmittance range of KTP (~4.5 μm). Theoretical calculations of the nonlinear coefficients of LaNbTe2O8 were performed using the computational 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 hybridization function B3LYP. The calculation results show that the band gap of LaNbTe2O8 is 4.246 eV, higher than that of KTP (3.8 eV); the maximum nonlinear coefficient d that LaNbTe2O8 can achieve phase matching is... 32 = 3.83 pm / V, comparable to KTP (d 32 =3.7pm / V). In summary, the nonlinear optical crystal described in this invention is a promising mid-infrared nonlinear material with excellent performance.

[0070] Example 2

[0071] The preparation of LaNbTe2O8 nonlinear optical crystals using a flux method includes the following steps:

[0072] Using TeO2 as a flux, La2O3 (0.651 g, 0.002 mmol), Nb2O5 (0.531 g, 0.002 mol), and TeO2 (1.915 g, 0.012 mol) were weighed and ground in a mortar until homogeneous. The mixture was then placed in a Φ20 mm × 10 mm platinum crucible. The temperature was increased to 700 °C at a rate of 20 °C / h until all the raw materials were melted. The temperature was then decreased to 650 °C at a rate of 2 °C / h until the solution was completely solidified. Finally, the temperature was decreased to room temperature at a rate of 20 °C / h. The resulting product was separated under a polarizing microscope to obtain colorless prismatic crystals LaNbTe2O8.

[0073] Example 3

[0074] The preparation of LaNbTe2O8 nonlinear optical crystals using a melt method includes the following steps:

[0075] 615.007 g of the synthesized LaNbTe2O8 compound (1 mol) was weighed, ground and mixed in a mortar, and then melted in batches in a muffle furnace and placed into a Φ70 mm × 70 mm crucible. The crucible after melting was placed in a vertical crystal growth furnace, heated to 800 °C, stirred at a constant temperature for 24 h, and then cooled to 5 °C above the saturation point. A seed crystal was introduced and cooled at a rate of 0.5 °C / day, with a rotation speed of 10 r / min to start crystal growth. After the crystal growth was completed, the seed crystal rod was lifted to remove the crystal from the liquid surface, and then cooled to room temperature at a rate of 50 °C / h to obtain a transparent LaNbTe2O8 nonlinear optical crystal.

[0076] Example 4

[0077] The preparation of LaNbTe2O8 nonlinear optical crystals using a flux method includes the following steps:

[0078] Using TeO2 as a flux, 615.007 g of the synthesized LaNbTe2O8 compound (1 mol) and 975.594 g of TeO2 (6 mol) were weighed out at a solute to flux molar ratio of 1:4. After grinding and mixing them in a mortar, they were melted in batches and placed into crucibles with a diameter of 100 mm × 80 mm. The crucibles were then placed in a vertical crystal growth furnace, heated to 750 °C, and stirred at a constant temperature for 24 h. Then, the temperature was lowered to 5 °C above the saturation point, and a seed crystal was introduced. The temperature was lowered at a rate of 0.5 °C / day, and the crystal growth was started at a rotation speed of 10 r / min. After the crystal growth was completed, the seed crystal rod was lifted, and the crystal was lifted out of the liquid surface. Then, the temperature was lowered to room temperature at a rate of 20 °C / h, thus obtaining a transparent LaNbTe2O8 nonlinear optical crystal.

[0079] The schematic diagram of the structure of the prepared LaNbTe2O8 nonlinear optical crystal in the above embodiments is shown below. Figure 4 As shown.

[0080] The working principle diagram of the nonlinear optical device prepared using the LaNbTe2O8 nonlinear optical crystal obtained in Examples 3-4 above is shown below. Figure 5 As shown. Figure 5 In the image, 1-laser, 2-lanthanum-niobium-tellurium nonlinear optical crystal, 3-beam splitter.

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

[0082] The Kurtz-Perry powder frequency doubling effect method was used. LaNbTe2O8 compounds and KDP samples (50-100 nm particle size) of equal particle size were placed in standard plastic sample holders and covered with transparent glass. The incident light wavelength of the Nd:YAG laser was 1064 nm. The test results are as follows: Figure 6 As shown, the test results indicate that the LaNbTe2O8 compound possesses nonlinear optical properties. Using the same method, the LaNbTe2O8 nonlinear optical crystal obtained in the above examples was also tested and found to possess nonlinear optical properties.

[0083] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all the implementation methods here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A lanthanum niobium telluride nonlinear optical crystal, characterized in that, The chemical formula of the crystal is LaNbTe2O8, the crystal is a non-central symmetric structure, belongs to the orthorhombic system, and the space group is Abm 2, the unit cell parameters are a=10.9602 Å, b=7.8406 Å, c=8.1507 Å, α=90 o , β=90 o , γ=90 o , Z=4, V=700.43 Å 3 .

2. The method of producing lanthanum niobium telluride nonlinear optical crystal according to claim 1, wherein comprising the following steps: grinding a lanthanum niobium tellurium 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; melting the grinding material and then placing it in a crystal growth furnace, heating to 780-820 ℃, constant temperature stirring for 20-48 h, then cooling to 2-10 ℃ above the saturation point of the melt, introducing a seed crystal, rotating the seed crystal rod while cooling, and growing the crystal, after the crystal growth is completed, removing the crystal, cooling to room temperature, to obtain the nonlinear optical crystal.

3. The preparation method according to claim 2, characterized in that, The cooling rate after introducing the seed crystal is 0.1-5 ℃ / day, and the rotation speed of the seed crystal rod is 15-30 r / min.

4. The production method according to claim 2, characterized by, The cooling rate during the cooling to room temperature is below 100 ℃ / h.

5. The preparation method according to claim 2, characterized in that, The cooling rate during the cooling to room temperature is below 20 ℃ / h.

6. The method of producing lanthanum niobium telluride nonlinear optical crystal according to claim 1, wherein comprising the following steps: a lanthanum niobium tellurium 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 grinding after mixing with a fluxing agent, to obtain a grinding material; heating the grinding material to melt, then cooling to complete solidification of the melt, and then cooling the solidified material to room temperature, to obtain the nonlinear optical crystal.

7. The preparation method according to claim 6, characterized in that, The heating rate of the grinding material to melt is 15-25 ℃ / h, and the temperature after heating is 650-750 ℃.

8. The preparation method according to claim 6, characterized in that, The cooling rate to solidify the melt is 0.5-2 ℃ / h.

9. The preparation method according to claim 6, characterized in that, The cooling rate of the solidified material to room temperature is 15-20 ℃ / h.

10. The method of producing lanthanum niobium telluride nonlinear optical crystal as claimed in claim 1, wherein, comprising the following steps: a lanthanum niobium tellurium 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 grinding after mixing with a fluxing agent, to obtain a grinding material; melting the grinding material and then placing it in a crystal growth furnace, heating to 650-750 ℃, constant temperature stirring for 20-48 h, then cooling to 2-10 ℃ above the saturation point of the melt, introducing a seed crystal, rotating the seed crystal rod while cooling, and growing the crystal, after the crystal growth is completed, removing the crystal, cooling to room temperature, to obtain the nonlinear optical crystal.

11. The method of claim 10, wherein, The cooling rate after introducing the seed crystal is 0.1-5 ℃ / day, and the rotation speed of the seed crystal rod is 15-30 r / min.

12. The method of claim 10, wherein, The cooling rate during the cooling to room temperature is below 100 ℃ / h.

13. The preparation method according to claim 10, characterized in that, The cooling rate during the cooling to room temperature is below 20 ℃ / h.

14. The method of any one of claims 2-13, wherein, The La-containing compound is selected from oxides, hydroxides, carbonates, halides, nitrates or oxalates of La; The Nb-containing compound is selected from oxides, hydroxides, halides, nitrates or oxalates of Nb; The Te-containing compound is selected from oxides, hydroxides, halides or nitrates of Te.

15. The method of any one of claims 6-13, wherein, The molar ratio of the lanthanum niobium tellurium compound to the fluxing agent is 1:(4-8).

16. The method of making according to any one of claims 6-13, wherein, The molar ratio of the La-containing compound, the Nb-containing compound and the Te-containing compound to the fluxing agent is 1:1:2:(4-8).

17. The method of making according to any one of claims 2-13, wherein, The chemical formula of the lanthanum niobium tellurium compound is LaNbTe2O8, and the preparation method of the lanthanum niobium tellurium compound comprises the following steps: 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 telluride compound.

18. The method of claim 17, wherein, The calcination temperature is 750 DEG C, and the time is more than 12 hours.

19. The method of claim 17, wherein, The La-containing compound is selected from an oxide of La, a hydroxide of La, a carbonate of La, a halide of La, a nitrate of La or an oxalate of La; The Nb-containing compound is selected from an oxide of Nb, a hydroxide of Nb, a halide of Nb, a nitrate of Nb or an oxalate of Nb; The Te-containing compound is selected from an oxide of Te, a hydroxide of Te, a halide of Te or a nitrate of Te.

20. Use of the nonlinear optical crystal according to claim 1 in the preparation of a nonlinear optical device.

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