CN1167076A

CN1167076A - Nonlinear optical crystal-magnesium niobic phosphate

Info

Publication number: CN1167076A
Application number: CN 96116947
Authority: CN
Inventors: 刘建国
Original assignee: Individual
Current assignee: Individual
Priority date: 1996-05-30
Filing date: 1996-05-30
Publication date: 1997-12-10

Abstract

The present invention relates to a new-type non-linear optic crystal magnesium niobo-phosphate (molecular formula is Mg2Nb1P2O17, MNP for short). Said invention adopts solid phase synthesis method and uses high-temp sintering process to obtain the MNP compound. Its chemical equation is 2Mg(OH)2.(MgCO3)4.5H2O+10Nb2O5+10NH4H2PO4=5Mg2Nb1P2O17+8CO2+10NH3+17H2O. It adopts molten salt method and uses KF and other fluoride as fusing agent so as to can be successful in monocrystal growth.

Description

Novel nonlinear optical crystal magnesium niobium phosphate

The invention relates to a novel photoelectric functional material, in particular to a brand new nonlinear optical crystal magnesium niobium phosphate (molecular formula is Mg)₂Nb₄P₂O₁₇Abbreviated MNP). By nonlinear effect of the crystal is meant an effect that: when a laser beam passes through a nonlinear optical crystal (e.g., MNP) with a certain polarization direction and incidence direction, the frequency of the laser beam changes.

Fig. 1 shows a typical schematic of this effect.

At present, two prominent crystals exist in the field of visible light nonlinear materials, potassium titanyl phosphate (KTiOPO)₄KTP for short) and lithium niobate (LiNbO)₃LN for short). The nonlinear effect of potassium titanyl phosphate (i.tordjman et al, zeit. fur. krist.139(1974)103) derives from distorted TiO₆Group which has theoutstanding advantage of large nonlinear optical coefficient, compared with potassium dihydrogen phosphate (KH)₂PO₄KDP for short) is higher than one order of magnitude, the light resistance is equivalent to KDP, the frequency doubling efficiency is high, the hardness is high, and the damping is avoided. However, the nonlinear optical coefficient of the magnesium niobate phosphate is not large enough and is slightly smaller than that of the magnesium niobate phosphate of the invention. Nonlinear optics of lithium niobate (g.d.boyd, r.c. miller, k.nassau, w.l.bond and a.sarage, appl.phys.lett., 4, 234(1964))Although the coefficient is large, it is easyAnd (4) light damage. The MNP of the invention, the crystal of which is composed of NbO₆Radical and PO₄Formed by linking radicals, on the one hand, a distorting group NbO within its molecular formula₆The density is relatively high, on the other hand, the crystal is made of NbO due to the structure similar to potassium titanyl phosphate₆Radical and PO₄The groups are connected, so that the magnesium niobate phosphate has higher light damage resistance, and the MNP property is better.

The invention aims to develop a novel optical crystal which can overcome potassium titanyl phosphate (KTiOPO)₄KTP for short) and lithium niobate (LiNbO)₃LN for short) the above-mentioned disadvantages of both crystals.

MNP compounds were synthesized by the following solid phase reaction:

the specific synthesis process is shown in example 1.

After synthesizing MNP polycrystal sample by solid phase reaction, the compound was confirmed to have 1 to 2 times the powder frequency doubling effect of KTP by powder frequency doubling effect measurement. We select molten salt method to proceed crystal growth, using KF, PbF₂Used as a fluxing agent, a platinum crucible used as a container, a resistance furnace used for heating and DWK-702 single machine used for controlling the temperature, and MNP single crystals are successfully grown.

The space group of the new compound is as follows through the measurement of single crystal structure: s₄ ²The unit cell parameter a is 15.60 (angstrom), c is 3.827 (angstrom), c/a is 0.244, hardness is 7Morse, melting point is higher than 1300 deg.c, no deliquescence in air and good mechanical properties.

Due to the invention of MNP, lithium niobate (LiNbO)₃) Meanwhile, for potassium titanyl phosphate, MNP has better nonlinear optical coefficient, and the number of groups which can generate nonlinear optical effect in unit volume is twice that of potassium titanyl phosphate, so the frequency multiplication coefficient ratio of MNP crystal is higher than that of potassium titanyl phosphatePotassium titanyl phosphate is large. Can predict that the MNP will beThe lithium niobate and the potassium titanyl phosphate are respectively substituted to be widely applied to various nonlinear optical fields (such as electro-optical devices, pyroelectric devices, harmonic generation devices, optical parameter and optical amplification devices, optical waveguide devices and the like).

The drawings are now described as follows:

fig. 1 is a typical schematic diagram of nonlinear optical effects when MNP crystals are applied as frequency doubling crystals, where ① is a laser, ②, ③ are mirrors, ④ is a half-wavelength plate, ⑤⑥ is a lens group, ⑦ is a nonlinear optical crystal MNP, a, c are crystal axes, θ is a phase matching angle, ③ is a dispersion prism, and ω and 2 ω are optical frequencies of fundamental and harmonic waves, respectively.

Fig. 2 and 3 are X-ray diffraction patterns, wherein fig. 2 is a diffraction pattern of a sample of solid-phase synthesized MNP powder, and fig. 3 is a diffraction pattern of a MNP single crystal after grinding into powder.

Finally, we present three typical ways of implementing the invention:

example 1, regarding the synthesis of the compound MNP, we obtained it by sintering at high temperature using a solid state synthesis method, whose chemical reaction equation is:

the purity and the manufacturer of the used chemical reagent are as follows: mg (OH)₂·(MgCO₃)₄·5H₂O

(second branch of Shanghai reagent general plant) with Ar content not less than 99.0% Nb₂O₅(the second branch of Shanghai reagent general plant) Ar content is more than or equal to 99.0 percentNH₄H₂PO₄

The feeding amounts of three reagents with Ar content more than or equal to 99.0 percent (the second branch of Shanghai reagent general plant) are as follows: mg (OH)₂·(MgCO₃)₄·5H₂O

48.58 g (0.1mole) Nb₂O₅132.91 g (0.5mole) NH₄H₂PO₄57.52 g (0.5mole)

The specific operation steps are that the raw materials are accurately weighed according to the molar ratio of 1: 1 and are put into a mortar for mixing and fine grinding, then the ground mixture is put into a crucible and is pressed and covered by a medicine spoon, the crucible is put into a muffle furnace for slowly heating to 950 ℃, burning is carried out for two days, the crucible is taken out after cooling is finished, and at the moment, the sample is loose. And then taking out the sample, grinding the sample uniformly again, putting the sample into a crucible, slowly heating the sample to 950 ℃ in a muffle furnace, burning the sample for two days, taking out the sample, and putting the sample into a mortar for grinding to obtain the product. The product was subjected to X-ray diffraction analysis, and the obtained spectrum was consistent with the X-ray diffraction pattern (fig. 2) of MNP single crystal ground into powder.

Example 2, the single crystal growth of MNP was controlled by molten salt method using a homemade resistance furnace and DWK-702 single machine, and the specific operations were: analytically pure KF is selected as fluxing agent, and is prepared with MNP compound (the product obtained in example 1) according to the following molar ratio, KF and MNP are 0.55: 0.45, then a platinum crucible with the diameter of 30 x 30mm is used as a container, the container is placed in a self-made growth furnace, the temperature is increased to 1000 ℃ to melt the raw materials, the temperature is kept for about 1 hour at constant temperature, and then the temperature is reduced to 800 ℃ according to the daily speed of 10 ℃ to obtain MNP crystal, the size of which is 3 x 2 x 1mm³。

Embodiment 3, regarding the application of MNP single crystal as frequency doubling crystal, fig. 1 is a typical schematic diagram, a laser fundamental wave light of a specific wavelength emitted from a laser ①, whose polarization direction is adjusted to be parallel to the a-axis direction of the crystal by a half wavelength plate ④, the traveling direction of the fundamental wave light in the MNP crystal is at an angle θ with the c-axis (i.e., optical axis) of the crystal, which is generally called a phase matching angle, whose value is determined by the wavelength of the laser beam, an outgoing beam of the laser beam after passing through the MNP crystal ⑦ includes both fundamental wave light and frequency doubling light dispersion of ω and 2 ω, respectively, which are separated by a prism ⑧, thereby obtaining an output of the frequency doubling light.

The above is one of the simplest applications of MNP crystals as a nonlinear optical crystal. Use ofThe MNP can also realize sum frequency and difference frequency output, namely when the frequency is respectively omega₁And ω₂The two beams of laser are incident into MNP crystal according to a certain angle and polarization direction and pass through the crystal, and omega can be respectively obtained₁+ω₂，ω₁-ω₂Laser beams of two frequencies. In addition, after a beam of pumping laser is made to enter the MNP crystal through the optical parametric oscillator and the optical parametric amplifier, the angle theta of the MNP crystal is changed to obtain a beam of laser with continuously tunable frequency.

Claims

1. A novel nonlinear optical crystal magnesium niobate phosphate (MNP for short) is characterized in that: the molecular formula is (the molecular formula is Mg)₂Nb₄P₂O₁₇The space group is S₄ ²The unit cell volume is 931 (angstrom), the unit cell parameter a is 15.60 (angstrom), c is 3.827 (angstrom), c/a is 0.244, the hardness is 7Morse (hardness unit), the melting point is higher than 1300 ℃, the paint does not deliquesce in air, and the paint has good mechanicalproperties.

2. A novel nonlinear optical crystal magnesium niobate phosphate (MNP for short) is characterized in that: single crystals can be successfully grown by a molten salt growth method using KF fluoride as a flux.

3. A novel nonlinear optical crystal magnesium niobate phosphate (MNP for short) is characterized in that: it can realize 2-frequency-doubled light output for 1.06 mu m laser beam.

4. A novel nonlinear optical crystal magnesium niobate phosphate (MNP for short) is characterized in that: it can be widely used in harmonic generation device, optical parameter and optical amplification device, and optical waveguide device in visible light region.