A preparation method and application of a Na.sub.3Ba.sub.2(B.sub.3O.sub.6).sub.2F birefringent crystal, the crystal having a chemical formula of Na.sub.3Ba.sub.2(B.sub.3O.sub.6).sub.2F, and belonging to a hexagonal crystal system, the space group being P6.sub.3/m, and the lattice parameters comprising a=7.3490(6) , c=12.6340(2) , V=590.93(12) .sup.3, Z=2; the crystal is used for an infrared/deep ultraviolet waveband, and is an uniaxial negative crystal, n.sub.e<n.sub.o, the transmission range being 175-3,350 nm, the birefringence of 0.090 (3,350 nm)-0.240 (175 nm), and the crystal being grown by employing a melting method or a flux method; the crystal prepared via the method has a short growth cycle, high crystal quality and large crystal size, is easy to grow, cut, polish and store, is stable in the air, and difficult to deliquesce, and can be used for preparation of various polarization beam polarization beam splitter prism and infrared/deep ultraviolet waveband optical communication elements.

The invention relates to a lithium metaborate crystal and a preparation method and use thereof. The crystal has a chemical formula of LiBO.sub.2, a molecular weight of 49.75, and is a member of the monoclinic crystal system. The crystal has a P2.sub.1/c space group and lattice constants of a=5.85(8) , b=4.35(7) , c=6.46(6) , =115(5) I, and Z=4. The crystal can be applied in wavelengths of infrared-visible-deep ultraviolet, and is grown by utilizing a melt crystallization method or a flux method. The crystal obtained using the method described in the invention is easily grown and processed, and can be used in the manufacture of a polarizing beam splitting prism such as a Glan prism, a Wollaston prism, a Rochon prism or a beam-splitting polarizer, and other optical components, enabling crucial applications in the fields of optics and communication.

The invention relates to a lithium metaborate crystal and a preparation method and use thereof. The crystal has a chemical formula of LiBO.sub.2, a molecular weight of 49.75, and is a member of the monoclinic crystal system. The crystal has a P2.sub.1/c space group and lattice constants of a=5.85(8) , b=4.35(7) , c=6.46(6) , =115(5) I, and Z=4. The crystal can be applied in wavelengths of infrared-visible-deep ultraviolet, and is grown by utilizing a melt crystallization method or a flux method. The crystal obtained using the method described in the invention is easily grown and processed, and can be used in the manufacture of a polarizing beam splitting prism such as a Glan prism, a Wollaston prism, a Rochon prism or a beam-splitting polarizer, and other optical components, enabling crucial applications in the fields of optics and communication.

A high-quality SiC single crystal and a method for producing such a SiC single crystal is provided. In the SiC single crystal, the threading dislocation density including screw dislocation, edge dislocation and micropipe defect is reduced. The method for producing the SiC single crystal according to a solution technique involves bringing an SiC seed crystal into contact with an SiC solution having a temperature gradient in which a temperature of the SiC solution is lower towards the surface of the SiC seed crystal. Growing an SiC single crystal includes setting the temperature gradient of the surface region of the SiC solution to 10 C/cm or below, bringing the (1-100) face of the SiC seed crystal into contact with the SiC solution, and growing an SiC single crystal on the (1-100) face of the seed crystal at a ratio (single crystal growth rate/temperature gradient) of less than 2010.sup.4 cm.sup.2/h.Math. C.

A high-quality SiC single crystal and a method for producing such a SiC single crystal is provided. In the SiC single crystal, the threading dislocation density including screw dislocation, edge dislocation and micropipe defect is reduced. The method for producing the SiC single crystal according to a solution technique involves bringing an SiC seed crystal into contact with an SiC solution having a temperature gradient in which a temperature of the SiC solution is lower towards the surface of the SiC seed crystal. Growing an SiC single crystal includes setting the temperature gradient of the surface region of the SiC solution to 10 C/cm or below, bringing the (1-100) face of the SiC seed crystal into contact with the SiC solution, and growing an SiC single crystal on the (1-100) face of the seed crystal at a ratio (single crystal growth rate/temperature gradient) of less than 2010.sup.4 cm.sup.2/h.Math. C.

Disclosed is a nonlinear optical (NLO) material for use in deep-UV applications, and methods of fabrication thereof. The NLO is fabricated from a plurality of components according to the formula A.sub.qB.sub.yC.sub.z and a crystallographic non-centrosymmetric (NCS) structure. The NLO material may be fabricated as a polycrystalline or a single crystal material. In an embodiment, the material may be according to a formula Ba.sub.3ZnB.sub.5PO.sub.14.

Disclosed is a nonlinear optical (NLO) material for use in deep-UV applications, and methods of fabrication thereof. The NLO is fabricated from a plurality of components according to the formula A.sub.qB.sub.yC.sub.z and a crystallographic non-centrosymmetric (NCS) structure. The NLO material may be fabricated as a polycrystalline or a single crystal material. In an embodiment, the material may be according to a formula Ba.sub.3ZnB.sub.5PO.sub.14.

Disclosed is a nonlinear optical (NLO) material for use in deep-UV applications, and methods of fabrication thereof. The NLO is fabricated from a plurality of components according to the formula A.sub.qB.sub.yC.sub.z and a crystallographic non-centrosymmetric (NCS) structure. The NLO material may be fabricated as a polycrystalline or a single crystal material. In an embodiment, the material may be according to a formula Ba.sub.3ZnB.sub.5PO.sub.14.

Disclosed is a nonlinear optical (NLO) material for use in deep-UV applications, and methods of fabrication thereof. The NLO is fabricated from a plurality of components according to the formula A.sub.qB.sub.yC.sub.z and a crystallographic non-centrosymmetric (NCS) structure. The NLO material may be fabricated as a polycrystalline or a single crystal material. In an embodiment, the material may be according to a formula Ba.sub.3ZnB.sub.5PO.sub.14.

GaAs IR window slabs having largest dimensions that are greater than 8 inches, and preferably greater than 12 inches, are grown using the Horizontal Gradient Freeze (HGF) method. Heat extraction is simplified by using a shallow horizontal boat that is only slightly deeper than the desired window thickness, thereby enabling growth of large slabs while also minimizing material waste and fabrication cost as compared to slicing and shaping thick plates from large, melt-grown boules. Single crystal seeds can be used to optimize the final orientation of the slabs and minimize secondary nucleation, thereby maximizing yield. A conductive doped GaAs layer can be applied to the IR window slab to provide EMI shielding. The temperature gradient during HGF can be between 1? C./cm and 3? C./cm, and the directional solidification can be at a rate of between 0.25 mm/h and 2.5 mm/h.