Research On Optic Properties Of MgF₂ And KLTN Crystals

In this paper, the optical properties of two series of crystals (MgF2 and KLTN crystal) were studied.Firstly, the microwave and far-infrared properties of MgF2 which is an important laser luminescence media and optical window material were studied. More than 130 line peaks in electron spin resonance (ESR) spectra were discovered from the shoulder part of the as-grown MgF2 and MgF2:Co crystal at room-temperature experiments. The signals are derived from three different types of multinuclear free radicals from a tentative simulation analysis. This fact indicates that the ground state is high degenerate, and split into near quasi-continuous energy levels like an energy band in an applied magnetic field. It may be a new starting point of solid laser exciter frequency modulation.THz (terahertz) properties of MgF2 crystal and MgF2:Co crystal were measured using transmission THz time domain spectroscopy at frequency range between 0.5 and 2.5 THz. The absorption band edge of the crystal lattice shifts to lower frequency area because of the dopant Co2+, and there is an absorption peak at 1.9THz and the absorption coefficient is more than 70cm-1, the force constant K of F--Co2+ ionic chemical bond stretch vibration calculated from this peak is 3.40×10-2 N/cm. The real part of dielectric functions between 0.5 and 2.5 THz of MgF2 crystal and MgF2:Co crystal are calculated by relations of optical constants. Theε1(ν) of MgF2 crystal varies from 4.67 to 4.73 andε1(ν) of MgF2:Co crystal varies from 4.62 to 5.01.Secondly, we also discussed the growth method and optical properties of a new kind photorefractive crystal K1-yLiyTa1-xNbxO3 (KLTN) used in paraelectric phase. KLTN and macroscopically transparent KLTN:Cu crystals have been grown by Top Seeded Solution growth (TSSG) method with temperature lowering rate 0.3oC/h, seed rotating rate 20r/min and temperature gradient 50oC/cm. X-ray diffraction (XRD) determined that the crystal structure is cubic perovskite structure with lattice...