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Formation of ordered defect structures in lithium niobate crystals of different chemical composition at non-equilibrium processes of different nature
摘要： Ordered defective structures in lithium niobate crystals have been established. The phenomenon is a result of non-equilibrium processes of a different nature: photo-induced light scattering, laser ablation, and creation of cracks during relieving mechanical stresses. The shape of such structures depends on the nature and energy that affect a crystal. A number of concentric areas with a different density of laser-induced defects with a changed refractive index appear during photoinduced light scattering. Concentric clusters of microdomains appear in a macrodomain of another sign at laser ablation as a result of local switching under impulse laser radiation. A number of microcracks with a fractal structure appear near main macro-crack during cracking under mechanical stress. Thus, appearance of ordered defective structure occurs not only in the local spot of direct exposure to laser radiation, mechanical stress, etc., but also in some volume of a crystal around it.
关键词： Doping,Laser ablation,Lithium niobate,Mechanical stress,Defective structure,Photorefractive effect
更新于2025-11-21 11:24:58
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Study of the scattered light with the strip beam incident to the LiNbO3:Fe crystal
摘要： In this paper, we systematically studied the scattered light when the stripe beam of ordinary polarized light and extraordinary polarized light are incident to the LiNbO3:Fe crystal, respectively. First, we observed the variation of scattered light with the different angle between the stripe beam and the c-axis. And find the scattered light is growing with time along the c-axis direction of the crystal when the e-light is incident; while the scattered light is growing along a special direction which is not the c-axis direction or the stripe direction, when o-light is incident to the crystal. Then we analyzed the causes of these phenomena. In addition, we also studied the diffraction efficiency of o-light and e-light, and the raster image in the crystal.
关键词： nonlinear optics,light scattering,photorefractive effect
更新于2025-09-23 15:23:52
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Optical Electronics (An Introduction) || 8. Fundamental of Nonlinear Optics
摘要： Nonlinear optics is an important branch of modern optics that emerged after the invention of laser. It covers the second, third, and higher-order nonlinear optic effects, and also studies some phenomena such as photorefractive effect and photon echo. In Section 8.2, we introduce the basic knowledge of nonlinear optics phase conjugate. Section 8.3 consider three-wave mixing as an example to discuss the second-order nonlinear optics effect. Sections 8.4 to 8.6 successively discuss the four-wave mixing, near-degenerate four-wave mixing, as well as harmonic oscillation four-wave mixing. In Section 8.8, we describe two kinds of elastic scattering that belong to the third order of nonlinear optics. Photon echo is a transient process along with a special nonlinear optics effect, Photorefractive phenomenon will be descripted in Sections 8.7 and 8.9. Phase conjugate waves can be produced in several nonlinear optics processes. Because phase conjugate wave can be used to correct distorted wavefront, it has important applications in laser nuclear fusion, lens-less imaging, and high-power, and high-light beam quality laser. These topics are also an important part of this chapter.
关键词： phase conjugate,Nonlinear optics,four-wave mixing,three-wave mixing,photon echo,photorefractive effect
更新于2025-09-16 10:30:52
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Biological Lenses as a Photomask for Writing Laser Spots into Ferroelectric Crystals
摘要： Red Blood Cells on the surface of Lithium Niobate crystal can be used as optical lenses for direct writing of laser-induced refractive index changes. The writing process by such photomask made of biological lenses is due to photorefractive effect. Wavefront analysis by digital holographic microscope is performed for deep and accurate evaluation of local refractive index changes. Different focusing properties can be imprinted on the crystal depending on which type of RBC is employed, discocytes or spherical-like ones. The possibility to fix into a solid material the optical fingerprint of RBCs will have impact on both diagnostics and cell\material interfacing.
关键词： photo-lithography,bio-lenses,photorefractive effect,digital holography,RBC
更新于2025-09-12 10:27:22
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High extinction ratio integrated optical modulator for quantum telecommunication systems
摘要： A method for increasing the extinction ratio of integrated optical Mach-Zehnder modulators based on LiNbO3 via the photorefractive effect is proposed. The influence of the photorefractive effect on the X- and Y-splitters of intensity modulators is experimentally studied. An increase in the modulator extinction ratio by 17 dB (from 30 to 47 dB) is obtained. It is shown that fabricated modulators with a high extinction ratio are important for quantum key distribution systems.
关键词： LiNbO3,extinction ratio,photorefractive effect,quantum telecommunication systems,integrated optical modulator
更新于2025-09-09 09:28:46