飞秒激光直写铌酸锂、钽酸锂光波导的非互易特性及其应用研究

Due to their excellent electro-optical and nonlinear optical properties, lithium niobate and lithium tantalate single crystals are widely used in the fields of nonlinear optics and integrated optics. The femtosecond laser direct writing method can be used to modulate the optical properties of optical materials to form integrated optical devices with versatile functions. The recent results show that when the femtosecond laser was focused into lithium niobate or lithium tantalate crystals, the tracks formed in the crystal and/or the ferroelectric micro-domain structure exhibit unique nonreciprocity. The nonreciprocity of scanning direction and forming track in lithium niobate mainly exhibits in the positive and negative y-axis direction, but the research results of lithium tantalate tracks are relatively few. Although the results show that the crystal anisotropy and the thermoelectric effect lead to nonreciprocity, the mechanism of its micro-mechanism is still unclear. Due to the widespread application of femtosecond laser in the field of micro/nano processing of optical materials, it is an urgent issue to clarify the nonreciprocal mechanism during the interaction of femtosecond laser with lithium niobate and lithium tantalate crystals. We intend to study the nonreciprocity and its mechanism of the track formation and ferroelectric domain reversion when the fiber femtosecond laser focused into lithium niobate and lithium tantalate crystals, which is critical for a more solid and abundant theoretical basis of interaction between the ferroelectric single crystal and femtosecond laser. Our project will lead to the fresh ideas and strategies for the demonstration of novel ferroelectric integrated optical thin film devices.

铌酸锂和钽酸锂晶体具有优良的电光和非线性光学性质，在非线性光学和集成光学中具有广泛的应用。飞秒激光直写方法可以对光学材料的光学性质进行有效的调制从而形成功能各异的光子集成器件。近来研究结果认为当飞秒激光脉冲与铌酸锂晶体相互作用时，晶体中形成的径迹以及铁电微畴结构体现出非同寻常的非互易特性 (Non-Reciprocity)。当飞秒激光沿着相反方向在铌酸锂晶体中扫描反时，所形成的径迹极为不同，但是对于钽酸锂晶体径迹的研究结果相对较少。尽管研究结果表明晶体的各向异性以及热电效应导致了非互易性，但是其微观机制机理尚不明晰。明晰飞秒激光与铌酸锂、钽酸锂晶体相互作用时的非互易性机制成为亟待解决的问题。我们拟研究光纤飞秒激光在铌酸锂、钽酸锂晶体中形成径迹和微观铁电畴改变的非互易性，为飞秒激光与铁电单晶体相互作用提供新的理论机制阐释，也为新型铁电集成光学薄膜器件的研制提供新的思路，开拓新途径。

铌酸锂和钽酸锂晶体具有优良的电光和非线性光学性质，在非线性光学和集成光学中具有.广泛的应用。飞秒激光直写方法可以对光学材料的光学性质进行有效的调制从而形成功能各异的光子集成器件。近来研究结果认为当飞秒激光脉冲与铌酸锂晶体相互作用时，晶体中形成的径迹以及铁电微畴结构体现出非同寻常的非互易特性 (Non-Reciprocity)。当飞秒激光沿着相反方向在酸锂晶体中扫描反时，所形成的径迹极为不同，但是对于钽酸锂晶体径迹的研究结果相对较少。尽管研究结果表明晶体的各向异性以及热电效应导致了非互易性，但是其微观机制机理尚不明晰。明晰飞秒激光与铌酸锂、钽酸锂晶体相互作用时的非互易性机制成为亟待解决的问题。我们拟研究光纤飞秒激光在铌酸锂、钽酸锂晶体中形成径迹和微观铁电畴改变的非互易性，为飞秒激光与铁电单晶体相互作用提供新的理论机制阐释，也为新型铁电集成光学薄膜器件的研制提供新的思路，开拓新途径。.我们在铌酸锂和钽酸锂中利用飞秒激光直写制备出了双线及cladding形式的波导，对其模式调制、掺入损耗等线性光学特性进行了详细研究，对所形成的铌酸锂、钽酸锂光波导的非线性性能，包括其在近红外波段的拉曼、可调谐激光输出等特性进行了探索。我们对x及z切向的晶体进行了多速度、多方向的飞秒激光扫描，结果如发现cladding形式的波导可以避免铌酸锂及钽酸锂晶体中的激光扫描非互易效应对波导性能所产生的影响，这极大的提高了飞秒加工在晶体中的兼容性和加工效率，为在晶体材料中高效构建三维光互联结构提供了实验基础。