绝热级联非线性频率转化和光学超晶格的结构设计

人们对光的研究有着长久的历史，到了现代随着技术的发展，已经不再满足与先前的激光技术，对其提出了更高的要求。其中较为常用和有效的方法是拓宽激光输出波长范围，这也是使用最多的方法。是利用晶体的非线性频率转化技术制作出光学超晶格。非线性光学，在频率转换以及获得新辐射光源领域扮演重要的角色。在波长转化进程中，不同频率的两束光入射到非线性介质材料中,会以倍频(SHG)，混频以及级联的形式产生第三束光。另外, 在超短脉冲光场中，宽带频率转换十分重要，但宽频带光场之间要同时满足相位匹配条件也是十分困难的。绝热演化，是一系列经典和量子系统中非常重要的动力学过程，它可以为系统提供一个强有力的方式使其达到想要的量子态。最近绝热概念被引进了频率变换领域，它不仅可以解决宽频带光场之间的转化问题，还可以同时获得近似完全的转化效率，并且成功的用于超短脉冲转化，获得了近100%超宽带光谱转化效率。利用无衰减泵浦近似下的非线性进程与多能级相干激发量子态系统的类比,获得了新的频率转化思想，即不产生中间光的级联波长转化。

本文主要采用理论分析的方法设计验证绝热超晶格的结构。首先对光学晶格场分布的数值模拟方法进行了介绍；后面对于绝热级联非线性频率转化介绍了级联非线性频率转化工程中的波动方程以及绝热频率的变换；在最后又对光学超晶格的结构又进行了详细的分析介绍，主要介绍准周期、非周期以及无周期的光学晶格。文章主要采用理论分析、验证为主的功能结构设计的方法。

关键词：光学超晶格，绝热级联频率，非线性光学

ABSTRACT

The development of modern optical technology, laser put forward newer and higher requirements. To broaden the range of laser output wavelength, the most commonly used and the most effective method of is using the technology of frequency conversion in a nonlinear crystal, nonlinear optics and in frequency conversion and obtain new radiation light source in the field play an important role. In the wavelength conversion in the process, different frequencies of the two beams of light incident to the nonlinear dielectric materials, with second harmonic generation (SHG) and mixing, as well as the form of cascade produces the third beam. In addition, the ultrashort pulse light field and broadband frequency conversion is very important, but broadband light field to satisfy the phase matching condition is very difficult. Thermal evolution, it is very important in a series of classical and quantum systems dynamics process, it can be for the system to provide a powerful way to achieve the desired quantum state. Recently adiabatic concept was introduced to the field of frequency transform. It can not only solve the problem of broad band optical field between the transformation, can also obtain approximate complete conversion efficiency, and successful for ultrashort pulse conversion, nearly 100% ultra wideband spectrum conversion efficiency. The attenuation pump approximation of nonlinear processes and multi level coherent excitation of analogy to the quantum state of the system were obtained. The new frequency conversion thought that does not produce the intermediate light cascaded wavelength conversion.

In this paper, using the theoretical analysis of the design method is verified for adiabatic superlattice structure. First of optical lattice field distribution numerical simulation methods are introduced; behind the adiabatic cascade nonlinear frequency conversion the cascade nonlinear frequency conversion project in the wave equation and adiabatic frequency transformation; finally the optical super lattice structure and detailed analysis is introduced in. It mainly introduces the quasi periodic, non periodic and non periodic optical lattice. This article mainly adopts theoretical analysis and verification based functional structure design method.