Abstract

We demonstrate theoretically cascaded fourth and second harmonics generation in a periodically oriented nonlinear crystal with a half-order of the periodical orientation. We consider a cascaded process in which four photons of the fundamental harmonic are initially converted into an intermediate photon of the fourth harmonic, which parametrically decays at the second stage into two photons of the second harmonic. We show that fractional phase matching can be achieved by using an asymmetric periodically poled grating. To describe the propagation and transformation of light inside a nonlinear crystal, the quantum spatial Heisenberg equations have been applied, using which the average numbers of photons of the fourth and second harmonics have been calculated as functions of the nonlinear crystal length.

中文翻译：

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具有半阶周期定向的级联第二谐波生成

摘要

我们演示了在周期性定向的非线性晶体中，理论上级联的第四和第二谐波的产生，该晶体具有周期定向的一半。我们考虑一个级联过程，其中基本谐波的四个光子最初被转换为第四谐波的中间光子，该参数在第二阶段参数衰减为第二谐波的两个光子。我们表明分数相位匹配可以通过使用不对称的周期性极化光栅来实现。为了描述光在非线性晶体内部的传播和转换，应用了量子空间海森堡方程，利用该方程，计算了四次和二次谐波的光子平均数，作为非线性晶体长度的函数。