• Chinese Optics Letters
  • Vol. 20, Issue 3, 031901 (2022)
Xiaojing Wang1、*, Xiaobo Li1, Hui Xu1, Longhui He1, Xuelei Li1, Yulan Dong1, and Xianfeng Chen2、3
Author Affiliations
  • 1Department of Applied Physics, Microelectronic and Physics, Hunan University of Technology and Business, Changsha 410205, China
  • 2Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China
  • 3Key Laboratory for Laser Plasma (Ministry of Education), IFSA Collaborative Innovation Center, Shanghai Jiao Tong University, Shanghai 200240, China
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    Abstract

    When two synchronized laser beams illuminate the inner surface of bulk lithium niobate crystals with magnesium doping (5%/mol MgO:LiNbO3) under the condition of total reflection, semi-degenerate four-wave mixing (FWM) is generated. On this basis, a more sophisticated frequency conversion process on the interface of nonlinear crystal has been researched. The generation mechanism of FWM is associated with the fundamental waves reflected on the inner surface of the nonlinear crystal. Analysis of the phase-matching mechanism confirms that the FWM is radiated by the third-order nonlinear polarized waves, which are stimulated by the third-order nonlinear susceptibility coefficient of the nonlinear crystal. Theoretically calculated and experimentally measured corresponding data have been presented in this article. These results are expected to provide new inspiration for further experimental and theoretical research on frequency conversion in nonlinear crystals.

    1. Introduction

    Researchers pay more and more attention to the investigation of low-dimensional nonlinear processes, such as material physical interface, artificial polarized crystal domain walls[1], and bonding or coating interface of different nonlinear materials[2]. The existence of discrete particles in the interface of nonlinear material[3] has significant impact on the nonlinear frequency conversion. Many second-order nonlinear frequency conversion effects at the interface of nonlinear crystals have been studied extensively. What is more, ultra-short pulses of light can also be observed through the stimulation of sum frequency generated on the domain walls of periodically polarized crystals[46]. Nonlinear Cherenkov cascading difference frequency[7], third harmonics, and other higher harmonics[8,9] generated in the superlattice structure have also been the extensive subject of numerous investigations.