A flexible functional module to regulate ultraviolet optical nonlinearity for achieving a balance between a second-harmonic generation response and birefringence

Liling Cao; Haotian Tian; Donghong Lin; Chensheng Lin; Feng Xu; Yinglei Han; Tao Yan; Jindong Chen; Bingxuan Li; Ning Ye; Min Luo

doi:10.1039/d2sc01910h

A flexible functional module to regulate ultraviolet optical nonlinearity for achieving a balance between a second-harmonic generation response and birefringence

Chem Sci. 2022 May 20;13(23):6990-6997. doi: 10.1039/d2sc01910h. eCollection 2022 Jun 15.

Authors

Liling Cao^{1

2}, Haotian Tian², Donghong Lin², Chensheng Lin², Feng Xu², Yinglei Han², Tao Yan², Jindong Chen², Bingxuan Li², Ning Ye³, Min Luo^{2

4}

Affiliations

¹ College of Chemistry and Materials Science, Sichuan Normal University Chengdu 610068 P. R. China.
² Key Laboratory of Optoelectronic Materials Chemistry and Physics, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences Fuzhou Fujian 350002 China, lm8901@fjirsm.ac.cn.
³ Tianjin Key Laboratory of Functional Crystal Materials, Institute of Functional Crystal, Tianjin University of Technology Tianjin 300384 China.
⁴ Fujian Science & Technology Innovation Laboratory for Optoelectronic Information of China Fuzhou Fujian 350002 China.

Abstract

Rigid planar π-conjugated groups are adopted for designing ultraviolet (UV) nonlinear optical (NLO) materials extensively. However, for these UV NLO crystals, the realization of a strong second harmonic generation (SHG) response is commonly accompanied by undesired overlarge birefringence. Herein, we propose a new functional gene, the flexible π-conjugated (C₃H₂O₄)^2- group, for designing a UV NLO crystal with a balance between the SHG response and birefringence. Furthermore, the combination of low-coordinated and high-coordinated alkali cations with the flexible (C₃H₂O₄)^2- group results in finding a new mixed alkali malonate, KLi(C₃H₂O₄)·H₂O (KLMW). As expected, KLMW exhibits a strong SHG efficiency (3 × KDP) and moderate birefringence (0.103 @ 1064 nm). In addition, it has a short UV cut-off edge of 231 nm and can be conveniently grown from solution. More importantly, it realized fourth harmonic generation with type-I phase-matching. Therefore, these excellent properties make KLMW a potential practical UV NLO material.