Achieving the Birefringence Optimization by Methyl Modulation in Organic Nonlinear Optical Crystals
Year: 2024
Type: article
Abstract: Non‐centrosymmetric organics are promising nonlinear optical (NLO) candidates, which always exhibit a short UV absorption cutoff edge, and a strong second harmonic generation (SHG) response, but an overlarge birefringence. Here, in order to optimize the birefringence, the methyl modulation of π‐conjugated organic planar units is proposed and implemented with the urea structure as a template. Thus, N‐methylurea and N,N'‐dimethylurea crystals are obtained by partially replacing hydrogen atoms with methyl groups. This replacement reduces hydrogen donors and weakens interchain hydrogen bonds, which facilitates the decreasing density and the parallel arrangement of π‐conjugated planar units. Hence, both N‐methylurea and N,N'‐dimethylurea crystals exhibit not only an optimized birefringence (N‐methylurea ≈0.099 and N,N'‐dimethylurea ≈0.072 at 546 nm) but also an enhanced SHG response (N‐methylurea ≈1.2 × β‐BaB2O4 and N,N'‐dimethylurea ≈1.9 × β‐BaB2O4), while maintaining a short UV absorption cutoff edge. Therefore, this work provides a novel strategy for the structural design and performance modulation of organic NLO crystals.
Source: Advanced Optical Materials
Authors: Dongling Yang, Hongyuan Sha, Zujian Wang, Rongbing Su, Chao He, Bin Su, Xiaoming Yang, Xifa Long
Institutions: Chinese Academy of Sciences, Fujian Institute of Research on the Structure of Matter, University of Chinese Academy of Sciences, Key Laboratory of Research on Chemistry and Physics of Optoelectronic Materials, Chinese Academy of Sciences, Fuzhou University, Xinjiang Technical Institute of Physics & Chemistry, Technical Institute of Physics and Chemistry
Language: English
Field: Materials Science
Domain: Physical Sciences
Open Access status: bronze
OpenAlex ID: W4402647236