Strong In-Plane Anisotropy and Giant Second Harmonic Generation Response of Organic Single-Crystalline Microwire Arrays

摘要

Organic nonlinear optical (NLO) crystals play an indispensable role inhigh-performance photonic devices due to their large nonlinear coefficient,fast response time, and low dielectric constant. However, in contrast tothe strides of bulk crystals, researches on the next generation of nanophotonicdevices are ignored to some extent. One of the bottlenecks is thecontrollable manufacturing and patterning of high-quality organic NLOcrystals with the nanometer-scale thickness. Herein, a confined assemblymethod for fabricating the microwire arrays of organic NLO crystal OH1and DAT2 with precise position, flat morphology, high crystallinity, andconsistent crystallographic orientation is reported. Two strong NLO effectsobserved in the experiments are comprehensively studied, includingsecond harmonic generation (SHG) and two-photon excited fluorescence.Furthermore, it is demonstrated that the anisotropic SHG effect dependson both the polarization of incident light and the crystallographic orientationof microwire arrays. Microwire arrays can exhibit large in-planeanisotropy with the polarization ratio up to 0.95 and second-order nonlinearcoefficient up to 55.1 pm V~(?1). This work provides new insights intothe potential applications of organic NLO crystals in integrated opticaldevices.