Open AccessOrganic Broadband THz Generators Optimized for Efficient Near‐Infrared Optical Pumping
Author(s) -
Shin MyeongHoon,
Kim Won Tae,
Kim SeIn,
Kim SeungJun,
Yu In Cheol,
Kim SangWook,
Jazbinsek Mojca,
Yoon Woojin,
Yun Hoseop,
Rotermund Fabian,
Kwon OPil
Publication year - 2020
Publication title -
advanced science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.388
H-Index - 100
ISSN - 2198-3844
DOI - 10.1002/advs.202001738
Subject(s) - terahertz radiation , materials science , optoelectronics , optical rectification , laser , femtosecond , infrared , energy conversion efficiency , crystal (programming language) , optics , nonlinear optics , refractive index , physics , computer science , programming language
New organic THz generators are designed herein by molecular engineering of the refractive index, phonon mode, and spatial asymmetry. These benzothiazolium crystals simultaneously satisfy the crucial requirements for efficient THz wave generation, including having nonlinear optical chromophores with parallel alignment that provide large optical nonlinearity; good phase matching for enhancing the THz generation efficiency in the near‐infrared region; strong intermolecular interactions that provide restraining THz self‐absorption; high solubility that promotes good crystal growth ability; and a plate‐like crystal morphology with excellent optical quality. Consequently, the as‐grown benzothiazolium crystals exhibit excellent characteristics for THz wave generation, particularly at near‐infrared pump wavelengths around 1100 nm, which is very promising given the availability of femtosecond laser sources at this wavelength, where current conventional THz generators deliver relatively low optical‐to‐THz conversion efficiencies. Compared to a 1.0‐mm‐thick ZnTe crystal as an inorganic benchmark, the 0.28‐mm‐thick benzothiazolium crystal yields a 19 times higher peak‐to‐peak THz electric field with a broader spectral bandwidth (>6.5 THz) when pumped at 1140 nm. The present work provides a valuable approach toward realizing organic crystals that can be pumped by near‐infrared sources for efficient THz wave generation.