Terahertz Phonon Mode Engineering of Highly Efficient Organic Terahertz Generators

• DOI: 10.1002/adfm.201605583
• Publication Date: 2017-03-03T12:52:50Z
• Authors: Seung‐Heon Lee; Bong Joo Kang; Ba‐Wool Yoo; Seung‐Chul Lee; Seung‐Jun Lee; Mojca Jazbinsek; Hoseop Yun; Fabian Rotermund; O‐Pil Kwon
• Keywords: Optical rectification; Crystal (programming language)

For terahertz (THz) wave generators based on organic electrooptic crystals, their intrinsic phonon modes are playing an essential role in THz generation characteristics. Here, this study proposes effective design strategy for mode engineering of salt crystals efficient optical‐to‐THz frequency conversion. To reduce phonon‐mode intensity, strongly electronegative trifluoromethyl group acting as strong hydrogen‐bond acceptor is incorporated into molecular anions. New 2‐(4‐hydroxy‐3‐methoxystyryl)‐1‐methylquinolinium 4‐(trifluoromethyl)benzenesulfonate (HMQ‐4TFS) exhibit a relatively small absorption coefficient the spectral range between 0.5 and 4 THz, which attributed to suppressed vibrations due hydrogen bonds involving 4TFS anion. In addition, HMQ‐4TFS possess very large macroscopic optical nonlinearity, comparable (or even higher) benchmark stilbazolium crystals. Based low‐intensity 0.37 mm thick crystal pumped with 150 fs infrared laser pulses facilitates by rectification, delivering 23 times higher peak‐to‐peak electric field than widely used standard inorganic ZnTe (1.0 thick) broader bandwidth. Therefore, groups introduced provide promising developing intense broadband sources.