High‐Density Organic Electro‐Optic Crystals for Ultra‐Broadband THz Spectroscopy

Abstract

Ultra‐broadband THz photonics covering the 0.3–20 THz range provides a very attractive foundation for a wide range of basic research and industrial applications. However, the lack of ultra‐broadband THz devices has yet to be overcome. In this work, high‐density organic electro‐optic crystals are newly developed for efficient THz wave generation in a very broad THz spectral range and are successfully used for a broadband THz time‐domain spectroscopy. The new organic THz generator crystals, namely the OHP‐TFS crystals, have very low void volume, high density, and are shown to cover the ultra‐broadband THz spectrum up to about 15 THz, which cannot be easily accessed with the more widely used inorganic‐based THz generators. In addition to the very favorable broadband properties, the generated THz electric‐field amplitude at the pump wavelength of 1560 nm is about 40 times higher than that generated by a commercial inorganic THz generator (ZnTe crystal). By using the newly developed OHP‐TFS as generation crystal in a compact table‐top all‐organic THz time‐domain spectrometer based on a low‐cost telecom fiber laser, the optical characteristics of a model material are successfully determined in the broad 1.5–12.5 THz range with high accuracy.

Phonon‐Suppressing Intermolecular Adhesives: Catechol‐Based Broadband Organic THz Generators

“…On the other hand, highly electronegative groups (SO 3 − and CF 3 ) on the TFS anion can also act as multiple interionic interaction capable groups; three negatively charged O atoms on the SO 3 − group and three partially negatively charged F atoms on the CF 3 group. [ 36–39 ]…”

“…Compared to DSTMS and HMQ‐TMS crystals, the overall absorption of DHP‐TFS crystals is lower at least in medium and high THz frequency regions (R2 and R3 regions; 2–12 THz). In comparison to analogous 4‐(4‐hydroxystyryl)‐1‐methylpyridinium‐1‐ium 4‐(trifluoromethyl)benzenesulfonate (OHP‐TFS) crystals with also a high density and a low void volume (see Figure S4, Supporting Information), [ 39 ] DHP‐TFS crystals exhibit a lower overall absorption in the medium THz frequency region (R2 region; 2–6 THz) as shown in Figure S7, Supporting Information. On the other hand, in the high THz frequency region; 6–12 THz, DHP‐TFS crystals exhibit a similar absorption with OHP‐TFS crystals.…”

“…On the other hand, in the high THz frequency region; 6–12 THz, DHP‐TFS crystals exhibit a similar absorption with OHP‐TFS crystals. [ 39 ]…”

“…b) Void volume and crystal density of benchmark organic THz generators (for additional details see Figure S4, Supporting Information). [ 18,19,25,36,38–41,44,47,50–63 ]…”

A Self‐Assembly Method‐Derived MoxC@N‐Doped Carbon Nanosheet Enabling Efficient Water Electrolysis

“…Water electrolysis has been regarded as a prospective method to gain the renewable hydrogen. [1][2][3][4][5][6][7] However, developing powerful nonprecious catalysts for the low-overpotential hydrogen evolution reaction (HER) still faces challenges. [8][9][10][11][12][13][14][15] At present, transition metallic molybdenum carbides has been considered as one kind of effective non-noble HER electrocatalysts, because of their high conductivity, excellent hydrogen adsorption performance, and especially the similar d-orbital electron state to platinum.…”