RESUMEN
Over the past decade, terahertz spectroscopy has evolved into a versatile tool for chemically selective sensing and imaging applications. In particular, the potential to coherently generate and detect short, and hence, broadband terahertz pulses led to the development of efficient and compact spectrometers for this interesting part of the electromagnetic spectrum, where common packaging materials are transparent and many chemical compounds show characteristic absorptions. Although early proof-of-principle demonstrations have shown the great potential of terahertz spectroscopy for sensing and imaging, the technology still often lacks the required sensitivity and suffers from its intrinsically poor spatial resolution. In this review we discuss the current potential of terahertz pulse spectroscopy and highlight recent technological advances geared towards both enhancing spectral sensitivity and increasing spatial resolution.
Asunto(s)
Técnicas de Química Analítica/métodos , Imágen por Terahertz/métodos , Radiación Terahertz , Animales , Técnicas de Química Analítica/instrumentación , Diseño de Equipo , Humanos , Microscopía/instrumentación , Microscopía/métodos , Modelos Moleculares , Imágen por Terahertz/instrumentaciónRESUMEN
We have measured the intermolecular dynamics of the 1,3-dialkylimidazolium-based room-temperature ionic liquids (RTILs) [emim][BF(4)], [emim][DCA], and [bmim][DCA] at 25 degrees C from below 1 GHz to 10 THz by ultrafast optical Kerr effect (OKE) spectroscopy and dielectric relaxation spectroscopy (DRS) augmented by time-domain terahertz and far-infrared FTIR spectroscopy. This concerted approach allows a more detailed analysis to be made of the relatively featureless terahertz region, where the higher frequency diffusional modes are strongly overlapped with librations and intermolecular vibrations. Of greatest interest though, is an intense low frequency (sub-alpha) relaxation that we show is in accordance with recent simulations that have reported mesoscopic structure arising from aggregates or clusters--structure that explains the anomalous and inconveniently high viscosities of these liquids.
RESUMEN
Experimental investigations of the microscopic electric and in particular the magnetic near-fields in metamaterials remain highly challenging and current studies rely mostly on numerical simulations. Here we report a terahertz near-field imaging approach which provides spatially resolved measurements of the amplitude, phase and polarization of the electric field from which we extract the microscopic magnetic near-field signatures in a planar metamaterial constructed of split-ring resonators (SRRs). In addition to studying the fundamental resonances of an individual double SRR unit we further investigate the interaction with neighboring elements.
RESUMEN
Precise dielectric spectra have been determined at 25 degrees C over the exceptionally broad frequency range of 0.1