Time and Frequency Resolved THz Spectroscopy of Micro- and Nano-Systems

Abstract

1. IntroductionTerahertz technology [1], at present a dynamically developing fleld, was en-abled by advances in ultra-short pulse lasers and semiconductor coherent sourcesin the frequency range of 1{50 THz. The extensive activities are focused on THzoptics, spectrally bright sources, and detectors. The terahertz time-domain spec-troscopy and terahertz imaging are main flelds, where terahertz technology flndsapplication. In this contribution we present our recent results in the fleld of tera-hertz time-domain spectroscopy (THz-TDS) applied to micro- and nano- systemsand in the development of THz optics.First, we report on a broadband absorptive anti-re°ection coating that sup-presses the re°ection of terahertz pulses within an electro-optic detector. Theanti-re°ection coating is made of a thin chromium layer. We prove functionalityof the layer in the THz time-domain spectroscopy. We estimate for the flrst timethe complex index of refraction of such layers in the spectral range of 0.1{4 THz.Second, in the contribution we also report on a complex permittivity of nanoscalecomposite material | the single-wall carbon nanotube (SWCNT) mats measuredby THz-TDS at frequencies from 0.1 THz up to 4 THz.2. THz time-domain spectroscopic set-upThe samples were evaluated by THz time-domain spectroscopy [2]. In ourlaboratory we have built such a system. It uses a Ti:sapphire laser with 80 fem-tosecond long near infrared (NIR) pulses to generate coherent THz radiation from(92)