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Thursday, May 3, 2018
Abstract-Flexible and tunable terahertz all-dielectric metasurface composed of ceramic spheres embedded in ferroelectric/ elastomer composite
A pulsed broadband (from 0.1 to 1.5 THz), in-line, terahertz (THz) time domain electro-optical sampling is applied for the visualization of phase objects by using a large-aperture electro-optical crystal (ZnTe, 1cm×1cm). The waveforms of the THz pulses are generated in a lithium niobate (LiNbO3) crystal pumped by femtosecond pulses with a tilted amplitude front, and measured by a 2D THz imaging system. This system images the object under study in the THz range via a polytetrafluoroethylene (PTFE) lens in the 2𝑓−2𝑓 geometry onto a ZnTe crystal and then images the crystal surface on a CMOS camera using electro-optical sampling. Reconstruction of the image in such a scheme is implemented by processing the received 3D spatial-temporal distributions of the THz field in three different ways: (i) by detecting the displacement of the maximum peak position of the THz pulse due to a phase delay in the object under study; (ii) by using a cross-correlation function analysis; and (iii) by a Fourier transformation of a THz waveform and subsequent extraction of the phase difference at each THz frequency. Images of transparent PTFE objects were obtained. Main features of the resulting imaging system are discussed.