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Liu F.,Center for Terahertz Waves | Hu X.,Center for Terahertz Waves | Li J.,Center for Terahertz Waves | Wang C.,Center for Terahertz Waves | And 8 more authors.
Chinese Optics Letters | Year: 2011

We present a review of the development of a compact and high-power broadband terahertz (THz) source optically excited by a femtosecond photonic crystal fiber (PCF) amplifier. The large mode area of the PCF and the stretcher-free configuration make the pump source compact and very efficient. Broadband THz pulses of 150 μW extending from 0.1 to 3.5 THz are generated from a 3-mm-thick GaP crystal through optical rectification of 12-W pump pulses with duration of 66 fs and a repetition rate of 52 MHz. A strong saturation effect is observed, which is attributed to pump pulse absorption; a Z-scan measurement shows that three-photon absorption dominates the nonlinear absorption when the crystal is pumped by femtosecond pulses at 1040 nm. A further scale-up of the THz source power is expected to find important applications in THz nonlinear optics and nonlinear THz spectroscopy. ©2011 Chinese Optics Letters.

Tian Z.,Center for Terahertz Waves | Xin K.,University of Arkansas | Wang M.,Nankai University | Wang M.,Oklahoma State University | And 4 more authors.
Journal of Nanoscience and Nanotechnology | Year: 2011

Far-infrared optical and dielectric properties of ferroelectric SrTiO 3 and BaTiO 3 nanofibers, prepared by hydrothermal syntheses, were studied using terahertz time-domain spectroscopy. The power absorption, refractive index, and complex dielectric function were characterized in the frequency range from 0.2 to 1.0 THz. The measured results are well reproduced by theoretical fittings based on the dielectric models and the effective medium model. The study reveals that the low-frequency dielectric properties of the ferroelectric SrTiO 3 nanofibers are associated with the lowest transverse optical (TO) soft mode TO1 at 2.70 THz (90.0 cm ?1-, and that of the ferroelectric BaTiO 3 nanofibers are related to the lowest pair of transverse optical (TO) and longitudinal optical (LO) modes near 5.35 THz, which are both consistent with their bulk single-crystal and thin-film counterparts. © 2011 American Scientific Publishers. All rights reserved.

Li H.,Tianjin Polytechnic University | Gong J.,Tianjin Polytechnic University | Zhang J.,Tianjin Polytechnic University | Wang C.,Center for Terahertz Waves | Tian Z.,Center for Terahertz Waves
Advanced Materials Research | Year: 2011

Along with the booming development of multi-component blending fabrics, the accurate detection of component of fabrics has become a major goal in textile testing. Terahertz sensing technology provides a new way for detecting the materials. THz time-domain spectroscopy (THz-TDS) is a novel spectroscopic technique which measures the electric field of the radiation through a sample and provides the phase and amplitude changes of the radiation, which can provide information unavailable through conventional methods such as microwave and X-ray techniques. In this investigation, THz-TDS technology was introduced into the textile differentiation. Three kinds of cellulose textile fibers, cotton fiber, bamboo fiber and viscose fiber, were prepared as the sample and detected by THz-TDS at room temperature in the absence of vapor. The temporal and frequency signals of the fibers were obtained. In the THz absorption spectrum, the characteristic absorption peaks of textile fibers in THz wave band were found, which can be used to recognize the fibers. This approach provides a novel non-contact examine method for fiber identification in complicated textiles.3. © (2011) Trans Tech Publications, Switzerland.

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