Detection of environmental pollutants and study of natural hormones using compact, robust, high-power terahertz (THz) radiation source

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Recently, chemical substances that have been artificially developed, particularly hormones that affect man's daily life as an endocrine disrupting substance have been ascertained to cause big environmental problems. These chemicals that mimics natural hormones are environmental concerns of global scale proportions, thus the detection of these environmental pollutants requires immediate attention and action. In addition to the existing environmental pollution monitoring devices, simple and highly sensitivity measurement technique is of vital importance. As such, we developed a system that detects and identifies endocrine disrupting substances using terahertz (THz) electromagnetic wave. An InAs semiconductor wafer was used in generating THz radiation and we succeeded in the enhancing the power of such radiation by applying a magnetic field from a novel and compact magnetic circuit consisting of eight permanent magnets. In this system, the InAs was excited using a portable (A4-size) and u … More ltrashort pulse mode synchronous fiber laser with a turn-key feature. Furthermore, we successfully developed a waveguide designed to operate in the THz frequency region. Until recently, strongly-polarization preserving and flexible THz waveguides have not been realized. We were able to overcome this obstacle problem by fabricating Teflon-based photonic crystal fiber waveguide whose transmissivity was found to be relatively high in the THz regime. In the previous year, the feasibility of THz absorption spectroscopy in the identification of hydroxy-substituted naphthalene (naphthol) isomers was demonstrated. The importance of such work was due to the fact that long-term exposure to naphthol, a biochemical that exhibits estrogenic like activity and is potentially mimic natural hormones, can cause liver problems. Using a similar experimental setup for this year, temperature-dependent transmission spectroscopy of a dihydroxy-substituted naphthalene, particularly the 1,4-naphthol, was utilized to observe the onset of its solid-state phase transition. An abrupt emergence of two distinct absorption peaks in the THz spectrum at 210K manifested evidence of an impending phase transition. The actual transition was verified by differential scanning calorimetry (DSC) analysis and temperature dependent x-ray diffractometry (XRD) measurements and was found to occur at 240K. Less