The terahertz (THz) emission properties of four kinds of bow-tie photoconductive antennas are studied. The
characteristic of THz radiation generated by them is compared. The emission spectra of the photoconductive antennas are
obtained by THz time domain spectroscopy (TDS) technology. The corresponding frequency domain spectra are
obtained by Fast Fourier Transformation (FFT). The results show that when we increase the bias voltage, the peak value
of THz radiation is increased and tends to saturation when the pump power is strong enough. Under the same bias
voltage and the pump power, the properties of THz radiation generated by four bow-tie photoconductor antennas are
compared. It shows that under low bias voltage, the full width of half maximum (FWHM) of frequency a domain
spectrum which is generated by small-aperture bow-tie photoconductor antenna is broader than that of the large aperture
one. The gap size of small-aperture photoconductive antenna is smaller, the FWHW is broader. On the other hand, under
the high bias voltage, the intensity of THz radiation of the large aperture photoconductor antenna is much larger than the
small aperture one. Our results provide a reference to investigate and fabricate the high efficient of THz emission source.
Experimental measurement and theoretical analysis of THz vibration spectra of four different kinds of vitamins are
presented. The refractive index and absorbance of these vitamins are measured at room temperature by THz-TDS in the
frequency region of 0.2-2.6 THz. The full-geometry optimizations and frequency calculations using the density
functional theory (DFT) are applied to obtain the structure and vibration frequencies of these vitamins. The calculated
results are in agreement with the experimental data. The simulation results show that the intermolecular interactions are
considerably weak so that the gas-phase simulations spectra are closely to the solid-phase. The calculated results confirm
that most of the absorption peaks result from the intra-molecular modes; the others have been ascribed to intermolecular
interaction or phonon modes.
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