Characterization of aminopyridinium based organic crystals for THz generation

Two aminopyridinium based novel organic materials, 2-amino-5-nitropyridinium p-phenolsulfonate (2A5NPP) and 2,6-diaminopyridinium-4-nitrophenolate-4-nitrophenol (DAP+NP-NP) were characterized in the 0-2 THz range by time-domain terahertz (THz) spectroscopy. Density functional theory calculations were carried out to find the molecular vibrational modes of the materials in 0-15 THz range and partially compared with the experimental results. THz absorption peaks were assigned to molecular vibration modes. THz pulse generation by optical rectification in both materials was studied using optical pump pulses of 1030 nm wavelength. The anisotropy of THz generation was investigated in detail by rotating the polarization of the optical pump with respect to the crystal axes.