Polarization Sensitive Raman Scattering and Stimulated Terahertz Emission From GUHP Molecular Crystal

The present article studies narrow-band terahertz (THz) emission stimulated by femtosecond laser pulse in molecular crystal guanylurea hydrogen phosphite (NH $_{2})_{2}$ CNHCO(NH $_{2}$ )H $_{2}$ PO $_{3}$ (GUHP). We demonstrate that this emission is closely connected with the excitement of high-quality phonon oscillations in the crystal, which is proved by the temperature dynamics of the spectra and DFT calculations. For the purposes of studying the origin of this stimulated THz emission and creation of the adequate model of the phenomenon, we analyzed the polarization sensitive spectra of spontaneous Raman scattering and THz transmission spectra while considering their polarization features in relation to crystallographic axes of GUHP crystal. In this article, we show that molecular crystals provide an effective means to convert vis-NIR laser light regardless of wavelength into the THz frequency range. This approach can lead to the creation of "laser-like" source with the desired THz frequency for a range of medical, scientific, and technological applications.