Full text loading...
(a) DAST crystal cut for phase-matched generation of terahertz radiation by DFG using NIR radiation with wavelength around 800 nm. Note that the small deviation from perpendicularity of the and axes with respect to the axis, and , respectively (Ref. 18), is neglected in the drawing of the figure. (b) Terahertz peak power generated by DFG in the cut DAST crystal using normal-incident NIR pump beams with the polarizations perpendicular to the axis (narrow solid line), or parallel to the axis (bold solid line).
(a) Optimal angle of incidence for terahertz generation by DFG in the DAST crystal using NIR laser radiation polarized parallel to the axis. A positive (negative) angle refers to NIR pump beams incident from the axis ( axis) side, i.e., . Shaded areas correspond to regions where no precise measurement could be made because of strong absorption by the DAST crystal. (b) Maximum enhancement achieved by tuning the crystal around the axis. (c) Terahertz peak power at 7.5 THz as a function of the angle of incidence for NIR polarization vector parallel to the axis and the wave vectors in the plane. (d) Terahertz peak power at 7.5 THz as a function of the angle between the NIR polarization vector and the axis ( defined in the inset). The wave vectors are kept in the plane that is perpendicular to both the plane and the cut surfaces of the crystal.
(a) Water absorption lines from the HITRAN database (Ref. 16). (b) Enlarged view of the terahertz spectrum of Fig. 1(b) showing the water absorption lines in the region of 4–8 THz. (c) The absorption spectrum of a pure rotational transition of HF . The center frequency is 4.91468257 THz (Ref. 17).
Article metrics loading...