Abstract
GaSe crystal has been expected as one of the promising nonlinear optical crystals for highly efficient Terahertz (THz) wave generation. However there are several reasons why it is difficult to grow the bulk crystals with fewer defects. To overcome the obstacles, temperature difference method under controlled vapor pressure (TDM-CVP) is applied for crystal growth. According to this method, crystals with stoichiometric composition can be grown at the constant growth temperature under the application of controlled Se vapor pressure and lower temperature growth enables the reduction of point defect concentration. In this article, surface morphology is observed by optical microscope. To identify polytypes, backscattered Raman spectra were measured. X-ray diffraction confirmed the polytypes and single crystalline phase. Infrared (λ=1 µm) and Terahertz wave (1~3 THz) transmittance measurements were performed to calculate the absorption coefficient in these wavelength regions. From these results, it is shown that the grown crystals have shown an ε-type single phase and the absorption coefficients of grown crystals have been improved according to the increase of applied Se vapor pressure during crystal growth.
