Yohei Sato
Tohoku University, Japan
Title: Liquid phase growth of GaSe crystal for highly efficient THz wave generation
Biography
Biography: Yohei Sato
Abstract
The applications of THz wave are expected in wide valiety of applications such as nondestructive inspection, medical science and ultra high density communication. In our laboratory, we research nondestructive inspection by using THz wave as follows: 1. Sensing of disconnection gaps covered with invisible insulator, 2. visualization of steel wire in the extradosed bridge cable and 3. qualitative and quantitative metal corrosion analysis etc. For these THz killer applications, non-linear optical gallium selenide (GaSe) is one of the most essential key materials for the highly effi cient, widely frequency tunable and compact THz light source via diff erence frequency generation. Th e power of THz wave from commercially available Bridgman grown GaSe crystal is limited by the native point defects due to high temperature growth at melting point and the deviation from stoichiometric composition. In our laboratory, GaSe crystal is grown by TDM-CVP which enables extremely low growth temperature and application of Se vapor pressure for stoichiometry control. Conversion effi ciency of THz wave generation at 9.41 THz using not-intentionally doped GaSe crystal grown by our TDM-CVP (1.2×10-6 J-1) was 4 times higher than that from Bridgman-grown crystal (3.0×10-7 J-1). In addition, we grew impurity doped GaSe crystal systematically for the fi rst time. In low THz frequency range, transparency of GaSe crystals grown by TDM-CVP are improved by doping of amphoteric impurity (Ge) and transition metal (Ti). In the case of doping issoerectronic impurity (Te), It was confi rmed to improve interlayer bonding force of GaSe crystal by doping of Te.