Cicėnas P, Geižutis A, Malevich V L, Krotkus A
Opt Lett. 2015 Nov 15;40(22):5164-7. doi: 10.1364/OL.40.005164.
We report on terahertz (THz) emission from a (111)-cut InAs crystal in the reflection and transmission directions, excited by femtosecond optical pulses in the direction of its surface normal. THz pulse amplitudes emitted from the crystal surface in this case were only ~20% smaller than for optimal photoexcitation at a 45° angle. This observation evidences that THz emission from InAs is caused by lateral photocurrent transients appearing due to a crystal anisotropy rather than directly by the photo-Dember effect, which creates fast changing electric polarization perpendicular to the surface. Such a simple geometry of the photoexcitation could greatly enhance the fields of surface THz emitter applications.
我们报告了在（111）切割的砷化铟晶体中，沿反射和透射方向的太赫兹（THz）发射情况，该晶体由沿其表面法线方向的飞秒光脉冲激发。在这种情况下，从晶体表面发射的太赫兹脉冲幅度仅比以45°角进行最佳光激发时小约20%。这一观察结果表明，砷化铟的太赫兹发射是由晶体各向异性导致的横向光电流瞬变引起的，而不是直接由光德姆效应引起的，光德姆效应会产生垂直于表面的快速变化的电极化。这种简单的光激发几何结构可以极大地拓展表面太赫兹发射器的应用领域。
