掺硫硒化镓晶体在太赫兹波段的光学特性

Optical properties of GaSe∶S crystals in terahertz frequency range

利用太赫兹时域光谱技术测量了掺硫硒化镓（GaSe1-xSx）晶体在太赫兹波段的光学参数,包括折射系数、吸收系数等。使用自由空间电光取样法获得了太赫兹电磁波的脉冲波形,对不同硫掺杂量的硒化镓晶体进行了研究,在硫的掺杂量为0,0.01,0.14,0.26,0.37时,在0.22.0 THz测得了GaSe1-xSx的折射系数、吸收系数等光学参数。此外还在吸收光谱上观察到E′^（2）和E″^（2）两个声子振动模态,其强度与频率会随着硫的掺杂量而改变,且即使是微量的硫掺杂也会影响吸收光谱上的声子振动模态。最后,在相位匹配ee-e的条件下,模拟了利用锁模钛蓝宝石激光使此类晶体产生太赫兹辐射的可能性。

The frequency-dependent optical constants of GaSe∶S crystals,refractive indexes,and obsorption conficients,were measured by using the terahertz time-domain spectroscopy.By the temporal-profile measurements of the terahertz pulse,the ordinary refractive index and absorption coefficients of GaSe1-xSx（x=0,0.01,0.14,0.26,0.37） crystals in the range of 0.2-2.0 THz were obtained directly.The vibration modes of two phonons（E′^（2） and E″^（2）） on the absorption spectra were measured,in which their intensities and frequencies change with the doped amounts of sulfur.Furthermore,for the first time to our knowledge,the possibility of ee-e down-conversion in the THz range was demonstrated by a simulation.