为了测量太赫兹波聚焦点附近不同位置的太赫兹时域信号图对飞秒脉冲强激光在空气中进行聚焦,在形成空气等离子体细丝通道的同时辐射出锥型太赫兹波,并用离轴抛物面金镜收集和聚焦太赫兹波。利用电光采样系统来探测太赫兹波,得到其频谱宽度约为4 THz。通过对比分析得出,会聚的太赫兹波同样具有古依相移效应。

The study on Gouy phase shift of Terahertz (THz) wave has been experimentally investigated by detecting the THz time-domain signals at different positions near the THz focus by using the free-space electro-optic sampling system. We generated conic THz wave from air plasma with an intense femtosecond laser, and collected and focused the THz wave with off-axis parabolic gold mirrors. The spectrum-width of the THz wave we obtained was about 4 THz. By comparison, we conclude that Gouy phase shift effect also exists in the convergent THz wave.