Visualization of the beam propagation and focusability of short-pulse THz-radiation

Recently, the generation and detection of THz radiation have attracted much attention from the viewpoint of fundamental and applied physics. We have previously reported the significant enhancement of THz-radiation power from an InAs surface in a magnetic field irradiated with femtosecond laser pulses. This intense THz-radiation source is useful for applications of time-resolved spectroscopy, imaging, sensing and optoelectronics in the far-infrared region. For such applications, it is necessary to know the accurate beam profile and focal size. In the presentation, we report the focusability and visualization of the THz radiation propagating in free space by the knife edge method.