Terahertz beam profiler using optical transmission modulation in silicon

A new type of beam profiler in the terahertz region using optical modulatio n of transmission in a silicon wafer is proposed and demonstrated. The prof ile of the beam emitted from a photoconductive antenna and focused by parab oloidal mirrors is obtained as a function of frequency. The beam profile at each frequency can be fitted well with a Gaussian function. The diameter o f the beam at a focal plane decreases with increasing frequency. The spatia l resolution of the beam profiler is approximately determined by the optica l beam size on the silicon wafer.