Fast scanning and real time monitoring of a pulsed terahertz signal

We present a fast measurement and real time monitoring of a pulsed terahertz signal generated by a femtosecond laser and a photoconductive antenna. Two types of high speed optical delay lines (ODLs) are considered: oscillating type and rotary type. The method to measure the amplitude of the retro-reflector in the oscillating optical delay line is proposed and the displacement of the retro-reflector is exactly calculated to acquire the optical delay time in the fast scan mode. A rotary optical delay line which gives a linear displacement with rotating angle will be described. The rotary ODL was successfully applied to scan a terahertz pulse. The linearity of rotary ODL was confirmed more than 200 ps by comparison with a linear stage ODL. The requirements and possibility of the rotary ODL for application in fast scanning and monitoring of terahertz pulse will be given.