Terahertz Pulse Detection Using Rotary Optical Delay Line

We report the first measurement of terahertz pulse using a rotary optical delay line (RODL). The delay line uses a rotating reflective surface that gives a linear delay length with respect to the rotation angle. Operation principles and the profile of the reflective surface are examined and the optical path as a function of the radius and the rotating angle is calculated. A comparison of the temporal waveform and frequency spectrum obtained by using the RODL and the linear stage optical delay line (LODL) confirms that the linearity of the RODL is up to 500 ps corresponding to a delay scan length of 7.5 cm, and the difference in time delay is less than 0.2 ps. The RODL is suitable for the high-speed scanning of terahertz pulses up to 400 Hz.