Multi-Period Fast Rotating Optical Delay Line With 228.47 ps Delay Time

Optical delay line (ODL) plays a crucial role in various detection techniques such as terahertz time-domain spectroscopy (THz-TDS), and optical pump detection. This letter proposes a novel multi-mirror array optical delay line (MMAODL) structure suitable for THz-TDS systems, which consists of a laser collimator, a rotating disk, a multi mirror array, a pyramid prism, and a plane mirror. Based on the principle of ray tracing, a theoretical mathematical model of MMAODL was constructed. Combined with simulation, the working angle of MMAODL was obtained to be 13 deg, and the theoretical delay time was 228.71 ps. Using the THz TDS system, the actual time length of the 8-cycle MMAODL structure, calibrated by the FP standard, was tested and demonstrated to be 228.47 ps, and the time-domain error of the collected signal was found to be approximately 0.014 ps. When an 8-cycle MMAODL is combined with a 4000-rpm motor, the theoretical waveform reproduction rate can reach 533 Hz, which simultaneously meets the requirements of a THz-TDS system for long delay time and high scanning frequency.