BROAD BAND MID-INFRARED THz PULSE: MEASUREMENT TECHNIQUE AND APPLICATIONS

We present in this article the recent development of the measurement technique for coherent free-space THz field and applications in the mid-infrared range. The technique is based on the second-order nonlinear optical interaction both for the generation and for the detection of THz pulse. Particularly the detection process based on free-space electro-optic sampling gives us a possibility to timely trace directly the ultrabroad band coherent THz field unparalleled by other technique. Using an ultrashort laser pulse our measurement system is feasible to measure the ultrashort THz pulse with a bandwidth up to 40 THz. We present a detailed comparative study on the generation and detection using different nonlinear material. We demonstrate applications of the coherent THz technique for time-resolved semiconductor spectroscopy, time-domain imaging with high spatial resolution and broad band refractive and absorptive characterization of material in the mid-infrared range.