Electro-optic sampling near zero optical transmission point

Summary form only given. Free space electro-optic detection has demonstrated a unique capability of parallel measurement for both spatial and temporal THz imaging. With the use of a CCD camera and a chirped optical probe pulse, real-time and single-shot images of THz field have been achieved. However, due to the limited dynamic range of most CCD cameras (<18 bit) and the lack of multi-channel lock-in amplifier, to image a weak THz modulated optical signal carried on a large laser background, it has to work at a near-zero optical bias point (near zero transmission point) to reduce the intense background light. One basic concern of this electro-optic measurement near the zero optical bias point is the optimal modulation depth, signal-to-noise ratio and the field quadratic dependence.