Evaluation of methods for measuring the field of an intense THz pulse

We compare two methods, that are commonly used, for measuring the peak field of intense terahertz (THz) pulses generated from organic crystals pumped by energetic, femtosecond near-infrared optical pulses. The first method evaluates the peak field directly from the intensity modulation of the probe pulse measured using electro-optic (EO) sampling. The second method calculates the peak field from the measured experimental parameters, such as the duration and the energy of the THz pulse with its spot size. We find that the latter method gives a peak field strength that is almost an order of magnitude higher than that obtained from the probe modulation. We mainly attribute this difference to the sensitivity of the devices used for this measurement, which is highly THz wavelength dependent.