Analysis of distortions in electro-optic T-ray detection with a chirped optical probe pulse

Three distortions of pulsed terahertz (T-ray) signal measured with a chirped optical probe pulse are analyzed theoretically. The first distortion originates from the mismatch of the relationship between the optimal chirped probe pulse duration T_co and the T-ray length T; the second one stems from the function f(t´/T₀); the third one occurs when k<<1 is not satisfied. It comes from the neglect of the quadratic term of the modulation depth k which reflects the strength of the THz signal in the retrieving process. These distortions affect the application of the spectral-encoding technique. Some possible methods are proposed to reduce the distortions.