Distortion reduction in strong terahertz signals using broadband attenuators with flat transmittance

Abstract

We demonstrate numerically and experimentally a simple approach to significantly reduce the distortion of a strong terahertz (THz) pulse signal measured by the spectral-encoding technique. We propose using broadband THz attenuators with flat transmittance to attenuate the input signal to a certain low level corresponding to the strongest spectrum difference ΔI for the main negative polar. The real THz waveform can be recovered by multiplying the attenuated THz waveform by the reciprocal of the attenuation factor of the main positive polar. Using a suitable number of broadband attenuators with flat transmittance, and considering an acceptable signal-to-noise ratio, the severely distorted strong THz signal from the air plasmas induced by two-color femtosecond laser pulses was reduced significantly.