Broadband THz Pulse Transmission Through the Atmosphere

We have transmitted a low-power beam of repetitive broadband THz pulses the record distance of 167 m through the atmosphere with 51% relative humidity at 21 degrees C and have observed the broadened transmitted pulses with a signal to noise ratio greater than 200. The measured transmitted pulses reshaped from a 0.5-ps input pulse into an output pulse structure with a 5-ps symmetric pulse at the leading edge followed by a frequency-swept, rapidly oscillating trailing edge extending with increasing frequency to beyond 150 ps. The leading pulse appearing in the output pulse structure is composed of phase-locked frequency components extending from 0.07 to 0.37 THz that experienced negligible attenuation and group velocity dispersion due to transmission through water vapor. Such a stable pulse shape is suitable for the THz bit in a digital THz communications channel. Our results demonstrate a bit rate-distance product of greater than 8 (Gb/s)-km, which is comparable to an optical fiber digital communications channel.