Abstract

Recently, there have been studies of broadband coherent THz pulse propagation under atmospheric weather conditions [1], which provides information for important applications in the atmosphere. In this study, the THz pulses were measured through a 159 m and 883 m distances for which the THz pulses propagated in an outdoor atmosphere with different water vapor density (WVD). The total round trip paths between the transmitter and receiver chips were 186 m and 910 m, which are approximately equal to 52 and 255 round-trips of the circulating 50 fs optical pulse within the mode-locked ring laser, thereby, giving sampling pulses delayed by 52 and 255 pulses down the pulse train from the excitation pulses, respectively. The time shift of the THz pulses was proportional to the WVD. Figure 1 shows the transmitted THz pulses through 186 m and 910 m with different WVDs. The THz pulse delays due to the distance and WVD with respect to the first maximum of the pulse. Finally, the time shift of the THz pulses of the 186- and 910-m distance, for which the outdoor propagation distances are 159 and 883 m with including 27 m indoor propagation distance for both measurements, can be measured as a function of WVD. THz long path WVD studies are necessary to investigate the proposed applications in the atmosphere such as THz communications and monitoring for pollutants and dangerous gases.

© 2017 Japan Society of Applied Physics, Optical Society of America