Time domain measurement of the THz refractivity of water vapor

Abstract

We report the measurement of the essentially frequency independent refractivity of water vapor from 0.1 to 1 THz, independent of the simultaneous strong THz pulse broadening and absorption. The humidity dependent transit time of THz pulses through a 170 m long round trip path was measured to a precision of 0.1 ps, using a mode-locked laser as an optical clock.

Comparison of Experimental and Theoretical Determined Terahertz Attenuation in Controlled Rain

“…4 for rain rates of 226, 303, and 380 mm/h. The strong peaks at 0.557 and 0.763 THz are caused by water vapor absorptions lines, which is consistent with Grischkowsky's study [28,29]. Using the measured attenuation data for different rain rates, the attenuation versus rain rate at a fixed frequency of 625 GHz is plotted in Fig.…”

Long-Path THz-TDS Atmospheric Measurements Between Buildings

“…The THz propagation length outside of the building in this measurement is 159 m and the propagation length through the chamber in the [10] is 137 m. The comparative slope is obtained by the following normalization, 3.63 ps (g/m) (137 m 159 m) 3.13 ps (g/m) , giving excellent agreement between the two values.…”

“…The slope of the solid line is 0.51 ps (g/m) larger than that of the dashed line because the THz propagation length outside of the building is 22 m longer than the sample chamber length used in [10]. The THz propagation length outside of the building in this measurement is 159 m and the propagation length through the chamber in the [10] is 137 m. The comparative slope is obtained by the following normalization, 3.63 ps (g/m) (137 m 159 m) 3.13 ps (g/m) , giving excellent agreement between the two values.…”

Experimental confirmation and physical understanding of ultra-high bit rate impulse radio in the THz digital communication channels of the atmosphere

“…As shown in figure 13, our 170 m long-path THz-TDS system includes a 137 m path in the RH-controlled sample chamber, outlined in red. This system has previously been described in detail [32,33]. The transit time of THz impulses propagated through the long-path is measured to a precision of 0.1 ps by the THz-TDS transceiver, using the mode-locked laser as an optical clock.…”

“…The transit time of THz impulses propagated through the long-path is measured to a precision of 0.1 ps by the THz-TDS transceiver, using the mode-locked laser as an optical clock. The transit time has been shown to have a linear relation with the RH (water vapor density) inside the RH-controlled sample chamber [33].…”