5 research outputs found
An Extraordinary Teotihuacan Mural
"A Teotihuacan mural with an indisputable notation of glyphs arranged in columnar form is a rarity. Such a mural is in the collections of the University of Missouri. We believe that it has considerable potential importance for the study of the Teotihuacan writing system."--First paragraph.Includes bibliographical reference
400 kHz repetition rate THz-TDS with 24 mW of average power driven by a compact industrial Yb-laser
We demonstrate a high average power terahertz time-domain (THZ-TDS)
spectrometer based on optical rectification in the tilted-pulse front geometry
in lithium niobate at room temperature, driven by a commercial, industrial
femtosecond-laser operating with flexible repetition rate between 40 kHz - 400
kHz. The driving laser provides a pulse energy of 41 uJ for all repetition
rates, at a pulse duration of 310 fs, allowing us to explore repetition rate
dependent effects in our TDS. At the maximum repetition rate of 400 kHz, up to
16.5 W of average power are available to drive our THz source, resulting in a
maximum of 24 mW of THz average power with a conversion efficiency of ~ 0.15 %
and electric field strength of several tens of kV/cm. At the other available
lower repetition rates, we show that the pulse strength and bandwidth of our
TDS is unchanged, showing that the THz generation is not affected by thermal
effects in this average power region of several tens of watts. The resulting
combination of high electric field strength with flexible and high repetition
rate is very attractive for spectroscopy, in particular since the system is
driven by an industrial, compact laser without the need for external
compressors or other specialized pulse manipulation
Temperature-independent non-linear terahertz transmission by liquid water
Liquid water is one of the most studied substances, yet many of its properties are difficult to rationalize. The uniqueness of water is rooted in the dynamic network of hydrogen-bonded molecules with relaxation time constants of about one picosecond. Terahertz fields oscillate on a picosecond timescale and are inherently suited to study water. Recent advances in non-linear terahertz spectroscopy have revealed large signals from water, which have been interpreted with different, sometimes competing, theoretical models. Here, we show that the non-linear transmission of liquid water at ~1 THz is equal at 21 and 4â°C, thus suggesting that the most appropriate microscopic models should depend weakly on temperature. Among the different mechanisms proposed to date, the resonant reorientation of hydrogen-bonded water molecules might be the most appropriate to describe all of the currently available experimental results