Terahertz
time-domain spectroscopy is a spectroscopic technique in which the properties
of a material are probed with short pulses of THz radiation. The
generation and detection scheme is sensitive to the sample material's effect on
both the amplitude and the phase of the terahertz radiation. Pulsed terahertz
radiation is generated by photoconductive switches (GaAs or InGaAs/InP)
irradiated by femtosecond lasers. At the end, a fact Fourier transform of
terahertz amplitude produces the terahertz spectrum in the frequency range 0.1
– 5 THz.
We
are glad to announce that our partners from AVESTA succeeded to reach an
enormous power of laser impulse which now equals 1.25 µm.
Hauri
group reports on high-field terahertz transients with 0.9-mJ pulse energy
produced in a 400 mm2 partitioned organic crystal by
optical rectification of a 30-mJ laser pulse centered at 1.25 μm wavelength.
The phase-locked single-cycle terahertz pulses cover the hard-to-access
low-frequency range between 0.1 and 5 THz and carry peak fields of more than 42
MV/cm and 14 Tesla with the potential to reach over 80 MV/cm by choosing
appropriate focusing optics. The scheme based on a Cr:Mg2SiO4 laser offers a
high conversion efficiency of 3% using uncooled organic crystal. The collimated
pump laser configuration provides excellent terahertz focusing conditions.
This
high-energy THz pulsed generator of AVESTA partners helped Terasense precisely
measure the ultrafast response time of our proprietary passive THz
detector. Such short response time opens up the possibility to observe and
resolve ultrafast transient processes in many THz applications.
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