Integration of a rapid scanning technique into THz time-domain spectrometers for nonlinear THz spectroscopy measurements

Abstract

We have implemented a rapid scanning technique into THz time-domain spectrometers using an oscillating frictionless delay line, especially adapted for nonlinear THz experiments. Thereby we were able to increase the dynamic range of THz measurements in the frequency range from 40 to 200 cm -1 by up to 24 dB and reduce the scanning time by up to a factor of 200. We report here test measurements on TDS-setups at repetition rates of 80 MHz and 5 kHz. The dynamic range exceeds 64 dB, which allows to record even small changes in the THz absorption upon optical excitation by a THz probe, covering the frequency range of the intermolecular modes and the phonon bands. We demonstrate the potential of this technique for optical-pump THz-probe experiments using a 70 μm thick high-resistivity silicon, excited by 400 nm, ∼50 fs pulses as a sample.

Nonlinear TeraHertz Transmission by Liquid Water at 1 THz

“…They performed typical z scan measurements [26], whereby the sample is moved through the beam focus and the intensity transmission is measured with a power detector, both with an open as well as with a partially closed aperture [27,28]. This experimental approach is restricted to the large sample volume required to run a recirculating liquid jet, which to our knowledge needs at least hundreds of milliliters of liquid sample [29]. However, this prevents applications to expensive solutes that are not available in large quantities.…”

“…However, this prevents applications to expensive solutes that are not available in large quantities. In addition, it is preferable to use field-sensitive rather than intensity detectors because of their superior dynamic range [29][30][31].…”

Solvent dynamics play a decisive role in the complex formation of biologically relevant redox proteins

“…THz-TDS measurements were carried out with a custom-built spectrometer setup similar to that previously described. 31,32 Briefly, the 800 nm output of a Ti:sapphire oscillator (Mai Tai EHP, Spectra Physics, United States) with a repetition rate of 80 MHz and pulse duration of 70 fs is split into pump and probe beams. The pump beam propagates to a photoconductive antenna (Tera-SED 3, Gigaoptics, Germany) that is biased at 20 V and modulated at 92 kHz to produce THz radiation.…”

Towards Intense THz Spectroscopy on Water: Characterization of Optical Rectification by GaP, OH1, and DSTMS at OPA Wavelengths

“…The first exploits current effects, i.e., the fact that a time-varying charge current can act as a radiation source [27]. This basic concept holds for antennas [28][29][30][31][32][33], which are widely used in conjunction with non-amplified pulsed lasers to perform terahertz time-domain spectroscopy, and for particle accelerators, where relativistic electron beams are deflected by magnets and thereby emit radiation of tunable wavelength [34][35][36] that can cover the THz range [37][38][39][40][41][42][43][44][45][46][47][48][49][50][51][52]. While accelerators can cover a large frequency range, these complex machines are often optimized for a certain range because optical elements have limited bandwidths [53].…”

“…The highest dynamic range (DR) reported to date is above 100 dbm when antennas are used in conjunction with multi-MHz laser oscillators [103,104]. For amplified NIR sources operating in the kHz range, we recently demonstrated [29] a fast scan acquisition technique based on the Pockels effect [37] with a DR of more than 60 dbm. Both techniques operate in a limited frequency range and can detect THz radiation up to~7 THz.…”