We investigated Terahertz generation in organic crystals DSTMS, DAST and OH1 directly pumped by a Cr:forsterite laser at central wavelength of 1.25 μm. This pump laser technology provides a ...laser-to-THz energy conversion efficiency higher than 3 percent. Phase-matching is demonstrated over a broad 0.1-8 THz frequency range. In our simple setup we achieved hundred μJ pulses in tight focus resulting in electric and magnetic field larger than 10 MV/cm and 3 Tesla.
We report on the experimental observation of high-power terahertz-radiation-induced damage in a thin aluminum film with a thickness less than a terahertz skin depth. Damage in a thin metal film ...produced by a single terahertz pulse is observed for the first time. The damage mechanism induced by a single terahertz pulse could be attributed to thermal expansion of the film causing debonding of the film from the substrate, film cracking, and ablation. The damage pattern induced by multiple terahertz pulses at fluences below the damage threshold is quite different from that observed in single-pulse experiments. The observed damage pattern resembles an array of microcracks elongated perpendicular to the in-plane field direction. A mechanism related to microcracks' generation and based on a new phenomenon of electrostriction in thin metal films is proposed.
We demonstrate a simple approach to retrieve the original peak electric field (E-field) strength of high-intensity THz pulses using an electro-optic sampling (EOS) technique and the Poynting flux ...approach. The latter supposes assessment of THz pulse intensity by measurement of pulse energy, duration and spot size, but its applicability to a few-cycle THz pulse needs detailed consideration. We applied a deconvolution procedure to the raw EOS data to retrieve the THz field waveform. We describe a two-step procedure that allows us to assess the field strength of an extreme THz field. First, the EOS measurements of the THz field should be performed at low pulse energies to retrieve the THz waveform and estimate pulse duration and amplitudes of each particular oscillation. Next, the field strength of an extreme THz pulse can be assessed from the Poynting flux approach with correction to the abovementioned data obtained from the EOS measurements. We show good experimental coincidence between peak strength estimation from the EOS directly and from the combined approach at 'low' field strength. Hence, an extreme THz E-field strength can also be assessed from preliminary EOS measurements and full energy measurements based on the Poynting flux approach. We also show that the Poynting flux approach for extreme few-cycle THz pulses gives prominent, at least two-fold, underestimation without preliminary EOS measurements.
•Three-temperature model for electron, phonon and spin subsystems in ferromagnetic metals was developed in 1946–1960.•First experiments on interaction of short laser pulses with nickel were conducted ...in 1984.
This piece was written in memory of Eric Beaurepaire and his two-day visit to Moscow in the late 1990s.
The ideal laser source for nonlinear terahertz spectroscopy offers large versatility delivering both ultra-intense broadband single-cycle pulses and user-selectable multi-cycle pulses at narrow ...linewidths. Here we show a highly versatile terahertz laser platform providing single-cycle transients with tens of MV/cm peak field as well as spectrally narrow pulses, tunable in bandwidth and central frequency across 5 octaves at several MV/cm field strengths. The compact scheme is based on optical rectification in organic crystals of a temporally modulated laser beam. It allows up to 50 cycles and central frequency tunable from 0.5 to 7 terahertz, with a minimum width of 30 GHz, corresponding to the photon-energy width of Δ
E
=0.13 meV and the spectroscopic-wavenumber width of Δ(
λ
−1
)=1.1 cm
−1
. The experimental results are excellently predicted by theoretical modelling. Our table-top source shows similar performances to that of large-scale terahertz facilities but offering in addition more versatility, multi-colour femtosecond pump-probe opportunities and ultralow timing jitter.
Abstract
Intense terahertz pulses and a process of second harmonic generation are promising methods for exciting and studying an ultrafast dynamic response in magnetically ordered systems, ...ferroelectrics, and multiferroics on the picosecond time scale. In the present work, we report experimental results on generation of second optical harmonic in centrosymmetric antiferromagnetic NiO induced by intense terahertz pulses with an electric field strength of up to 20 MV cm
−1
.
The experimental findings on the second harmonic generation (SHG) in centrosymmetric crystal silicon are reported. The SHG is induced by extremely high electric field (up to 15 MV/cm) parallel to the ...crystal surface of a short terahertz (THz) pulse while probing by an infrared femtosecond optical pulse. The SHG under such unique conditions is reported for the first time. At the electric field amplitude above 8 MV/cm, the quadratic dependence of the SHG yield integrated over the THz pulse duration on the electric field is violated and SHG yield is not changed with a further increase of the THz field. Saturation of SHG intensity at high electric fields is explained in terms of carrier density increase due to impact ionization and destructive interference of electric-field induced and current induced nonlinear polarizations.
The study examines aspects of the generation of the second optical harmonic in the centrosymmetric antiferromagnet NiO when exposed to narrowband terahertz pulses with an electric field strength on ...the order of 1 MV/cm. It was found that when exposed to terahertz pulses with a frequency of 1 THz, which corresponds to the antiferromagnetic resonance frequency of NiO, a significant decrease in the intensity of the second harmonic is observed versus exposure to pulses with a frequency of 1.5 THz. It is shown that the observed decrease in the intensity of second harmonic generation can be explained by multipath interference during the propagation of a narrowband terahertz pulse in a thin sample.
Damage in a thin nickel film irradiated by subpicosecond pulses of terahertz (THz) radiation in the range of 1–3 THz at electric-field strengths up to 20 MV/cm at the center of a focal spot is ...observed. The damage threshold fluence is evaluated for single-pulse experiments. The damage pattern induced by multiple THz pulses has the appearance of a complex periodic structure in the form of elongated channels of metal film discontinuity that are perpendicular to the in-plane electric field direction of THz radiation.
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