Balazs Monoszlai

Pump pulse width and temperature effects in lithium niobate for efficient THz generation

We present a study on THz generation in lithium niobate pumped by a powerful and versatile Yb:CaF(2) laser. The unique laser system delivers transform-limited pulses of variable duration (0.38-0.65 ps) with pulse energies up to 15 mJ and center wavelength of 1030 nm. From previous theoretical investigations, it is expected that such laser parameters are ideally suited for efficient THz generation. Here, we present experimental results on both the conversion efficiency and the THz spectral shape for variable pump pulse durations and for different crystal temperatures, down to 25 K. We experimentally verify the optimum pump parameters for the most efficient and broadband THz generation.

A scheme for a shot-to-shot, femtosecond-resolved pulse length and arrival time measurement of free electron laser x-ray pulses that overcomes the time jitter problem between the FEL and the laser

The recent entry of X-ray free electron lasers (FELs) to all fields of physics has created an enormous need, both from scientists and operators, for better characterization of the beam created by these facilities. Of particular interest is the measurement of the arrival time of the FEL pulse relative to a laser pump, for pump-probe experiments, and the measurement of the FEL pulse length. This article describes a scheme that corrects one of the major sources of uncertainty in these types of measurements, namely the jitter in the arrival time of the FEL relative to an experimental laser beam. The setup presented here uses a combination of THz streak cameras and a spectral encoding setup to reduce the effect of an FELs jitter, leaving the pulse length as the only variable that can affect the accuracy of the pulse length and arrival time measurement. A discussion of underlying principles is also provided.

Terahertz emission in organic crystals pumped by conventional laser wavelength

Intense Terahertz radiation in organic crystals is typically generated by optical rectification of short wavelength infrared femtosecond lasers between 1.3 and 1.5 μm. In this wavelength range high energy ultrashort pump sources are hardly available. Here we present results on powerful THz generation by using DAST and DSTMS pumped directly by the widely used and well-established Ti:sapphire laser technology, emitting at 0.8 μm. This approach enables straightforward THz generation by optical rectification. We present systematic studies on nIR-to-THz conversion efficiency, damage threshold, and on the emitted THz spectrum and field strength.

MV/cm Terahertz transients in the THz gap (1–20 THz) from organic crystals

We demonstrate highly efficient Terahertz production and absolute phase control in the hardly accessible THz frequency gap by optical rectification in organic crystals leading to single-cycle field oscillations beyond 150 MV/m and 0.5 Tesla.