High energy Yb:CaF2 femtosecond laser for efficient terahertz generation in lithium niobate

We present a study on THz generation in lithium niobate pumped by a powerful and versatile Yb:CaF2 laser. The unique laser system delivers transform-limited pulses of variable duration (0.38-0.65 ps) with pulse energy of up to 15 mJ at a center wavelength of 1030 nm. From theoretical investigations it is expected that those 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 most efficient and broadband THz generation

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:CaF2 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. (C) 2013 Optical Society of Americ

800-fs, 330-µJ pulses from a 100-W regenerative Yb:YAG thin-disk amplifier at 300 kHz, and THz generation in LiNbO3

Yb:YAG thin-disk lasers offer extraordinary output power, but systems delivering femtosecond pulses at a repetition rate of hundreds of kilohertz are scarce, even though this regime is ideal for ultrafast electron diffraction, coincidence imaging, attosecond science, and terahertz (THz) spectroscopy. Here we describe a regenerative Yb:YAG amplifier based on thin-disk technology, producing 800-fs pulses at a repetition rate adjustable between 50 and 400 kHz. The key design elements are a short regenerative cavity and fast-switching Pockels cell. The average output power is 130Wbefore the compressor and 100Wafter compression, which at 300 kHz corresponds to pulse energies of 430 and 330 μJ, respectively. This is sufficient for a wide range of nonlinear conversions and broadening/ compression schemes. As a first application, we use optical rectification in LiNbO3 to produce 30-nJ single-cycle THz pulses with 6Wpump power. The electric field exceeds 10 kV∕cm at a central frequency of 0.3 THz, suitable for driving structural dynamics or controlling electron beams

Challenges in simulating beam dynamics of dielectric laser acceleration

Dielectric Laser Acceleration (DLA) achieves the highest gradients among structure-based electron accelerators. The use of dielectrics increases the breakdown field limit, and thus the achievable gradient, by a factor of at least 10 in comparison to metals. Experimental demonstrations of DLA in 2013 led to the Accelerator on a Chip International Program (ACHIP), funded by the Gordon and Betty Moore Foundation. In ACHIP, our main goal is to build an accelerator on a silicon chip, which can accelerate electrons from below 100 keV to above 1 MeV with a gradient of at least 100 MeV/m. For stable acceleration on the chip, magnet-only focusing techniques are insufficient to compensate the strong acceleration defocusing. Thus, spatial harmonic and Alternating Phase Focusing (APF) laser-based focusing techniques have been developed. We have also developed the simplified symplectic tracking code DLAtrack6D, which makes use of the periodicity and applies only one kick per DLA cell, which is calculated by the Fourier coefficient of the synchronous spatial harmonic. Due to coupling, the Fourier coefficients of neighboring cells are not entirely independent and a field flatness optimization (similarly as in multi-cell cavities) needs to be performed. The simulation of the entire accelerator on a chip by a Particle In Cell (PIC) code is possible, but impractical for optimization purposes. Finally, we have also outlined the treatment of wake field effects in attosecond bunches in the grating within DLAtrack6D, where the wake function is computed by an external solver