The generation and use of THz radiation for electron acceleration and manipulation of electron bunches has progressed over the last decade to a level where practical devices for THz guns, acceleration and a wide range of beam manipulations have become possible. Here, we present our progress on generation of single-cycle THz pulses at the two-hundred micro- Joule level to drive advanced acceleration and beam manipulation devices. Specifically, we use pulses centered at 0.3 THz to power a segmented terahertz electron accelerator and manipulator (STEAM) capable of performing multiple high-field operations on the 6D-phase-space of ultrashort electron bunches. Using this STEAM device, we demonstrate record THzacceleration of >60 keV, streaking with <10 fs resolution, focusing with >2 kT/m strength, compression to ~100 fs as well as real-time switching between these modes of operation. The STEAM device demonstrates the feasibility of THz-based electron accelerators, manipulators and diagnostic tools enabling science beyond current resolution frontiers with transformative impact.
The generation and use of THz radiation for electron acceleration and manipulation of electron bunches has progressed over the last decade to a level where practical devices for THz guns, acceleration and a wide range of beam manipulations have become possible. Here, we present on our progress to generated single-cycle THz pulses at the twohundred micro- Joule level to drive advanced acceleration and beam manipulation devices. Specifically, a segmented terahertz electron accelerator and manipulator (STEAM) capable of performing multiple high-field operations on the 6D-phase-space of ultrashort electron bunches is demonstrated using these pulses. Using this device, powered by single-cycle, 0.3 THz pulses, we demonstrate record THz-acceleration of <60 keV, streaking with <10 fs resolution, focusing with <2 kT/m strength, compression to ~100 fs as well as real-time switching between these modes of operation. The STEAM device demonstrates the feasibility of THz-based electron accelerators, manipulators and diagnostic tools enabling science beyond current resolution frontiers with transformative impact.
The generation of THz-frequency radiation via nonlinear parametric frequency down-conversion has long been driven by the spectroscopy and imaging communities. As a result, little efforts have been undertaken toward the generation of high energy THz-frequency pulses. THz-frequency radiation has however recently been identified has a promising driver for strong-field physics and an emerging generation of compact particle accelerators. These accelerators require THzfrequency pulses with energies in the multi-millijoule range therefore demanding orders of magnitude improvements from the current state-of-the-art.
Much can be gained by improving the intrinsically low efficiency of the down-conversion process while still resorting to existing state-of-the-art lasers. However, the fundamental Manley-Rowe limit caps the efficiency of parametric downconversion from 1-μm wavelength lasers to sub-THz frequency to the sub-percent range.
We present methods that promise boosting the THz radiation yield obtained via parametric down-conversion beyond the Manley-Rowe limit. Our method relies on cascaded nonlinear three-wave mixing between two spectrally neighboring laser pulses in periodically poled Lithium Niobate. Owing to favorable phase-matching, the down-conversion process avalanches, resulting in spectral broadening in the optical domain. This allows in-situ coherent multiplexing of multiple parametric down-conversion stages within a single device and boosting the efficiency of the process beyond the ManleyRowe limit. We experimentally demonstrated the concept using either broadband, spectrally chirped optical pulses from a Joule-class laser or using two narrowband lasers with neighboring wavelengths. Experimental results are backed by numerical simulations that predict conversion efficiencies from 1 μm to sub-THz radiation in the multi-percent range.
A cryogenically cooled Yb:YLF laser with 224-W output power at 995 nm, linearly polarized along the c-axis, has been
demonstrated, and laser oscillation has also been obtained polarized along the a-axis. The beam quality had an M2 ~ 1.1
at 60-W output and M2 ~ 2.6 at 180-W output for c-axis polarization. This level of average power is approximately two
orders of magnitude higher than demonstrated previously in cryogenic Yb:YLF. A cryogenic Yb:YLF mode-locked
oscillator is under development, which will be used to as the input to a Yb:YLF amplifier to generate a short pulses at
high average power.
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