Frequency-shifted sources for terahertz-driven linear electron acceleration

Vincent A. Leroux, Michael Hemmer, Giovanni Cirmi, Koustuban Ravi, Frederike Ahr, Luis Zapata, Anne-Laure Calendron, Huseyin Cankaya, Spencer W. Jolly, Hideki Ishizuki, Takunori Taira, Nicholas Matlis (+5 others)
2018 Nonlinear Frequency Generation and Conversion: Materials and Devices XVII  
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
more » ... 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 Manley-Rowe 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.
doi:10.1117/12.2295357 fatcat:bu6hgt4d2velrm6ji2a4o2dqry