München 2019 – scientific programme
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K: Fachverband Kurzzeit- und angewandte Laserphysik
K 4: Laser Systems II
K 4.1: Talk
Tuesday, March 19, 2019, 16:30–16:50, HS 3
Front-end for highly efficient multi-cycle THz generation — •Wenlong Tian1,2, Halil Olgun1,3,4, Yi Hua1,3, Damian Schimpf1, Nicholas Matlis1, and Franz Kartner1,3 — 1Center for Free-Electron Laser Science (CFEL), Deutsches Elektronen Synchrotron (DESY), Notkestraße 85, 22607 Hamburg, Germany — 2School of Physics and Optoelectronic Engineering, Xidian University, Xi'an 710071, China — 3Department of Physics and The Hamburg Centre for Ultrafast Imaging (CUI), University of Hamburg, 20355 Hamburg, Germany — 4Helmholtz-Institut Jena, Froebelstieg 3, 07743 Jena, Germany
High energy (>10 mJ) multi-cycle pulses in the frequency range of 0.1 THz ~1 THz are desired for powering THz-based electron accelerators capable of reaching energies up to ~10-100 MeV. The highest conversion efficiency in generating such THz pulses by optical means achieved to date is around 0.13%. Recent theoretical work predicts 1.6% total conversion efficiency using laser pulses comprised of two narrow spectral lines separated by the desired terahertz frequency. There are several methods to generate such line pairs such as spectral filtering. Our strategy is to build a front-end source with two phase-stable laser lines and then amplify them jointly. As reported here, the front-end comprises two single-frequency continuous-wave lasers, which are subsequently chopped to sub-ns duration, and has several advantages: (1) Both the frequency separation between the two lines and the pulse duration are controllable; (2) flat-top pulses rather than Gaussian temporal profile are achievable, which is beneficial for the THz generation.