Author: van der Zande, W.J.
Paper Title Page
TUP067
 Influence of the Lower Frequency Branch on the Performance of a Waveguided THz FEL  
 
  • V.O. Yatsyna, V. Zhaunerchyk
    University of Gothenburg, Gothenburg, Sweden
  • R.T. Jongma, W.J. van der Zande
    Radboud University, Nijmegen, The Netherlands
  
  Funding: We would like to acknowledge the financial support from Swedish Research Council and Swedish FEL Center.
The Ter­a­hertz (THz) fre­quency range is highly rel­e­vant in many ap­pli­ca­tions rang­ing from med­i­cine to se­cu­rity and com­mu­ni­ca­tion. Among dif­fer­ent avail­able THz sources, free elec­tron lasers (FELs) are the most pow­er­ful and ver­sa­tile sources that pro­vide tun­able light in the whole THz re­gion. THz FELs usu­ally op­er­ate as os­cil­la­tors and em­ploy a wave­guide to sup­press dif­frac­tion losses. When a wave­guide cov­ers only a part of the op­ti­cal cav­ity, sub­stan­tial drops of the out­put power at cer­tain wave­lengths are ob­served *. The THz FEL FLARE op­er­at­ing in the wave­length range of 0.1-1.5 mm com­prises a wave­guide which cov­ers the whole cav­ity length**. Sur­pris­ingly, the spec­tral gaps are still ob­served. To get in­sight into ori­gin of the gaps, we per­form nu­mer­i­cal sim­u­la­tions tak­ing into ac­count both lower and higher res­o­nant fre­quency branches, as well as in­ter­ac­tion be­tween 150 THz pulses that si­mul­ta­ne­ously prop­a­gate through the FLARE cav­ity. Sim­u­la­tions pre­dict that the lower fre­quency branch can ham­per am­pli­fi­ca­tion of the other branch and, thus, can lead to the spec­tral gaps.
* R. Prazerez et al. Phys. Rev. ST Accel. Beams 12, 010701 (2009)
** R. Chulkov et al. Multi-Mode Dynamics in a Short-Pulse THz FEL. Phys. Rev. ST Accel. Beams, to be published in 2014 		 
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