• D. Kipnis, E. Dyunin, A. Gover
  University of Tel-Aviv, Faculty of Engineering, Tel-Aviv

Smith-Purcell radiation is the emission of electromagnetic radiation by an electron beam passing next to an optical grating. Recently measurement of relatively intense power of such radiation was observed in the THz-regime [1]. To explain the high intensity and the super-linear dependence on current beyond a threshold it was suggested that the radiating device operated in the high gain regime, amplifying spontaneous emission (ASE) [1,2]. We contest this interpretation and suggest an alternative mechanism. According to our interpretation the device operates as a distributed feedback (DFB) laser oscillator, in which a forward going surface wave, excited by the beam on the grating surface, is coupled to a backward going surface wave by a second order Bragg reflection process. This feedback process produces a saturated oscillator. We present theoretical analysis of the proposed process, which fits the reported experimental results, and enables better design of the radiation device, operating as a Smith-Purcell DFB laser.

[1] A.Bakhtyari, J.E.Walsh, J.H.Brownell, Phys.Rev. ·10⁶⁵ 006503 (2002). [2] H.L. Andrews, C.A. Brau, Phys.Rev. ST-AB 7, 070701 (2004).