Power efficient relativistic multi-stagell stable UV channel formation in underdense plasmas

Summary form only given. One of the chief attractive properties of the relativistic and ponderomotive self-channeling of ultraintense laser pulses in underdense plasmas [1,2] is the ability to control the stability of channel formation even when the initial peak power of the pulse P₀ substantially exceeds the critical power P_cr and the initial radius of the beam r₀ is much larger than the channel radius r_ch - the situation that typically leads to unstable self-channeling in initially uniform plasmas [3]. The essence of the stability control is the multi-stage channel formation with an appropriately increasing electron density gradient at the initial stage of the self-channeling [4]. This paper reports the results of recent experimental and numerical studies of the stability, efficiency, and robustness of the relativistic self-channeling of multi-TW UV pulses in underdense plasmas. The key findings are (1) the substantially increased power efficiency of the multi-stage relativistic self-channeling compared with the channel formation in initially uniform plasmas and (2) an exceptional level of stability and robustness of the relativistic channel formation.The characteristic dynamics of stable relativistic multi-TIN UV channel formation in underdense plasmas in the case of multi-stage self-channeling and channel formation in initially uniform plasma are presented in figure 1. For the multi-stage relativistic self-channeling the power losses due to the channel formation are reduced to 5 - 10% and the channeling power efficiency exceeds 90%; the characteristic corresponding figure for the stable multi-TIN relativistic self-channeling in initially uniform plasma is-60%. The stable power efficient relativistic self-channeling was one of the key factors for recent observation of nonlinear optical coupling in the keV x-ray regime [5].