Plasma effects in harmonic emission in relativistic laser interactions with overdense plasma targets examined from single particle radiation models

Abstract

Multiple attosecond pulse generation in relativistically laser-driven overdense plasmas X Lavocat-Dubuis, F Vidal, J-P Matte et al.High-order harmonic generation using plasma mirrors F Quéré, C Thaury, H George et al. Abstract. Intense femtosecond laser pulses incident on supercritical plasmas can generate reflected high-order harmonics of the fundamental frequency that extend over the xuv spectral region, characterized by a power decay Pm ∼ m −p , where m is the harmonic number. It has been shown in earlier reports that plasma effects can modify the emission spectrum producing decay indexes p significantly weaker than the universal value 8/3 predicted by the similarity theory, these being within the range 4/3 ≤ p ≤ 8/3. In this paper we employ two single particle radiation models to demonstrate that plasma density effects substantially modify the emission radiated by a relativistic electron accelerated by the electric field of the laser pulse, and show that the harmonic power decay is commonly characterized by the indexes 4/3 and 5/3, with remarkable similitudes to those particle-in-cell results recently reported in ultrarelativistic laser-plasma interactions.