Generation of relativistic Bessel-Gaussian beams by conical plasma mirrors

Relativistically intense Bessel-Gaussian beams hold significant promise for high-intensity laser-plasma interactions, yet an effective method for their generation remains unexplored. Here we numerically demonstrate the direct generation of such beams by reflecting Gaussian beams off conical plasma mirrors in the relativistic and extreme nonlinear regime. Three-dimensional particle-in-cell simulations reveal that high-quality Bessel-Gaussian beams can be produced with above fivefold intensity enhancement and over 85% energy conversion efficiency. Furthermore, this scheme enables the generation of high-harmonic Bessel-Gaussian beams with short wavelengths and attosecond pulse durations. The proposed method is experimentally straightforward, offering a practical pathway for applications requiring intense Bessel-Gaussian beams.