Intense laser–plasma interactions generate high-order harmonics, providing a route to coherent extreme ultraviolet and x-ray sources, but their complex spatial properties limit practical applications. Two-dimensional particle-in-cell simulations show that tailoring the laser transverse profile controls the spatial characteristics of high-order harmonics through modification of the plasma surface curvature. At fixed peak intensity, increasing the beam waist radius from to reduces the full width at half maximum (FWHM) of the harmonic emission by approximately 26%. Under fixed laser energy, a larger beam waist radius improves harmonic collimation at the expense of intensity, revealing a trade-off between brightness and beam confinement. Compared with a Gaussian laser, a super-Gaussian laser reduces the harmonic FWHM by approximately 65% while increasing the peak intensity by more than 150%. These results identify the beam waist radius and transverse laser profile as key parameters for optimizing harmonic collimation and brightness.
Development and successful application of a new optically pumped far-infrared laser for polarimeter-interferometer on the EAST tokamak