Fig. 4: Simulated harmonic spectra for laser beams interacting with structured targets.
From: Laser harmonic generation with independent control of frequency and orbital angular momentum
a–c Surface height profiles of reflective targets with a conical dent (q = 1), and structures of q = −1 and q = −4, respectively. d–f The corresponding 2-D harmonic spectra from 3D simulations of these targets interacting with a CP pump pulse with ℓ = 0. g–l Same, for a circular aperture and structured targets of 2- and 5-fold symmetry, respectively (equivalent to q = 1, q = −1 and q = −4), with the profiles displayed as cross-sectional density maps at Z = 0.5λL.
