Generation of tunable relativistic bichromatic counterrotating circularly-polarized laser pulses

Abstract Circularly-polarized (CP) high harmonics (HHs) are pivotal for investigating chirality-sensitive light-matter interactions. While bichromatic counterrotating (BC) CP lasers have proved effective in diverse applications, particularly in producing CP HHs, their generation at relativistic intensities remains challenging because of the damage threshold of conventional optics. Here, we propose a novel and highly integrated approach to generate relativistic BCCP pulses, where a magnetized plasma slab is utilized to serve as an indestructible waveplate and filter simultaneously. When a bichromatic linearly-polarized laser pulse propagates through this plasma optic, each branch of the incident pulse will split into two CP pulses with opposite helicity and different dispersion relations. We identify a parameter window where the plasma optic acts as a filter that allows only the right CP pulse at lower frequency and the left CP pulse at higher frequency to propagate, constructing a BCCP field. Its topological properties can be easily manipulated via adjusting the initial components of the incident lasers. Three-dimensional particle-in-cell simulations demonstrate the feasibility of our approach with currently available laser facilities. This paves the way for producing intense CP HHs and manipulating the topology of materials and particle beams.