We numerically study the propagation of a Laguerre-Gaussian beam through polar molecular media via the exact solution of full-wave Maxwell-Bloch equations where the rotating-wave and slowly-varying-envelope approximations are not included. It is found that beyond the coexistence of odd-order and even-order vortex harmonics due to inversion asymmetry of the system, the light propagation effect results in the intensity enhancement of a high-order vortex harmonics. Moreover, the orbital momentum successfully transfers from the fundamental laser driver to the vortex harmonics which topological charger number is directly proportional to its order.
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We develop a wave representation to characterize the propagation evolution of vortex lattice beams, which are produced through a frequency-doubling process of various high-order laser modes, followed by mode conversion. Their phase fields and phase gradients are further analyzed to verify the topological charge for each isolated vortex, as well as the symmetry and net charges of the vortex lattices. In the experiment, we demonstrate the generation of frequency-doubled high-order modes by utilizing an off-center pumped solid-state laser combined with intracavity second-harmonic generation.
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Article Synopsis
- Toroidal vortices are advanced light structures that could have applications in fields like quantum information and photonic topology.
- The study explores how these vortices interact with atoms to produce unique harmonic spectra, showcasing a new type of high-order topological vortices due to their rotating fields.
- By combining toroidal and optical vortices, researchers can create optical hopfions in the extreme ultraviolet range, leading to new ways to control their topological properties and direct specific harmonics through a single mode.
The generation of tunable extreme-ultraviolet (EUV) vortex beams is highly sought after for optoelectronic applications in the EUV region. In this study, we investigate the generation of vortex high-order harmonics using a ring Pearcey-Gaussian vortex beam as the driving source. We analyze the beam's spatial structure through phase-matching conditions and simulate high-order harmonic generation by solving the Maxwell wave equations.
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