Moiré lattices are photonic lattices featuring moiré patterns.Quasiperiodic photonic moiré lattices possess flat energy bands,enabling the localization of the beam and long-distance optical guiding.However,intense lasers alter the induced refractive index of photorefractive crystals,limiting milliwatt-level guiding in quasiperiodic moiré lattices based on such materials.To realize effcient optical guiding with long-distance and low-dispersion propagation,this study introduces the concept of moiré lattices into plasmas,leveraging the high damage threshold of plasmas,and proposes a plasma moiré lattice.
Theoretical calculations were performed by approximating quasiperiodic moiré lattices with periodic ones constructed using specific adjacent angles and employing the finite difference method.It is demonstrated that plasma moiré lattices also exhibit flat energy bands where the propagation constant remains independent of the transverse wavenumber,providing a theoretical foundation for long-distance guiding.
Three-dimensional particle-in-cell simulations were conducted to investigate the guiding characteristics of relativistic intense laser pulses (a₀=1,corresponding to E_z =4 × 10¹² V/m) in plasma moiré lattices.Under the given parameters,the lattice can effectively confine laser pulses of different initial spot sizes to a similar channel depth,enabling stable long-distance propagation over d=1000λ₀.When the initial spot size exceeds the channel depth,part of the beam energy converges toward the center,leading to an increase in the peak intensity by a factor of two,while the other part is scattered,resulting in a decrease in total energy.
Under conditions of matched average density,compared to conventional preformed parabolic plasma density channels,the plasma moiré lattice significantly suppresses laser redshift usually caused by wakefield excitation.For example,for a high-energy short pulse (W=25.4 mJ,τ₀=15λ₀) or a low-energy long pulse (W=2 mJ,τ₀=30λ₀),the redshift in the moiré lattice is markedly less than that in the parabolic channel after propagating d=800λ₀,as stronger wakefield is excited in the latter.
By scaling the moiré lattice up 75 times,the plasma moiré lattice can effectively guide intense terahertz pulses (center frequency f₀=5 THz,λ₀=60 µm,a₀=0.45,W=24.7 mJ).During long-distance propagation up to 5Z_R(Rayleigh length) in the moiré lattice,intense terahertz pulses experience negligible photon deceleration,maintain their original central frequency,and achieve low-dispersion transmission.
The plasma moiré lattice provides a new approach for high-effciency,low-dispersion transmission of intense lasers and terahertz pulses.Potential experimental implementations could involve generating such lattices using two-beam interference with masks or dielectric barrier discharge methods,allowing tunable lattice constants for optimized guiding of diverse electromagnetic pulses.