Can dielectric laser accelerators reach staged MeV gain with useful charge
In plain words
Laser-driven glass chips have accelerated electrons, giving up to about half an MeV in a single structure; whether many structures can be chained for MeV-scale gain while keeping the beam focused and carrying useful charge is unknown.
Precise statement
Dielectric laser accelerators with alternating-phase focusing have shown coherent acceleration and transport of sub-relativistic electrons over sub-millimeter lengths (2021-2023), and single unstaged gratings driven by pulse-front-tilted lasers have given energy modulation up to $\sim 0.5\,\mathrm{MeV}$ for relativistic electrons (UCLA, 2024-2025). Determine whether a staged DLA can deliver net energy gain above $1\,\mathrm{MeV}$ with transverse and longitudinal confinement and at least $1e4$ electrons per optical microbunch train, given apertures of order the laser wavelength ($\sim 1e-4\,\mathrm{cm}$), wakefields, space charge and laser damage.
What would settle it
A demonstration of $> 1\,\mathrm{MeV}$ net gain in a chained DLA with measured transmission and emittance, or a proof that wakes and space charge forbid it at the stated charge.
Status in the literature
Unverified note
Sub-relativistic phase-space control on chips (2021-2023) and up to $\sim 0.5\,\mathrm{MeV}$ unstaged energy modulation of relativistic electrons (Crisp et al., Phys. Rev. Accel. Beams 27, 051303, 2024, https://doi.org/10.1103/PhysRevAccelBeams.27.051303, extended in a 2025 UCLA thesis) are reported; staged, confined MeV gain is not.