Coherent electron cyclotron maser emission in laser-ionized plasmas

We show that circularly polarized lasers create plasmas with long-lasting ring-shaped weakly relativistic momentum distributions that are prone to electron cyclotron maser instability in the presence of an ambient magnetic field. Theoretical results and particle-in-cell simulations show that current laser technology can effectively induce field-ionized tailored distribution functions and probe the electron cyclotron maser in controlled conditions. This provides direct experimental evidence of coherent radiation processes driven by ring-shaped or Landau-inverted momentum distributions relevant in extreme astrophysical conditions.