Quantum reflection of photons off spatio-temporal electromagnetic field inhomogeneities

Understand

We reconsider the recently proposed nonlinear QED effect of quantum reflection of photons off an inhomogeneous strong-field region.

• We present new results for strong fields varying both in space and time.
• While such configurations can give rise to new effects such as frequency mixing, estimated reflection rates based on previous one-dimensional studies are corroborated.
• On a conceptual level, we critically re-examine the validity regime of the conventional locally-constant-field approximation and identify kinematic configurations which can be treated reliably.