Artist’s view of radial pressure distribution in water excited by a 9-ns laser pulse. The probe beam is illustrated in red. [M. Partanen, Aalto University]
One of the most fascinating debates in classical electrodynamics is the Abraham–Minkowski controversy—the question of a photon’s momentum inside dielectric media. The problem grew out of separate work by the physicists Max Abraham and Hermann Minkowski early in the 20th century that resulted in different, conflicting expressions for photon momentum. And, while numerous researchers have argued that the controversy is resolved, a complete understanding remains elusive. Indeed, the photon-momentum problem has drawn renewed attention in recent years, as researchers have explored complex optical behavior in materials such as conductors, semiconductors, plasmas and metamaterials.