Controlling light emission with shaped electron wavefunctions

Abstract

The extent to which can one change the nature of spontaneous emission from a free electron by shaping the its wavefunction has been a long-standing question. In this work, we use both a semi-classical formalism and a QED formalism to show that Bremsstrahlung radiation can be tailored by altering the electron superposition states. Using the semi-classical formalism, we show that wavefunction shaping can greatly enhance the collimation of radiation from electron beams passing through spatially periodic electromagnetic fields, such as those in undulators. Moreover, the radiation from rapidly decelerated shaped electrons can be made directional and monochromatic. Using the QED formalism, we show that the radiation can be markedly different from an incoherent sum of the radiations of the two states because of interference between the scattering amplitudes from the two components of the superposition. The ability to control free electron spontaneous emission via interference may eventually result in a new degree of control over radiation over the entire electromagnetic spectrum in addition to the ability to deterministically introduce quantum behavior into normally classical light emission processes.