Twisted-light-induced intersubband transitions in quantum wells at normal incidence

摘要

We examine theoretically the intersubband transitions induced by laser beamsof light with orbital angular momentum (twisted light) in semiconductor quantumwells at normal incidence. These transitions become possible in the absence ofgratings thanks to the fact that collimated laser beams present a component ofthe light's electric field in the propagation direction. We derive the matrixelements of the light-matter interaction for a Bessel-type twisted-light beamrepresented by its vector potential in the paraxial approximation. Then, weconsider the dynamics of photo-excited electrons making intersubbandtransitions between the first and second subbands of a standard semiconductorquantum well. Finally, we analyze the light-matter matrix elements in order toevaluate which transitions are more favorable for given orbital angularmomentum of the light beam in the case of small semiconductor structures.