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

TL;DR

This paper theoretically investigates how twisted light with orbital angular momentum can induce intersubband electronic transitions in quantum wells at normal incidence, expanding understanding of light-matter interactions in nanostructures.

Contribution

It derives the matrix elements for twisted-light-induced intersubband transitions and analyzes their dependence on orbital angular momentum in quantum wells.

Findings

Certain intersubband transitions are more favorable with specific orbital angular momentum values.

Normal incidence excitation of intersubband transitions is possible with twisted light due to electric field components along the propagation direction.

Theoretical framework for twisted-light interaction with semiconductor nanostructures is established.

Abstract

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