Multi-photon absorption in optical gratings for matter waves

TL;DR

This paper develops a comprehensive theory for the diffraction of large molecules and nanoparticles by optical gratings, considering absorption, phase modulation, and recoil effects, to better understand matter wave interference.

Contribution

It introduces a unified model combining absorption, phase shifts, and recoil in matter wave diffraction, accounting for internal degrees of freedom and dynamic internal state evolution.

Findings

The theory explains how absorption and phase modulation affect diffraction patterns.

Recoil effects resemble a quantum random walk in photon momentum steps.

Validation through dynamic internal state evaluation confirms the model's accuracy.

Abstract

We present a theory for the diffraction of large molecules or nanoparticles at a standing light wave. Such particles can act as a genuine photon absorbers due to their numerous internal degrees of freedom effecting fast internal energy conversion. Our theory incorporates the interplay of three light-induced properties: the coherent phase modulation due to the dipole interaction, a non-unitary absorption-induced amplitude modulation described as a generalized measurement, and a coherent recoil splitting that resembles a quantum random walk in steps of the photon momentum. We discuss how these effects show up in near-field and far-field interference schemes, and we confirm our effective description by a dynamic evaluation of the grating interaction, which accounts for the internal states.