Photon recoil momentum in dispersive media

TL;DR

This paper experimentally demonstrates that the photon recoil momentum in a dilute atomic gas is proportional to the gas's index of refraction, affecting high-precision atom interferometry.

Contribution

It provides the first direct measurement of how the index of refraction alters photon recoil momentum in dispersive media.

Findings

Recoil momentum is nħk, with n being the index of refraction.

Recoil frequency shifts were measured using a two-pulse light grating interferometer.

The effect is significant for precision measurements in atom interferometry.

Abstract

A systematic shift of the photon recoil due to the index of refraction of a dilute gas of atoms has been observed. The recoil frequency was determined with a two-pulse light grating interferometer using near-resonant laser light. The results show that the recoil momentum of atoms caused by the absorption of a photon is n\hbar k, where n is the index of refraction of the gas and k is the vacuum wavevector of the photon. This systematic effect must be accounted for in high-precision atom interferometry with light gratings.