Analysis of Kapitza-Dirac diffraction patterns beyond the Raman-Nath regime

TL;DR

This paper investigates Kapitza-Dirac diffraction of Bose-Einstein condensates beyond the traditional Raman-Nath regime, revealing how pulse duration and Fourier width influence diffraction patterns and providing insights for optical lattice calibration.

Contribution

It extends the understanding of Kapitza-Dirac diffraction by analyzing pulse duration effects and relating them to Fourier width and Rabi dynamics, beyond the standard Raman-Nath approximation.

Findings

Short pulses follow Raman-Nath predictions with reduced modulation depth

Fourier width of pulses affects diffraction patterns

Numerical models assist in calibrating optical lattices

Abstract

We study Kapitza-Dirac diffraction of a Bose-Einstein condensate from a standing light wave for a square pulse with variable pulse length but constant pulse area. We find that for sufficiently weak pulses, the usual analytical short-pulse prediction for the Raman-Nath regime continues to hold for longer times, albeit with a reduction of the apparent modulation depth of the standing wave. We quantitatively relate this effect to the Fourier width of the pulse, and draw analogies to the Rabi dynamics of a coupled two-state system. Our findings, combined with numerical modeling for stronger pulses, are of practical interest for the calibration of optical lattices in ultracold atomic systems.