Enhancing the Contrast of Matter-Wave Gratings using Optical Channeling and Optimization of Near Resonant Bragg Scattering

We investigate methods to increase the visibility of a density grating formed by exposing a sample of ultracold atoms to an optical standing-wave pulse. We show that channeling oscillations, which transiently increase grating contrast, can be imprinted on the free-induction decay signal following standing wave excitation as well as on the echo signal associated with a two-pulse atom interferometer (Carlse et al. Phys. Rev. A, 109, 043307 (2024)). We further explore how both the grating free-induction decay and grating echo can be optimally read-out by Bragg scattering a near-resonant travelling wave optical pulse (Carlse et al. Phys. Rev. A, 110, 043306 (2024)). We find that a 20-fold increase in scattering efficiency can be achieved when the channeling and Bragg scattering processes are optimized. Experimental work is supported by a simple model for grating formation which describes the density modulation as the combination of classical channeling and momentum-state interference resulting in Pendellösung-like oscillations in the grating contrast. We show that grating reflectivity spectra are well-modelled using a transfer matrix approach to describe the coherent scattering process, which also yields a quantitative characterization of atomic confinement resulting from optical channeling.