Numerical simulation of atomic diffraction in the Raman-Nath regime

Ewan M. Wright, Pierre Meystre

A. P. Alodzhants, Sergei M. Arakelyan, Gagik Yu. Kryuchkyan

Alexander M. Lazaruk

Tao Shui, Wen‐Xing Yang, Shaopeng Liu +2 more

We propose and analyze an efficient scheme for the lopsided Raman-Nath diffraction of one-dimensional ($1\mathrm{D}$) and two-dimensional ($2\mathrm{D}$) atomic gratings with periodic parity-time ($\mathcal{PT}$)-symmetric refractive index. The atomic grating is constructed by the cold-atomic vapor with two isotopes of rubidium, which is driven by weak probe field and space-dependent control field. Using experimentally achievable parameters, we identify the conditions under which $\mathcal{PT}$-symmetric refractive index allows us to observe the lopsided Raman-Nath diffraction phenomenon and improve the diffraction efficiencies beyond what is achievable in a conventional atomic grating. The nontrivial atomic grating is a superposition of an amplitude grating and a phase grating. It is found that the lopsided Raman-Nath diffraction at the exceptional point (EP) of $\mathcal{PT}$-symmetric grating originates from constructive and destructive interferences between the amplitude and phase gratings. Furthermore, we show that the $\mathcal{PT}$-phase transition from unbroken to broken $\mathcal{PT}$-symmetric regimes can modify the asymmetric distribution of the diffraction spectrum and that the diffraction efficiencies in the non-negative diffraction orders can be significantly enhanced when the atomic grating is pushed into a broken $\mathcal{PT}$-symmetric phase. In addition, we also analyze the influence of the grating thickness on the diffraction spectrum. Our scheme may provide the possibility to design a gain-beam splitter with tunable splitting ratio and other optical components in integrated optics.

Tapio Simula, Atom Zh. Muradyan, Klaus Mølmer

We present an analysis of atomic diffraction due to the interaction of an atomic beam with a pair of Gaussian light pulses. We derive a simple analytical expression for the populations in different diffraction orders. The validity of the obtained solution extends beyond the Raman-Nath regime, where the kinetic energy associated with different diffraction peaks is neglected, into the so-called channeling regime where accurate analytical expressions have not previously been available for the diffraction. Comparison with experimental results and exact numerical solutions demonstrate the validity of our analytical formula.

Lilit A. Hovhannisyan

We extend the study of Kapitza-Dirac diffraction in Raman-Nath regime removing the limitations put on resonance detuning. Discussing the case of extended Raman-Nath regime we develop an approximation for the case of strong standing waves which will correspond to the well known tight-binding approximation for periodic structures. Due to internal structure of the diffracting particles the system eigenvalues and eigenfunctions show important differences from the generally known cases.