Intriguing phenomena in cold atomic gasses caused by radiation pressure (Prof. T. Ban)

In the first part of the talk I will show how the frequency-comb excitation of cold rubidium atoms can probe the boundary between the quantum and the classical worlds, complicating the calculation of the radiation pressure force on atoms induced by the frequency comb [1]. We experimentally investigate the radiative force and laser-induced fluorescence (LIF) in cold rubidium atoms induced by pulse-train (frequency-comb) excitation. Three configurations are studied: (i) single-pulse-train excitation, (ii) two in-phase counterpropagating pulse trains, and (iii) two out-of-phase counterpropagating pulse trains. In all configurations, measured LIF is in agreement with calculations based on the optical Bloch equations. The observed forces in the first two configurations are in qualitative agreement with the model(s) used for calculating mechanical action of a pulse train on atoms; however, this is not the case for the third configuration. Possible resolution of the discrepancy will be discussed.

Second part of the talk will be devoted to the investigation of the synthetic Lorentz force in cold (but still classical) atomic gasses via radiation pressure and Doppler effect. Recently we proposed a new scheme for synthetic magnetism, based on the Doppler effect and radiation pressure [2]. I will provide the first experimental results which demonstrate a radiation pressure force on cold atomic cloud which depends on the velocity of the cloud, and is perpendicular to it [3]. Our experiments are performed with 87Rb atoms in a magneto-optical trap.

References:
[1] G. Kregar, N. Šantić, D. Aumiler, H. Buljan, T. Ban: Frequency-comb-induced radiative force on cold rubidium atoms, Phys. Rev. A 89, 053421 (2014).
[2] T. Dubček, N. Šantić, D. Jukić, D. Aumiler, T. Ban, H. Buljan: Synthetic Lorentz force in classical atomic gases via Doppler effect and radiation pressure , Phys. Rev. A 89, 063415 (2014).
[3] N. Šantić, T. Dubček, D. Aumiler, H. Buljan, and T. Ban: Experimental demonstration of synthetic Lorentz force on cold atomic gasses using radiation pressure, in preparation.