Mode competition in superradiant scattering of matter waves

Abstract

Superradiant Rayleigh scattering in a Bose gas released from an optical lattice is analyzed with incident light pumping at the Bragg angle for resonant light diffraction. We show competition between superradiance scattering into the Bragg mode and into end-fire modes clearly leads to suppression of the latter at even relatively low lattice depths. A quantum light-matter interaction model is proposed for qualitatively explaining this result.PACS numbers: 03.75. Gg; 03.75.Hh; 42.50.Nn; 42.50.Gy The coherent nature of Bose-Einstein condensates has led to new and rapid developments in atom optics and studies on coherent interaction between light and matter waves, with the demonstration of efficient matter wave interferometers, Bragg diffraction, wave mixing, matter wave amplifiers. Superradiant scattering was for the first time analyzed using a Bose-Einstein condensate (BEC) in a seminal experiment by Ketterle et al. [1]. In this experiment the initial matter grating, formed due to Rayleigh scattering of a pumping beam by an elongated Bose-Einstein condensate and subsequent recoil into a moving matter wave, was self amplified by resonant light diffraction in a phenomenon called amplification of matter waves. Absorption of pumping photons and preferential scattering into so-called end-fire modes along the BEC's long axis lead to the observation of patterns of coherently recoiling atoms. Amplification of matter waves was further characterized with the use of an initial matter wave seed formed via Bragg diffraction of a Bose condensate and its coherence nature was demonstrated [2,3].For an elongated BEC, superradiant Rayleigh scattering light is emitted along the long axis because the gain for superradiance is maximum in this direction. However, different superradiant modes can be obtained when a matter wave seed with non-zero momentum is created before pumping since light can then be resonantly diffracted in a different direction [4]. No precise analysis of competition between different superradiant scattering modes has been carried out yet. Such analysis would be useful for calibrating precisely superradiance gains and initial Rayleigh scattering rates if one wants to use quantitatively superradiance for the analysis of coherence in Bose gases [5,6]. Analyzing superradiance with non common configurations is also important as combining early stage superradiance described with quantum theory and long timescale superradiance which is well captured within a semi-classical theory taking into account propagation effects is currently a topic of high interest [7,8] We present in this article an experimental analysis of mode competition in superradiance scattering. Rather than relying on an initial matter wave seed formed via Bragg diffraction of a BEC [2-4] our superradiance experiment is performed after initial adiabatic loading of a BEC along its long axis inside a 1D optical lattice [9]. The choice of contra propagating optical beams (wave vector ± k L ) for the optical lattice loading leads to the formation of a matte...

Second-order coherence of superradiance from a Bose-Einstein condensate

“…and, as a result, a complex nomenclature has evolved including the terms superradiance, superfluorescence, amplified spontaneous emission, mirrorless lasing, and random lasing [2, 4,[6][7][8][9], the distinctions among which we will not attempt to summarize here. The problem has recently seen renewed interest in the field of cold atoms [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25]. This is partly because cold atoms provide a reproducible, easily characterized ensemble in which Doppler broadening effects are small and relaxation is generally limited to spontaneous emission.…”

The scientific career and contributions of Prof. Wang Yiqiu

“…For example, they studied sequential scattering in superradiance from a Bose-Einstein condensate pumped by a two-frequency laser beam, which revealed that the frequency overlap between the end-fire modes related to different side modes plays an essential role in the dynamics of sequential superradiant scattering [90]. [91,92] studied the high-order momentum modes and mode competition in the superradiant scattering of matter waves. [93] studied superradiant scattering from a Bose-Einstein condensate using a pump laser incident at a variable angle and showed the presence of asymmetrically populated scattering modes.…”

Study to improve the performance of interferometer with ultra-cold atoms

“…The macroscopic coherent properties of ultra-cold atoms (29)(30)(31)(32)(33)(34)(35)(36)(37)(38)(39) are conducive to precise measurement. To make full use of the advantages of ultra-cold atomic coherence properties, one method is to reduce the manipulation time and another is to suppress the attenuation of coherence.…”