Elimination, reversal and directional bias of optical diffraction

Abstract

We experimentally demonstrate the manipulation of optical diffraction, utilizing the atomic thermal motion in a hot vapor medium of electromagnetically-induced transparency (EIT). By properly tuning the EIT parameters, the refraction induced by the atomic motion may completely counterbalance the paraxial free-space diffraction and by that eliminates the effect of diffraction for arbitrary images. By further manipulation, the diffraction can be doubled, biased asymmetrically to induced deflection, or even reversed. The latter allows an experimental implementation of an analogy to a negative-index lens.Any image, imprinted on a wave field and propagating in free space, undergoes a paraxial diffraction spreading and eventually blurs. In many disciplines, the possibility to reduce or manipulate the diffraction is explored, for purposes such as imaging, wave guiding, microlithography, and all-optical light processing. As was recently demonstrated, arbitrary images can be imprinted on light pulses which are dramatically slowed when traversing a medium of room-temperature atoms [ 1,2], via the process of electromagnetically induced transparency [ 3,4]. In addition to the regular free-space diffraction, the slow-light images undergo diffusion due to the thermal atomic motion [ 5,6]. Here we report an experimental demonstration of a novel technique to eliminate

Generation and delayed retrieval of spatially multimode Raman scattering in warm rubidium vapors

“…The values measured for Krypton are consistent with collisions cross sections [27]. However, the value for Neon is higher than recently reported, by a factor of 4 [8] or 40 [28]. We have no good explanation for this observation, however owing to large discrepancies between reported values we display the data as a reference for possible future studies.…”

Uniform phase modulation via control of refractive index in a thermal atom vapor with vanishing diffraction or absorption

“…Paraxial diffraction of the probe beam throughout its propagation originates from the second term ∼ k 2 ⊥ on the left hand side. In the following, we will calculate the linear susceptibility χ(k ⊥ ) of the thermal medium in which [30,32,33]. At the same time, the remaining constant part c 0 of Re [χ] gives rise to a phase modulation to the probe field such that π-phase flips can be achieved overs short propagation lengths.…”

“…The lower Λ subsystem is in electromagnetically induced transparency configuration. Due to atomic motion and collisions, for a negative two-photon detuning between the probe and the control fields, paraxial diffraction for the probe can be exactly canceled, as initially proposed theoretically [29][30][31][32] and later demonstrated experimentally [33,34]. In essence, the elimination of diffraction is achieved, since each component of the probe field in the transverse momentum (k ⊥ ) space couples stronger with atoms moving in the opposite direction in the transverse plane, and is effectively dragged back towards the main axis.…”

Quantum state tomography of slow and stored light

“…Several experiments have demonstrated impressive fidelity (state preservation) and efficiency (amplitude preservation). [1][2][3][4][5][6][7] Despite these results, stored-light systems are typically evaluated using single-mode detection methods. 8 While the single mode approximation is valid for infinitely large ensembles, the finite spatial extent of all practical ensembles leads instead to a spatial distribution of the stored stationary excitation.…”