Structured beams invariant to coherent diffusion

Abstract

Bessel beams are renowned members of a wide family of non-diffracting (propagation-invariant) fields. We report on experiments showing that non-diffracting fields are also immune to diffusion. We map the phase and magnitude of structured laser fields onto the spatial coherence between two internal states of warm atoms undergoing diffusion. We measure the field after a controllable, effective, diffusion time by continuously generating light from the spatial coherence. The coherent diffusion of Bessel-Gaussian fields and more intricate, non-diffracting fields is quantitatively analyzed and directly compared to that of diffracting fields. To elucidate the origin of diffusion invariance, we show results for non-diffracting fields whose phase pattern we flatten.

Angular dependence of spatial frequency modulation in diffusion media

“…Our findings here provide a new interpretation mechanism for some imperfect experimental results, which were ignored in previous works [22,23]. In some scenarios where misalignment between the control and the probe is anticipated, such as spatially filtering the control noise from the weak probe beam when storing single-photon level quantum states [34] in hot atomic vapor [19], such diffusion influence should be taken into consideration.…”

“…Another prominent motional-induced effect is coherent diffusion. In the general light storage experiments associated with collinear probe-control configuration, coherent diffusion operates as a low-pass filter in the spatial frequency (SF) space (q-space) and wipes out the high SF components of the stored probe field [22][23][24]. For a scalar field or * wcy199202@gmail.com an optical image, the details of its spatial structure depend on the high SF components, and the loss of which would result in a blurry image.…”

A practical guide to electromagnetically induced transparency in atomic vapor

“…As a result, a uniform drift velocity of the atoms results in transverse drag of the probe field [64], while a diffusive motion of the atoms results in spatial diffusion of the field [65][66][67]. Notably, the diffusion here is of a complex quantity (a 'coherent diffusion' of both the argument and the phase of the field) and it therefore demonstrates interference phenomena, such as self-similar expansion and contraction of the probe field [68][69][70]. More intriguing results occur slightly off the EIT resonance, such as negative drag and negative diffraction [71,72].…”

Anomalous transport in periodic photonic chains with designed loss

“…In the space-continuous regime (i.e, when the discrete number of the mode is changes to continuous variable) Eq. ( 2) describes coherent diffusion of field spatial coherence 31,32 . Such coherent diffusion of a complexvalued fields can be found also in other fields of physics, for example, when studying atomic coherence in a gas of diffusing atoms 33,34 , or restricted diffusion in a magnetic field 35 , or spin-transport in semiconductors 36 .…”