Observation of transverse coherent backscattering in disordered photonic structures

Abstract

Coherent backscattering, also referred to as weak localization, is an exciting multidisciplinary phenomenon that appears in disordered systems of multiple coherent-wave scattering. Providing proper scattering conditions in (2 + 1) dimensional randomized photonic systems, we optically implement, observe, and analyse transverse coherent backscattering. Ensembles of disordered wave-guide structures are prepared by random-intensity nondiffracting writing entities according to the beam’s intensity distribution. The structure size of the induced potentials naturally define an effective mobility edge, and thus, we identify a crucial impact of the plane probe waves’ spatial frequency on the strength and shape of the spectral coherent backscattering signal. We additionally observe transverse elastic scattering as a precursor of weak localization. To testify the coherent character as a fundamental condition for coherent backscattering, we propose a scheme to continuously reduce the spatial coherence of the probe beam which directly reduces the degree of localization and coherent backscattering. With our experiments, we propose a testing platform that allows comprehensive examination of coherent backscattering with a broad set of preparation parameters and under uncritical laboratory conditions. Our results are directly transferable to more complex systems of disordered wave potentials, not being restricted to photonic systems.

Anisotropic nonlinear refractive index measurement of a photorefractive crystal via spatial self-phase modulation

“…arrays of coupled waveguides. It has been widely used to observe various families of optical discrete solitons [3][4][5], to study wave properties of quasicrystals [6] and graphenelike structures [7,8] as well as to evidence weak or strong transverse localisation in disordered lattices [9,10]. On the other hand, in homogeneous configuration, nonlinear patterns formation dynamics [11][12][13] as well as quantum hydrodynamical features of light [14][15][16] have been investigated.…”

Quantum boomeranglike effect of wave packets in random media

“…From an experimental point of view, this signature of Anderson localization could be observed in experiments on cold atomic gases, where wave-packet spatial distributions are customarily imaged. In optics, the retroreflection could be probed as well in transversally disordered photorefractive crystals or optical fibers where the coordinate of the optical axis plays the role of time: by illuminating such systems with a spatially narrow beam, one should observe a quantum boomerang of the beam center of mass in the transmitted, near-field intensity distribution [33,34].…”

Coherent multiple scattering of light in ( 2+1 ) dimensions

“…In Kerr media this idea was recently applied to study optical analogues of quantum matter-wave phenomena, like Bose condensation [3,4] or superfluidity [5,6]. In a similar spirit, in spatially disordered materials paraxial light propagation was exploited to observe the coherent backscattering (CBS) effect without interface [7], in a configuration that reproduces cold-atomic setups [8,9]. In the same context, transverse Anderson localization of optical wave packets [10] was reported in the paraxial limit [11,12].…”