Wave localization at the boundary of disordered photonic lattices

Abstract

We report on the experimental observation of reduced light energy transport and disorderinduced localization close to a boundary of a truncated one-dimensional (1D) disordered photonic lattice. Our observations uncover that near the boundary a higher level of disorder is required to obtain similar localization than in the bulk.OCIS codes: 130.2790, 240.6690 Light and particle dynamics in disordered media is a topic of continuously renewed interest. In solid-state physics, particles scattered by lattice defects generate a random walk, resulting in a transition from ballistic transport to complete suppression of transport when disorder exceeds certain level [1]. Due to this transition, the infinitely extended eigenmodes of the system are transformed into localized modes [2]. This is a universal concept applicable to a variety of physical settings [3,4]. Optical setups proved to be promising candidates to observe localization in random media [5][6][7][8][9][10] due to analogy of a solid and photonic lattice, where longitudinally invariant disorder can be realized [11,12]. Since the localization relies on fluctuations imposed on otherwise periodic structure, a truncation of a disordered lattice yields distortions of the underlying periodicity, which may have a strong impact on wave localization.In this Letter we observe wave-packet localization at the edge of disordered truncated 1D lattices for sufficiently large levels of disorder. A higher degree of disorder (as compared to disorder required for localization in the lattice center) is required to achieve the same degree of localization at the surface of the lattice, which we attribute to a repulsive potential arising in the vicinity of the boundary [13].

The random mass Dirac model and long-range correlations on an integrated optical platform

“…If that region is large enough and the disorder conditions are homogeneous across it, such a spatial average will be entirely equivalent to an ensemble average over many realizations of the same disorder on a smaller region 48 . This equivalence is commonly exploited in the optical observation of Anderson localization 18,49,50 and has recently been empirically verified 51 .…”

Probing the effect of interaction in Anderson localization using linear photonic lattices

“…In this way, one can obtain a strong interaction regime in the experimentally accessible 2D waveguide geometry without nonlinear materials. Randomized on-site energy for the diagonal disorder can be introduced by a controlled variation of the width [16] or the refractive index [45,46] of each waveguide while keeping the tunneling rates between waveguides constant. Randomized tunneling strength can be introduced by a controlled variation of the separation between adjacent waveguides [2,19,47], while keeping the symmetry with respect to the diagonal axis.…”

Light localization in nonuniformly randomized lattices

“…Under suitable conditions, disorder can even enhance wave transport in finite systems instead of arresting it [13]. In this context, upon analysis of Anderson light localization the disorder strength is usually considered invariable across the sample [6][7][8][9][10][11][12][13][14]. In contrast, in this Letter we study Anderson localization of light in non-uniformly randomized systems and show that if the statistical properties of disorder depend on the transverse coordinate, a specific statistical inhomogeneity emerges that drastically affects the light evolution.…”

“…Anderson localization has been observed in optically-induced [5] and fabricated [6][7][8] uniform lattices. While in unbounded disordered samples all eigenmodes would be localized, the presence of boundaries drastically affects light propagation [7,[9][10][11][12]. Under suitable conditions, disorder can even enhance wave transport in finite systems instead of arresting it [13].…”