Ultrafast laser inscribed waveguide lattice in glass for direct observation of transverse localization of light

Abstract

We present initial results of the direct observation of the signature of localized light in an ultrafast laser-inscribed (ULI) disordered lattice that contains an array of evanescently coupled, one-dimensional optical waveguides in glass in which certain amount of disorder in refractive index was introduced. Numerical simulations were carried out to test the feasibility of the initial experimental design. Such configurable ULI disordered waveguide lattices should open up a platform for investigating the phenomenon of transverse localization of light and its statistical nature.

Analysis of transverse Anderson localization in refractive index structures with customized random potential

“…Furthermore, important experimental work was done to demonstrate AL of light waves, for instance in a granular medium of high refractive index modulation in three dimensions [6]. Transverse localization [8] in a medium with a refractive index modulation in one or two dimensions was explored in semi-conductor substrates including nonlinear effects [15] and direct laser written random photonic systems [16,17], but also in disordered optical glass fibers [18] as well as in photorefractive crystals [19,20].…”

Confinement of Light in Disordered Photonic Lattices: A New Platform for Waveguidance

“…We consider an evanescently coupled waveguide array (as photonic lattice) consisting of a large number (N) of unit cells, and in which all the waveguides spaced equally apart are buried inside a medium of constant refractive index n 0 [5,7]. The overall structure is homogeneous in the longitudinal (z) direction along which the incident optical beam is assumed to propagate.…”

“…The dependence of the localized state on the shape of an optical beam when it is coupled into an evanescently coupled, disordered, waveguide lattice has been studied. We had performed an experiment using ultrafast laser inscription (ULI) technique to demonstrate our numerical findings [7]. We have studied the nature of input light coupling to different localized modes of a disordered medium under different input excitation conditions.…”

Effect of a weak longitudinal modulation in refractive index on transverse localization of light in 1D disordered waveguide lattices

“…To design a discrete photonic system to study light localization, we consider an evanescently coupled waveguide lattice consisting of a large number (N) of unit cells, and in which all the waveguides spaced equally apart are buried inside a medium of constant refractive index n 0 [4,5,9,10]. The overall structure is homogeneous in the longitudinal (z) direction along which the optical beam is assumed to propagate, as shown in Fig.…”

“…However this scheme was first experimentally implemented in 2007 [3], which was the first experimental observation of Anderson localization in any periodic system containing disorder in its original context. Numerous works followed up this scheme [3][4][5] and in recent years, there has been a resurgence of interest in this area from fundamental physics point of view, as well as applications in photonics like disordered/random lasing in disordered medium [6,7]. Various platforms are being investigated in all three dimensions of multilayer photonic structures to realize these disordered lasing systems.…”