Tunable Anomalous Scattering and Negative Asymmetry Parameter in a Gain-Functionalized Low Refractive Index Sphere

Abstract

Usually, low refractive index passive spheres exhibit strong forward scattering and a positive asymmetry parameter due to weak interference between the electric and magnetic scattering channels. In this work, we investigate, analytically and numerically, the forward scattering of light by a gain-functionalized low refractive index dielectric sphere. It is shown that by tuning the optical gain one can optimize the interference, which provides a novel paradigm to achieve the zero forward scattering and negative asymmetry parameter even for a low refractive index sphere. As a result, a low-density collection of such identical back scatterers provides an anomalous regime, where the scattering mean free path and extinction mean free path are greater than the transport mean free path. Furthermore, we also provide the numerical guideline to achieve the larger extinction mean free path without achieving preferential back-scattering.

Tailoring radiation pressure on infinite slab using pair of non-collinear plane waves

“…3: (a It is clear that for passive slab, radiation pressure is positive for Im(n s ) ≥ 0. On the other hand, pressure is negative when slab is active [32,39,40] i. e. Im(n s ) < 0 as demonstrated in Fig. 3 (black lines).…”

Enantioselective optical forces in gain-functionalized single core-shell chiral nanoparticles

“…For concreteness, we consider a realistic gain model, where the dielectric core is doped with judicious amount of dye molecules [28][29][30]. For our purpose, we consider the gain properties of solvatochromic LDS 798 dye molecules [28,31,32] in a dielectric d host, which is a well established combination to achieve active particles [33,34]. The dye molecules are modelled as four level atomic systems with occupation number density N i , and 4 0 N i = N dye represents the total number of dye molecules per cubic meter.…”