Abstract
We carry out an experimental campaign to investigate the nonlinear self-defocusing propagation of singular light beams with various complex structures of phase and intensity in a colloidal suspension of gold nanoparticles with a plasmonic resonance near the laser wavelength (532nm). Studying optical vortices embedded in Gaussian beams, Bessel vortices and Bessel-cosine (necklace) beams, we gather evidence that while intense vortices turn into two-dimensional dark solitons, all structured wavepackets are able to guide a weak Gaussian probe of different wavelength (632.8 nm) along the dark core. The probe confinement also depends on the topological charge of the singular pump.
Highlights
The engineering of nanostructured materials has led to an important revolution across several disciplines, including medicine, biology, chemistry, optics and optoelectronics, materials science, and physics [1,2,3,4]
While it was previously believed that fifthorder focusing was a crucial ingredient of the Kerr-like response to support stable lightinduced waveguides, as we demonstrate in the following the biosynthesized gold nanocolloid (BGN) material provided stable confinement, with ring-shaped vortices, but with all the singular beams
The maximum intensity employed in our experiments was five orders of magnitude lower than that employed in silver nanocolloids [12], indicating a significantly larger nonlinearity owing to a plasmon resonance at the pump wavelength
Summary
The engineering of nanostructured materials has led to an important revolution across several disciplines, including medicine, biology, chemistry, optics and optoelectronics, materials science, and physics [1,2,3,4]. In particular, the optical characteristics of materials have been tuned by properly tailoring size, shape and composition of the embedded nanostructures, as in the case of nanocolloids [5]. Colloidal suspensions of metallic nanoparticles (NP’s) have shown to exhibit unique optical, electrical and catalytic properties, stimulating the research on various physical and chemical processes for their synthesis. A few applications of metallic nanocolloids in photonics exploit their nonlinear optical response, which entails, for instance, the generation of self-confined wavepackets [5,6,11,12,13,14,15,16]
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