Abstract
Nonlinear processes are at the core of many optical technologies whose further development require optimized materials suitable for nanoscale integration. Here we demonstrate the emergence of a strong bulk second-order nonlinear response in a plasmonic nanorod composite comprised of centrosymmetric materials. We develop an effective-medium description of the underlying physics, compare its predictions to the experimental results, and analyze the limits of its applicability. We demonstrate strong tunable generation of the p-polarized second-harmonic light in response to either s- or p-polarized excitation. High second-harmonic enhancement is observed for fundamental frequencies in the epsilon-near-zero spectral range. The work demonstrates emergence of structurally tunable nonlinear optical response in plasmonic composites and presents a new nonlinear optical platform suitable for integrated nonlinear photonics.
Highlights
Second-harmonic generation (SHG), a phenomenon in which the incoming radiation of a frequency ω is converted into the signal at a double frequency 2ω, is a fundamental nonlinear optical process that enables high-resolution microscopy, laser technology, and surface studies [1,2,3,4,5]
We show that re-shaping of electromagnetic fields in metamaterials with plasmonic components can be used to transform SHG from surface- to volume-dominated regime and engineer strong tunable bulk nonlinear response in plasmonic composites
We experimentally demonstrate tunable SHG from plasmonic nanorod metamaterials, develop a theoretical description of the observed phenomena, and prove that the nonlinear response can be engineered by changing structural parameters of the composite
Summary
Second-harmonic generation (SHG), a phenomenon in which the incoming radiation of a frequency ω is converted into the signal at a double frequency 2ω, is a fundamental nonlinear optical process that enables high-resolution microscopy, laser technology, and surface studies [1,2,3,4,5]. Materials with strong second-order nonlinear response can further advance a broad class of photonic applications, including frequency conversion, optical information processing, sensing, security, and healthcare. Natural optical materials with strong second-order nonlinearity are few, and new solutions are needed to develop nonlinear optics in compact, wavelength-scale, and integrated systems. Recent advances in nano- and microfabrication have brought into play a new class of composite media, often called metamaterials, whose optical properties are determined by shape and mutual arrangement of their components [6,7,8,9,10]. We show that re-shaping of electromagnetic fields in metamaterials with plasmonic components can be used to transform SHG from surface- to volume-dominated regime and engineer strong tunable bulk nonlinear response in plasmonic composites. We experimentally demonstrate tunable SHG from plasmonic nanorod metamaterials, develop a theoretical description of the observed phenomena, and prove that the nonlinear response can be engineered by changing structural parameters of the composite
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