Coherent Visible-Light-Generation Enhancement in Silicon-Based Nanoplasmonic Waveguides via Third-Harmonic Conversion

Abstract

We report visible third-harmonic conversion at λ=517 nm in subwavelength silicon-based nanoplasmonic waveguides at an unprecedented conversion efficiency of 2.3×10^{-5}. This marks both the highest third-harmonic conversion efficiency in a silicon-based or nanoplasmonic structure and the smallest silicon waveguide structure demonstrated to date. The high conversion efficiency is attributed to tight electric field confinement and strong light-matter coupling arising from surface plasmon modes in the nanoplasmonic waveguide, enabling efficient nonlinear optical mixing over micrometer length scales. The nonresonant geometry of the waveguide enables the entire λ=1550 nm femtosecond pulse spectrum to be converted to its third harmonic, which may be easily extended to the entire visible spectrum. We envisage that third-harmonic generation in silicon-based nanoplasmonic waveguides could provide a platform for integrated, broadband visible light sources and entangled triplet photons on future hybrid electronic-silicon photonic chips.

Light-induced metal-like surface of silicon photonic waveguides

“…Maximum impact is expected when the optical confinement is pushed so deeply into the subwavelength scale that the effective waveguide size approaches that of its own surface: this is for instance the case of nanoplasmonic structures, where the electric field is strongly localized and dramatically enhanced at a metal-Si interface25. In this case, a massive density of free carriers is expected to be generated by SSA well below the intensity threshold of non-linear effects.…”

Integration of silicon-loaded nanoplasmonic waveguides onto a micro-machined characterization beam for nonlinear optics applications

“…In the case of a nanoplasmonic waveguide, fields can be enhanced by several times their original strength. The enhanced fields can be used to magnify light-matter interaction processes, such as chemical detection [3] or nonlinear optical processes [4,5]. While plasmonic waveguides have several attractive characteristics, strong interaction of the radiation with metals results in propagation losses that are higher than photonic waveguides.…”

A compact frequency stabilized telecom laser diode for space applications

“…Furthermore, iodine lines around 515 nm have remarkable quality factor (Q > 2 x 10 9 ) [6], achievable with simple and compact experimental interrogation configurations using the well-known MTS technique. [7,8]. In early 2002, a first attempt to observe iodine lines via a THG of a telecom laser has been described using two second order nonlinear processes in a unique crystal [9].…”