Abstract
Abstract Nonlinear optical materials are cornerstones of modern optics including ultrafast lasers, optical computing, and harmonic generation. The nonlinear coefficients of optical materials suffer from limitations in strength and bandwidth. Also, the nonlinear performance is typically monotonous without polarization selectivity, and to date, no natural material has been found to possess nonlinear coefficients with positive or negative signs simultaneously at a specific wavelength, all of which impede practical applications in the specific scenario. Here, we realize broadband large optical nonlinearity accompanied with ultrafast dynamics in a coupled system composed of gold dolmens and an epsilon-near-zero material for dual orthogonal polarizations simultaneously. The system also shows the polarization-selected nonlinearity transition properties, where the sign of the optical nonlinear refractive indexes can be converted via polarization switching. This guarantees active transitions from self-focusing to self-defocusing by polarization rotation without tuning wavelength in practical utilizations. The measured nonlinear refractive index and susceptibility demonstrate more than three orders of magnitude enhancement over a 400-nm-bandwidth compared with the constituents, while maintaining the sub-1 ps time response. The realized enhanced, ultrafast response, and the polarization tunability ensure the designed system a promising platform for the development of integrated ultrafast laser sources, all-optical circuits and quantum chips.
Highlights
Material’s all-optical nonlinearity, i.e., the dynamic change of refractive index with an injected pump laser and the ability for wavelength conversion, is the basis for the realization of integrated all-optical switches, ultrafast laser sources, active polarization controllers, and quantum optical circuits, which are essential for building next-generationThis work is licensed under the Creative Commons Attribution 4.0X
We propose a material system formed by composite gold dolmen nanostructures that are strongly coupled to an ultrathin ENZ film placed beneath, and it demonstrates simultaneous large and ultrafast all-optical nonlinearity in both the orthogonal polarizations in a broadband spectral range simultaneously
In a 400-nm-bandwidth measurement range, this coefficient with a large enhancement can be maintained without polarization limitation
Summary
Material’s all-optical nonlinearity, i.e., the dynamic change of refractive index with an injected pump laser and the ability for wavelength conversion, is the basis for the realization of integrated all-optical switches, ultrafast laser sources, active polarization controllers, and quantum optical circuits, which are essential for building next-generation. We propose a material system formed by composite gold dolmen nanostructures that are strongly coupled to an ultrathin ENZ film placed beneath, and it demonstrates simultaneous large and ultrafast all-optical nonlinearity in both the orthogonal polarizations in a broadband spectral range simultaneously. Benefiting from efficient coupling between the plasmonic and ENZ modes, the large nonlinearity and sign-controlled is realized in a broadband range, which covers the entire measured 400-nm-range This provides the possibility for application in all-optical processing chips supporting wavelength-division multiplexing and partial division multiplexing with high capacity. Our system opens up opportunities for on-demand engineering a large ultrafast broadband optical nonlinear response accompanied with a positive or negative sign of nonlinear coefficients by polarization switching This lays the foundation for applications including ultrafast polarization control, all-optical active networks, and integrated quantum optics
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