RESUMO
Spatio-spectral and spatio-temporal transfer and intensity propagation of truncated ultrashort-pulsed Bessel-Gauss beams were investigated. Extended needle-shaped focal zones were generated using a compact setup with a reflective small-angle axicon and self-apodized truncation by an adapted aperture. Spectral maps of Bessel-Gauss beams were analyzed on the basis of higher order statistical moments. Compared to focused pulsed Gaussian beams with their spectrally dependent propagation, an ultrabroadband spatio-spectral transfer function was detected over Rayleigh ranges exceeding 10 cm. These results indicate favorable pseudo-nondiffracting characteristics not only from the point of view of spatial propagation but also with respect to the spectral and temporal stability.
Assuntos
Cor , Desenho Assistido por Computador , Modelos Teóricos , Óptica e Fotônica/instrumentação , Processamento de Sinais Assistido por Computador/instrumentação , Simulação por Computador , Desenho de Equipamento , Análise de Falha de Equipamento , Distribuição Normal , Reprodutibilidade dos Testes , Sensibilidade e EspecificidadeRESUMO
We report the first observation of subradiance in plasmonic nanocrystals. Amplitude- and phase-resolved ultrafast transmission experiments directly reveal the coherent coupling between surface plasmon polaritons (SPPs) induced by periodic variations in the dielectric function. This interaction results in the formation of plasmonic band gaps and coupled SPP eigenmodes with different symmetries, as directly shown by near-field imaging. In antisymmetric modes, radiative SPP damping is strongly suppressed, increasing the SPP lifetime from 30 fs to more than 200 fs. The findings are analyzed within a coupled resonance model.