Author Affiliations
Abstract
1 Advanced Photonics Center, Southeast University, Nanjing 210096, China
2 Nanjing Normal University, Nanjing 210023, China
Plasmonic resonance with Fano lineshape has attracted a great deal of recent interest. Here we design a new structure with a dimer grating upon a gold film separated by a layer of silica spacer, which has two resonant modes corresponding to the dimer’s localized surface plasmon resonance and the surface plasmon resonance excited by the dimer grating. This structure has three advantages for near-infrared detection in water. First, it provides two resonant modes to enhance the excitation and scattered signals of surface-enhanced Raman scattering. Second, coupling of these two modes results in a Fano resonance, providing a higher electric field enhancement. Finally, the dimer provides more flexible tunability compared to a single disk structure.
Plasmonics Plasmonics Surface-enhanced Raman scattering Surface-enhanced Raman scattering Photonics Research
2015, 3(6): 06000313
Author Affiliations
Abstract
Advanced Photonic Center, Southeast University, Nanjing 210096, China
“Giant” CdSe/CdS core/shell nanocrystals (NCs) were synthesized with thick CdS shell (15 monolayers), and the x-ray diffraction (XRD) measurement indicates there is a zinc blende phase in the thick CdS shell, whereas it transformed into wurtzite phase under 5 min radiation with a 400 nm, 594 μJ∕cm2 femtosecond (fs) laser beam. The evolution of the NCs’ spontaneous emission under the fs laser radiation was recorded with a Hamamatsu streak camera. The as-synthesized NCs exhibit an amplified spontaneous emission (ASE) at 530 nm, which comes from a bulk-like CdS shell due to the interfacial potential barrier, which could slow down the relaxation of holes from the shell to the core. After being annealed by an fs laser, the ASE of the g-NCs is transferred from a bulk-like CdS shell to a quantum-confined CdSe core because the phase transformation determined with the XRD measurement could remove the interfacial barrier. Besides the ASE at 643 nm, two shorter-wavelength ASE peaks at 589 and 541 nm, corresponding to optical transitions of the second (1P) and third (1D) electron quantization shells of the CdSe core, also appear, thus indicating that Auger recombination is effectively suppressed.materials
Laser materials processing Laser materials processing Semiconductor lasers Semiconductor lasers Laser Laser Photonics Research
2015, 3(5): 05000200
