Yanmin Wu

Analysis of Asymmetric Dipoles Interacting in Heterogeneous Metal Nanorod Dimers

The localized electric field enhancement of Au-Ag nanorods dimer is theoretically investigated based on finite element method (FEM). An analytical mutual-interference model between asymmetric dipole-dimer has been built to describe the dipoles coupling with different resonance modes in heterogeneous dimer. Three prominent enhancement peaks could be observed from ultraviolet to visible spectrum, in which the ultraviolet resonance especially corresponds to a higher mode in both Ag and Au nanorods. The results reveal the strong coupling mechanism among different dipoles existing in the asymmetric dipole system, which could support the design of plasmonic nanodevices in larger resonance wavelength range.

Ultrafast thermal excitation behaviors of Au films irradiated by polarization-shaped femtosecond laser

We theoretically investigated the ultrafast thermal excitation behaviors on Au films surface irradiated by polarization-shaped femtosecond laser. The spatio-temporal dynamics of temperature evolution in Au film with polarization-shaped femtosecond laser excitation are obtained based on Finite Element Method (FEM). It is revealed that the phonon temperature fields can be flexibly adjusted by optimizing the polarization state combinations of polarization-shaped double femtosecond laser pulses. The results are attributed to pulse synthetic effect, which closely depends on the polarization state combinations of double femtosecond laser pulses. The study provides the basic for understanding of the thermal excitation dynamics for optimizing laser micro and nano-fabrications via tailoring the polarization state of temporally shaped femtosecond laser.

Tuning near-field enhancements on an off-resonance nanorod dimer via temporally shaped femtosecond laser

We theoretically investigated ultrafast thermal dynamics tuning of near-field enhancements on an off-resonance gold nanorod dimer via temporally shaped femtosecond (fs) laser double pulses. The nonequilibrium thermal excitation is self-consistently coupled into a near-field scattering model for exploring the ultrafast near-field enhancement effects. It is revealed that the near electric-field localized within the gold nanorod dimer can be largely promoted via optimizing the temporal separation and the pulse energy ratio of temporally shaped femtosecond laser double pulses. The results are explained as thermal dynamics manipulation of plasmon resonances in the nanorod dimer via tailoring temporally shaped femtosecond laser. This study provides basic understanding for tuning near-field properties on poorly fabricated metallic nano-structures via temporally shaped femtosecond laser, which can find potential applications in the fields such as fs super-resolution near-field imaging, near-field optical tweezers, and fs photothermal therapy.

Ultrafast dynamics of near-field enhancements at an off-resonance nano-dimer via femtosecond laser excitations

Giant electric-field enhancements localized on nano-antennas are important for the optical near-field applications in fields such as super-resolution imaging, near-field optical tweezers, and photothermal therapy. Physically, the field enhancement requires plasmon resonance with respect to structure matching. We report a tunable near-field effect, including localized electric-field enhancement and resistive heating at an off-resonance Au nano-sphere dimer via femtosecond laser irradiation. The near field was strongly modified (up to 81 times) with respect to time evolution at a laser fluence of . The results are explained as thermal dynamics manipulation of the Au nano-sphere dimer plasmon resonances. This study provides a new alternative route to tailoring the near-field enhancement for wide applications in nano-antennas.