Plasmonic effects upon optical trapping of metal nanoparticles

Laser manipulation (Nuclear physics);Surface plasmon resonance;Nanoparticles;Metals--Optical properties;Micrurgy

Dienerowitz, Maria ; Dholakia, Kishan ; Dholakia, Kishan

University:University of St Andrews

Department:Physics & Astronomy (School of)

关键词: Laser manipulation (Nuclear physics);    Surface plasmon resonance;    Nanoparticles;    Metals--Optical properties;    Micrurgy;   

Others  :  https://research-repository.st-andrews.ac.uk/bitstream/handle/10023/1634/Maria%20Dienerowitz%20PhD%20thesis.PDF?sequence=6&isAllowed=y

来源: DR-NTU

【 摘 要 】

Optical trapping of metal nanoparticles investigates phenomena at the interface of plasmonics and optical micromanipulation. This thesis combines ideas of optical properties of metals originating from solid state physics with force mechanism resulting from optical trapping. We explore the influence of the particle plasmonresonance of gold and silver nanospheres on their trapping properties. We aspireto predict the force mechanisms of resonant metal particles with sizes in the Mieregime, beyond the Rayleigh limit.Optical trapping of metal nanoparticles is still considered difficult, yet it providesan excellent tool to investigate their plasmonic properties away from any interfaceand offers opportunities to investigate interaction processes between light andnanoparticles. Due to their intrinsic plasmon resonance, metal nanoparticles showintriguing optical responses upon interaction with laser light. These differ greatlyfrom the well-known bulk properties of the same material.A given metal nanoparticle may either be attracted or repelled by laser light,only depending on the wavelength of the latter. The optical forces acting on theparticle depend directly on its polarisability and scattering cross section. Theseparameters vary drastically around the plasmon resonance and thus not only changethe magnitude but also the direction and entire nature of the acting forces. Wedistinguish between red-detuned and blue-detuned trapping, that is using a trappingwavelength shorter or longer than the plasmon resonance of the particle. So faroptical trapping of metal nanoparticles has focussed on a wavelength regime farfrom the particle’s resonance in the infrared. We experiment with laser wavelengthsclose to the plasmon resonance and expand the knowledge of metal nanoparticletrapping available to date. Existing theoretical models are put to the test when wecompare these with our real experimental situations.