Study On Interaction Between Surface Plasmon Polaritons And Molecules And Its Time Resolved Spectroscopy

The development of information field has been one of the critical factors affectthe developing process of human society. There has being more and more requirementpresented for the information technology. Because of the quantum effect,microelectronic chip which has played an important role in information field couldhardly develop forward as Moore’s Law. Integrated optics has presented manypotential applications in the field of optical communication, because of its uniquefeatures such as highly integrated, fast response and fast transmission of information.But the optical diffraction limitation is the bottleneck to achieve micro/nanointegrated optical circuit in the scale of submicron. Surface plasmon polaritons(SPPs)provides a solution for breaking through the optical diffraction limitation to realize thenano-scale optical devices, so it has attracted a lot of researchers into this field.However, for surface plasmon polaritons, loss caused by the metal materials isrelatively significant, sometimes gain medium should be induced. In addition,interaction between surface plasmon polaritons and matter is somewhatworking-basement for many devices. There has been greater and greater importancein the study on interaction between surface pasmon polaritons and molecules, for thenature and relevant applications.Until now, the understanding on interaction between surface plasmon polaritonsand molecule is not still completed, especially using the time-resolved spectroscopy.For the weak coupling interaction, surface plasmon polaritons coupled emission isalways interfered by surface plasmon polaritons induced absorption enhancement, andits dynamic properties are not brought to light completely. In the case of strongcoupling interaction, all the reported works are performed under the non-resonanceexcitation condition, where the thermal effect dominates the relaxation process, the intrinsic property is not clear.Considering the discussion above, the main research contents of this thesis arelisted as follows:(a) Set up time-resolved fluorescence anisotropy measurement system based ontime corrected single photo courting setups, using single channel method, timeresolution0.2ns, range of measurement window50ns.(b) Set up wide spectra femtosecond pump-probe system, range of wavelengthfrom350nm to800nm, excitation wavelength tunable from350nm to700nm, timeresolution100fs, range of measurement window1500ps.(c) Fabricated Alq3on silver grating structures which exhibited the re-shapedemission spectra due to the mixing of the SPCE and the original emission offluorophores. The designed parameters in our experiments allowed us to observe theangular distribution and the p-polarized characteristics of the extra emission peakswithout the interference of surface plasmon induced absorption and the results ofFDTD simulations were in excellent agreement with the experimental data. Thetime-resolved fluorescence anisotropy experiments were performed and we obtainedthe value of-0.45, which could present the nature of the time-resolved fluorescenceanisotropy for SPCE during the relaxation process and was a deeper understanding forthe SPCE using time-resolved techniques. The unique characteristics of SPCE, suchas wavelength resolution ability and enhanced fluorescence emission with highlypolarization enable it with numerous potential applications on optical switches,increasing the efficiency of OLED devices, medical diagnostics and biologicalsensors.（d）We have constructed a molecule-coated Au-nanorod hybrid structure andstudied the photophysics of hybrid states using a ultrafast pump-probe approach.Under nonresonant excitation, the transient spectral features are simply caused by thethermal effect of Au-nanrods, and the kinetics reflects the electron-phonon relaxationprocess of Au electrons. Under resonant pump, the transient results demonstrate thatthe excitation energy is indeed shared by the longitudinal SP mode of Au-nanorodsand the excited state of Thia J-aggregates, and the SP and exciton decay with exactlyIV same rate. This gives a robust proof of coherent coupling between exciton and SPmode. The coherent coupling lasts very short, a level of200fs, which is dominated byultrafast damping of SP mode. The photophysics has very similar behaviors as thepolaritons in optical microcavity. So, it opens a very good opportunity to realize thesame function as expected from an optical microcavity such as polariton laser atnanoscale and also related quantum optical study.