Applied Optics
Our group participates in several applied optics projects and provides a theoretical support for them. One of such projects aims at developing the "Quantum Proximity Microscopy." It started as collaboration with the experimental groups of Profs Y. Prior, A.Shanzer and Dr. G. Haase from our Institute. We concentrated on introducing novel concepts and developing theoretical aspects of the operation of the apertureless Scanning Near-Field Optical Microscope (SNOM). The latter uses dielectric or metallized AFM tip for scanning over nanoobjects (or even single molecules) in the presence of an external laser field. Metallized tips are known to enhance the field intensity due to their sharp shape and localized plasmon excitations. The size of the strong-field domain around the tip may be much smaller than the wavelength of light, thus providing the basis for the sub-wavelength resolution. We study coherent and collective effects in the elastic light scattering from the "tip+single molecule" complex. In particular, we showed that the light scattering occurs via two main channels: direct scattering from the tip, and tip-mediated molecular scattering. In the latter case, the tip not only enhances the external field, but also serves as an efficient “antenna” for the molecular dipole oscillations. The total intensity of the scattered light that is detected in the far-field zone shows interference of the channels. Being an extremely sensitive effect, this interference can be used for enhancing the spatial resolution, especially in the case of a strong coupling between plasmon excitations of the tip and a resonant molecular transition. In addition, we investigated in detail the process of radiationless energy transfer between resonant molecules in the presence of a nano-sized tip, and revealed different mechanisms for controlling the Forster-type processes in the near-field zone. Another recent project concerns metal, semiconductor and soft matter processing by femtosecond laser pulses. This is German-Israeli collaboration with C. Fallnich (Laser Zentrum, Hannover) and P. Simon (Laser Laboratorium, Gottingen) and Y. Prior of our Department. The project aims at development and improvement of the tools for precision material processing with ultrashort shaped femtosecond pulsed lasers. Although this area has advanced significantly in recent years, practical and useful theoretical and numerical tools for the simulation of the ablation process are not yet common, mostly due to the complexity of the ablation process. We perform quantitative analysis and numerical modeling of the processes involved in the short-time interaction of the intense laser fields with the samples. |