Imaging And Photolithography Beyond Diffraction Limit Based On Surface Plasmon Resonant Cavity

The capability of optical resolution of a traditional optical system is limited by the optical diffraction effect,which in turn limits the application of the optical system in the fields that require high resolutions,such as super large-scale integration and fabrication technology of micro-and nano-structures in photonic devices and super-resolution microscopy technology.The fast development of surface plasmonic photonics in recent years provides a novel and effective method to solve the problem of optical diffraction limit.This thesis presents an investigation on technology of surface plasmon resonant cavity.Physical mechanism,characteristics and applications of surface plasmon resonant cavity in super resolution microscopic imaging and photolithography are investigated in detail.The main work is as follows:1)A novel super-resolution optical microscopic imaging technique using a surface plasmon resonant cavity?SPRC?is proposed,in which surface plasmonic waves?SPWs?with a much larger wave vector than that of either the direct illumination light of the same frequency or the SPWs without the SPRC structure are generated to serve as the illumination of the microscopy.Numerical results show that an imaging resolution of 26nm can be achieved based on the proposed SPRC method under an illumination of 532nm light,which is 8.4-fold or 3.2-fold better than that of conventional high numerical aperture fluorescence microscopy or conventional surface plasmon excitation,respectively.It is also found that the wave vector of the SPRC structure and hence the resolution of the microscopy can be tunable by varying the cavity length.The physical origin of the much enhanced resolution and also the tunability of the proposed method are analytically confirmed by the dispersion relation derived from the SPRC system.2)A nanolithography interference technique using double surface plasmon resonant cavities is proposed.Based on the single surface plasmon resonant cavity formed by an Ag grating and an Ag thin-film layer separated by a photoresist layer,another surface plasmon resonant cavity is formed by adding an Ag thin-film layer between the Ag grating and the photoresist layer with a SiO₂ layer separation between the Ag grating and the newly added Ag film.The physical mechanism of the proposed technique is analyzed and verified by both Maxwell electromagnetic theory and the numerical calculation.Results show that the resolution of interference pattern can be further improved by employing the double surface plasmonic resonant cavities.It opens a new way for further improving the resolution of photolithography and exposure depth without changing metallic grating.3)A superlens based on the double surface plasmon resonant cavities is also proposed,from which high-quality imaging photolithography of arbitrary patterns can be achieved.The double-cavity superlens is formed by silver mask/PMMA/superlens as the object cavity and superlens/photoresist/silver layer as the imaging cavity.Results show that much improved quality of image with much suppressed sidelobes and better image contrast can be obtained with the double cavities structure when compared with the single cavity structure.The physical mechanism of the double cavities structure is analyzed theoretically and the analytical expression of the optical transfer function of the double-cavity system is derived.Theoretical results show that the transfer function of the double-cavity structure becomes flatter than the single cavity structure,which means that double-cavity structure can significantly suppress the long range plasmon mode and amplify the short range plasmon mode to improve image quality.