Studies On The Tunable Sub-wavelength Imaging And Nanolithography Based On Planar Superlens

The Positive refraction space acts as a low-pass filter, which allows low-space-frequency waves transmitting but restrains the high-space frequency waves. The resolution limitation of the traditional optical imaging system is ascribed to the loss of evanescent information. In recent years, the novel characters of surface plasmon polaritons, such as sub-wavelength transmission, sub-wavelength mode volume and local field enhancement, attract more and more attentions. The sub-wavelength imaging using the coupling and transmitting of SPPs has been developed to be an important research field. In this thesis, we mainly focus on theoretical research on tuning the work-wavelength of sub-diffractive-limited imaging and the resolution of nanolithography.1. The theoretical model of planar metal/dielectric film for sub-wavelength imaging is built, and the limitation of the work-wavelength of traditional superlens is interpreted via mode analysis; the SP mode tuning capability of ultra thin dielectric layers is studied, which shows that with the aid of the dielectric layers, the SPR wavelength can be tuned from ultraviolet to visible range; a simple relationship between OTF and SP modes is demonstrated base on Pode plot theory.2. A superlens which can work at visible wavelength and whose wor wavelength can be manipulated is proposed. The relationship between the dielectric layer and the SPPs is analyzed, and its sub-wavelength imaging law is given. The results show that a sub-wavelength imaging with high transmittance and resolution of λ/6 can be obtained in the range of 375～515 nm. The fabrication tolerance and surface roughness can be greatly reduced, ascribed to its quite simple structure. The designed structure can be used in sub-diffractive-limited lithography, imaging, and high intensity storage.3. A surface plasmon interference nanolithography technique based on MIM structure is studied. The resolution of the nanolithography can be tuned by changing the illumination wavelength or the thickness of the dielectric layer under the condition of keeping the mask the same. Attributed to the surface plasmon cavity resonance, the resolution and exposure depth can be greatly improved compared with traditional SPIN technique. At the wavelength of 550 nm, a resolution of 22 nm (about λ/25) is achieved.