High resolution imaging and lithography using interference of light and surface plasmon waves

• Main Author: Kim, Yang-Hyo
• Other Authors: Peter T.C. So.
• Format: Others
• Language: English
• Published: Massachusetts Institute of Technology 2008
• Subjects: Mechanical Engineering.
• Online Access: http://hdl.handle.net/1721.1/42303

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2007. === Includes bibliographical references (leaf 28). === The resolution of optical imaging and lithography is limited by the wave nature of light. Studies have been undertaken to overcome the diffraction limit for imaging and lithography. In our lab, the standing wave surface plasmon resonance fluorescence (SW-SPRF) microscopy was developed. It is a combination of standing wave total internal reflection fluorescence (SW-TIRF), one of structured illumination techniques, with surface plasmon resonance (SPR). The SW-TIRF approach decreases the excitation wavelength by interfering two coherent light rays on the substrate and producing an evanescent standing wave field between the object and a high refractive index substrate. Evanescent standing wave illumination generates a sinusoidal interference pattern with 2n times higher-spatial frequency than original light, where n is the refractive index of the substrate allowing higher lateral resolution. Surface plasmon is generated by reflecting a light on the gold surface through the cover glass at a specific angle inducing collective excitation of electrons in the metal. The SPR contributes a better signal-to-noise ratio by inducing an enhanced evanescent electric field to excite fluorophores. With the SW-TIRF instrument, about 100 nm resolution was obtained. In this thesis, we aim to produce less than 50 nm resolution lithography and imaging using corrugated gold surface. The induction of surface plasmon wave with large wave number is made possible by the sinusoidal gold surface allowing wave number matching between the excitation light and the surface plasmon wave. This wave number matching requires proper optimization of parameters like grating constant, perturbation depth, incidence angle of the beam, and excitation wavelength. The fabrication of the corrugated gold surface would be done by e-beam etching with varying parameters. === (cont.) For lithography, nano-patterns would be investigated on azo dye thin films, Congo-Red dye with spin-coating, exposed by an interference of evanescent waves propagating on a substrate. The result patterns would be measured with AFM. For imaging, sub-diffraction limited fluorescent particle would be used for point spread function measurement and high-resolution demonstration. === by Yang-Hyo Kim. === S.M.