CharacterizationandFabricationofplasmonicwaveguides.ppt

Nano-Photolithography and an Introduction to Fabrication and Characterization of Plasmonic Waveguides Hamid Nejati ELEC 527 Professor Tour, Professor Zhong 03/29/2007 Outline Motivation and Introduction Nano-photolithography Excitation Fabrication Characterization Conclusion Motivation Photolithography: Diffraction limit of light: resolution 100nm Higher speed and repeatable Lift off process E-beam lithography: Higher resolution: around 20nm Lower speed and non repeatable Nano-imprint Industrial Motivation Photolithography (Mercury lamp) Diffraction limit of light Plasmonics Sub wavelength operation Plasmonic Review Plasmonics Surface plasmon polaritons (SPPs) Plasmonic waveguides Comparing the plasmon printing to photolithography Field enhancement Plasmon nano-sphere field profile Plasmon Printing Final resolution Plasmon Excitation Plasmonic waves have bigger K vector in comparison to the light waves Sources: He-Ne Laser (632.8 nm) Excimer laser 248nm Laser diode 1550nm Excitation ideas Trick1: excitation from a high index medium for surface plasmon at air/metal interface (prism) Trick2: K vector in periodic structures due to Bloch theorem is not single (periodic with reciprocal lattice vector) (grating) Excitation ideas Trick3: excitation with dots Trick4: array of dots Methods of excitation Methods: Prism coupling (Kretschmann technique) = MI,IMI Grating or roughness coupling = MI,IMI, MIM End-fire excitation technique = MIM, IMI Prism coupling Excitation of MI, IMI setups, and Asymmetric mode Excitation angle is dependent on the thickness of the film Cons: Adjustment of gap separation beam position, poor stability Expensive high-index prism and adjustment system Pros: High efficiency and Selecting any guide mode (K-matching) Adjusting in experiment (detachable prism) Inherent Roughness of the Metal Film Inherent roughness of the metal film acts as a statistically determined distribution of inelastic scatter centers for an SPP = scattered light m