臺灣博碩士論文加值系統

　Due to the diffraction theory, light transmission through a subwavelength hole is very low, but by excitation of surface plasmon, it could be overcome. Hole arrays, and surface corrugation on metal shows the enhanced transmission in this way. A similar result was done in microwave regime.

　Our work uses Finite-Difference Method to observe the enhanced transmission phenomenon with subwavelength apertures. With a normal incident wave of which the wavelength is about 10 times larger than the slit, the result is consistent with the previous work.

　However, in our simulation, what the surprising result is that we found the enhanced transmission is not mainly due to the surface plasmon effects but by the dipole/quadrapole field emission. The physical mechanism of the enhanced transmission provides us a more fundamental explanation which is different from previous work.

1Introduction…………………………………..………………………1
2 Transmission Light through small holes...............................................4
2.1 Theory of Diffraction by Small Holes .......................................4
2.2 Extraordinary optical transmission............................................5
2.2.1 Strong Enhancement of transmitted light due to the
hole array ......................................................................6
2.2.2 Theory of Enhanced Transmission Resonances through
narrow slits on metallic gratings...................................7
2.3 Transmission Light through subwavelength aperture with
metallic surface corrugations.....................................................9
2.3.1 Beaming light from a subwavelength aperture............10
2.3.2 Highly Directional Emission from a single
subwavelength aperture surrounded by surface
corrugation ...................................................................12
2-4 Enhanced transmission of microwave radiation .....................15
3Simulation Model .............................................................................17
3.1 Simulation System ...................................................................17
3.2 Finite-Difference Time-Domain Method.................................18
3.2.1 Introduction to Maxwell’s Equation ............................19
3.2.2 Reduction to two dimensions.......................................21
3.2.3 The Yee Algorithm.......................................................21
3.2.4 Finite-Difference Expressions for Maxwell’s Equations
......................................................................................23
3.3 Boundary Conditions ...............................................................26
3.3.1 Absorbing Boundary Conditions .................................27
3.3.2 Periodic Boundary Conditions.....................................27
3.4 Dielectric constant of metal .....................................................29
4 Simulation results ............................................................................32
4.1 Simulation system....................................................................32
4.2 Simulation result......................................................................33
4.3 Physical Process.....................................................................36
4.3.1 Transmission Phenomenon.......................................36
4.3.2 Beaming light..............................................................44
4.4 Dipole/quadrapole effect..........................................................52
4.4.1 Quadrapole vs. Dipole radiation.................................52
4.4.2 Quadrapole Radiation vs. Suface plasmon resonances.....58
4.5 Conclusion ...............................................................................61
5 Sumarry.............................................................................................62

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