Applications of Polarization Control by One-Dimensional Sub-Wavelength Metallic Gratings
Date Issued
2009
Date
2009
Author(s)
You, Ting-Yu
Abstract
Grating is an important type of optical element since there are lots of applications. Sub-wavelength gratings can be used as a polarizer or a filter. They can also be added gratings on light emitting diode to increase the light extraction efficiency.he purpose of this research is to study the 0th diffraction efficiency of the sub-wavelength metallic gratings. Two suites of commercial software “GSolverTM” and “ComsolTM” are used to design the sub-wavelength metallic gratings. We investigate the influences of the 0th diffraction efficiency of the sub-wavelength metallic gratings with different parameters, including grating period, grating height, grating width, and groove material. At first, we analyze the optical properties of the sub-wavelength metallic gratings in free space as the TM and TE waves are normally incident on them. By plotting the field distribution, we discuss what kind of resonant effect leads the electromagnetic wave to propagate through the sub-wavelength metallic grating. Then we put these gratings on certain substrates and discuss the influences on the diffraction efficiency. To discuss sub-wavelength gratings on light emitting diodes, we put a very thin contact metal layer between the grating and n-GaN and then analyze the 0th order diffraction efficiency. y optimizing the geometrical parameters and the groove material, we can design: for a TM wave polarizer at lambda=460nm, the 0th order transmittance of TM wave is 80% and the 0th order transmittance for TE wave is smaller than 10%. For a TE wave polarizer at lambda=460nm, the 0th order transmittance of TE wave is 90% and the 0th order transmittance for TM wave is smaller than 10%. For a dichroic Mirror on SiO2 substrate, the 0th order transmittance of TE wave at lambda=450nm is 90% and the 0th order transmittance of TM wave at lambda=550nm is 90%. For a compound grating with different groove materials, TM and TE waves can co-propagate through it with a certain ration. We design a compound grating with 78% of the 0th order transmittance of TM wave and 40% of the 0th order transmittance of TE at lambda=460nm.
Subjects
sub-wavelength metallic grating
surface plasmon
polarization control
Type
thesis
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