Analyzing Diffraction Limit and Optical Phase Conjugation via FDTD Method
Date Issued
2010
Date
2010
Author(s)
Lee, Chiang-Suo
Abstract
In this thesis, the finite-difference time-domain (FDTD) technique is applied to analyze the relationship of evanescent wave and diffraction limit. We employ 2D FDTD to simulate sub-wavelength single slit diffraction and observe the instantaneous Poynting vector in steady-state. We find that the magnitude of the instantaneous Poynting vector varies periodically, while the direction remains unchanged. By comparing the result with the instantaneous Poynting vector of total internal reflection evanescent wave, we think that the diffracted waves of sub-wavelength single slit diffraction are all propagating waves rather than evanescent waves. We simulate the playback of the sub-wavelength (slit width is 2λ/5) single slit diffraction via 3-sided phase conjugate mirror and the phase conjugate waves re-focus back onto the spot with dimension below the diffraction limit. Furthermore, the cross-sectional shape of slit is modified from a rectangular to a Gaussian function. For the slit width is 2λ, a perfect re-focusing profile is generated.
Subjects
finite-difference time-domain method
evanescent wave
diffraction limit
optical phase conjugation
Type
thesis
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