Nonlinear optical interaction in photonic structures / Lee Choo Yong

Lee, Choo Yong (2013) Nonlinear optical interaction in photonic structures / Lee Choo Yong. PhD thesis, University of Malaya.

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Abstract

In this thesis, we investigate second harmonic generation (SHG) in nonlinear 1 dimensional (1D) bilayer periodic photonic crystal with various microstructure designs. The transfer matrix is used to model propagation of fundamental field (FF) and second harmonic field inside photonic crystal and numerical simulations are studied. Firstly, we investigate SHG caused by interaction between continuous wave and dielectric magnetic photonic crystal. For nondispersive material, constant and real permittivity and permeability are used being good approximation for frequency far away from the resonant region. We find interesting features in the SH fields versus pump frequency and relative thickness of the bilayers for the same real value of permittivity and permeability but with different signs. Negative permeability is a substitute to periodical poling, giving stronger SH signal when one of the layers has negative refractive index. For certain parameters, backward and forward SH signals can be generated over a broad frequency range. For dispersive material, around resonant region, the FF spectra show more predictable features of bandgap and transparency windows. SH spectra show irregular patterns that depend on the magnetic and dielectric resonances of each layer. The results provide insights for designing efficient nonlinear photonics devices with dieletricmagnetic materials like efficient frequency converter. Secondly, ultrashort pulse propagation and SHG in photonic crystal with superconducting layer is studied by using a combination of Fourier transform and transfer matrix for arbitary pulse propagation. Two fluid model is used to describe electromagnetic propagation in the superconducting layer at nonzero temperature. The focus is on temperature dependence and negative index using superconducting layer and magnetic materials when the superconducting transition frequency is close the magnetic resonance. At low temperature, the superconducting layer provides higher SHG conversion efficiency. Interesting features observed include output pump and second harmonic pulses that could be strongly modulated with the transmitted pulses being delayed by slow light effect. The result demonstrates a new mechanism for reshaping and converting short pulse by combining resonant multiple scattering and nonlinear optical process.

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