Two Dimensional Silicon Photonic Crystal Band Gap Applications for Optical Bio-sensing and Modulation

2021-9
Kılıç, Selahattin Cem
In this thesis, we presented mainly two applications that utilize two dimensional Silicon photonic crystals. One application is an optical refractive index based gas/bio-sensor. The device is constructed by rod-type square lattice photonic crystal cavity. The rod-type is chosen to confine the electric field in the low-index medium and maximize the light-matter interaction. The resonance characteristics is selected as Fano-like resonance due to its sharp and asymmetric shape that is suitable for such an application. The rods are sandwiched between two metal plates so that the out-ofplane light confinement is achieved by reflection. First the theory of the design is described and numerical analysis and characterization of the device is conducted. An air gap is introduced on top of the rods which acts like a slot structure to confine the light a spatially small region, decreasing the mode-volume and also increasing the sensitivity by amplifying light-matter interaction further. By introducing an internal tuning mechanism the size of the air gap is externally controlled by an electrical signal. This results in the resonance frequency of the device is externally controlled so that the design is highly suitable for different operation regions, environmental and fabrication errors. Another application is the experimental confirmation of a two dimensional photonic crystal Mach-Zehnder interferometer that is being utilized as an optical modulator. The modulation is done by optical carrier injection method by utilizing plasma dispersion effect and taking advantage of the negative refractive index phenomenon which achieves a much smaller phase-shifter length compared to the similar devices in the literature.

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Citation Formats
S. C. Kılıç, “Two Dimensional Silicon Photonic Crystal Band Gap Applications for Optical Bio-sensing and Modulation,” M.S. - Master of Science, Middle East Technical University, 2021.