Dispersion and polarization engineering in silicon and plasmonic nanophotonic structures
Plasmonics and silicon photonics are the two main branches of nanophotonics that have been advanced over the last decade. Plasmonics use metallic nanostructures to confine the light down to the subwavelength scale and to enhance the field intensity for a strong light-matter interaction; however, the main drawback is a high metallic loss and a lack in large-scale fabrication technique. Meanwhile, silicon or on-chip photonics use a low-loss dielectric to guide and manipulate the light in micro/nanoscale chips, and can take advantage of the current CMOS manufacturing system; yet, further scaling down is limited by the diffraction limit. In this thesis, three sets of nanophotonic devices — silicon, plasmonic, and hybrid — are presented to address the aforementioned issues. First, a large-area patterning of metal nanostructures is examined with a resistless nanoimprinting. This approach provides a simple, reproducible, and accurate means to fabricate metallic nanopatterns, and the demonstrated plasmonic nanocavities effectively absorb the light. The reflection phase-shift at the metal-dielectric interface is also studied, and an omnidirectional bandpass filter is designed. Second, I propose using a silicon/plasmonic hybrid nanostructure to balance the advantages of plasmonics and Si photonics; the subwavelength feature from plasmonics; and the low-loss propagation and CMOS compatibility from Si photonics. Three examples of polarization-managed hybrid devices are presented, with ultra-compact device sizes. Finally, a waveguide modal dispersion engineering is explored with mode-coupling. Broadband second-harmonic phase-matchings are achieved, and degenerate-optical-parametric-amplifications and second-harmonic-generations are examined.
Qi, Purdue University.
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