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Probing Optical 'Dark' Effects in Artificial and Natural Nano-Structures

Dr. Ziliang Ye

Advisor: Professor Xiang Zhang, Department of Mechanical Engineering

My dissertation is devoted to study the range of fascinating optical 'dark' effects that emerge in the nanoscale and usually cannot be probed by the linear optical spectroscopy or imaging in the far field zone. The studied systems are consisted of two parts: artificlal plasmonic antennas and natural two dimensional transiiton metal dichalcogenides (TMCDs). With plasmonic antennas, I realize the classical analog of a few intriguing quantum mechanical effects, including electromagnetic induced transparency, anti-Hermitian coupling induced super-radiance, and spin Hall effect for photon. Because most of these effects only occur in the subdiffractional scale, I develop a nearfield scanning tunneling microscopy with a super-resolution to observe these 'dark' effects. In the study of 2D TMDC, I discover several excitonic states are originated from a  very large exciton binding energy in the unique 2D semiconducting material. Using another nonlinear optical probe, second harmonic generation spectroscopy, I further identify an edge response at the domain boundary of a continuous TMDC crystal synthesized by the chemical vapor deposition technique. Finally, a TMDC exciton based light emitting device is demonstrated as a practical application. 

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