Manipulating Light with Nano-Photonic Structures

Manipulation light in the nano scale, by controlling its phase or magnitude, is key to efficient and compact designs in modern photonic technology. Its application ranges from tele-communication, biological imaging to probing electronic phenomena and quantum computation. High Quality factor (Q) resonators for both dielectric and metallic devices with two dimensional form factors, and high on-off ratio wave modulators where light transmission can be tuned in situ are exemplary ideas and of great interest and importance in those applications. Among the light waves, terahertz radiation, known as the last frontier connecting microwave and optical regime in the electromagnetic spectrum, has been an increasingly active field of research. Recent development of THz sources and detection has led to an increasing demand of active devices for its wave manipulation. In the thesis, we focus our effort on developing novel nano photonic structures that act as better light modulator and resonators. We first develop theories regarding principles and techniques to achieve tunable high Q resonances in dielectric photonic structures using a new “diatomic” design. The essence of the “diatomic” design is that it can dramatically improve Q of the resonating modes by minimizing the radiative far-field coupling. We then extend the concept of “diatomic” in dielectric gratings to “diatomic” metallic cavities that results in high Q plasmonic metamaterial resonators compared to conventional designs. Lastly, we demonstrate, in simulation and experiment, a hybrid metamaterial design showing much larger modulation power by combining metallic nano-slits with graphene, a promising THz-active 2D material. Our investigation into THz metamaterial designs combines device fabrication, numerical simulation, semi-analytical modelling and ultra-fast time domain THz measurements. Our theoretical and experimental results could provide insight to the physical understanding and future development of THz metamaterial devices, as well as being of value to the THz community that seeks application with high performance modulator/resonators in general.