From solid state to soft matter [electronic resource] : photonic nanocavities as advanced optoelectronic devices and single-cell biomedical probes
Keywords: Electrical Engineering.

Photonic nanocavities are wavelength-scale dielectric structures that possess remarkable properties due to their intrinsic small sizes and high quality factors. Simply by modifying the device materials and optical properties, one can realize nanocavities for diverse applications ranging from lasers to quantum optics and even biosensing. In this dissertation work, two drastically different functions of nanocavities are presented, both of which make them more practical for real-world adoption. The first part of this dissertation will focus on engineered optical devices for interconnect applications in computing and communications. We have shown that heavily doped germanium on silicon can be used as a CMOS-compatible light source with peak emission at 1.5 microns. Microdisk resonators were fabricated and shown to sustain cavity resonances through both photoluminescence (PL) and electroluminescence (EL) measurements. To access these microresonators, we developed a coupling process using a tapered optical fiber and further showed the versatility of these fibers by using them to tune the cavity wavelength. High performance optical sources were then demonstrated in a gallium arsenide platform containing embedded quantum dots (QDs). We have developed a new platform for efficiently driving photonic crystal (PC) cavities using a lithographically defined, lateral p-i-n junction. With our lateral junction we have demonstrated a world record low threshold laser with a threshold power of only 208 nW at 50K. At room temperature we find that these same devices behave as ultra-fast light-emitting diodes which can be directly modulated at up to 10 GHz with operational energies below 1 fJ/bit. Additional active photonic devices incorporating a lateral junction such as electro-optic modulators and photodetectors were also created using this same platform. The second part of this dissertation describes the demonstration of a whole new class of tools geared towards biomedical photonics that marry PC cavities to the tips of optical fibers. The form factor of the optical fiber lends itself to operation of the tool in exotic environments never before accessible to a nanocavity. Fiber-cavity hybrid devices were constructed using a custom epoxy-based assembly procedure which successfully relocates the small semiconductor templates containing nanocavities. The completed device, called a fiberPC, was then used as a sensor to detect gold nanoparticles through optical readout. We have used our probes to interrogate single human prostate cells with internalized PC cavities showing, for the first time, resonant photonic modes inside biological cells. The beams can be loaded in cells and tracked for days at a time, with cells undergoing regular division and migration. Furthermore, we present in vitro label-free protein sensing with our probes as a path towards quantitative, real-time biomarker detection in single cells. The developed tool may find future applications in drug screening, cancer detection, and fundamental cell biology.