Physics and applications of photonic crystal nanocavities
Abstract
The capability to confine and manipulate photons at nanometer scales opens up unprecedented opportunities in classical and quantum information processing technologies, and also in life sciences. There have been various demonstrations of sub-micron light confinement, but yet the most critical issue ahead is the development of new device concepts and technologies that will reliably operate at such length scales. In this thesis, I present my work along this direction. The large aggregated bandwidths of the optical interconnects require memory and delay components to launch, buffer, and collect optical signals at the nodes. To realize them, I propose two-dimensional coupled nanocavity array structures that have flat electromagnetic bands. With these structures, I experimentally demonstrate group velocity reduction below 0.008 c. I also show that by reducing their rotational symmetries they can be used to strongly control polarization of light. The performance of lasers such as their speed and efficiencies can be dramatically enhanced with the use of nanocavities due to the spontaneous emission rate enhancement via the modification of vacuum field density in a cavity. I present ultra-fast lasers with turn-on and turn-off times as short as 1-2 ps, which is enabled by up to 75-fold spontaneous emission enhancement. I demonstrate direct signal modulation speeds in excess of 100 GHz, which is far exceeding today's state of the art semiconductor lasers. To achieve nanocavity lasers with higher output powers and efficiencies, I introduce a new device composed of coherently coupled nanocavity laser arrays. This unique laser design combined with strong cavity quantum effects enable high differential quantum efficiencies, and orders of magnitude larger output powers while preserving low lasing threshold and high operation speeds. Nanocavities can also dramatically increase sensitivity of bio and chemical sensors. Furthermore, a network of such nanocavity detection centers can be integrated with microfluidic circuits for high throughput and compact lab-on-a-chip system. As an initial step along this direction, I present my work on detection of refractive index changes in nanocavities with high sensitivity levels. I also present nanofabrication procedures that I have developed for indium phosphide and silicon material systems for the realization of all these devices.
- Publication:
-
Ph.D. Thesis
- Pub Date:
- 2007
- Bibcode:
- 2007PhDT........27A