Current Research

Long-Distance, High Data-Rate Quantum Communication with Ultra-low Loss Photonic Band Gap Fiber
The discovery of the omnidirectional reflection criteria has opened new possibilities for guiding and localizing light. In particular a novel all dielectric hollow fiber has been designed and fabricated which guides light in air. Recent theoretical analysis has predicted extremely low propagation loss characteristics for this fiber. The objectives of this study are to: Expand the theoretical understanding of the system and the relations between the physical structure and the electromagnetic modes supported by it. Identify and synthesize glasses which have substantially disparate indices of refraction yet similar thermo-mechanical properties which can be thermally co-processed. This project will make use of the state-of-the-art optical fiber draw tower which we have recently constructed at MIT. The fibers will be designed to enable a long distance high data-rate quantum communication system. (DARPA/ARO/MRSEC/NSF)

Fiber Based Optical Devices
This research project is part of a comprehensive effort aimed at developing novel optical fibers and devices which make use of omnidirectional reflectors.
Here we will study the effect of periodic index modulations along the propagation axis of the fiber on the mode structure. It is predicted that the large axial modulations will result in the opening substantial photonic band gaps in the direction of propagation which will in turn allow for the control of the properties of the transmitted light. Inserting defects in the otherwise perfect axial modulation will provide the basis for constructing optical cavities in the fiber. The conditions leading to high quality factors (Q) with correspondingly small modal volumes will be theoretically as well as experimentally examined. Applications to passive devices such as DWDM filters as well as active devices such as high speed all-optical switching and signal re-shapers are expected.
The ability to construct all-optical devices in a fiber has many advantages, reduction of coupling losses to transmission line - not being the least. It may also open new opportunities for efficient fabrication of optical devices based on fiber drawing techniques. (NSF)

Self Assembled Block Copolymers as Photonic Band Gap Materials
A conceptual framework for creating photonic crystals from self-assembling block copolymers has been formulated. In order to form useful band gaps in the visible regime, periodic dielectric structures made of typical block copolymers need to be modified to obtain appropriate characteristic distances and dielectric constants. Moreover, the absorption and defect concentration must also be controlled. This affords the opportunity to tap into the large structural repertoire, the flexibility and intrinsic tunability that these self-assembled block copolymer systems offer.
The objectives of this project will be to anionically synthesize high molecular weight block copolymers, to explore methods of increasing the dielectric contrast in these systems by incorporating semiconductor nanometer size crystals. We will also study the possibility of using block copolymers as a core material in optical fibers. (NSF)

Biocompatible Photonic Crystals
The objective of this project is to develop methods for creating photonic crystals made of biocompatible materials. Possible applications include benign food coloring and light actuated drug delivery systems.