Anomalous phenomena and spectral tailoring in photonic crystals

Photonic crystals are recently discovered meta-materials whose optical properties arise from periodic refractive index variations. In this thesis I examine various aspects of photonic crystals including a self-assembled photonic crystal, anomalous properties arising from periodicity, and tailoring absorption and emission spectra. Fabricating photonic crystals with the desired properties in the infrared and optical frequencies, including a complete photonic bandgap, is an experimental challenge. Self-assembly can provide a solution. In Chapter 2, I examine a new type of colloidal photonic crystal of tetrahedral building blocks in a fcc lattice that is found to possess a robust and complete bandgap. In Chapter 3, I explore the photonic states that exist around a zero-group velocity point. Motivated by negative refraction, a measure of the effective wavevector is constructed that distinguishes various types of zerogroup velocity modes. Around one type of zero-group velocity mode, an anomalous region of backward effective wavevector is found that enables superior light confining properties of a mirror-less cavity. In the last two chapters I look at the problem of efficiently converting radiant energy to electrical power. In Chapter 4, I explore the extent to which ID multi-layer thin films can enhance the short circuit current of a 2 [mu]-thick silicon solar cell. Though such cells are limited by their size, for two front-layers a relative boost of 45% is possible. Finally, in Chapter 5, motivated by the problem of low efficiency in thermophotovoltaics, I look at selective emissivity of a 2D metallic photonic crystal. A semi-analytical theory is developed using only the material dispersion and geometrical parameters. Applications of the selective emitter, including power generation and lighting, are discussed.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Physics.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2010

Author dc:creator

• Ghebrebrhan, Michael

Advisor dc:contributor.advisor

• John D. Joannopoulos.

• Physics.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/68970

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/68970