. Author manuscript; available in PMC: 2014 May 23.
Published in final edited form as: Photonics. 2013 Dec 15;1(1):9–32. doi: 10.3390/photonics1010009
© 2013 by the authors
licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution license (http://creativecommons.org/licenses/by/3.0/).