Engineering Photonic Crystal Impurity Bands for Waveguides, All-Optical Switches and Optical Delay Lines

Sheng LAN  Satoshi NISHIKAWA  Hiroshi ISHIKAWA  Osamu WADA  

IEICE TRANSACTIONS on Electronics   Vol.E85-C   No.1   pp.181-189
Publication Date: 2002/01/01
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Issue on Ultrafast Optical Signal Processing and Its Application)
photonic band gap,  defects and impurity bands,  coupled cavity waveguides,  all-optical switches,  optical delay lines,  

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We investigate the engineering of the impurity bands in photonic crystals (PCs) for realizing high-efficiency wave guiding, all-optical switching and optical delay for ultrashort optical pulses. It is found that quasi-flat impurity bands suitable for the transmission of ultrashort pulses can be achieved by properly controlling the configuration of coupled cavity waveguides (CCWs). At sharp corners, high bending efficiency is obtained over the entire impurity band. All-optical switching can be realized by creating a dynamical band gap at the center of an impurity band. The concentration of electromagnetic wave at defect regions leads to high switching efficiency while the tunable feature of PC defects makes all-optical control possible. It is also revealed that CCWs with quasi-flat impurity bands provide efficient group delay for ultrashort pulses with negligible attenuation and distortion. From the viewpoint of practical fabrication, the effect of disorder on the transmission property of impurity bands is discussed and the criterion for localization transition is determined.