Submitted on: 13 January 2007.
Revised on: 18 April 2007.
Accepted on: 07 June 2007.
___________________IEEE Transactions on Terahertz Science and Technology
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Submitted on: 14 December 2007.
Revised on: 06 February 2008.
Accepted on: 02 April 2008.
___________________IEEE Transactions on Terahertz Science and Technology
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