1. Institute for Lasers, Photonics and Biophotonics and Department of Chemical and Biological Engineering, University at Buffalo, The State University of New York, Buffalo, New York 14260-4200, Centre for Optical and Electromagnetic Research, Zhejiang University, Hangzhou 310058, China, and Department of Pathology and Oncology, The Sol Goldman Pancreatic Cancer Research Center, CRB-2, Suite 345, Johns Hopkins University School of Medicine, 1550 Orleans Street, Baltimore, Maryland 21231