1. Britton Chance Center
for Biomedical Photonics, Wuhan National Laboratory for Optoelectronics-Huazhong University of Science and Technology, and ‡Key Laboratory
of Biomedical Photonics of Ministry of Education, Department of Biomedical
Engineering, Huazhong University of Science and Technology (HUST), 1037 Luoyu Road, Wuhan 430074,
P. R. China