1. Caltech Optical Imaging Laboratory, Andrew and Peggy Cherng Department of Medical Engineering, Department of Electrical Engineering, California Institute of Technology, Pasadena, CA 91125, USA.
2. Department of Anatomy and Structural Biology, and Gruss Lipper Biophotonics Center, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
3. Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA.