1. Department of Materials Science and Engineering, The Pennsylvania State University, University Park, PA 16802, USA
2. Department of Physics, Engineering Physics and Astronomy, Queen’s University at Kingston, Kingston, Ontario, K7L 3N6, Canada
3. Laser Depth Dynamics Inc., Kingston, Ontario, K7L 2L1, Canada
4. Applied Research Laboratory, The Pennsylvania State University, University Park, PA 16802, USA