1. Materials Science and Technology Division, The U.S. Naval Research Laboratory, Washington, DC 20375, USA
2. Acoustics Division, The U.S. Naval Research Laboratory, Washington, DC 20375, USA
3. Naval Undersea Warfare Center, 1176 Howell St., Newport, Rhode Island 02841, USA
4. Quattrone Nanofabrication Facility, University of Pennsylvania, 3205 Walnut St. Philadelphia, Pennsylvania 19083, USA
5. Carnegie Mellon University Nanofabrication Facility, 5000 Forbes Ave. Pittsburg, Pennsylvania 15213, USA