1. Physical Science and Engineering Division, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia
2. Department of Physics and Astronomy, University of Sussex, Brighton BN1 9RH, U.K.
3. Core Labs, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia
4. Department of Applied Science and Technology, Polytechnic University of Turin, Alessandria 15121, Italy