Journal of Nonlinear Optical Physics & Materials Vol. 24, No. 1 (2015) 1550008 (10 pages) c  World Scientific Publishing Company DOI: 10.1142/S0218863515500083 Third-order optical nonlinearity effect of DNA- and polyvinylpyrrolidone-functionalized carbon nanotubes Liangmin Zhang ∗ Department of Physics, Physical Sciences and Geology, California State University – Stanislaus, Turlock, California 95382, USA lzhang@csustan.edu Benjamin Steckling Arkansas Center for Laser Applications and Science, Department of Chemistry and Physics, Arkansas State University, State University, Arkansas 72467, USA Adrian Lucero, Andreas Schmitt-Sody, William White and Donald Shiffler Air Force Research Laboratory, Kirtland Air Force Base, Albuquerque, New Mexico 87117, USA Received 8 January 2015 We have used single-stranded DNA (ssDNA) and polyvinylpyrrolidone (PVP) to disperse multiwalled carbon nanotubes (MWNTs) in water solution through sonication and cen- trifuge procedures. The advantage of these two polymers is that they do not need toxic organic solvents to distribute the carbon nanotubes. The scanning electron microscope (SEM) technique has been used to investigate the interaction between polymer molecules and MWNTs. The images show that MWNTs can be distributed effectively into the two polymer solutions. The third-order optical susceptibility, nonlinear optical absorp- tion coefficient and optical power limiting of these dispersions have been characterized experimentally using a femtosecond laser system with a tunable range of 750–850 nm. The imaginary part of the third-order optical susceptibility has also been computed. Keywords : Multiwalled carbon nanotube; third-order optical nonlinear susceptibility; optical power limiting; nonlinear optical absorption; z-scan technique. 1. Introduction Carbon nanotubes are important optical and electronic materials. In simple terms, carbon nanotubes are materials of tubular structures made entirely of rolled-up layers of interconnected carbon atoms with diameters ranging from about one ∗ Corresponding author. 1550008-1