The linear and nonlinear optical properties of a series of polymethine molecules are investigated to study the effects of molecular structure and the host environment on overall nonlinear absorption performance. The linear characterization includes measuring the solvatochromic shifts between absorption and fluorescence peaks and studying the excited-state orientational diffusion kinetics. The nonlinear characterization involves measuring the excited-state absorption spectra with a femtosecond white-light-continuum pump–probe technique and performing Z scans and nonlinear transmission measurements from the picosecond to the nanosecond time regimes. The results of these experiments allow us to develop an energy-level structure for the polymethines, which accurately predicts nonlinear absorption properties from the picosecond to the nanosecond time regimes. From this model we are able to identify the key molecular parameters for improved nonlinear absorption.
© 2005 Optical Society of America
(140.3360) Lasers and laser optics : Laser safety and eye protection
(190.4180) Nonlinear optics : Multiphoton processes
(190.4710) Nonlinear optics : Optical nonlinearities in organic materials
Vol. 1, Iss. 1 Virtual Journal for Biomedical Optics
Richard S. Lepkowicz, Claudiu M. Cirloganu, Jie Fu, Olga V. Przhonska, David J. Hagan, Eric W. Van Stryland, Mikhail V. Bondar, Yuriy L. Slominsky, and Alexei D. Kachkovski, "Femtosecond-to-nanosecond nonlinear spectroscopy of polymethine molecules," J. Opt. Soc. Am. B 22, 2664-2685 (2005)