Characterization of 2PA Chromophores
Abstract
We review several experimental methodologies for the determination of nonlinear absorption coefficients of organic chromophores in either solution or thin film form. The goal here is to also be able to identify and quantify the nonlinear absorption process or processes, e.g. the essentially instantaneous two-photon absorption (2PA) or the cumulative excited-state absorption (ESA). These methods include the direct methods of nonlinear transmission and Z-Scan, along with the indirect methods of two-photon-induced fluorescence, exciteprobe approaches, and Degenerate Four-Wave Mixing. We also discuss both frequency degenerate and frequency nondegenerate processes with emphasis on 2PA. It is important to note that a single method is generally incapable of both measuring and identifying the source of the nonlinearity, thus it is usually necessary to employ more than a single method to determine the sign, magnitude and physical processes involved. For example, single beam experiments cannot give the temporal response of the nonlinearity while excite-probe methods do; however, single beam measurements lend themselves better to absolute calibration. In addition we include information on nonlinear refraction, which always accompanies nonlinear absorption processes. For example, the nondegenerate bound-electronic nonlinear refraction and ultrafast nondegenerate nonlinear absorption come from the real and imaginary parts of the nondegenerate third-order nonlinear susceptibility and are related by Kramers-Kronig relations via causality.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 01, 2016
- Accession Number
- AD1015059
Entities
People
- David J Hagan
- Eric W. Van Stryland
Organizations
- University of Central Florida