Nonlinear optical kramers-kronig relation in organic solutions

• Main Author: 吳正文
• Other Authors: 魏台輝
• Format: Others
• Language: zh-TW
• Published: 2004
• Online Access: http://ndltd.ncl.edu.tw/handle/60146847571735492007

碩士 === 國立中正大學 === 物理系 === 92 === In this thesis, we investigate the Kramers-Kronig Relation between the excited state absorption and refraction of organic solutions. Using Z-scan technique with 20 picosecond (ps) laser pulses at a wavelength of 532 nanometer (nm), we have characterized nonlinear absorption and refraction of C60 and C70, both dissolved in toluene. While we attribute both molecules’ nonlinear absorption and refraction to excited state excitation, the signs of their excited state refractive cross section are opposite: positive for C60/toluene and negative for C70/toluene. Given the excited state absorptive spectra of both solutions, we calculate, via Kramers-Kronig Relation, their excited state refractive cross section at 532 nm using two different approaches: (i) direct numerical integration, and (ii) Laurentian decomposition. As a result, both approaches yield the same signs as our measurements show, although further effort is needed to reduce the discrepancy between the values obtained via these two approaches.