We show that a very large enhancement of third-order optical nonlinearity (γ) of π -conjugated molecules can be realized without a major redshift of the absorption spectrum that disturbs optical transparency in the visible region. By changing the number (n) of C=C bonds of β carotene (n=11) from 7 to 15, a remarkable 3.4-fold increase in the γ value was observed when n=15 relative to that of β carotene. This enhancement of γ mainly originates from three-photon resonance of a lowest optically allowed excited state. The controversial higher-lying essential state is not important for generating the large value of γ.
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|Publication status||Published - Oct 7 2008|
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics