Two-Photon Coherence and Ultrafast Optical Storage in Organic Molecules
Final Peformance rept. 1 Apr 2001-31 Mar 2004
MONTANA STATE UNIV BOZEMAN DEPT OF PHYSICS
Pagination or Media Count:
This project explored structure-property relationships relevant to enhancement of two-photon absorption 2PA in organic dendritic molecules for optical power limiting. We synthesized and studied two series of novel monodisperse dendrimers built of identical blocks of thriphenylamine-based chromophores, BDPAS and BDPADSB. With both series, we observed strong cooperative enhancement of two- and three-photon absorption. We showed that this effect is due to conjugation between constituent branches. For lower generation dendriemers, the peak 2PA cross section was found to increase faster than linearly with the number of pi-electrons. For the largest dendrimer, 4SG2, the largest absolute values of molecular 2PA- and 3PA cross section was shown, 1.1 x 10exp-46 cmexp 4s s and 10exp-79 cmexp 6sexp2, respectively. We compared the 2PA cross section of the two dendrimer series, and concluded that enlarging the conjugation system between the adjacent nitrogen atoms can create remarkably large sigma value. We developed a new method for quantitative determination of the extent of conjugation by comparing one- and three-photon absorption measurements. Coherent domain structure was deduced from 3PA measurements in the BDPAS series. It was found that, in terms of largest coherence domain size, 4SG0 is the optimum dendrimer generation, which corresponds to an effective maximum number of 150 conjugated pi-electrons.
- Organic Chemistry
- Electrooptical and Optoelectronic Devices