Novel Two- and Three-Photon Pumped Lasing Dyes: Design, Synthesis, and Characterization

摘要

In this proposed research project, efforts have been focused on the synthesis and optical properties characterization of some multi-photon absorbing chromophores especially with frequency up-converted stimulated emission behavior. This research project was originally aimed to study some structural parameters that may affect the multi-photon pumped stimulated emission properties in dye molecules. The structural parameters that was attempted to investigate include the substituent effects (types and/or positions) and chromophoric unit number density effect. Significant amount of time and man-power was spent to accomplish the synthesis and characterization of some of the designed model compounds. Most of these compounds possess strong two- and three-photon absorption (2PA & 3PA) induced up-converted emission covering various spectral regions. One of the synthesized stibazolium-type chromophore also shows strong 2PA-induced stimulated emission when pumped by femtosecond laser pulses at approx. 775 nm. Specifically, four stilbazolium chromophores have been stabilized for 2PP stimulated emission property studies. Only one of the synthesized compounds possesses 2PP-induced up-converted cavityless lasing when pumped by femtosecond laser pulses. To the best of author's knowledge, this compound is so far the only stilbazolium salt with symmetrical di-substitution in its molecular structure that exhibits 2PP- induced stimulated emission in femtosecond regime. Although the currently collected data could not provide any clear picture of the relationship between molecular structure and stimulated emission property, using thiophene unit(s) as part of pi-bridge in designing symmetrically di-substituted two-photon lasing dyes might be a direction that worthy to explore. On the other hand, the blueshifted forward lasing is an interesting phenomenon that worth to put more efforts on studying its origin.