Advanced Multi-Photon Chromophores for Broad-Band Ultra-Fast Optical Limiting

: The goal is to design, synthesize and fully characterize new multi-functional organic chromophores that show high two photon absorption (2PA) cross section and high excited state absorption (ESA) efficiency, and thus provide for greatly improved optical power limiting functionality in a broad range of wavelengths. We optimize 2PA and ESA simultaneously by combining different chromophore modules by using pi-conjugating linkers. The modular approach takes advantage of cooperative enhancement effect whereby the combined chromophore acquires much larger nonlinear absorption than the sum of the component chromophores. This allows us to greatly improve key photophysical properties, such as fast response time, high multi-photon absorption efficiency as well as chromophore solubility for high concentration materials. We also strive to improve our ability to project expected nonlinear-optical properties of new chromophores by testing validity limits of few essential state models with the ultimate goal of developing practical guidelines for designing new materials.