Ultrafast optical limiting ability of trans-stilbene enhanced and broadened by a donor-π-acceptor structure

It has been shown that trans-stilbene (TSB) has great potential as an ultrafast optical limiting material through the process of three-photon absorption (3PA)-induced excited state absorption (ESA). The present paper shows that the main transitions in the absorption bands of TSB are mostly local excitation. In order to improve the optical limiting performance of TSB, a series of TSB derivatives with an electron donor-π-acceptor structure are designed. The analysis of π electron localized orbital locators (LOL-π) reveals that the distribution of π electrons in the derivatives of TSB is much more continuous compared to that in the original TSB. This results in the main transitions in the ground state absorption (GSA) and ESA of the TSB derivatives showing obvious charge transfer characteristics, and the GSA, ESA and 3PA bands are largely enhanced and broadened compared to those of the original TSB molecule. These observations are well supported by the enlarged transition dipole moments of the main transitions in GSA and ESA. With these results, it is clearly shown that the TSB derivatives are promising optical limiting materials. Our observations provide clues for the development of optical limiting materials based on TSB.