Nur Aisyah Mohamad DaudQin Ai WongBi Sheng Ooi0000-0003-4296-5145Nor Azlili HassanShivaraj R. MaidurYip Foo WinVenugopal Rao SomaChing Kheng Quah2026-10-222026-10-222026-0810.1016/j.optmat.2026.118075https://dspace-cris.utar.edu.my/handle/123456789/11834Strategic modification of molecular structures for optimized nonlinear optical (NLO) responses requires an understanding of the charge transfer mechanisms that govern the optoelectronic properties. This work systematically examines the structure-NLO relationship in polycyclic aromatic hydrocarbons (PAHs)-based chalcone derivatives focusing on effective design strategies such as extending ?-conjugation and incorporating strong electron-donating/withdrawing substituents. Three anthracenyl chalcones with aroyl terminal groups of naphthalene (3AP35), benzofuran (3AP40), and p-cyanophenyl (MTP100) were subjected to femtosecond Z-scan measurements under input intensity variation from 49.87 to 93.50 GW cm-2 using 800 nm laser excitation. Consistent ?2 values derived across all intensities for 3AP35 and MTP100 signify the pure two-photon absorption (2PA) process. Whereas the deviating ?2 values in 3AP40 were discovered to arise from fifth-order NLO contributions, resulting in a transition from pure-2PA to 2PA-induced excited-state absorption (2PA-ESA) beyond 56.10 GW cm-2. Separate fitting equations were explicitly used to model the third- and fifth-order NLO processes and to extract their corresponding nonlinear absorption coefficients (?2 and ?3). Molecules exhibiting a lower magnitude of solvatochromic shifts showed weakest NLO responses, while the strongest responses correlated with the greatest sensitivity to solvent polarity. Wavefunction analysis revealed a stronger push-pull character, a lower HOMO-LUMO gap, and greater electron delocalization, which are associated with a reduced optical energy gap and enhanced molecular polarizability. This work investigates the electronic process underlying the NLO response in PAH-based chalcones, which combine ?-conjugation extension with strategic donor-acceptor modulation, providing new insights into materials development for photonic applications. © 2026 Elsevier B.V.en-USCharge transferDFTFemtosecond Z-scanNLOPolycyclic aromatic hydrocarbonsControl nonlinearitiesDesign for testabilityExcited statesLaser excitationMolecular polarityNaphthaleneNonlinear opticsStrategic materialsTwo photon processesChalconesFemtosecondsNon-linear opticalNonlinear optical responseOptical nonlinearityPolycyclic aromaticsPush pullTwo photon absorptiontext::journal::journal article