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Graphical abstract Highlights • α-InPcCl and β-InPcCl are excellent optical limiting materials due to the fast rate of intersystem crossing transition. • The position of peripheral substituents can strongly influence the OL performance during the laser propagation. • β-InPcCl shows better OL characteristics with picosecond pulse trains, which is opposite to the case with single nanosenond pulse. Abstract We studied the optical dynamics and propagating properties of two chloroindium phthalocyanines with α- and β-alkoxyl substituents interacting with picosecond pulse trains. The pulse train contains 35 picosecond subpulses with 12 ns spacing, and the width of each subpulse is 100 ps. We applied a five-level model to simulate the interaction by solving two-dimensional paraxial field equation coupled with rate equations. Photophysical parameters of molecules are extracted from the experiment and we employed Crank–Nicholson numerical method to get accurate and credible results. The sequential (singlet-singlet) × (triplet-triplet) two-photon absorption is the vital optical limiting channel for long pulse trains. Our work indicates that chloroindium phthalocyanine with β-alkoxyl substituent shows better optical limiting behaviors for picosecond pulse trains, which is opposite with the result for one single nanosecond laser. [ABSTRACT FROM AUTHOR]

We investigated nonlinear optical dynamics of asymmetric benzothiazole substituted phthalocyanines and their covalent attachments to glutathione functionalized cadmium telluride quantum dots (CdTe QDs) interaction with picosecond pulse trains. A pulse train with 50 subpulses of 100 picosecond width which was separated by 12 nanosecond spacing was employed as the laser source. A generalized five-level model was adopted to retrench the studied materials. In our simulation, we solved two-dimensional paraxial field equation entangled with the rate equations by Crank–Nicholson numerical method. Interacting with long pulse trains, the principal absorption channel in substituted phthalocyanines and their covalent attachments is the two-step two-photon absorption (TPA). All materials show excellent optical limiting behaviours and the results indicated that the covalent attachments of phthalocyanines to CdTe QDs are much better than phthalocyanines with long pulse trains. [Display omitted] • Phthalocyanines with or without quantum dots are all good optical limiting materials. • Quantum dots can strongly influence the OL performance during the laser propagation. • Phthalocyanines with quantum dots had better OL effects with picosecond pulse trains. [ABSTRACT FROM AUTHOR]

• Phthalocyanines and their corresponding materials with semiconductor quantum dots are excellent optical limiting materials. • The quantum dots can strongly influence the OL performance during the laser propagation. • Phthalocyanines with quantum dots show better OL characteristics with picosecond pulse trains. Optical interaction of aminophenoxy substituted phthalocyanines with picosecond pulse trains were studied in this work. Additionally, the covalent attachments of phthalocyanines to glutathione (GSH) functionalized cadmium telluride quantum dots (CdTe QDs) were also discussed. A five-level model was applied to simplify the materials. The pulse train has 50 subpulses with 100 ps width for each one and 12 ns spacing. We simulated the dynamical interaction by solving two-dimensional paraxial filed equation coupled with the rate equations based on Crank–Nicholson numerical method. The two-step two-photon absorption (TPA) is the fundamental channel of optical absorption for long pulse trains. Our results indicated that the covalent attachments of phthalocyanines to CdTe QDs show better optical limiting effects than phthalocyanines at the same densities. The cross-sections of one-photon absorption and lifetimes of lowest triplet state as well as the intersystem crossing play important roles in optical limiting effects. [ABSTRACT FROM AUTHOR]

• Tetra- α -(2-ethylbutoxy) and tetra- β -(2-ethylbutoxy) chloroindium phthalocyanines are both excellent optical limiting materials. • Fast response time of the population transfer will promote two-step sequential two-photon absorption. • The position of substituent together with the molecular concentration can strongly influence the molecular optical limiting performance. • Tetra- β -(2-ethylbutoxy) chloroindium phthalocyanine shows better optical limiting characteristics with nanosecond pulses. In this work we presented the study on nonlinear dynamics of tetra- α -(2-ethylbutoxy) chloroindium phthalocyanine (α -InPcCl) and tetra- β -(2-ethylbutoxy) chloroindium phthalocyanine (β -InPcCl). We replaced the electronic structure of molecules with the five-level model, and solved two-dimensional paraxial field equation and rate equations by Crank-Nicholson numerical method. The main passageway of photon absorption for optical limiting is the sequential (singlet-singlet) × (triplet-triplet) two-photon absorption. Both phthalocyanines showed distinctive optical limiting behaviors with a 532 nm–7 ns nanosecond laser. α -InPcCl shows better optical limiting effect, and we took it as an example to studied the optical dynamics in detail. [ABSTRACT FROM AUTHOR]