Third-order nonlinear optical properties of axially modified indium phthalocyanines with alkyl chains

Increasing the electron density on the phthalocyanine (Pc) ring is an effective approach for ensuring an excellent third-order nonlinear optical (NLO) property. Herein, a series of axially substituted indium Pcs (axial substituent: ethyl, n-propyl, n-butyl, n-pentyl) were synthesized on the basis of tetra-[3-(2-ethoxy)ethoxy] indium phthalocyanine chloride (InClPc). The third-order nonlinear optical properties were investigated by the Z-scan technique at 532 nm with 4 ns laser pulses. All the axially alkyl substituted InPcs showed a better nonlinear absorption response than InClPc. The NLO properties of the axially substituted Pcs got better with the increased length of the alkyl chain. The effect of alkyl chain substituents on the nonlinear absorption of indium phthalocyanine was demonstrated through their optical physical parameters (ΦF, kST, ΦT, and τT).