Efficient Strategy for Investigating the Third-Order Nonlinear Optical (NLO) Properties of Solid-State Coordination...

Area of Science:

• Materials Science
• Optics
• Chemistry

Background:

• Investigating third-order nonlinear optical (NLO) properties of solid coordination polymers (CPs) is challenging but vital for applications.
• Existing methods for studying solid-state NLO properties are difficult, limiting practical use.

Purpose of the Study:

• To develop a method for preparing high-quality CP films in a polymer matrix for studying solid-state third-order NLO properties.
• To investigate the third-order NLO performance of novel azobenzene-based CPs doped into poly(vinyl alcohol) (PVA).

Main Methods:

• Synthesized two novel azobenzene-based CPs: [CdL(DMAc)(H₂O)] (1) and {[CuL(4,4'-azobpy)]·3H₂O} (2).
• Doped microcrystals of these CPs (average grain size 3 μm) into PVA to form CP films (1-MC/PVA and 2-MC/PVA).
• Employed third-order NLO measurements and Density Functional Theory (DFT) calculations.

Main Results:

• The prepared CP films (1-MC/PVA and 2-MC/PVA) exhibited NLO absorption switching behavior from saturable absorption (SA) to reverse saturable absorption (RSA) with increasing pulse energy.
• NLO properties were efficiently modulated by photostimulation due to the trans → cis isomerization of the azobenzene moiety.
• DFT results indicated that narrower band gaps and denser electron density distribution correlate with better third-order NLO performance.

Conclusions:

• A feasible method for preparing CP films in a polymer matrix was established for studying solid-state third-order NLO properties.
• The azobenzene-based CP films demonstrate tunable NLO absorption switching and photomodulation capabilities.
• This approach facilitates the broader practical application of solid materials with excellent third-order NLO performance.