Second-harmonic generation in poled polymers: pre-poling history paradigm.

Area of Science:

• Nonlinear Optics
• Materials Science
• Polymer Chemistry

Background:

• Electric-field poling of nonlinear optical polymers like PMMA-DR1 is crucial for applications.
• Understanding the concentration dependence of nonlinear optical properties is essential for material optimization.

Purpose of the Study:

• To investigate the concentration dependence of second harmonic generation (SHG) in electric-field poled PMMA-DR1.
• To elucidate the underlying mechanisms, particularly the role of pre-poling history, using computational modeling.

Main Methods:

• Experimental measurements of nonlinear optical tensor components (χ(2)) in PMMA-DR1 at varying DR1 concentrations.
• Monte Carlo (MC) modeling to simulate and analyze the influence of pre-poling history on dipolar structures.

Main Results:

• A maximum in SHG susceptibility (χ(2)) was observed at approximately 15 mol% DR1 concentration.
• Above 15% concentration, SHG susceptibility rapidly decreased and then stabilized.
• MC modeling indicated that the pre-poling interval and subsequent entanglement of linear dipolar structures dictate the observed concentration dependence and SHG strength.

Conclusions:

• The concentration dependence of SHG in PMMA-DR1 is strongly influenced by the pre-poling history and the resulting entanglement of dipolar structures.
• The kinetics of polar phase build-up, determined by pre-poling duration, are critical for achieving desired nonlinear optical properties.