Size-dependent two-photon absorption and ultralow optical-limiting response in atomically-thin rhodonite

Area of Science:

• Materials Science
• Optics
• Nanotechnology

Background:

• Two-dimensional (2D) materials exhibit unique properties surpassing their bulk counterparts.
• Non-layered 2D silicates, like rhodonite, have underexplored nonlinear optical characteristics.
• Understanding size-dependent nonlinear optical responses is crucial for novel applications.

Purpose of the Study:

• To investigate the size-dependent nonlinear optical response of 2D rhodonite nanoflakes.
• To analyze the optical limiting characteristics of few-layer rhodonite.
• To elucidate the underlying mechanisms of enhanced nonlinear optical properties.

Main Methods:

• Femtosecond laser excitation was used to probe nonlinear optical properties.
• Two-photon absorption and optical limiting thresholds were measured.
• Density functional theory (DFT) was employed to analyze electronic structure and optical mechanisms.

Main Results:

• Two-photon absorption significantly enhances as rhodonite thickness decreases to few-layer structures (∼2.5 nm).
• The two-photon absorption coefficient increases to the 10³–10⁴ cm GW⁻¹ range.
• Few-layer rhodonite demonstrates an ultralow optical limiting threshold of 0.38 mJ cm⁻², surpassing benchmarks like graphene, TMDCs, and MXenes.

Conclusions:

• Dimensional tuning of 2D rhodonite dramatically influences its nonlinear optical response.
• Enhanced two-photon absorption is attributed to Fe orbital contributions and Si-O p orbital hybridization.
• 2D rhodonite is a strong candidate for next-generation photonic devices like optical switches and for 3D microfabrication.