Opto-optical edge defect mitigation in solution-processed WSe₂ thin films for high-efficiency optical modulation.

Area of Science:

• Materials Science
• Optoelectronics
• Nanotechnology

Background:

• Two-dimensional (2D) optical modulators face efficiency limitations due to defect-induced losses and weak light-matter interactions.
• Edge defects in solution-processed WSe2 nanosheets, characterized by metallic 1T domains and semiconducting 2H interiors, contribute to these limitations.

Purpose of the Study:

• To investigate the dynamic saturation of edge defects in WSe2 nanosheets via carrier trap filling.
• To enhance the performance of 2D optical modulators by engineering defect states and controlling carrier distribution.

Main Methods:

• Solution processing of WSe2 nanosheets with controlled lateral size.
• Dynamic saturation of edge defects through optical or electrical excitation.
• Characterization of modulation efficiencies, complex refractive index changes, and device performance in C-band modulators integrated with micro-ring resonators.

Main Results:

• Defect saturation reduced nonradiative recombination and reshaped carrier distribution, enhancing excitonic response.
• Achieved improved photoluminescence peak modulation efficiencies: 0.025 eV·V⁻¹ (electro-optic) and 0.1 eV·mW⁻¹ (opto-optic).
• Demonstrated efficient C-band modulation (1530-1565 nm) with a tuning efficiency of 1.84 × 10⁻⁵ pm⁻¹·mW·m², alongside fast modulation dynamics (~48.1 ns rise, ~79.4 ns fall).

Conclusions:

• Engineered defect regulation in WSe2 is a viable and scalable strategy for high-performance 2D optical modulators.
• The findings establish a new pathway for overcoming efficiency bottlenecks in 2D photonic devices.