Second-Order Nonlinear Optical Responses of AlN Two-Dimensional Monolayer: A Real-Time First-Principles Study

Area of Science:

• Materials Science
• Condensed Matter Physics
• Quantum Chemistry

Background:

• Two-dimensional (2D) materials are extensively studied for their unique physical properties and potential applications.
• Aluminum nitride (AlN) is a promising 2D material with a wide direct band gap.

Purpose of the Study:

• To investigate the electronic, linear, and second-order nonlinear optical properties of AlN monolayer.
• To explore the potential applications of AlN monolayer in ultraviolet (UV) nonlinear optics.

Main Methods:

• Real-time first-principles approach based on Green's function theory.
• Inclusion of quasi-particle corrections, crystal local field effects, and excitonic contributions.
• Calculation of linear and nonlinear optical responses.

Main Results:

• AlN monolayer possesses a wide direct band gap (~6.45 eV).
• Strong absorption and second-harmonic generation resonances observed in the UV range.
• Significant second-order nonlinear susceptibility peaks (~430 pm/V) in the 2.8-5.3 eV range, exceeding existing UV nonlinear materials.

Conclusions:

• AlN monolayer demonstrates exceptional second-order nonlinear optical properties in the UV spectrum.
• The findings suggest AlN monolayer is a highly suitable material for UV nonlinear optical applications.
• Potential applications include nonlinear imaging, spectroscopy, and nanophotonics.