Dopant-driven photonic nonlinear optical responses in Mg₄O₃ electrides

Area of Science:

• Materials Science
• Condensed Matter Physics
• Quantum Chemistry

Background:

• Electrides show promise for nonlinear optical (NLO) materials in photonics and laser technologies.
• Precise control over their optoelectronic properties is a significant challenge.
• Mg4O3 serves as a promising host material for developing novel NLO applications.

Purpose of the Study:

• To systematically design and characterize pristine and alkali metal halide-doped Mg4O3 electrides.
• To investigate the impact of dopant integration on electronic structure and NLO properties.
• To explore dopant chemistry and positional engineering for tuning NLO responses.

Main Methods:

• Density Functional Theory (DFT) and time-dependent DFT were employed for systematic design and characterization.
• Calculations focused on electronic restructuring, HOMO-LUMO gap, charge-transfer characteristics, and orbital redistribution.
• Static and dynamic NLO responses, including hyperpolarizability and electro-optic effects, were evaluated.

Main Results:

• Dopant integration reduced the HOMO-LUMO gap and enhanced charge-transfer characteristics.
• Static first hyperpolarizability (β) surged over 3-fold upon doping, peaking at 2.87 × 10^4 a.u. for KCl@Mg4O3-p1.
• Dynamic NLO responses, such as the electro-optic Pockels effect (EOPE) and second-harmonic generation (SHG), were markedly enhanced, with NaF@Mg4O3-p1 showing the highest EOPE (50063 a.u.) and NaCl@Mg4O3-p1 exhibiting the strongest SHG (1,201,472 a.u.).

Conclusions:

• Alkali halide doping and positional engineering are effective strategies for tuning the NLO properties of Mg4O3 electrides.
• Doped Mg4O3 electrides exhibit significantly enhanced static and dynamic NLO responses.
• These findings position Mg4O3 electrides as leading candidates for next-generation optoelectronic applications.