Breaking the Deep-UV Transparency/Optical Nonlinearity Trade-Off: Three-Parameter Optimization in Oxyfluorides by...

Area of Science:

• Materials Science
• Solid-State Chemistry
• Optics and Photonics

Background:

• Balancing optical parameters like bandgap, second-harmonic generation (SHG), and birefringence is crucial for nonlinear optical (NLO) materials.
• Existing NLO materials often face trade-offs between these critical optical properties, limiting their applications.
• Deep-ultraviolet (deep-UV) transparent materials with NLO properties are highly sought after for advanced photonic devices.

Purpose of the Study:

• To synthesize and characterize novel deep-UV transparent mixed d⁰-metal oxyfluorides with optimized optical properties.
• To explore a synergistic dual-site strategy for reconciling trade-offs in NLO material performance.
• To investigate the structure-property relationships governing the linear and nonlinear optical behavior of the new materials.

Main Methods:

• Synthesis of mixed d⁰-metal oxyfluorides A₅(NbOF₄)(TaF₇)₂ (ANTOF) using a synergistic dual-site strategy.
• Crystallization of noncentrosymmetric polar structures incorporating distorted d⁰-metal octahedra.
• Characterization of optical properties, including bandgap, SHG responses, and birefringence, supported by theoretical calculations.

Main Results:

• Successfully synthesized ANTOFs (A = K, Rb, Cs, NH₄) exhibiting deep-UV transparency.
• Achieved record-high phase-matchable SHG responses for deep-UV transparent d⁰-metal oxyfluorides.
• Demonstrated wide bandgaps (> 6.36 eV) and suitable birefringence (Δn = 0.093-0.105 @ 546 nm).

Conclusions:

• The synergistic dual-site strategy effectively reconciles trade-offs in optical properties for NLO materials.
• The ANTOFs exhibit superior linear and nonlinear optical properties due to the interplay between [NbO₂F₄] and [TaF₇] polyhedra.
• These findings pave the way for developing advanced deep-UV transparent NLO materials for next-generation photonic applications.