Large second harmonic generation in alloyed TMDs and boron nitride nanostructures

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nonlinear Optics

Background:

• Second harmonic generation (SHG) is a key nonlinear optical process.
• Two-dimensional (2D) materials like transition metal dichalcogenides (TMDs) and Boron Nitride (BN) are promising for optoelectronic applications.
• Understanding and enhancing SHG in 2D materials is crucial for developing advanced photonic devices.

Purpose of the Study:

• To explicitly calculate the nonlinear susceptibility (χ(2)) for SHG in 2D semiconducting materials.
• To investigate the effects of alloying, stoichiometry, and curvature on SHG properties.
• To identify materials with superior SHG performance for potential applications.

Main Methods:

• First principles calculations were employed to determine the nonlinear susceptibility.
• The study focused on various transition metal dichalcogenides (TMDs) and Boron Nitride (BN) based materials.
• Analysis included hexagonal alloys, stoichiometry variations (Mo_xSe_yS_z), and curved structures.

Main Results:

• Alloying TMDs significantly improves their SHG response, with MoTeS alloys showing the highest among hexagonal structures at low photon energies.
• SHG intensity in Mo_xSe_yS_z alloys can be precisely tuned by altering the stoichiometry.
• Hypothetical TMD Haeckelites (NbSSe, Nb_0.5Ta_0.5S₂) and a 3D porous hBN structure exhibited exceptionally high nonlinear susceptibility (χ(2)).

Conclusions:

• Alloying and precise stoichiometric control are effective strategies for enhancing SHG in 2D materials.
• Curved materials and specific TMD alloys demonstrate potential for high-performance nonlinear optical applications.
• The findings pave the way for designing novel 2D materials with tailored SHG properties for photonic technologies.