Symmetry Engineering in Heterometallic TMDC Mo_(1-x)Nb_xSe₂: A Systematic Route Toward Enhanced Nonlinear Optical...

Area of Science:

• Materials Science
• Condensed Matter Physics
• Photonics

Background:

• Semiconducting MoSe₂ and metallic NbSe₂ have limited nonlinear optical (NLO) performance due to photon reabsorption and low optical damage thresholds, respectively.
• Developing 2D materials with enhanced NLO properties is crucial for advanced photonic devices.

Purpose of the Study:

• To investigate the NLO properties of equimolar heterometallic Mo_(1-x)Nb_xSe₂ alloys.
• To explore the structural and electronic mechanisms behind enhanced NLO responses.
• To demonstrate the potential of these alloys in NLO applications and laser protection.

Main Methods:

• Synthesis of equimolar heterometallic Mo_(1-x)Nb_xSe₂ alloys.
• Characterization of NLO responses using second harmonic generation (SHG) and nonlinear optical absorption (NOA) measurements.
• Evaluation of optical damage thresholds and saturable/reverse saturable absorption (SA/RSA) properties.
• Fabrication of an ultrafast laser system utilizing the material.

Main Results:

• The Mo_(1-x)Nb_xSe₂ alloy exhibits significantly enhanced SHG, with odd layers showing pronounced effects and even layers displaying anomalous SHG due to strain-induced symmetry breaking.
• The alloy possesses a 32.5% higher optical damage threshold than NbSe₂.
• Prominent SA at 1 µm was observed, enabling ultrafast laser pulse generation (2.292 ps), and exceptional RSA at 1.5 µm, demonstrating improved optical limiting capabilities.
• The material's unique properties enable integration into piezoelectric, ferroelectric, and spin-valley-coupling platforms.

Conclusions:

• Equimolar heterometallic Mo_(1-x)Nb_xSe₂ alloys offer a promising strategy for enhancing NLO functionalities in 2D materials.
• The alloy's superior NLO performance, high damage threshold, and tunable absorption characteristics make it suitable for advanced photonic devices and laser protection.
• This work provides a pathway for engineering functional NLO materials by alloying binary 2D compounds.