Exploiting extraordinary topological optical forces at bound states in the continuum

Area of Science:

• Photonics
• Optical physics
• Condensed matter physics

Background:

• Polarization singularities and topological vortices in photonic crystal slabs are linked to zero amplitude of polarization vectors.
• Bound states in the continuum (BICs) are unique optical states within photonic structures.

Purpose of the Study:

• To investigate topological features in optical forces near BICs.
• To explore the potential of these topological forces for nanoparticle manipulation.

Main Methods:

• Analysis of optical forces in the vicinity of BICs in photonic crystal slabs.
• Tailoring the asymmetry of photonic crystal slabs to control force characteristics.
• Investigating the behavior of topological forces around off-Γ BICs.

Main Results:

• Topological features, similar to polarization vortices, are observed in optical forces around BICs.
• Optical forces exhibit winding behavior in momentum space near BICs, carrying a topological charge.
• Tailoring slab asymmetry leads to spinning behavior and shifted force zeros, enabling 3D asymmetric trapping.
• Off-Γ BICs generate multiple force zeros with diverse force distribution patterns.

Conclusions:

• Introduces the concept of topology to optical forces around BICs.
• Demonstrates the potential for creating optical force vortices for nanoparticle manipulation.
• Highlights opportunities for enhanced reversible forces in manipulating nanoparticles and fluid flow.