On-chip multiple beam splitting assisted by bound states in the continuum

Area of Science:

• Photonics
• Metamaterials
• Integrated Optics

Background:

• On-chip beam splitting typically relies on total internal reflection and manipulating iso-frequency curves (IFCs).
• Existing methods often require high-index dielectric materials for efficient light confinement.

Purpose of the Study:

• To achieve on-chip beam splitting without total internal reflection.
• To explore the use of linear-crossing metamaterials (LCMMs) and bound states in the continuum (BICs) for light manipulation.

Main Methods:

• Utilizing a two-dimensional photonic crystal (PhC) slab to mimic an LCMM.
• Employing a bound state in the continuum (BIC) for vertical light confinement, operating beyond the light cone.
• Controlling light propagation via the rotation angle of silicon pillars within the PhC slab.

Main Results:

• Demonstrated on-chip beam splitting in an LCMM without requiring total internal reflection.
• Achieved flexible control over light propagation by adjusting pillar rotation angles.
• Designed on-chip triple beam splitting by combining LCMMs with opposite rotation angles.

Conclusions:

• The developed method enables light beam splitting beyond the light cone through BIC and LCMM spatial dispersion manipulation.
• This work advances integrated optics devices like on-chip focusing, switching, and (de)multiplexing.