Giant angle-insensitive photonic spin Hall effect empowered by Brillouin zone folding

Area of Science:

• Photonics
• Metrology

Background:

• The photonic spin Hall effect (PSHE) is crucial for fundamental photonics and precision measurements.
• Developing robust PSHE phenomena is essential for advanced optical applications.

Purpose of the Study:

• To theoretically propose an angle-insensitive high-Q toroidal dipole (TD) mode.
• To realize an elliptical phase singularity for enhanced PSHE.
• To design an ultrasensitive environmental sensor.

Main Methods:

• Utilizing Brillouin zone folding to support the TD mode.
• Exploiting polarization-dependent guide mode resonance to create an elliptical phase singularity.
• Employing elliptical amplitude detection for sensing.

Main Results:

• Achieved an angle-insensitive elliptical phase singularity tunable at any incident angle.
• Demonstrated enhanced PSHE with high robustness against incident angle variations.
• Developed an environmental sensor with a sensitivity of 1200 rad/RIU.

Conclusions:

• The proposed TD mode offers structural tolerance and angle insensitivity for PSHE.
• The steep phase gradient near the singularity enables ultrasensitive environmental sensing.
• This work advances polarization-engineered photonic devices for high-precision sensing.