Ultracompact Orbital Angular Momentum Sorter on a CMOS Chip.

Area of Science:

• Optics and Photonics
• Integrated Photonics
• Metasurfaces

Background:

• Exponential growth in data traffic necessitates efficient optical communication solutions.
• Current orbital angular momentum (OAM) sorting techniques face challenges with efficiency and system compactness.
• On-chip integration of OAM sorting is crucial for next-generation communication systems.

Purpose of the Study:

• To experimentally demonstrate an ultracompact OAM sorter.
• To integrate OAM sorting functionality onto a complementary metal-oxide-semiconductor (CMOS) camera chip.
• To overcome the limitations of existing OAM demultiplexing methods.

Main Methods:

• Utilized titanium dioxide (TiO2) metasurfaces for OAM sorting.
• Integrated metasurfaces onto a CMOS camera for on-chip functionality.
• Employed propagation phases to implement log-polar transformation, beam copying, focusing, phase correction, and Fourier transform.
• Leveraged unitary transformation theory for bulky systems.

Main Results:

• Achieved ultracompact OAM sorting integrated onto a camera chip.
• Successfully separated OAM beams with topological charges from m = -3 to 3.
• Demonstrated an average crosstalk of -6.43 dB.
• Enabled OAM sorting directly within a CMOS camera.

Conclusions:

• The developed TiO2 metasurface doublet provides a compact and efficient solution for OAM sorting.
• This on-chip integration paves the way for next-generation OAM mode processing in optical communication.
• The approach overcomes the trade-offs between efficiency and compactness in current OAM demultiplexing techniques.