Standalone, CMOS-based Faraday rotation in a silicon photonic waveguide

Area of Science:

• Photonics and Optical Engineering
• Semiconductor Device Fabrication
• Electromagnetism

Background:

• Nonreciprocity is crucial for optical communication signal isolation.
• Current on-chip optical isolator designs are impractical due to post-processing or magnetic biasing requirements.
• There is a need for standalone, nonreciprocal devices using standardized fabrication.

Purpose of the Study:

• To design and simulate an electromagnetic coil integrated with a waveguide using the complementary metal-oxide-semiconductor (CMOS) process flow.
• To demonstrate the feasibility of achieving nonreciprocal effects through CMOS-compatible electromagnetic induction.
• To establish a foundational building block for commercially viable on-chip optical isolators.

Main Methods:

• Designed an electromagnetic coil compatible with the standard CMOS process flow.
• Simulated the magnetic flux density generated by the coil when carrying an electric current.
• Analyzed the induced optical rotation for the fundamental transverse-magnetic mode at a specific wavelength.

Main Results:

• The designed electromagnetic coil supported currents up to 14 mA.
• Simulations showed an alternating magnetic flux density up to 1.16 mT within a strip waveguide.
• An optical rotation of 50.71 picodegrees was induced at 1352 nm wavelength for the fundamental transverse-magnetic mode.

Conclusions:

• The study presents the first CMOS-compatible electromagnetic coil for on-chip optical nonreciprocity.
• The demonstrated methods offer potential for increasing optical rotation by orders of magnitude.
• This work serves as a key component for developing practical, on-chip optical isolators.