High-efficiency unidirectional vertical emitter achieved by an aperture-coupling nanoslot antenna array.

Area of Science:

• Photonics and Integrated Optics
• Antenna Engineering
• Nanotechnology

Background:

• Efficient light coupling is essential for photonic integrated circuits (PICs).
• Traditional grating couplers exhibit low upward coupling efficiency due to bidirectional radiation.
• A need exists for high-efficiency unidirectional couplers for advanced PICs.

Purpose of the Study:

• To propose a compact aperture-coupling nanoslot antenna array for high-efficiency unidirectional light radiation.
• To enhance light coupling from in-plane guided modes to free space or optical fibers.
• To overcome the limitations of conventional grating couplers.

Main Methods:

• Utilizing a two-dimensional high-contrast grating (HCG) as a mirror to suppress downward radiation.
• Employing a low-index spacing layer between the HCG and a thin silver film.
• Patterning H-shaped slots on the silver film to control aperture fields and direct radiation.

Main Results:

• Achieved a front-to-back (F/B) ratio exceeding 10 dB across the 1500–1600 nm wavelength range.
• Demonstrated high radiation efficiency over 75% within a 100 nm bandwidth.
• Reported a maximum radiation efficiency of 87.6% for the proposed nanoslot antenna array.

Conclusions:

• The proposed nanoslot antenna array offers high-efficiency unidirectional radiation, overcoming traditional coupler limitations.
• This technology is promising for various integrated photonic applications, including wireless optical communications and fiber input/output couplers.
• The design provides a significant advancement for efficient light management in photonic integrated circuits.