High efficiency DBR assisted grating chirp generators for silicon nitride fiber-chip coupling

Area of Science:

• Integrated photonics
• Materials science
• Optoelectronics

Background:

• Silicon Nitride (SiN) is a key material for integrated photonics.
• Low index contrast in SiN presents challenges for efficient coupler design.

Purpose of the Study:

• To propose and demonstrate high-efficiency grating couplers for SiN photonic platforms.
• To address the challenge of low index contrast in SiN for improved light coupling.

Main Methods:

• Utilized a combination of a bottom reflector and a chirp generating algorithm.
• Designed and fabricated grating couplers on two distinct SiN platforms (partially and fully etched).
• Employed numerical simulations to explore variations in SiN film thickness and claddings.

Main Results:

• Predicted peak efficiencies of -0.5 dB (partially etched) and -0.4 dB (fully etched).
• Experimentally measured efficiencies of -1.17 dB and -1.24 dB in the C-L band.
• Simulations indicate potential per coupler loss between -0.33 to -0.65 dB across various SiN configurations.

Conclusions:

• The proposed chirp algorithm combined with a bottom reflector effectively enhances grating coupler efficiency in SiN photonics.
• This approach offers a versatile solution for optimizing light coupling across a range of SiN platform designs.
• The demonstrated method holds promise for advancing SiN-based integrated photonic devices.