Efficient and fabrication error tolerant grating couplers on the InP membrane on silicon platform

Area of Science:

• Photonics
• Integrated Optics
• Materials Science

Background:

• Grating couplers are essential for interfacing optical fibers with photonic integrated circuits.
• Achieving low insertion loss is critical for efficient signal transmission in photonic systems.
• Indium Phosphide (InP) platforms are widely used for high-performance photonic devices.

Purpose of the Study:

• To design and fabricate deep and shallow-etched grating couplers with a metal back-reflector.
• To achieve record low insertion losses in InP-based grating couplers.
• To investigate the fabrication error tolerances of shallow-etched grating couplers.

Main Methods:

• Design and simulation of grating coupler structures.
• Fabrication of deep and shallow-etched gratings on InP.
• Experimental measurement of insertion losses.
• Analysis of fabrication tolerances (grating period, fill factor).

Main Results:

• Measured insertion losses of 2.4 dB for deep-etched and 2.6 dB for shallow-etched gratings.
• Demonstrated record low insertion losses for InP-based grating couplers.
• Shallow-etched gratings exhibit high tolerance to variations in grating period and fill factor.

Conclusions:

• The developed grating couplers offer highly efficient light coupling for InP photonic integrated circuits.
• The shallow-etched design shows robustness against fabrication imperfections, enabling reliable manufacturing.
• These results advance the performance and manufacturability of grating couplers for optical communication.