A dual-detector optical receiver for PDM signals detection.

Area of Science:

• Photonics and Optical Engineering
• Integrated Optics
• Semiconductor Devices

Background:

• Polarization Division Multiplexing (PDM) is crucial for increasing data rates in optical communication.
• Efficient and cost-effective receivers are needed to handle PDM signals, especially for short-reach applications.
• Existing solutions may face challenges in terms of speed, responsivity, or cost.

Purpose of the Study:

• To propose and fabricate a novel silicon-based dual-detector optical receiver.
• To achieve polarization diversity and demultiplexing for PDM signals using a 2D grating coupler.
• To enhance photodetector performance through a specific double-sided illumination design.

Main Methods:

• Fabrication of a silicon-based dual-detector optical receiver integrating a 2D grating coupler and two germanium photodetectors (Ge PDs).
• Implementation of a double-sided illumination design for the Ge PDs to improve space charge density, responsivity, and saturation power.
• Characterization of the receiver's performance, including dark current, responsivity, bandwidth, DC currents, and eye diagrams.

Main Results:

• The fabricated receiver demonstrated a dark current of 0.86 μA, responsivity of 1.06 A/W, and bandwidth of 36 GHz at 3 V reverse bias.
• The device successfully demultiplexed and detected PDM signals, validated by DC current and eye diagram measurements.
• A low power penalty of approximately 1.9 dB was observed for both Ge PDs at 10 and 20 Gb/s.

Conclusions:

• The proposed direct detection receiver for PDM signals offers high speed, high responsivity, and large saturation power.
• The cost-effective design is a promising solution for short-reach optical communication systems.
• The integrated 2D grating coupler and dual Ge PDs effectively achieve polarization diversity and demultiplexing.