On-chip gain elements for integrated photonics

Area of Science:

• Photonics and Materials Science
• Semiconductor Device Engineering

Background:

• Hybrid integration of active gain elements with passive photonic integrated circuits (PICs) is crucial for advanced optical systems.
• III-V semiconductor gain materials are essential for optical amplification in PICs.
• Efficient coupling and stable performance are key challenges in hybrid integration.

Purpose of the Study:

• To investigate the design of quantum dot (QD)-based gain chips for hybrid integration with PICs.
• To evaluate the benefits of incorporating a multi-mode interference reflector (MMIR) within the gain chip.
• To assess the performance improvements offered by MMIR-equipped gain chips compared to traditional structures.

Main Methods:

• Design and fabrication of quantum dot gain chips featuring an integrated multi-mode interference reflector (MMIR).
• Characterization of ridge waveguide (RWG) lasers incorporating the MMIR.
• Performance comparison of MMIR-based lasers with Fabry-Perot structures, focusing on threshold current and slope efficiency.

Main Results:

• Quantum dot gain chips with MMIR demonstrate fabrication simplicity and strong O-band performance.
• The inclusion of an MMIR reduced threshold current by 87% (6 mA vs 46 mA for 1 mm length).
• Higher slope efficiency was observed, indicating over 90% mirror reflectivity, surpassing Fabry-Perot designs.

Conclusions:

• MMIR-equipped QD gain chips offer significant performance enhancements for hybrid integration.
• Both 1- and 2-port designs simplify waveguide alignment for large-scale PIC applications.
• These gain chips are strong candidates for widespread adoption in future PICs.