O-band 32 × 32 silicon photonic switch with double Mach-Zehnder switch elements.

Area of Science:

• Photonics and Optical Engineering
• Integrated Optics
• Semiconductor Devices

Background:

• Silicon photonic switches are crucial for energy-efficient data centers and AI/ML clusters.
• Existing switches face challenges in crosstalk and insertion loss.
• Advancements in complementary metal-oxide-semiconductor (CMOS) technology enable complex photonic integrated circuits.

Purpose of the Study:

• To develop and characterize a strictly non-blocking 32x32 silicon photonic switch.
• To improve crosstalk performance using double Mach-Zehnder (MZ) switch elements.
• To demonstrate high-speed data transmission capabilities.

Main Methods:

• Fabrication of a 32x32 silicon photonic switch using 45-nm CMOS technology.
• Integration of 2048 thermo-optic MZ switches with a path-independent insertion-loss topology.
• Flip-chip bonding to a land-grid-array (LGA) ceramic interposer for control circuit connection.
• Electrical wiring of a single arm per MZ switch for simplified control.

Main Results:

• Successfully operated 99.2% of the 2048 MZ switches.
• Achieved on-chip insertion loss between 9.3 and 15.6 dB (average 11.8 dB).
• Demonstrated crosstalk below -20 dB over a 70-nm bandwidth.
• Successfully transmitted 100-Gbps signals with a bit error ratio below 1x10^-3.

Conclusions:

• The developed silicon photonic switch meets the requirements for high-performance data center networks and AI/ML applications.
• The path-independent insertion-loss topology and double MZ switch design effectively reduce crosstalk.
• The fabricated device demonstrates the potential of silicon photonics for future high-speed optical communication systems.