Compact low-loss 8 × 8 silica optical switch based on large fan-in/fan-out couplers

Area of Science:

• Photonics and Optical Engineering
• Integrated Optics
• Semiconductor Device Fabrication

Background:

• Traditional optical switches face limitations in size, loss, and scalability.
• Multimode interference (MMI) couplers offer potential for compact optical switching.
• Achieving uniform channel performance and low loss in N x N switches is challenging.

Purpose of the Study:

• To propose and demonstrate a novel optical switch scheme using large fan-in/fan-out MMI couplers.
• To achieve compact, low-loss, and uniform N x N optical switching.
• To facilitate high-density photonic integration.

Main Methods:

• Designed an 8x8 optical switch using two identical 8x8 MMI couplers connected by equal-path-length waveguides.
• Fabricated the switch using CMOS-compatible processes.
• Characterized insertion loss, crosstalk, and 3-dB bandwidth at 1550 nm.

Main Results:

• Demonstrated an 8x8 silica switch with an insertion loss of 2.7 ± 0.6 dB.
• Achieved crosstalk levels of -14.7 ± 4 dB across all switching scenarios.
• Observed a 3-dB bandwidth covering the C-band (1535-1565 nm) with crosstalk below -10 dB.

Conclusions:

• The proposed MMI coupler-based optical switch scheme enables compact and low-loss N x N switching.
• The scalable design overcomes limitations of traditional switches.
• Facilitates high-density photonic integration for advanced optical networks.