Ultra-compact and efficient photonic waveguide bends with different configurations designed by topology optimization.

Area of Science:

• Photonics and Optical Engineering
• Materials Science (Silicon-on-Insulator)

Background:

• Optical signal transmission through bends in integrated circuits typically incurs high loss and mode distortion.
• Conventional large-radius bends limit device integration density.
• Minimizing optical loss in compact waveguide bends is crucial for advanced photonic applications.

Purpose of the Study:

• To propose and design novel topology-optimized L-bend and U-bend structures for a 220 nm silicon-on-insulator (SOI) platform.
• To minimize optical insertion loss and mode distortion in compact waveguide bends.
• To enhance integration density in photonic integrated circuits.

Main Methods:

• Topology optimization techniques were employed to design L-bend and U-bend structures.
• Simulations were performed on a 220 nm SOI platform.
• Experimental verification was conducted using a meander line with optimized U-bends.

Main Results:

• Optimized L-bends with footprints as small as 1 µm × 1 µm exhibited maximum insertion losses of 0.78 dB.
• Optimized U-bends with footprints as small as 1.5 µm × 1.5 µm showed maximum insertion losses of 3.16 dB.
• Optimized bends achieved over 50% reduction in insertion loss compared to arc-type bends across 1450-1650 nm.
• Experimental results for a meander line with 16 optimized U-bends showed an average insertion loss of 1.23 dB (1520-1580 nm).

Conclusions:

• Topology-optimized L-bends and U-bends offer significant reductions in optical loss for compact photonic circuits.
• These optimized bends are suitable for high-density integration on SOI platforms.
• The findings demonstrate a high potential for loss reduction in integrated photonics using optimized bend designs.