Ultra-compact broadband higher order-mode pass filter fabricated in a silicon waveguide for multimode photonics

Area of Science:

• Photonics
• Materials Science
• Optical Engineering

Background:

• Photonic crystal waveguides offer unique light manipulation capabilities.
• Efficient filtering of specific optical modes is crucial for advanced optical communication systems.
• Existing filters often lack compactness or broadband operation.

Purpose of the Study:

• To propose and demonstrate an ultra-compact, broadband higher-order mode pass filter.
• To utilize 1D photonic crystals for selective mode filtering in silicon waveguides.
• To achieve high extinction ratios and low insertion loss for targeted optical modes.

Main Methods:

• Designing a 1D photonic crystal structure to create a bandgap for lower-order modes and an air band for higher-order modes.
• Fabricating a silicon waveguide device incorporating the designed photonic crystal.
• Experimentally measuring the filter's performance, including insertion loss and extinction ratio across a specified wavelength range.

Main Results:

• A ~15-μm-long filter successfully passed first-order modes with ~1.8 dB insertion loss.
• Measured extinction ratios reached approximately 50 dB within the 1480-1580 nm range.
• Calculations indicate extinction ratios exceeding 50 dB over a 170 nm bandwidth.

Conclusions:

• The demonstrated photonic crystal filter enables efficient, compact, and broadband higher-order mode selection.
• This technology holds promise for integrated optical devices and signal processing.
• The design offers a significant advancement in controlling light propagation in silicon waveguides.