Spectral engineering of subwavelength-grating-based contradirectional couplers

Area of Science:

• Photonics
• Integrated Optics
• Materials Science

Background:

• Silicon photonic devices are crucial for optical communication and sensing.
• Contradirectional couplers (Contra-DCs) are key components for wavelength (de)multiplexing.
• Subwavelength gratings (SWGs) offer unique optical properties for device design.

Purpose of the Study:

• To tailor the spectral characteristics of silicon photonic Contra-DCs.
• To improve device performance for optical (de)multiplexing applications.
• To explore the potential of SWG-based couplers in integrated sensing.

Main Methods:

• Designing Contra-DCs by integrating SWG waveguides with strip waveguides.
• Tapering the gap distance between SWG and strip waveguides to optimize performance.
• Introducing a π phase shift in SWG gratings to create resonant transmission peaks.

Main Results:

• Achieved sidelobe suppression ratios of 10 dB to 20 dB and extinction ratios of 15 dB to 35 dB for various bandwidths (12 nm, 9 nm, 6 nm).
• Demonstrated a resonant transmission peak with 1 nm bandwidth and 7 dB extinction ratio in the stop-band.
• Showcased high sensitivity of the resonant peak to cladding material changes due to the SWG waveguide.

Conclusions:

• The tailored SWG-based Contra-DC design offers a promising approach for high-performance optical (de)multiplexers.
• The demonstrated resonant peak exhibits significant sensitivity to cladding materials, making it suitable for integrated sensing.
• This work advances the development of versatile silicon photonic devices for telecommunications and sensing.