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Subwavelength-grating contradirectional couplers for large stopband filters
Optics Letters
|February 15, 2018
Summary
Researchers created broadband and narrow-band Bragg filters using subwavelength gratings (SWG) and asymmetric contradirectional couplers (contra-DCs). These compact silicon photonic devices achieved record bandwidths for integrated photonics applications.
Area of Science:
- Integrated photonics
- Nanophotonics
- Waveguide optics
Background:
- Subwavelength gratings (SWG) offer unique optical properties at the nanoscale.
- Contradirectional couplers (contra-DCs) are key components in photonic integrated circuits.
Purpose of the Study:
- To demonstrate asymmetric contra-DCs using sidewall-corrugated SWG waveguides.
- To achieve broadband and narrow-band Bragg filters on a silicon-on-insulator platform.
Main Methods:
- Fabrication of SWG waveguides with sidewall corrugations.
- Design and characterization of asymmetric contra-DCs for Bragg filters.
- Photonic band structure simulations and experimental spectral measurements.
Main Results:
- Achieved a record experimental bandwidth of 4.07 THz (33.4 nm) for broadband add-drop Bragg filters.
- Demonstrated a narrow-band filter (near 100 GHz) using a phase-shifted Bragg grating SWG contra-DC.
- Devices fabricated on a 220-nm silicon-on-insulator platform with lengths < 150 μm.
Conclusions:
- SWGs effectively increase mode overlap and photonic band gap size.
- Compact SWG contra-DCs enable versatile, high-performance integrated photonic filters.
- These filters have potential applications in band splitting, reconfigurable switching, and dispersion engineering.
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