Thermo-optically tunable slot waveguide-based dual mode-splitting resonators with enhanced sharp lineshapes.

Area of Science:

• Photonics
• Integrated Optics
• Nanophotonics

Background:

• Slot waveguides are crucial for high-performance on-chip photonic sensors and nonlinear devices due to their large evanescent field ratio and strong electric field intensity.
• Microring resonators (MRRs) based on slot waveguides typically exhibit a less steep spectral slope, a consequence of low quality factors caused by high optical propagation losses.

Purpose of the Study:

• To propose and demonstrate a novel dual mode-splitting resonator (MR) based on slot waveguides.
• To enhance the spectral slope of MRRs for improved performance in photonic applications.
• To address the challenge of low quality factors and high optical loss in conventional slot waveguide MRRs.

Main Methods:

• The proposed device utilizes two racetrack resonators integrated with a slot waveguide and a feedback waveguide.
• Coherent optical mode interference is introduced to induce mode-splitting resonance (MR).
• Fabrication is performed using standard complementary metal-oxide-semiconductor (CMOS) technologies on a silicon-on-insulator (SOI) platform.

Main Results:

• The fabricated device exhibits dual MRs with a large extinction ratio (ER) of 45.0 dB.
• A significantly steeper slope rate (SR) of 58.3 dB/nm was achieved compared to conventional MRRs.
• The resonance characteristics were efficiently tunable via applied voltages to a TiN microheater.

Conclusions:

• The novel dual mode-splitting resonator effectively steepens spectral lineshapes, overcoming limitations of conventional slot waveguide MRRs.
• The device demonstrates high extinction ratio and slope rate, suitable for advanced photonic applications.
• Potential applications include optical switching, modulation, and on-chip optical sensing.