Mid-Infrared Gas Sensing Based on Electromagnetically Induced Transparency in Coupled Plasmonic Resonators

Area of Science:

• Photonics and Plasmonics
• Materials Science
• Sensor Technology

Background:

• Surface plasmon polaritons (SPPs) in doped silicon enable new applications in sensing, imaging, and photonics.
• CMOS-compatible fabrication is crucial for integrating plasmonic devices into existing technologies.

Purpose of the Study:

• To propose and investigate a CMOS-compatible doped silicon plasmonic sensor.
• To demonstrate tunable plasmon resonance in the mid-infrared region.
• To evaluate the sensor's performance for gas detection (methane and ethane).

Main Methods:

• Fabrication of a doped silicon sensor using phosphorus at 5 × 10^20 cm^-3 concentration.
• Utilizing coupled metal-insulator-metal (MIM) ring resonators.
• Characterizing plasmonic mode profiles, bend loss, and resonance shifts.
• Measuring sensor sensitivity and selectivity towards methane and ethane.

Main Results:

• Achieved surface plasmon resonance in the mid-infrared region.
• Demonstrated tunable resonance by controlling carrier density.
• Obtained a sensitivity of 7539.9 nm/RIU at 7.7 μm wavelength.
• Achieved a Figure of Merit (FOM) of 6732 for gas sensing.

Conclusions:

• The proposed silicon plasmonic sensor offers high sensitivity and selectivity for mid-infrared gas sensing.
• Coupled ring resonators enhance sensing performance, leading to a smaller FWHM and increased sensitivity.
• The sensor's CMOS compatibility and performance make it suitable for advanced modulation and sensing applications.