Absorptive resonant mirrors enabling high-Q perfect absorption for refractive index sensing

Area of Science:

• Photonics
• Nanotechnology
• Sensing technology

Background:

• Prism-coupled layered structures like surface plasmon resonance (SPR) and resonant mirror (RM) sensors are vital for refractive index sensing.
• Existing RM sensors face challenges with sophisticated signal detection, while SPR sensors suffer from limited sensing performance due to low quality factors.

Purpose of the Study:

• To propose and theoretically investigate a novel absorptive resonant mirror (RM) sensor.
• To achieve independently tunable radiative and absorptive losses for enhanced sensing performance.
• To enable perfect absorption with ultra-narrow bandwidth for improved label-free sensing applications.

Main Methods:

• Theoretical investigation of an absorptive RM structure.
• Independent tuning of radiative quality factor (Qr) and absorptive quality factor (Qa) by controlling buffer layer thickness and waveguide extinction coefficient.
• Achieving critical coupling condition for perfect absorption.

Main Results:

• Demonstrated independent control over Qr and Qa without crosstalk.
• Achieved perfect absorption with ultra-narrow bandwidth when Qr and Qa are matched at critical coupling.
• Proposed a simple layer stack compatible with existing prism-coupled schemes.

Conclusions:

• The proposed absorptive RM offers a promising platform for label-free sensing.
• Independent tunability of losses enhances sensing capabilities.
• Compatibility with existing setups facilitates practical implementation.