Extraordinarily high spectral sensitivity in refractive index sensors using multiple optical modes.

Area of Science:

• Photonics and Sensing Technologies
• Optical Metrology

Background:

• Surface plasmon resonance (SPR) sensors are known for high spectral sensitivity.
• This sensitivity is often attributed to modal overlap or unique surface plasmon dispersion properties.

Purpose of the Study:

• To investigate the underlying mechanism responsible for the extraordinary spectral sensitivity in SPR sensors.
• To explore the applicability of this mechanism to dielectric sensing systems.
• To identify fundamental limitations in multi-mode sensing approaches.

Main Methods:

• Theoretical analysis of multi-mode excitation in plasmonic and dielectric systems.
• Investigating the relationship between spectral sensitivity and sensor parameters.

Main Results:

• Demonstrated that the high spectral sensitivity of SPR sensors originates from the multi-mode nature of the sensing scheme.
• Showed that the multi-mode sensing concept can be extended to dielectric systems for enhanced spectral sensitivity.
• Identified a fundamental constraint between spectral sensitivity and quality factor in multi-mode sensing.

Conclusions:

• The multi-mode nature of the sensing scheme is the primary driver of extraordinary spectral sensitivity in SPR sensors.
• Multi-mode sensing offers a viable pathway to achieve high spectral sensitivity in dielectric systems.
• A fundamental trade-off exists between spectral sensitivity and quality factor in multi-mode sensing.