Sub-Micron-Thick Si Membrane Surface Plasmon Coupling Structure For Reducing Unwanted Propagation Modes Inside Si

We propose a Surface Plasmon Resonance (SPR) sensor for efficient signal detection unaffected by propagation modes, utilizing a sub-micron-thick silicon (Si) membrane. Electrical detection SPR sensors are suitable for miniaturization, but conventional methods suffer from problems due to the interaction of incident light with the measured liquids. To address this, we employed a back-irradiation configuration, where light enters opposite the solution. In this configuration, measurements are challenging because the propagation modes inside Si generate noise. Theoretical models demonstrate that reducing the Si thickness decreases the number of modes. The fabricated device increased the current across all irradiated wavelengths, confirming its functionality.