Double-Sided Illumination Grating-Coupled Surface Plasmon Resonance Sensors Using Direct Optical Discs

Area of Science:

• Plasmonics
• Nanophotonics
• Sensor Technology

Background:

• Surface Plasmon Resonance (SPR) sensors offer high sensitivity for detecting refractive index changes.
• Fabricating SPR sensors often requires specialized and costly grating substrates.
• Optical discs present a potential low-cost alternative for creating grating substrates.

Purpose of the Study:

• To investigate the feasibility of using commercial optical discs as substrates for grating-coupled surface plasmon resonance (GC-SPR) sensors.
• To compare the performance of GC-SPR sensors fabricated on different types of optical discs (BD-R, DVD-R, CD-R).
• To evaluate the impact of illumination geometry (front-side vs. back-side) and metal coating (silver vs. copper) on sensor performance.

Main Methods:

• Optical discs (BD-R, DVD-R, CD-R) were utilized as grating substrates.
• Silver (Ag) and copper (Cu) films were deposited onto the discs via magnetron sputtering to create plasmonic gratings.
• Wavelength-modulated SPR spectroscopy was employed to measure plasmonic responses.
• Rigorous Coupled Wave Analysis (RCWA) was used for theoretical prediction of sensor behavior.

Main Results:

• Ag-coated gratings exhibited sharper SPR resonances than Cu-coated gratings, which showed broader peaks due to higher damping.
• Front-side illumination resulted in stronger and more reproducible SPR excitation compared to back-side illumination.
• Refractive index sensitivities of 394, 321, and 290 nm/RIU were achieved using Ag-coated CD-R, BD-R, and DVD-R, respectively.

Conclusions:

• Commercial optical discs are viable, low-cost substrates for GC-SPR sensors.
• Sensor performance is significantly influenced by the choice of disc type, metal coating, and illumination strategy.
• Front-side illumination and silver coatings are recommended for optimal SPR sensor performance using optical disc substrates.