Nanophotonics, Plasmonics, and Metamaterials

A: The hard boundary here is the minimum detectable shift, often 5–10 nm for these arrays under controlled NA and polarization. If the optical setup drifted between FAT and site, a 12 nm shift may be an artifact. Geometry and material checks matter, but they don't explain a test-to-test delta without first locking down measurement equivalence.

A: The deciding number is the imaginary part of permittivity at 1550 nm, where silver still beats gold by roughly a factor of two in loss. HTOL pushes you to cap it, not abandon it. Aluminum shifts the loss problem into the NIR, and ITO's advantage shows up when tunability is required, not minimum loss.

A: The number that matters is the gap size relative to the skin depth, typically tens of nanometers. At ~10 nm gaps, capacitive coupling pushes enhancements into the 10^2–10^3 range before nonlocal and damping effects clamp it. Claims beyond that ignore loss mechanisms you can't wish away.

A: The trap here is the phase reference, often a few millimeters translating into large index swings for thin slabs. Until the reference plane and thickness are aligned, −1.2 versus −0.6 is a data handling problem, not physics. Magnitude-only checks won't rescue a bad phase.