Dielectric-Grating-Coupled Surface Plasmon Resonance From the Back Side of the Metal Film for Ultrasensitive Sensing

We propose a dielectric grating that can launch surface plasmon resonance (SPR) modes efficiently on the other side of flat metal films, which is similar to the conventional prism coupling mechanism. Importantly, this structure can excite SPR under the normal incident light, which is particularly suitable for the integration with optical fiber tips. By launching the SPR mode near the wavelength of 1.55
$\mu\text{m}$
with a very narrow resonance line width (∼4 nm), this structure is promising for the development of high-performance portable, flexible, and real-time refractometric sensing applications.