Plasmon Mediated Optical Transmission Through an Optically Opaque Plasmonic Metagrating

Extra-ordinary optical transmission (EOT) through subwavelength plasmonic nano-apertures is possible due to the funneling of light via surface plasmons (SPs) at the resonant wavelengths through the apertures. In this letter, we experimentally demonstrate optical transmission through an optically opaque plasmonic metagrating (PM). The PM was fabricated by deposition of silver (Ag) on a 1-dimensionally patterned flexible and transparent polydimethylsiloxane (PDMS) grating obtained via pattern imprinting and subsequent peeling off a commercially available blue ray disk (BD). For normal incidence of TM-polarized light on the top surface of PM, transmission of light through the PM was obtained in the visible wavelength range of electromagnetic (EM) spectrum. Control experiments on variation of Ag film thickness were performed to attain optimal parameters for maximum transmission, followed by polarization and refractive index (RI) dependent performance of the PM. Electric field with Poynting vector profile was simulated using finite element method (FEM) to explain the interaction of light with the PM and the mechanism of plasmon mediated optical transmission. Such a large optical transmission is possible because the SP modes generated at metal air interface penetrate through PM and couple with those supported by the metal- substrate interface. As a model application, RI sensing using the PM was demonstrated. The present study shows that optical transmission is possible from opaque structures and enriches literature with better understanding of EOT. Moreover, it opens avenues for development of flexible, cost-effective PMs for sensors, spectral filters, polarizers etc.