Optimization of 1D Silver Grating Devices for Extraordinary Optical Transmission Tahir Iqbal 1 & Muhammad Umar Farooq 2 & Mohsin Ijaz 1 & Sumera Afsheen 3 & Muhammad Rizwan 1 & Muhammad Bilal Tahir 1 Received: 29 October 2018 /Accepted: 26 December 2018 # Springer Science+Business Media, LLC, part of Springer Nature 2019 Abstract This paper reports the behavior of extraordinary optical transmission (EOT) through 1D plasmonic nanostructure devices when thickness and periodicity of silver film simulated on glass substrate are fixed and only slit width is varied. Transverse magnetic (TM) polarized photon incident normally at the grating structure and zero-order transmission spectra has been extracted. Fano-resonance associate with the excitation of the surface plasmon polaritons (SPPs) has been evaluated carefully to calculate EOT. Excited plasmons along with the Febry-Perot mode have contributed toward the EOT through the periodic slits in the grating device. It has been found that its numerical value of EOT is maximum at a particular slit width, i.e., 409 nm, which is greater than one half and less than two third of periodicity, when wavelength of light is comparable with periodicity. This unique behavior is associated with the maximum incident energy coupled to the excited plasmon due to fundamental plasmonic mode being the most efficient. Such optimal devices find many applications in real world, e.g., light-emitting diodes (LEDs), biosensing, and SERs. Keywords Enhanced optical transmission (EOT) . Surface plasmon resonance (SPR) . Periodicity . Slit width . Gating structure Introduction Extraordinary optical transmission (EOT) is the occur- rence of greatly increased transmission of electromagnetic radiation through sub wavelength slits on metallic film that has been decorated with a continuous periodic struc- ture. The shape and size of structure play a vital role in quantity of light absorbed or scattered after interaction from nanostructure. These parameters are studied in number of ways in advanced nanoscience and nanotech- nology [1–6]. The confinement of electromagnetic radia- tions of desired wavelength in vicinity of metallic film poses an unrelenting challenge. In 1944, Bethe studied light transmission through infinitely thin, perfectly conducting metal screen including a sub wavelength hole. Bethe found that transmission of light is proportional to the forth power of hole radius to wavelength ratio [7] which can be given as: T ≈ 64 27π 2 r λ  4 . In 1998, Ebbesen research group demonstrated the EOT through arrays of holes created by focused-ion- beam milling through numerous metals. The presence of surface plasmon resonance (SPR) and constructive interference is the major cause of this phenomenon [8, 9]. Recent works show a powerful contribution to EOT from overlapping evanescent wave coupling which ex- plains why this result is increased by surface plasmon resonance on each side of a metallic film at optical frequencies [ 10]. Explanations on this development showed the similarity between arrays of particles and arrays of holes. Metal films like gold and silver show less transmission in optical range but it increases con- siderably when the incident light is coupled with surface plasmon polaritons (SPPs) [11, 12]. Tahir Iqbal and Muhammad Umar Farooq contributed equally to this work. * Tahir Iqbal tiqbal02@qub.ac.uk * Mohsin Ijaz mohsin@live.no 1 Department of Physics, Faculty of Science, University of Gujrat, Hafiz Hayat Campus, Gujrat 50700, Pakistan 2 Department of Physics, Allama Iqbal Open University (AIOU), Islamabad, Pakistan 3 Department of Zoology, Faculty of Science, University of Gujrat, Hafiz Hayat Campus, Gujrat 50700, Pakistan Plasmonics https://doi.org/10.1007/s11468-018-00898-2