Far field superfocusing along with enhanced near field emission from hybrid spiral plasmonic lens inscribed with nano corrals slit diffractor

Abstract

Here, we have numerically calculated electric field intensity and phase of the emission from various hybrid spiral plasmonic lenses (HSPL) in near field as well as in far-field. We have proposed a novel HSPL inscribed with nano corrals slit (NCS) and compared its focusing ability with other HSPLs inscribed with circular slit and circular grating. With the use of nano corrals slit, we have been able to improve light intensity in the far-field without compromising near-field intensity. Our NCS-HSPL outperforms other HSPLs and standalone SPL in near-field as well as far-field. We have also found that proposed circular slit diffractor is far more superior than previously reported circular grating diffractor. We have been able to extend the focal length of hybrid plasmonic lens upto 3 um and observed a two-fold increment in the far field intensity compared to existing spiral plasmonic lens even though size of focal spot remains same. Optical complex fields produced by NCS based HSPL can be used for various applications such as super resolution microscopy, nanolithography, bioimaging and sensing, angular momentum detectors, etc. Moreover, enhanced near-field intensity in conjunction with far-field superfocusing with reasonable focal length may lead to the development of novel multifunctional lab-on-chip devices.