Experimental demonstration of controllable flat focusing mirror excited by surface plasmon polaritons

In this study, we investigate an optical modulation of the focusing mirror based on photonic jet effect working in the reflection mode The photonic jet effects excited by surface plasmon polariton (SPP) in the near-field on the front-side of different core–shell micro-cuboids positioned on a substrate are presented. The core–shell micro-cuboid consists of a metallic shell (silver or gold) and a dielectric core (polydimethylsiloxane). The specific localized intensity distributions of the generated photonic jet at different core–shell micro-cuboids are simulated by using finite-difference time-domain technique. The experimental observations of focusing modulation are performed by a scanning optical microscope with oblique illumination. Due to the nature of SPP, the highly focused electric field near the metal–dielectric interface of the gold-coating micro-cuboids is enhanced by about 4 times. The generation of the focusing mirror based on SPP photonic jet can be flexibly controlled by varying the metallic shell. The controllable focusing mirror is a great possibility for integrated plasmonic circuits, surface optical tweezers, and biosensing.