Wireless communication has evolved significantly, over the past several decades, to meet the ever-growing demand for high data rates over the wireless medium. Systems have been designed for indoor applications and outdoor applications where mobility is a very important aspect of system specification. One of the key elements in the design of such systems is understanding the characteristics of the wireless channel [7, 10, 13, 16, 22, 23, 25, 28, 31, 30, 34].
Recently, in-plane wireless communication systems are being developed to be compatible with the modern on-chip technology1. Some of the advantages that in-plane wireless communication offers are, among others, lower losses and reduction in the number of required waveguides1 or even electrical isolation2. Most modern on-chip optical technology uses near-infrared wavelengths3, but for visible wavelengths, an ideal candidate to perform in-plane communication is the surface plasmon (SP), i.e. the collective oscillation of electrons coupled to an electromagnetic field at a dielectric-metal interface. As has been demonstrated, SPs have the capability to highly confine energy on the interface where they propagate on subwavelength scales4. An additional property of SPs is their capability to be strongly confined to the surface of metallic subwavelength structures, including implementations called plasmonic antennas (PAs)5. In this sense, PAs exploit the special properties of the localized surface plasmon. It has been demonstrated that specially designed PAs can collect free-space radiation (photons) and convert it into propagating surface plasmons (SPs) by a momentum up-conversion process (k-UC)6,7,8,9. Conversely, PAs can perform a momentum down-conversion process (k-DC) by converting SPs into photons10,11. In this sense, several reports have appeared using PAs as receivers or broadcasters of electromagnetic radiation12,13,14. One limitation of these systems is that the free-space radiation is emitted predominantly out-of-plane15,16 and little effort has been done to facilitate in-plane emission and collection, i.e., in the direction of the SP propagation17,18. Such an in-plane communication concept could be a significant advancement in on-chip photonic technology, due to better impedance matching between the emitted and received radiation.
Here, we present the realization of the first nanoscale wireless communication system (nWCS) operating at visible wavelengths and based on plasmonic antennas. Such a system is implemented in an in-plane configuration, meaning it allows information transmission and recovery via SPs propagating in the same plane. Communication is achieved across a distance of several wavelengths. We demonstrate the operation of our system by using near-field scanning optical microscopy (NSOM). Numerical calculations confirm the operational principle of the realized system and show good agreement with experimental data. Beyond proof-of-concept, we show two example applications of the system for in-plane information transmission. 2b1af7f3a8