Plasmon Drag Effect enabled by Metallic Nanowires inside Optical Fibers: fundamentals and optoelectronic aspects

• Applicant: Professor Dr. Markus A. Schmidt
• Subject Area: Experimental Condensed Matter Physics
• Term: from 2016 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 318570041

Detecting radiation of various frequencies is key feature of any practically-relevant photonic system. One promising detection scheme is the Photon Drag Effect currently being employed for high-speed detection of mid-infrared radiation. The effect operates by free carrier absorption and a transfer of the photon momentum to electrons, leading to an electrical current. Metals are principally ideal candidates for exploiting the drag effect due to large carrier concentration and high electrical conductivity. However, metals strongly reflect, leading to only little overlap of electromagnetic wave and electrons and thus to negligibly small drag effect-induced currents.The solution to this problem are the surface plasmon polaritons (SPPs), which are polaritonic states bounded to metal/dielectric interfaces with a substantial overlap of field and metal. Hence SPPs principally allow a strong momentum transfer, giving rise to the plasmon drag effect (PDE). Very promising first results have been achieved, but only few prove-of-effect investigations have been conducted up to date, with the underlying physics remaining undiscovered. This lack of hard data mainly results from the poor electrical conductivity of planar plasmonic films, from suboptimal excitation schemes and from insufficient light/metal interaction lengths.The objectives of the project are to unlock the basic physics of the PDE from an experimental perspective and evaluate its potential for plasmonic optoelectronic detection. The experiments will rely on SPPs propagating on longitudinal metallic nanowires (NWs) inside optical fibers - a novel plasmonic platform solving all above-mentioned problems. The NWs can be several centimeters long with diameters of just several hundreds of nanometers, thus combining an unprecedentedly long light/metal interaction length with a bulk electrical conductivity. The NWs will be electrically connected, allowing to straightforwardly measuring the PDE and analyzing its characteristics under various conditions. Beside direct transmission experiments, the flexible fiber handling will enable investigating the PDE from ambient down to cryogenic temperatures, revealing the influence of phonons and NW-morphology. The fiber also provides the ideal platform for analyzing the dynamic response of the PDE by launching short optical pulses. In terms of application, this project will evaluate, if the PDE can be employed for efficient plasmonic, semiconductor-free optoelectronic detection. This is especially interesting for optical fibers, as the PDE represents a unique way to integrate a high-speed detection scheme into fibers for reaching a fully monolithic in-fiber detector.In summary, this project aims to investigate the PDE on the basis of metallic NWs in optical fibers with two objectives: (i) revealing the underlying physics of the PDE and (ii) evaluating the potential of the PDE in plasmonically optoelectronic detection.

• DFG Programme: Research Grants