6533b7d3fe1ef96bd1260612

RESEARCH PRODUCT

Génération et détection d'électrons chauds dans des dispositifs plasmoniques

subject

description

Hot carrier-based devices are quite promissing for ultrafast photodetection and toset off enhanced physicochemical reactions. Controlling their generation at the nanoscale within plasmonic devices is a key for the future development of hybrid hot carriers technologies. Indeed, Surface PlasmonPolaritons (SPPs) can be exploited to confine light and enhance the number of excited hot carriers. We aim at studying the excitation and dynamics of hot carriers, enhanced by plasmonics, with two different approaches.In a first approach, we aim at controlling the delocalized generation of hot carriers by a propagative SPP. A plasmonic waveguide with a grating coupler is employed. Hot electrons are indirectly probed by the (MPL) collected in the near-field along with the waveguide propagation axis by hyperspectral nearfield imaging technique. We found that propagative SPPs control the spatial and energy distribution of hot electrons. Moreover, using propagating SPPs to produce hot electrons gives new insight in understanding hot carriers physics.In a second approach, the transfer and dynamics of hot carriers are studied by a plasmonic metalsemiconductormetal device. Rigorous coupledwave analysis (RCWA) method simulations demonstrate that Au gratings on SOI (silicon oninsulator) wafers can resonantly enhance the absorption of light at 1.55 µm wavelength. With an optimization algorithm, perfect absorbtion has been reached for given filling factor and periodicity. The outcome is to increase the efficiency of hot carriers generation and transfer towards the semiconductor. This plasmonic device shows sub band gap absorption with a responsivity above 15 µA/W. Under pulsed excitation, we have demonstrated that a coexistence between two processes are occuring : a) the plasmonic linear absorption of Au and b) the non linear two-photon absorption (TPA) of Si. It has been shown that the relaxation time of hot carriers is in the ps range. Therefore, harvesting their energy efficiently and faster than their decay is a key challenge to detect photons at THz rates.