Unveiling Long-Lived Hot-Electron Dynamics via Hyperbolic Meta-antennas

Abstract

Conventional plasmonic nanoantennas enable scattering and absorption bands at the same wavelength region, making their utilization to full potential impossible for both features simultaneously. Here, we take advantage of spectrally separated scattering and absorption resonance bands in hyperbolic meta-antennas (HMA) to enhance the hot-electron generation and prolong the relaxation dynamics of hot carriers. First, we show that HMA enables extending plasmon-modulated photoluminescence spectrum toward longer wavelengths due to its particular scattering spectrum, in comparison to the corresponding nanodisk antennas (NDA). Then, we demonstrate that the tunable absorption band of HMA controls and modifies the lifetime of the plasmon-induced hot electrons with enhanced excitation efficiency in the nearinfrared region and also broadens the utilization of the visible/NIR spectrum in comparison to NDA. Thus, the rational heterostructures designed by plasmonic and adsorbate/dielectric layers with such dynamics can be a platform for optimization and engineering the utilization of plasmon-induced hot carriers.

New Horizons in Near-Zero Refractive Index Photonics and Hyperbolic Metamaterials

“…With this view, the question becomes how can we push the strength of the base nonlinearity ( n 2,eff ) further to mitigate the need for such high irradiance levels? While gains are predicted when shifting ENZ to the mid infrared using lower-bandgap materials with lower doping levels, , the tried-and-true method of adding structure is one avenue to continue to engineer the dispersion and improve nonlinear interactions. − This can be done by structuring the base material (such as forming nanoresonators, i.e., meta antennas), coupling the material with a structured layer (such as plasmonic antennas) − or by mixing multiple materials to achieve an effective ENZ property. ,− In general, these approaches allow additional freedom to control the dispersion of the device by introducing resonance(s), anisotropy, or both. Recent efforts include coupling to ENZ/Berreman/plasmonic modes within thin layer(s), ,− incorporating resonant metallic nanoantennas on top of an ENZ layer, ,, and utilizing layered metal-dielectric stacks to produce an effective ENZ condition. , These approaches have been successful in reducing the irradiance required to achieve strong control over nonlinear interactions to ∼1–10 GW/cm 2 (a 10–100x reduction), as well as transitioning ENZ into the visible region where natural ENZ materials, such as the doped oxides, are unable to reach.…”

Probing Temperature Changes Using Nonradiative Processes in Hyperbolic Meta-Antennas

“…8 They also present an almost infinite density of states 9 and are widely used for nanoscale light confinement and guiding, 10−14 as well as manipulating scattering, absorption and nonreciprocal propagation of light, 15−22 generating optical vortex beams 23 and tailoring optical nonlinearities, 24−30 as well as for highly sensitive detection 31−35 and ultrafast all-optical switching. 36−38 In addition, metal−insulator multilayers display hyperbolic optical dispersion, 39,40 and thanks to this property they have successfully been implemented as negative index materials 41−43 and superabsorbers driving resonant gain singularities, 44−47 as well as for hot-electron generation and manipulation, 48,49 super resolution imaging, 50 ultracompact optical quantum circuits, 51 and lasing. 52 In this context, it has been shown that multilayered metaldielectric antennas displaying hyperbolic dispersion have two separated radiative and nonradiative channels 19 and that this property can be exploited to manipulate electron dynamics on ultrafast time scales 49 as well as for practical applications such as localized hyperthermia 53 and enhanced spectroscopy.…”

“…36−38 In addition, metal−insulator multilayers display hyperbolic optical dispersion, 39,40 and thanks to this property they have successfully been implemented as negative index materials 41−43 and superabsorbers driving resonant gain singularities, 44−47 as well as for hot-electron generation and manipulation, 48,49 super resolution imaging, 50 ultracompact optical quantum circuits, 51 and lasing. 52 In this context, it has been shown that multilayered metaldielectric antennas displaying hyperbolic dispersion have two separated radiative and nonradiative channels 19 and that this property can be exploited to manipulate electron dynamics on ultrafast time scales 49 as well as for practical applications such as localized hyperthermia 53 and enhanced spectroscopy. 21 The unique property of having two separated spectral regions where either a radiative or a nonradiative process is dominating on the other, and vice versa, can open plenty of opportunities in developing multifunctional systems which can behave at the same time as optimal scatterers and absorbers.…”

“…These structures offer the possibility to bring the refractive index close to zero, − enabling novel optical phenomena such as perfect transmission through distorted waveguides, cloaking , and inhibited diffraction . They also present an almost infinite density of states and are widely used for nanoscale light confinement and guiding, − as well as manipulating scattering, absorption and nonreciprocal propagation of light, − generating optical vortex beams and tailoring optical nonlinearities, − as well as for highly sensitive detection − and ultrafast all-optical switching. − In addition, metal–insulator multilayers display hyperbolic optical dispersion, , and thanks to this property they have successfully been implemented as negative index materials − and superabsorbers driving resonant gain singularities, − as well as for hot-electron generation and manipulation, , super resolution imaging, ultracompact optical quantum circuits, and lasing …”

Ultrafast control of exciton dynamics by optically-induced thermionic carrier injection in a metal-semiconductor heterojunction

“…After the development of femtosecond lasers for the generation of ultrashort light pulses 20,21 , it became clear that we can use such technology to drive ultrafast electronic processes at the nanoscale, including plasmonic excitations [22][23][24][25][26][27][28] . In this context, heterojunctions of metals and dielectric materials allow a lot of possibilities for the manipulation and exploitation of light-matter interactions, including ultrafast hot electrons dynamics, magnetooptical effects and nonlinear optical processes 18,[29][30][31][32][33][34][35][36][37][38] . In particular, if the dielectric material is replaced by a semiconducting transition metal dichalcogenide (TMD), we can further boost the control of nanoscale optical excitations [39][40][41][42] , including plasmonic-induced charge injection [43][44][45][46][47][48] , as well as enhance charge dynamics in transistors 49 and photovoltaic devices 50 .…”