Metallic nanostructures for efficient LED lighting

Light-emitting diodes(LEDs)are driving a shift toward energy-efficient illumination.Nonetheless,modifying the emission intensities,colors and directionalities of LEDs in specific ways remains a challenge often tackled by incorporating secondary optical components.Metallic nanostructures supporting plasmonic resonances are an interesting alternative to this approach due to their strong light–matter interaction,which facilitates control over light emission without requiring external secondary optical components.This review discusses new methods that enhance the efficiencies of LEDs using nanostructured metals.This is an emerging field that incorporates physics,materials science,device technology and industry.First,we provide a general overview of state-of-the-art LED lighting,discussing the main characteristics required of both quantum wells and color converters to efficiently generate white light.Then,we discuss the main challenges in this field as well as the potential of metallic nanostructures to circumvent them.We review several of the most relevant demonstrations of LEDs in combination with metallic nanostructures,which have resulted in light-emitting devices with improved performance.We also highlight a few recent studies in applied plasmonics that,although exploratory and eminently fundamental,may lead to new solutions in illumination.

High-Q collective Mie resonances in monocrystalline silicon nanoantenna arrays for the visible light

Dielectric optical antennas have emerged as a promising nanophotonic architecture for manipulating the propagation and localization of light.However,the optically induced Mie resonances in an isolated nanoantenna are normally with broad spectra and poor𝑄-factors,limiting their performances in sensing,lasing,and nonlinear optics.Here,we dramatically enhance the𝑄-factors of Mie resonances in silicon(Si)nanoparticles across the optical band by arranging the nanoparticles in a periodic lattice.We select monocrystalline Si with negligible material losses and develop a unique method to fabricate nanoparticle arrays on a quartz substrate.By extinction dispersion measurements and electromagnetic analysis,we can identify three types of collective Mie resonances with𝑄-factors∼500 in the same nanocylinder arrays,including surface lattice resonances,bound states in the continuum,and quasi-guided modes.Our work paves the way for fundamental research in strong light-matter interactions and the design of highly efficient light-emitting metasurfaces.

Long-range surface plasmon polaritons at THz frequencies in thin semiconductor layers

We present a theoretical investigation of THz long-range surface plasmon polaritons propagating on thin layers of InSb.The metallic behavior of doped semiconductors at THz frequencies allows the excitation of surface plasmon polaritons with propagation and confinement lengths that can be actively controlled.This control is achieved by acting on the free carrier density,which can be realized by changing the temperature of InSb.