Silicon nanophotonics for on-chip light manipulation

The field of silicon nanophotonics has attracted considerable attention in the past decade because of its unique advantages,including complementary metal–oxide–semiconductor（CMOS） compatibility and the ability to achieve an ultra-high integration density. In particular, silicon nanophotonic integrated devices for on-chip light manipulation have been developed successfully and have played very import roles in various applications. In this paper, we review the recent progress of silicon nanophotonic devices for on-chip light manipulation, including the static type and the dynamic type. Static onchip light manipulation focuses on polarization/mode manipulation, as well as light nanofocusing, while dynamic on-chip light manipulation focuses on optical modulation/switching. The challenges and prospects of high-performance silicon nanophotonic integrated devices for on-chip light manipulation are discussed.

Hot hole multiplication from silver plasmon-resonated gold interband transitions for enhanced photoelectrochemical sensing

Compared with the widespread exploitation of hot electrons in plasmonic nanoparticles(NPs),hot holes generated from plasmonic metal interband transitions,are often overlooked in photoelectrochemistry,including photoelectrochemical sensing.Motivated by the subtle spectral overlap between the characteristic plasmonic bands of Ag NPs and interband transitions of Au,herein,we construct unusual core-shell Ag@Au NPs via an anti-galvanic reaction to promote the generation of hot holes.Benefiting from the unique plasmon resonances of Ag cores in specific wavelength regimes,Ag@Au can excite multiplied hot holes while Au cannot under the same conditions.With satisfactory accuracy and good practicability,the photoelectrochemical sensing platform based on Ag@Au NPs possesses a detection limit of 77 nmol/L for glucose,exhibiting significantly higher sensitivity compared to that using Au NPs.This work exemplifies the applications of interband hot-hole accumulation initiated by plasmons and may inspire more strategies to explore the utilization of hot holes in photoelectrochemistry.

Nonlinear,tunable,and active optical metasurface with liquid film

Optical metamaterials and metasurfaces,which emerged in the course of the last few decades,have revolutionized our understanding of light and light–matter interaction.While solid materials are naturally employed as key building elements for construction of optical metamaterials mainly due to their structural stability,practically no attention was given to study of liquid-made optical two-dimensional(2-D)metasurfaces and the underlying interaction regimes between surface optical modes and liquids.We theoretically demonstrate that surface plasmon polaritons and slab waveguide modes that propagate within a thin liquid dielectric film trigger optical self-induced interaction facilitated by surface tension effects,which leads to the formation of 2-D optical liquid-made lattices/metasurfaces with tunable symmetry and can be leveraged for tuning of lasing modes.Furthermore,we show that the symmetry breaking of the 2-D optical liquid lattice leads to phase transition and tuning of its topological properties,which allows the formation,destruction,and movement of Dirac-points in the k-space.Our results indicate that optical liquid lattices support extremely low lasing threshold relative to solid dielectric films and have the potential to serve as configurable analogous computation platform.

Empowering magnetic strong coupling and its application for nonlinear refractive index sensing

In the context of quantum strong coupling,the magnetic dipole(MD)emitters are largely overlooked due to the rarity of MD source and the non-magnetic nature of matters at high frequencies.Based on a semi-classic model,we theoretically demonstrate magnetic strong coupling between an MD cluster(Er^(3+):4 I13/2→4 I15/2 transition at 1,550 nm)and an antenna-in-cavity structure.It is found that placing the plasmonic diabolo/s-diabolo nanoantenna,which supports strong electric/magnetic dipole mode,inside a dielectric cavity could largely improve the strong coupling coefficient while suppressing the cavity loss rate compared to the bare nanoantenna counterparts,empowering the magnetic quantum strong coupling at a level of 104 emitters,which is remarkable considering the weak MD dipole momentum and small hotspot region at high frequency.Furthermore,the two Rabi resonance branches undergo highly asymmetrical changes upon a small variation on the environmental refractive index,which leads to an exotic exponential sensitivity profile by tracing the ratio between the two resonances widths.The proposed magnetic strong coupling for nonlinear refractive index sensing may add a new category to quantum plasmonic sensors.

Evolution of stellated gold nanoparticles:New conceptual insights into controlling the surface processes

Understanding the surface processes(deposition and surface diffusion)that occur at or close to the surface of growing nanoparticles is important for fabricating reproducibly stellated or branched gold nanoparticles with precise control over arm length and spatial orientation of arms around the core.By employing a simple seed-mediated strategy,we investigate the key synthetic variables for precise tuning of in situ surface processes(competition between the deposition and surface diffusion).These variables include the reduction rate of a reaction,the packing density of molecules/ions on the high surface energy facets,and temperature.As a result,the thermodynamically stabilized nanoparticles(cuboctahedron and truncated cube)and kinetic products(cube,concave cube,octapod,stellated octahedron,and rhombic dodecahedron)in different sizes with high quantitative shape yield(>80%)can be obtained depending on the reduction rate of reaction and the packing density of molecules/ions.With computer simulation,we studied the stability of stellated(branched structure)and non-stellated(non-branched structure)gold nanoparticles at high temperature.We construct a morphology phase diagram by varying different synthetic parameters,illustrating the formation of both stellated and non-stellated gold nanoparticles in a range of reaction conditions.The stellated gold nanoparticles display shape-dependent optical properties and can be self-assembled into highly ordered superstructures to achieve an enhanced plasmonic response.Our strategy can be applied to other metal systems,allowing for the rational design of advanced new stellated metal nanoparticles with fascinating symmetry dependent plasmonic,catalytic,and electronic properties for technological applications.

Silver nanoislands on cellulose fibers for chromatographic separation and ultrasensitive detection of small molecules

High-throughput small-molecule assays play essential roles in biomedical diagnosis,drug discovery,environmental analysis,and physiological function research.Nanoplasmonics holds a great potential for the label-free detection of small molecules at extremely low concentrations.Here,we report the development of nanoplasmonic paper(NP-paper)for the rapid separation and ultrasensitive detection of mixed small molecules.NP-paper employs nanogap-rich silver nanoislands on cellulose fibers,which were simply fabricated at the wafer level by using low-temperature solid-state dewetting of a thin silver film.The nanoplasmonic detection allows for the scalable quantification and identification of small molecules over broad concentration ranges.Moreover,the combination of chromatographic separation and nanoplasmonic detection allows both the highly sensitive fluorescence detection of mixed small molecules at the attogram level and the label-free detection at the sub-nanogram level based on surface-enhanced Raman scattering.This novel material provides a new diagnostic platform for the high-throughput,low-cost,and label-free screening of mixed small molecules as an alternative to conventional paper chromatography.