Month: January 2021

News On Plasmonic

The Journal of ACS Photonics published a paper entitled as “Reducing the Complexity: Enantioselective Chiral Near-Fields by Diagonal Slit and Mirror Configuration”

ABSTRACT: We report an easy-to-fabricate plasmonic design consisting of diagonal slits in a metallic film on top of a mirror for the generation of chiral near-fields of one single handedness. Our numerical investigations show that the distance between the two layers is crucial for the properties of this design. While the far-field response can be used to identify layer distances with strong chiral near-fields, this distance must be small enough to additionally ensure single-handedness of the respective fields close to
the slit area. The fields of interest can be easily accessed by chiral molecules because they are located within the slits. Based on this finding, we propose and numerically verify a novel technique for chiroptical spectroscopy in a reflection geometry.

Congratulations for our new paper in Optik Journal

Red and Blue color production by flexible all-dielectric structure

N. Roostaei, N. S. Shnan, S. M. Hamidi

Color production by using plasmonic structures has been extensively studied. Due to the inherent damping of plasmons, such plasmonic structures are challenging to produce high-resolution color. Recently, color production by using all-dielectric metasurfaces has attracted much attention. Here, all-dielectric structure with different dimensions were fabricated by a nanoimprint lithography method. Color production in both reflection and transmission modes and imaging using metasurfaces were performed. The refractive index of our fabricated metasurface was calculated, and the effect of refractive index changes onto the loss, transparency, and also resolution of image and color production has been investigated. By considering the low cost and high resolution, this research will be useful for the structural color production in industrial applications.

News On Magnetic Metasurface

In this days, the Journal of Nature communications publishes a new paper entitled as “All-dielectric magnetic metasurface for advanced light control in dual polarizations combined with high-Q resonances”

Nanostructured magnetic materials provide an efficient tool for light manipulation on subnanosecond and sub-micron scales, and allow for the observation of the novel effects which are fundamentally impossible in smooth films. For many cases of practical importance, it is vital to observe the magneto-optical intensity modulation in a dual-polarization regime. However, the nanostructures reported on up to date usually utilize a transverse Kerr effect and thus provide light modulation only for p polarized light. We present a concept of a transparent magnetic metasurface to solve this problem, and demonstrate a novel mechanism for magneto-optical modulation. A 2D array of bismuth-substituted iron-garnet nanopillars on an ultrathin iron-garnet slab forms a metasurface supporting quasi-waveguide mode excitation. In contrast to plasmonic structures, the all-dielectric magnetic metasurface is shown to exhibit much higher transparency and superior quality-factor resonances, followed by a multifold increase in light intensity modulation. The existence of a wide variety of excited mode types allows for advanced light control: transmittance of both p- and spolarized illumination becomes sensitive to the medium magnetization, something that is fundamentally impossible in smooth magnetic films. The proposed metasurface is very promising for sensing, magnetometry and light modulation applications.

Congratulations for our new paper in Journal of Physica Scripta

Plasmonic wideband and tunable absorber based on semi etalon nano structure in the visible region

Neda Roostaei1, Hossein Mbarak2, Sekineh Almasi Monfared2 and Seyedeh Mehri Hamidi3

In this study, a plasmonic meta-surface absorber by semi-etalon structure is introduced due to the importance of wideband absorbers in the visible region as solar absorber. For this purpose, soft nanolithography method was adopted to construct semi-etalon absorber based on poly-dimethyl-siloxane flexible membrane and gold grating structure onto its top and down side. In parallel, the structure was simulated by the aid of finite difference time domain method, and obtained good agreement between the measured and simulated results. The results indicated the etalon-based absorber achieved light absorption from 500 to 700 nm compared to one face gold grating which works in the wavelength range 500 to 600 nm with half of absorbed power. In addition, color production was evaluated via the proposed structure, and tunable colors were produced by changing the polarization and incidence angle. Thus, the proposed structure as a good wide-band absorber, and can be used for producing tunable colors under different polarization and incidence angles. The absorber can offer new insight in larger area solar absorber based on soft nano-lithography method because of the low cost and flexibility.

News On Magneto-plasmonics

In this days, the Journal of Physics: Photonics publishes a new paper entitled as “Observation of strong magneto plasmonic nonlinearity in bilayer graphene discs” Graphene patterned into plasmonic structures like ribbons or discs strongly increases the linear and nonlinear optical interaction at resonance. The nonlinear optical response is governed by hot carriers, leading to a red-shift of the plasmon frequency. In magnetic fields, the plasmon hybridizes with the cyclotron resonance, resulting in a splitting of the plasmonic absorption into two branches. Here we present how this splitting can be exploited to tune the nonlinear optical response of graphene discs. In the absence of a magnetic field, a strong pump-induced increase in on-resonant transmission can be observed, but fields in the range of 3 T can change the characteristics completely, leading to an inverted nonlinearity. A two temperature model is provided that describes the observed behavior well.

News On Nonlinear Plasmonics

In this days, the Journal of Sensors publishes a new paper entitled as “Few Percent Efficient Polarization-Sensitive Conversion in Nonlinear Plasmonic Interactions Inside Oligomeric Gold Structures”

Abstract: The backscattering spectra of a 500 nm thick gold film, which was excited near the 525 nm transverse localized plasmon resonance of its constituent, self-organized, vertically-aligned nanorods by normally incident 515 nm, 300 fs laser pulses with linear, radial, azimuthal and circular polarizations, revealed a few-percent conversion into Stokes and anti-Stokes side-band peaks. The investigation of these spectral features based on the nanoscale characterization of the oligomeric structure and numerical simulations of its backscattering response indicated nonlinear Fano-like plasmonic interactions, particularly the partially degenerate four-wave mixing comprised by the visible-range transverse plasmon resonance of the individual nanorods and an IR-range collective mode of the oligomeric structure. Such oligomeric structures in plasmonic films may greatly enhance inner nonlinear electromagnetic interactions and inner near-IR hotspots, paving the way for their engineered IR tunability for broad applications in chemosensing and biosensing.