Congratulations on publishing “Fabrication methods of plasmonic and magnetoplasmonic crystals: a review” in The European Physical Journal Plus.
This paper is written by Foozieh Sohrabi under the direct supervision of Dr Seyedeh Mehri Hamidi.
Abstract. In recent years, plasmonic crystals have embraced a wide range of applications from medical to optoelectronic ones due to their outstanding and extraordinary properties such as enhanced optical transmission, large field enhancements, collimation of light through a subwavelength apertures and tunable multimode plasmonic resonances. For achieving optimized metallic nanostructures, a great effort is made to propose versatile fabrication methods that support interesting geometries and materials. In this paper,
we have made a comprehensive review of fabrication methods of plasmonic crystal and one of its main subgroups entitled “magnetoplasmonic crystals”. The fabrication methods are divided into two main groups of bottom-up and top-down approaches and their weak and strong points, besides their applications are discussed.
Lasing at the nanometre scale promises strong light-matter interactions and ultrafast operation. Plasmonic resonances supported by metallic nanoparticles have extremely small mode volumes and high field enhancements, making them an ideal platform for studying nanoscale lasing. At visible frequencies, however, the applicability of plasmon resonances is limited due to strong ohmic and radiative losses. Intriguingly, plasmonic nanoparticle arrays support non-radiative dark modes that offer longer life-times but are inaccessible to far-field radiation. Here,،they show lasing both in dark and bright modes of an array of silver nanoparticles combined with optically pumped dye molecules. Linewidths of 0.2 nm at visible wavelengths and room temperature are observed. Access to the dark modes is provided by a coherent out-coupling mechanism based on the finite size of the array. The results open a route to utilize all modes of plasmonic lattices, also the high-Q ones, for studies of strong light-matter interactions, condensation and photon fluids.
The rotation of the polarization of light by magneto-optical materials is well exploited by macroscale devices such as optical isolators, however, demonstrations in nano-optics or plasmonics are lacking due to issues such as dissipation and phasematching. Now, Curtis Firby and colleagues from Canada have proposed an integrated magnetoplasmonic Faraday rotator. They predict 99.4% polarization conversion over an 830-μm-long device using low-loss modes that can propagate over a distance of 1 mm. The proposed structure, designed for 1,550 nm wavelength operation, is a 450-nm-wide ridge waveguide with multilayers stacked vertically within. A 25-nm-thick silver layer is surrounded by two 20-nm-thick SiO2 layers. A highindex ‘hat’ for the ridge is formed by a 725-nm-thick layer of TiO2 while the bottom high-index ridge region is a 320-nm-thick Bi:YIG rib on top of a 260-nm-thick Bi:YIG platform. The team designed the waveguide structure such that transverse electric and transverse magnetic modes are phase matched and low-loss but with sufficient mode overlap in the Bi:YIG medium to cause the polarization rotation. The design could lead to miniature integrated circuitry that is capable of modulating polarization at speeds as fast as 10 GHz.
Liu and his colleagues present a scheme for realizing a narrow-dual-band perfect absorber based on the plasmonic analogy of the electromagnetically induced reflection (EIR)-like effect. In their scheme, two short gold bars are excited strongly by incident plane wave serving as the bright mode. The middle gold bar is excited by two short gold bars. Due to the strong hybridization between the two short gold bars and the middle gold bar, two absorption peaks occur. The corresponding absorption rates are both over 99%. The quality factors of the two absorption peaks are 41.76 (198.47 THz) and 71.42 (207.79 THz), respectively, and the narrow-distance of the two absorption peaks is 9.32 THz. Therefore, they are narrow enough for the absorber to be a filter and a dual-band plasmonic sensor.
The phenomenon of plasmon-induced transparency (PIT) is realized a in surface plasmon polariton waveguide at near-infrared frequencies. The right-angled slot and rectangle cavity placed inside one of the metallic claddings are respectively utilized to obtain bright and dark modes in a typical bright-dark mode waveguide. A PIT transmission spectrum of the waveguide is generated due to the destructive interference between the bright and dark modes, and the induced transparency peak can be manipulated by adjusting the size of the bright and dark resonators and the coupling distance between them. Subsequently, spectral splitting based on the PIT structure is studied numerically and analytically. Simulation
results indicate that double electromagnetically induced transparency (EIT)-like peaks emerge in the broadband transmission spectrum by adding another rectangle cavity, and the corresponding physical mechanism is presented. Yu and his colleagues’ novel plasmonic structure and the findings pave the way for new design and engineering of highly integrated optical circuit such as nanoscale optical switching, nanosensor, and wavelength-selecting nanostructure.
Plasmons provide excellent sensitivity to detect analyte molecules through their strong interaction with the dielectric environment. Plasmonic sensors based on noble metals are, however, limited by the spectral broadening of these excitations. Yu and his colleagues identify a new mechanism that reveals the presence of individual molecules through the radical changes that they produce in the plasmons of graphene nanoislands. An elementary charge or a weak permanent dipole carried by the molecule are shown to be sufficient to trigger observable modifications in the linear absorption spectra and the nonlinear response of the nanoislands. In particular, a strong second-harmonic signal, forbidden by symmetry in the unexposed graphene nanostructure, emerges due to a redistribution of conduction electrons produced by interaction with the molecule. These results pave the way toward ultrasensitive nonlinear detection of dipolar molecules and molecular radicals that is made possible by the extraordinary optoelectronic properties of graphene.
Fig. 1. Schematic of the tilted slit-groove interferometer: (a)top view,(b)excitation scheme.
Melentiev and his colleagues have realized a plasmonic interferometer formed by a nanoslit and a nanogroove in a single-crystal gold film. The possibility of measuring laser pulses of ultimately short durations, corresponding to two periods of a light wave (6 fs pulse duration), has been demonstrated using this interferometer.
Guner and his colleagues demonstrate a surface plasmon resonance imaging platform integrated with a smartphone to be used in the field with high-throughput bio-detection. Inexpensive and disposable SPR substrates are produced by metal coating of commercial Blu-ray discs. A compact imaging apparatus is fabricated using a 3D printer which allows taking SPR measurements from more than 20.000 individual pixels. Real-time bulk refractive index change measurements yield noise equivalent refractive index changes as low as4.12 × 10−5RIU which is comparable with the detection performance of commercial instruments. As a demonstration of a biological assay, they have shown capture of mouse IgG antibodies by immobilized layer of rabbit anti-mouse (RAM) IgG antibody with nanomolar level limit of detection. Their approach in miniaturization of SPR biosensing in a cost-effective manner could enable realization of portable SPR measurement systems and kits for point-of-care applications.
The developments in nanophotonics demand more efficient and delicate control of light. It has recently been proposed to achieve this goal by combining plasmonics and magneto-optics in so-called magnetoplasmonic nanostructures. However, significant challenges still remain because of the difficulty in the design of spectrally tunable systems exhibiting novel plasmonic and magneto-optical responses simultaneously. Here Chen and his colleagues report a magnetoplasmonic structure which consists of a two-dimensional nickel nanodisk array on top of a cobalt film substrate. They demonstrate that a tunable Fano resonance can be generated in this system with properly designed geometric parameters. Furthermore, the magneto-optical Kerr responses in this system can be manipulated due to the concerted actions of free electrons in the resonance. Their results reveal the possibility of fabricating large-area magnetoplasmonic structures by a simple, mass-producible method, and tuning the plasmonic and magneto-optical responses simultaneously.
Congratulations on publishing “Neuroplasmonics: From Kretschmann configuration to plasmonic crystals” in The European Physical Journal Plus.
This paper is written by Foozieh Sohrabi under the direct supervision of Dr Seyedeh Mehri Hamidi.
Abstract: Recently, a worldwide attempt for understanding the functions of brain and nervous system has been made. Hence, various aspects of neuroscience have been investigated through different techniques. Among these techniques, neuroplasmonics as a newborn branch of this science tries to seize the realm of in vitro and in vivo neural imaging, recording and healing. Neuroplasmonics offers advantages comprising rapidity, high sensitivity, biological compatibility, label-free and real-time detection by benefiting from the sensing and thermal characteristics of surface plasmon resonances (SPRs). This paper reviews four main branches of neuroplasmonics comprising prism coupler configurations, the combination of SPR and fluorescence microscopy and methods based on nanorods and plasmonic crystals. For each division, the advantages, disadvantages and the provided facilities will be discussed in detail.
Reference: Sohrabi, F. & Hamidi, S. Eur. Phys. J. Plus (2016) 131: 221. doi:10.1140/epjp/i2016-16221-5
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