Abstracts:The basis of modern optical engineering involves makes finding ways to design predefined optical (and in general – physical) properties of nanoscopic patterns. The boundary parameters of nano-patterns depend on (small) dimensions and the type of nanostructure substance, the external environment, as well as the form and the technical–technological of aspect of production. Fundamental properties of nano-structures can be drastically changed by changing these parameters. We have investigated the optical specificities of molecular dielectric crystal nanofilm under the influence of different confinement conditions. This paper presents a model of crystalline ultrathin molecular film and an analysis of dielectric, i.e. optical properties of these spatially much bounded structures – in their entirety. Using the two-time dependent Green's functions, the energy spectrum, the possible exciton states and their space distribution were determined and the dynamic permittivity was calculated. It was shown that the appearance of localized states in the boundary layers of the film depends on the thickness and the changing values of the system parameters in the boundary areas of the film. These localized states define the schedule and determine the number of resonant absorption peaks in the infrared region of the external electromagnetic radiation (EMR). Analytical analysis of the impact of the boundary parameters on the changes of the dielectric and optical properties of the nanofilm, as compared to the same properties of bulk samples with identical crystalline and chemical structure, is impossible. Thus, a software package (dubbed JOIG_S) has been developed and applied to perform the numerical analysis and plot graphic displays of the relation between microscopic (exciton) and macroscopic (dielectric and optical) properties as a function of the frequency of an external electromagnetic field (EMF), for a specified set of values of the boundary parameters. Optical, i.e. absorption and refraction properties of observed nanostructures demonstrate very narrow and strictly discrete characteristics. Characteristic resonant peaks appear in the dependence of the absorption index on the frequency of external EMF. All peaks fall into infrared region and indicate absorption of corresponding external EM frequencies. The number and distribution of these peaks depend on the number of layers in the film and the perturbation parameters, as a consequence of the quantum size and confinement effects. This proved that the outer environment of the film affects the given fundamental properties of a nano film, i.e. their choice/change directly controls the optical properties of the film. Such an approach could be considered as a kind of optical engineering.

Abstracts:We study the interaction of gold nanoparticles with a graphene film. Graphene is used as a spacer, as thin as possible, between the gold nanoparticles and the detection dielectric medium, and one of the advantages of graphene is to protect the structure, which allows to avoid the oxidation of nanoparticles. We focus our study on the variation of the resonant structure (LSPR) depending on the thickness of the graphene layer (0.34–5 nm). A stronger resonance behavior of positions in the absorption spectrum shows a strong coupling between the LSP on gold nanoparticles and the covering film. Numerical simulations indicate a significant shift of the resonance wavelength structure SiO x /AuNPs/Graphene/SiO x (657.90 nm) compared with experimental results obtained on SiO x /AuNPs/SiO x (574.71 nm) and optimized for the required parameters proposed LSPR system we achieve the highest detection sensitivity range, while the location of points of the electric field on the best corners of the gold-graphene nanoparticles.

Abstracts:In the present study, surface plasmon resonance (SPR) based biosensor with SF-10 glass prism/zinc oxide/gold/MoS2/graphene hybrid structure is reported. The angular interrogation method is used for the reflectance spectra analysis. From the spectral analysis, we study the different performance parameters like sensitivity, detection accuracy, quality parameter and electric field intensity enhancement factor (EFIEF) of the proposed SPR based biosensor. Numerical results show that the base ZnO (zinc oxide) layer which have a large real value of the dielectric constant in combination with gold, MoS2 and graphene, is responsible for enhancing the sensing performance of the proposed SPR based biosensor. The present biosensor can attain a maximum sensitivity (101.58 deg/RIU), detection accuracy (1.81) and quality parameter (15.11 RIU^-1) for a large dynamic range of refractive index change from 1.33 to 1.45.

Abstracts:Two photonic crystal optical refractive index sensors have been proposed in this paper. These sensors can be used for detection of basal cell cancer. A rod-type square lattice of GaAs is used for this purpose. The sensor topologies are based on a photonic crystal ring-shaped resonator coupled to two and waveguides respectively. Instead of using ultra-high quality factor cavities for improving the sensitivity, the resonance profile is localized and concentrated on the analyte to achieve good distinction. A 13 nm cavity resonance frequency shift for normal and cancer cells is obtained for detection of basal cell carcinoma. Finite difference time domain method and plane wave expansion methods are used to simulate and analyze the structures. The proposed biosensors have a sensitivity equal to 720 and 638 nm/RIU. The simplicity of the design and its high sensitivity make it a suitable choice for bio-sensing applications.

Abstracts:Single crystalline rutile TiO2 nanorod arrays (NRAs) have been grown on fluorine doped tin oxide (F: SnO2) coated glass substrate by using hydrothermal technique. The influence of precursor concentration on the morphological, structural, optical and electrical properties of TiO2 nanorods (NRs) was studied. X-ray diffraction studies show that the TiO2 NRs are highly oriented with respect to the substrate surface. FESEM measurements of TiO2 films display that the length of the rods are ranged from (1.54 to 2.44) μm. The transmittance, absorption coefficient, and energy gap at different precursor concentration were measured and calculated. Results show that rods length decreased the transmittance and energy gap, whereas it increased the absorption coefficient. The electrical measurements of TiO2 exhibit the effect of rods length on the resistivity of single crystalline rutile TiO2 nanorod array. The sample with optimum precursor concentration and with 2.44 μm in length was employed as photoanode in Dye sensitized solar cell (DSSC).The effect of multiple growth cycles of TiO2 NR on Photoanode Performance in DSSC was investigated. The spectral response of Dye sensitized solar cell showed one peak of response and its maximum value approaching 0.16 A/W at λ = 500 nm. The prepared DSSC reveals a conversion efficiency of 2.15% under illumination of 100 mW cm⁻² by one time of growth cycle.

Abstracts:Magneto-plasmonic response in planar multilayer with prism coupling composed from Fe/Au bi-layer supplied by photonic crystal (Ta2O5 / SiO2 bi-layers) is studied. Modeled structure is intended as a sensor unit combining magneto-optical (MO) and surface-plasmon-resonance (SPR) effects. The sensitivity of MO-SPR system by small variations of analyte refractive index is tested to obtain optimal resolution ability. The non-reciprocal MO-SPR response is studied by means of the function ρ(φ) = (Rp ⁽⁺⁾ − Rp ⁽⁻⁾)/(Rp ⁽⁺⁾ + Rp ⁽⁻⁾), where the reflectance Rp depends on the incidence angle φ and external magnetic field orientation by a fixed wavelength. The detection ability is characterized by the angular shift Δφ0 between the null-points of the function ρ that corresponds to the change Δna of analyte refractive index. Besides the key role of metallic layers thicknesses the number and size of Ta2O5/SiO2 bi-layers of photonic crystal are discussed. The magneto-plasmonic response in planar multilayer with prism coupling composed from Fe and Au bilayer supplied by photonic crystal (Ta2O5 / SiO2) is studied. Modeled structure is intended as a sensor unit combining MO and SPR effects.

Abstracts:The first experimental realization of the non-diffracting Bessel beam technique for micro-structuring of thin rubidium metallic films on the sapphire surface is reported. Rubidium atoms were deposited onto the cool sapphire windows from the heated central region of the evacuated cell under simultaneous illumination by a Bessel beam at 532 nm wavelength and 4.5 W/cm² intensity. The approach of the optically controlled atomic deposition is based on the strong non-thermal photo-desorption of atoms from illuminated areas of dielectric surface diminishing the surface density of adsorbed atoms below the threshold of nucleation process, while in the dark areas concentration of adsorbed atoms exceeds the critical value and a metal film starts to grow. As a result, the annular Bessel beam optical pattern with 40 μm periodicity was reproduced with high contrast in the Rb deposits, thus creating the annularly micro-structured metal film on the sapphire surface. The diffraction efficiency of the metal grating with the estimated thickness of ∼40 nm was measured to be about 1.8%.

Abstracts:In this communication, a visible frequency plasmonic perfect absorber (PPA) made of a thin metal layer (gold and aluminum) with an array of cylindrical grooves is demonstrated and studied numerically using the finite difference time domain solver. A novel design concept is used to achieve perfect absorption at tunable wavelengths between 400 and 1000 nm. The PPA unit cell is made of a cylindrical groove of appropriate depth, and the size of the groove is typically set to half the array period. By simply changing the array period, the perfect absorption (100%) spectral position is set to a desired wavelength. The PPA is observed to be very effective for wide incident angles and polarization states of input radiation. The study reports an attractive alternative way of designing all-metal-based PPA that may have potentials for various plasmonic and photonic applications.

Abstracts:In most of the cases the magnetooptic Kerr effect (MOKE) techniques rely solely on the effects linear in magnetization ( M ). Nevertheless, a higher-order term being proportional to M ² and called quadratic MOKE (QMOKE) can additionally contribute to experimental data. Handling and understanding the underlying origin of QMOKE could be the key to utilize this effect for investigation of antiferromagnetic materials in the future due to their vanishing first order MOKE contribution. Also, better understanding of QMOKE and hence better understanding of magnetooptic (MO) effects in general is very valuable, as the MO effect is very much employed in research of ferro- and ferrimagnetic materials. Therefore, we present our QMOKE and longitudinal MOKE spectroscopy setup with a spectral range of 0.8–5.5 eV. The setup is based on light modulation through a photoelastic modulator and detection of second-harmonic intensity by a lock-in amplifier. To measure the Kerr ellipticity an achromatic compensator is used within the setup, whereas without it Kerr rotation is measured. The separation of QMOKE spectra directly from the measured data is based on measurements with multiple magnetization directions. So far the QMOKE separation algorithm is developed and tested for but not limited to cubic (001) oriented samples. The QMOKE spectra yielded by our setup arise from two quadratic MO parameters G s and 2G 44, being elements of quadratic MO tensor G , which describes perturbation of the permittivity tensor in the second order in M .

Abstracts:Here, by using a square-lattice-type photonic crystal (PhC) and an ISO-centric all-circular ring resonator (RR), a high efficiency in-plane multichannel drop filter (MCDF) is realized. By conducting full-spectrum transmission studies on available tuning parameters such as RR radius, RR refractive index, PhC lattice high and low refractive indices, and PhC lattice constant, the transmission behavior of each parameter is found in terms of blue or red shift wavelength dependencies. The single unit of the PhC-based filter is optimized to work at a desired optical wavelength (e.g., λ0  = 1550 nm). The MCDF is formed by cascading a desired number of the basic unit (e.g., five units), whereas using the knowledge learned from full-spectrum transmission behavior, each unit is proportionally tuned to operate at a desired different wavelength with an appropriately engineered channel spacing and crosstalk. The high efficiency dropping task of MCDF was successfully acquired with reasonable drop efficiencies as low as 76%, up to 100%. The crosstalk across all channels varied from −10 db as the worst case down to −50 db as the best case; this ensures a hopeful application of the MCDF.