Here we report on the interplay between the magnetic, optical and magneto-optical properties of magnetoplasmonic crystals (MPC) based on the 1D diffraction gratings. A wide range of the characteristic parameters is examined to be effective for magnetic field sensor application. The gratings with periods of 320 nm and 740 nm with corresponding profile heights of 20 nm and 100 nm were used. Using ion-beam sputtering the diffraction gratings were covered by combination of following functional layers: noble metal - silver or gold with thicknesses of 50 or 100 nm; ferromagnetic metal - iron, silver, permalloy with thicknesses of 5, 20, 50, 100 nm; passivation layer of silica nitride with thicknesses of 20, 30 or 40 nm. The details of fabrication and characterization of magnetoplasmonic crystals will be discussed. We show how the 1D MPC can operate as highly sensitive and local sensor of DC magnetic field by utilizing the magneto-modulation sensor technique combined with the magneto-optical probes. As a result, the design of sensor prototype was optimized and the achieved sensitivity was found to be up to 10 μOe at a local area of 1 mm2. The main contribution to effect of MPC design on sensor parameters is geometry-driven magnetic properties formed during fabrication and depended on characteristic parameters of MPC. The developed sensor has sensitivity suitable for in biomedical applications and can be further improved by optimizing the sensing element and the sensor’s setup overall design.
Plasmonic band gap is a range of frequencies, within which, surface plasmon polaritons cannot propagate for any wavevector. Unfortunately the first plasmonic band gap cannot be observed directly in reflectance spectroscopy . To detect it, biharmonic metal-air surface structuring is conventionally utilized [2,3]. However in this case experimental geometry is strictly limited to normal angle of incidence, which is not compatible with large range of applications.
In current work we introduce biperiodic plasmonic crystals. We experimentally demonstrate, that biperiodic structuring allows to tune band gap spectral-angular position.
Laser interference lithography (LIL) is a well-established technique for creating periodic planar nanostructures over a large surface area. LIL allows to precisely control the modulation period and depth and thus perfectly match diffraction coupling conditions and tune plasmonic band gap properties.
We used LIL experimental setup based on Lloyd interferometer. The radiation from the laser source (He-Cd, wavelength 325 nm, average power 14 mW) was spatially filtered and then formed interference pattern on the silicon wafer, covered with a thin layer of SU-8 2015. The structure period was defined by the incident angle on the interferometer. Modulation depth was defined by exposure time. By applying subsequent second exposure with another angle of incidence, we obtained biperiodic structure. Exposed samples were washed in corresponding developer, dried in air and later sputtered with 100 nm of aluminium.
We fabricated a set of biperiodic plasmonic crystals with different periods and modulation depths. The quality and geometrical parameters of biperiodic plasmonic crystals were monitored by scanning electron microscopy and atomic force microscopy. The appearance of plasmonic band gap was measured by spectral-angular polarisation spectroscopy. We experimentally determined the dependance of plasmonic band gap properties (width and position) on geometrical parameters of biperiodic plasmonic crystals. We also performed FDTD numerical simulations (Lumerical). The experimental results are in good agreement with numerical calculations.
 Raether, Heinz. [Surface Plasmons on Smooth and Rough Surfaces and on Gratings.], Springer Berlin Heidelberg, 91-105 (1988).
 Barnes, William L., et al. "Physical origin of photonic energy gaps in the propagation of surface plasmons on gratings." Physical Review B 54.9 (1996): 6227.
 Kocabas, Askin, S. Seckin Senlik, and Atilla Aydinli. "Plasmonic band gap cavities on biharmonic gratings." Physical Review B 77.19 (2008): 195130.
The results of experimental observation of magneto-optical Kerr effect (MOKE) enhancement caused by surface
plasmon-polaritons (SPP) excitation in 1D and 2D magnetoplasmonic crystals are presented. One-dimensional
nickel magnetoplasmonic crystals have periodic structure formed by periodic nickel grooves made on nickel
surface. The period of the structure is 320 nm and the depth of the grooves is 50 nm. The second group of the
samples represents itself a 2D self-assembled hexagonally ordered monolayer of polystyrene (PS) microspheres
with diameters from 500 to 760 nm and covered by 100- nm - thick nickel film. MOKE measurements performed
in transversal configuration demonstrate that SPP excitation lead to transversal Kerr effect (TKE) enhancement
resulting as a sharp peak in TKE spectrum.
One-dimensional photonic microstructures with optical thicknesses chosen according to the fractal sequence of
the Cantor's ladder are considered. Experimental samples made by electrochemical etching of porous silicon are
studied. Both numerical calculations and experimental results demonstrate self-similarity in reflection spectrum.
Numerical calculations demonstrate self-similarity in space distribution and time-resolved response caused by
self-similarity in morphology.