ABSTRACT
We describe the details of a procedure to obtain low mean-squared-error (MSE) values for the extraction of permittivity tensors of hyperbolic metamaterials (HMMs) using spectroscopic ellipsometry. We have verified our procedure through characterization of three different HMM samples having varying materials, periods, and fill factors. Our procedure eliminates the need for complicated ellipsometric measurements and modeling techniques, as well as the need for any additional optics such as prisms or index-matching gels. Therefore, a time-efficient and cost-effective approach is introduced, which is only dependent on software; hence, it can be easily and widely adopted. All the MSE values obtained in this Letter are below 1.00 while, at the same time, meaningful and reasonable permittivities are extracted from HMMs.
ABSTRACT
An ultracompact polarizing beam splitter (PBS) is designed and fabricated based on a single-material birefringent photonic crystal structure. The fabrication method is based on e-beam physical vapor deposition where an oblique angle deposition technique is also incorporated. The PBS is designed for high tolerances in volume production. The main ingredient of the PBS is an alternating high- and low-refractive-index modulation created from titanium dioxide deposited at angles of 0° and 70°. The measurements exhibited successful separation of two states of polarization with efficiencies of more than 92% over a total device length of under 6 µm.
ABSTRACT
We investigate the visible range, less-than-one index bandwidth, n(λ)<1, of an optical metamaterial structure composed of plasmonic gold nanoparticles, and show that it is highly dependent on the polarization of incident light. The full-wave finite element method is used to obtain the spectral characteristics of the structure. We have found spectral bands over which the structure shows the desired low index. Further, a possible increase of the bandwidth by as much as 270% is demonstrated by a change in the incident polarization that extends the low-index bandwidth range (503-600 nm) asymmetrically into a wider range (485-750 nm) covering longer wavelengths close to near infrared. This asymmetric overlap might have the potential for new optical applications.
ABSTRACT
We have introduced a method to find optimized structured media exhibiting large internal electric field amplitudes. The method is based on a genetic algorithm in which a spatial fitness function according to the computed field distribution in the interior of media is defined and maximized. The main feature of our method is that it enables localization of light at a desired layer (or more) within the structure. The enhancements are demonstrated to be up to about 70-fold in |E|(2) by use of only seven layers. The results are interesting for nonlinear and sensor applications, which due to compact size and few number of structure layers, are also desirable for fabrication purposes.
ABSTRACT
In this article, we introduce a simple magnetophotonic crystal structure for magnetic field sensing applications. Design procedure, which is performed using a global optimization tool called genetic algorithm, provides great flexibility for structures with layers having nonquarter-wavelength thickness. Results show that our proposed genetic sensor comparatively exhibits higher simplicity, sensitivity, and spatial resolution, with better photo-response and performance. We also analyze the underlying physical phenomenon responsible for such improvement by inspection of electric field distribution in the interior of the structure.
