<p>When metallic nanostructures are illuminated under resonance condition, part of the intercepted light is dissipated through nonradiative damping, resulting in a dramatic rise in temperature in the nanometer-scale vicinity of the particle surface. This nanoscale heat has been of great interest for applications in biomedicine and solar energy. We investigate the generation of heat in gold nanostructures at a constant metal volume and different morphologies under excited surface plasmonic resonance conditions using the finite-difference time-domain method and solving the thermal equation as well. Heat power as a measure of thermal efficiency has been obtained for different morphologies. Two kinds of structures including colloidal-like nanoparticles and lithographic planar nanostructures are discussed. It has been observed that as the surface-to-volume ratio in the structure increases, the heat power also increases along with a redshift, and the maximum increase is obtained for the porous structure. The amount of light transmission through porous nanostructure has also been investigated, compared with the nonporous structure, and it has been observed that they present better optical transmission. And therefore, they would have more desirable performance in multilayered structures. Moreover, the influence of surrounding medium on thermal and transmission characteristics of the nanostructures has been studied. Finally, the temperature distribution has been obtained for porous nanostructure for different absorbed powers by solving the heat transfer equation.</p>
The micromixer is a very common component in the state-of-the-art lab-on-chip devices and occupies large chip areas to fulfill the rather challenging process of mixing in microscales. Two various design micromixers are introduced, which show a step over efficiency in the microlevel mixing. Finite-element method (FEM) tools were utilized to assess the mixing efficiency of the presented micromixers versus common T- and zigzag-shaped mixers. Using the availability of three-dimensional printing features, the chaotic advection is maximized as a mainstream factor affecting microscale behavior of the mixer. Both FEM and experimental results prove a 95% improvement in the performance of micromixers for low Reynolds numbers at 1 versus 8 cm for conventional devices.
Plasmonic nanostructures enable considerable control and manipulation of light at the subwavelength scale and are promising for demonstration of optical metamaterials with enhanced spectral response. In this paper, we introduce a generation of terahertz bandpass filters that exploit the characteristics of subwavelength plasmonic nanoparticles. The design procedure is discussed based on a well-known complementary split ring resonator with a resonant feature at the THz region (∼1.5 THz), and it has been shown that device design based on plasmonic nanoparticles can conquer the poor off-resonance selectivity limit of common THz filters and exhibit higher transmission response, faster roll-off, and almost ripple-free operation. A much larger coupling capacitance for nanoparticles in the touching condition can modify the resonance wavelength, and localized hot spots enhance the device sensitivity for special applications. The effect of plasmonic nanoparticle size on the filtering characteristics is also discussed. A simple fabrication procedure based on discontinuous islandized surface morphology of thin metallic films on a dielectric has been proposed for demonstration of the THz filters introduced here.
A comprehensive study has been performed to achieve all-angle self-collimation in basic two-dimensional square array photonic crystals with cylindrical scatterers. Based on plane wave expansion and finite difference time domain analysis for both rod- and hole-type structures, we report on all-angle self-collimation (SC) in the first band of the structure, which results in loss suppression due to out-of-plane scatterings. A lower threshold for index contrast has been obtained to achieve all-angle SC, which offers more design flexibility regarding structural parameters. Furthermore, it has been shown that a minimum and maximum coupling efficiency enhancement of ∼40% and 80% can be achieved for the proposed structure, respectively, by introducing a row of scatterers with proper radius at the input and the output air/photonic crystal interfaces.
In this paper, we derive an equivalent circuit model for quantum dot semiconductor optical amplifier (QDSOA)
by employing rate equations for electronic transitions between QD's levels and also the optical power
propagation. The different parts of equivalent circuits interact together to represent the gain recovery process,
saturation properties and chirp behaviour in both linear and nonlinear operation regimes of QD-SOA. The
equivalent circuits are then used for SPICE simulation. We have shown that SPICE simulation results agree
well with the full numerically calculated results.
In this paper, a novel structure for detection of two different wavelengths in mid-infrared region is proposed. By
attaching a capturing well to the active region, a common transportation path for electron excited by two different
wavelengths is introduced. Calculated values for responsivity and detectivity in the designed Quantum Cascade
Photodetector structure at 120K are: R<sub>1</sub> (λ=6.85μ m) =67.5 mA/W, R<sub>2</sub> (λ=12.35μ m) =118.5mA/W and D<sub>1</sub> (λ=6.85) =6.89×10<sup>7</sup>J, D<sub>2</sub> (λ=12.35) =1.2×10<sup>8</sup>J, respectively.