| 1. |
- Akram, Nadeem
(författare)
-
Lateral current injection (LCI) multiple quantum-well 1.55 mu m laser with improved gain uniformity across the active region
- 2004
-
Ingår i: Optical and quantum electronics. - 0306-8919 .- 1572-817X. ; 36:9, s. 827-846
-
Tidskriftsartikel (refereegranskat)abstract
- A simulation study of lateral current injection 1.55 mum laser with strain-compensated multiple quantum-well (MQW) active region (InGaAsP well, InGaAlAs barrier) is presented using self-consistent 2D numerical simulations. The effects of different mesa width and p-doping in the QWs on the carrier and gain uniformity across the active region are explored. A high p-doping in the quantum wells is found to increases the carrier and gain non-uniformity across the active region. The QW region close to the n-contact side does not provide much gain at high optical powers. An asymmetric optical waveguide design is proposed to help reduce the gain non-uniformity across the active region. By shifting the optical modal peak toward the p-side, the modal overlap between the gain region and the optical mode is improved and a more even carrier and gain distribution is obtained. However, due to reduced bandgap of the quaternary InGaAsP p-cladding, an enhanced electron leakage out of the QWs into the p-cladding degrades the laser efficiency and increases the threshold current. Transient time - domain simulations are also performed to determine the small-signal modulation response of the laser promising a simulated high modulation bandwidth suitable for direct-modulation applications.
|
|
| 2. |
- Arof, A. K., et al.
(författare)
-
Quasi solid state dye-sensitized solar cells based on polyvinyl alcohol (PVA) electrolytes containing redox couple
- 2014
-
Ingår i: Optical and Quantum Electronics. - : Springer Science and Business Media LLC. - 0306-8919 .- 1572-817X. ; 46:1, s. 143-154
-
Tidskriftsartikel (refereegranskat)abstract
- Quasi solid state dye-sensitized solar cells (DSSCs) have been fabricated with electrolytes containing I-/I-3(-) redox couple using 80% hydrolyzed polyvinyl alcohol (PVA) doped with potassium iodide (KI) and a mixture of potassium iodide and tetrapropyl ammonium iodide (Pr4NI) salts. The quasi solid state gel polymer electrolytes were prepared using 1: 1 ethylene carbonate (EC): propylene carbonate (PC) mixture. The solar cells have the structure of ITO/TiO2/N-3-Dye/electrolyte/Pt/ITO. The conductivity of the electrolytes has been calculated from the bulk resistance value determined using the electrochemical impedance spectroscopy. The performance of the DSSCs has been studied by varying the concentration of the doping salts in the electrolyte and incident light intensity. The DSSC fabricated with the KI salt electrolyte containing 9.9 wt% PVA, 39.6 wt% EC, 39.6 wt% PC, 10.9 wt% KI(+I-2) exhibited the best power conversion efficiency of 1.97 %. However, the DSSC with a double-salt electrolyte containing 9.9 wt% PVA: 39.6 wt% EC: 39.6 wt% PC: (6.5 wt% KI: 4.4 wt% Pr4NI) (+I-2) exhibited a higher efficiency of 3.27% under 100 mW/cm(2) light intensity. The efficiency of this cell increased to 4.59 % under dimmer light of intensity of 54 mW/cm(2).
|
|
| 3. |
|
|
| 4. |
- Dai, Daoxin, et al.
(författare)
-
Calculation of the spectral response of an arrayed-waveguide gating demultiplexer with a wide-angle beam propagation method in a cylindrical coordinate system
- 2004
-
Ingår i: Optical and quantum electronics. - : Springer Science and Business Media LLC. - 0306-8919 .- 1572-817X. ; 36:11, s. 967-979
-
Tidskriftsartikel (refereegranskat)abstract
- The spectral response of an arrayed-waveguide grating (AWG) demultiplexer is calculated by simulating the field propagation in the output section of an AWG with a wide-angle beam propagation method (BPM) in a cylindrical coordinate system. As in a practical design of an AWG demultiplexer, each output waveguide consists of two straight sections connected by a bending section. The spectral response obtained by the present algorithm is more accurate than those obtained with two popular approximate methods, namely, the conventional overlapped integral method and the standard BPM for radially straight and infinitely long output waveguides. With the present algorithm, the dependence of the spectral response on the parameters of the output section is analyzed. The channel crosstalk and the 3 dB passband width of the spectral response depend mainly on the length of the first straight section, the end separation and the angular separation of the output waveguides. The bending section results in an asymmetrical spectral response with remarkable sidelobes which can be reduced by increasing the bending radius.
|
|
| 5. |
- Dalarsson, Mariana, et al.
(författare)
-
Exact analytical solution for fields in a lossy cylindrical structure with hyperbolic tangent gradient index metamaterials
- 2016
-
Ingår i: Optical and quantum electronics. - : Springer Science and Business Media LLC. - 0306-8919 .- 1572-817X. ; 48:3
-
Tidskriftsartikel (refereegranskat)abstract
- The advent of metamaterials with tailorable frequency dispersion ensured the emergence of transformation optics with proposed applications that include cloaking devices, superconcentrators, superabsorbers, beam shapers and benders, field and polarization rotators, etc. A crucial property of interest for transformation optics is the possibility to custom design the spatial dependence of optical properties, i.e. to attain a gradient of effective refractive index. The cylindrical geometry has been one of the prototypal proposed forms and actually the first theoretical and experimental cloaking devices had radial symmetry. In this contribution we present an exact analytical approach to the solution of Helmholtz' equations applied to radial propagation of electromagnetic waves through a cylinder containing negative and positive refractive index parts. A hyperbolic tangent gradient of refractive index is assumed. Our approach is inspired by the correspondence between transformation optics and quantum mechanics. A remarkably simple exact analytical solution is derived that takes into account realistic losses in negative-positive refractive index material composites.
|
|
| 6. |
- Ebadi, Seyed Morteza, et al.
(författare)
-
Design of a tetra-band MIM plasmonic absorber based on triangular arrays in an ultra-compact MIM waveguide
- 2023
-
Ingår i: Optical and quantum electronics. - : Springer Nature. - 0306-8919 .- 1572-817X. ; 55:6
-
Tidskriftsartikel (refereegranskat)abstract
- This paper presents design and numerical investigations of an ultra-compact, and highly-efficient plasmonic absorber based on metal-insulator-metal waveguides. The proposed device offers multiple narrow-band absorption at visible and near-infrared wavelengths with peak absorbance between 81 and 100%. The finite element method has been used to simulate the proposed structure. The simulation results show that the resonance wavelengths can be easily modulated by tuning the coupling distances between the input and output ports and the triangular resonators. To find the optimized size of the proposed structure, maximize its efficiency, and attain narrow-band resonances, a parameterized genetic algorithm has been used. Taking into account the obtained notable specifications of the proposed structure, it can contribute to the development of miniaturized and efficient optical components for photonic integrated circuits.
|
|
| 7. |
- Ebadi, Seyed Morteza, et al.
(författare)
-
Design of miniaturized wide band-pass plasmonic filters in MIM waveguides with tailored spectral filtering
- 2024
-
Ingår i: Optical and quantum electronics. - : Springer Nature. - 0306-8919 .- 1572-817X. ; 56:5
-
Tidskriftsartikel (refereegranskat)abstract
- This paper reports the design and numerical results of three new extremely compact and efficient flat-top band-pass plasmonic filters operating in the near-infrared region. The proposed structures are realized in metal–insulator-metal plasmonic waveguides based on stub, tilted T-junction and right-angle trapezoid configurations. A built-in parameterized genetic algorithm is applied to maximize the transmission efficiency, while at the same time contributing to shrinking down the size of the device structures. It is shown that the tunability of the optical filters can be realized by modulating their structural parameters to gain control over the band-pass filtering wavelengths. Numerical calculations are conducted based on the finite element method of CST Microwave Studio and demonstrate that the suggested ultra-compact plasmonic waveguide filters offer wide bandwidths of more than 270 nm, 424 nm, and 289 nm, with transmission efficiencies of higher than 80%, 74.2%, and 74.3%, respectively. The sizes of the proposed wavelength filters are 490 nm × 575 nm, 350 nm × 180 nm, and 420 nm × 150 nm, respectively, which make them attractive candidates for applications in high density photonic integrated circuits (PICs). As a result, because of the promising characteristics of the proposed topologies such as their high efficiency, compact size, tunability, and simple structure they may find applications in on-chip integration, laser technology, and multi-photon fluorescence.
|
|
| 8. |
- Gevorgian, Spartak, 1948, et al.
(författare)
-
The Optical Power Distribution and Scattering Losses in Symmetric Channel Waveguide X-Junction
- 1991
-
Ingår i: Optical and Quantum Electronics. - 0306-8919 .- 1572-817X. ; 23, s. 649-656
-
Tidskriftsartikel (refereegranskat)abstract
- It is shown theoretically and experimentally that there is sufficient light radiation at the crossing points of wave-guides, and sufficient coupling between input branches and output branches of integrated optic symmetric crossing channel wave-guides. For straight X-junctions the crosstalk could be changed in a wide range varying the crossing angle, while for widened X-junction with a fixed crossing angle the crosstalk could be changed by varying the length of the central straight waveguide section.
|
|
| 9. |
- Grayeli, A., et al.
(författare)
-
Structural, morphological, and optical bandgap properties of ZnS thin films : a case study on thickness dependence
- 2024
-
Ingår i: Optical and quantum electronics. - : Springer. - 0306-8919 .- 1572-817X. ; 56:7
-
Tidskriftsartikel (refereegranskat)abstract
- Thin films of zinc sulfide (ZnS) with varying thicknesses have been successfully fabricated using radio frequency magnetron sputtering on glass substrates at a temperature of 300 K. Structural analysis via X-ray diffraction and selected area electron diffraction confirmed the presence of nanocrystalline cubic ZnS phases in the films. The crystallite size, determined from X-ray diffraction lines, ranged between 42 and 55 nm. We also explored the morphological attributes of these surfaces and observed significant changes in both grain shape and size. Our atomic force microscopy analyses revealed that the thinner film displayed a topography marked by thinner, elongated rough peaks. As the film thickness increased, these rough peaks gradually transformed into wider, flatter features. Additionally, the films exhibited distinct percolation properties, which were undeniably tied to the alterations in the shape and size of the ZnS grains on their surfaces. Thinner samples demonstrated more pronounced surface percolation (FS > 0.5) compared to thicker samples, which displayed reduced surface percolation. Furthermore, we noted that the 250 nm film predominantly showcased strongly multifractal 3D spatial patterns in contrast to the other films. Spectroscopic measurements in the UV–visible-near infrared region revealed high transparency across the 350–850 nm spectra, with a noticeable blue shift in the absorption edge. Calculations yielded direct allowed band gaps within the range of 3.69–3.85 eV. These results indicate that the optical properties of films can be tailored by their structural and morphological characteristics, thereby offering valuable guidance for their appropriate applications.
|
|
| 10. |
|
|
