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Photonics, Volume 3, Issue 1 (March 2016)

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Open AccessArticle
Lateral Modes in Quantum Cascade Lasers
Photonics 2016, 3(1), 11; https://doi.org/10.3390/photonics3010011 - 22 Mar 2016
Viewed by 1263
Abstract
We will examine the waveguide mode losses in ridge-guided quantum cascade lasers. Our analysis illustrates how the low-loss mode for broad-ridge quantum cascade lasers (QCLs) can be a higher-order lateral waveguide mode that maximizes the feedback from the sloped ridge-wall regions. The results [...] Read more.
We will examine the waveguide mode losses in ridge-guided quantum cascade lasers. Our analysis illustrates how the low-loss mode for broad-ridge quantum cascade lasers (QCLs) can be a higher-order lateral waveguide mode that maximizes the feedback from the sloped ridge-wall regions. The results are in excellent agreement with the near- and far-field data taken on broad-ridge-guided quantum cascade lasers processed with sloped ridge walls. Full article
(This article belongs to the Special Issue Quantum Cascade Lasers - Advances and New Applications)
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Open AccessArticle
Increasing Surface Plasmons Propagation via Photonic Nanojets with Periodically Spaced 3D Dielectric Cuboids
Photonics 2016, 3(1), 10; https://doi.org/10.3390/photonics3010010 - 21 Mar 2016
Cited by 11 | Viewed by 1687
Abstract
A structure based on periodically arranged 3D dielectric cuboids connected by photonic nanojets (PNJs) is proposed with the aim of increasing the propagation distance of surface plasmon polaritons (SPPs) at the telecom wavelength of 1550 nm. The performance of the structure is evaluated [...] Read more.
A structure based on periodically arranged 3D dielectric cuboids connected by photonic nanojets (PNJs) is proposed with the aim of increasing the propagation distance of surface plasmon polaritons (SPPs) at the telecom wavelength of 1550 nm. The performance of the structure is evaluated and compared with the case without the cuboids demonstrating that the SPPs propagation length is enhanced by a factor greater than 2, reaching a value of approximately 19λ0, when the gap between the cuboids is 2.5λ0. Also, the dependence of the propagation length with the height of the cubes is evaluated, showing that this parameter is critical for a good performance of the chain. A subwavelength resolution is obtained for all the jets generated at the output of the cuboids. Full article
(This article belongs to the Special Issue 3D- and 2D-Nanofabrication for Photonic Devices)
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Open AccessCommunication
Absorption Properties of Simply Fabricated All-Metal Mushroom Plasmonic Metamaterials Incorporating Tube-Shaped Posts for Multi-Color Uncooled Infrared Image Sensor Applications
Photonics 2016, 3(1), 9; https://doi.org/10.3390/photonics3010009 - 11 Mar 2016
Cited by 17 | Viewed by 2246
Abstract
Wavelength-selective infrared (IR) absorbers have attracted considerable interest due to their potential for a wide range of applications. In particular, they can be employed as advanced uncooled IR sensors that identify objects through their radiation spectra. Herein, we propose a mushroom plasmonic metamaterial [...] Read more.
Wavelength-selective infrared (IR) absorbers have attracted considerable interest due to their potential for a wide range of applications. In particular, they can be employed as advanced uncooled IR sensors that identify objects through their radiation spectra. Herein, we propose a mushroom plasmonic metamaterial absorber incorporating tube-shaped metal posts (MPMAT) for use in the long-wavelength IR (LWIR) region. The MPMAT design consists of a periodic array of thin metal micropatches connected to a thin metal plate via tube-shaped metal posts. Both the micropatches and posts can be constructed simultaneously as a result of the tube-shaped structure of the metal post structure; thus, the fabrication procedure is both simple and low cost. The absorption properties of these MPMATs were assessed both theoretically and experimentally, and the results of both investigations demonstrated that these devices exhibit suitable levels of LWIR absorption regardless of the specific tube-shaped structures employed. It was also found to be possible to tune the absorption wavelength by varying the micropatch width and the inner diameter of the tube-shaped metal posts, and to obtain absorbance values of over 90%. Focal plane array structures based on such MPMATs could potentially serve as high-performance, low-cost, multi-spectral uncooled IR image sensors. Full article
(This article belongs to the Special Issue 3D- and 2D-Nanofabrication for Photonic Devices)
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Open AccessArticle
Lithographically Fabricated Magnifying Maxwell Fisheye Lenses
Photonics 2016, 3(1), 8; https://doi.org/10.3390/photonics3010008 - 08 Mar 2016
Cited by 1 | Viewed by 1363
Abstract
Recently suggested magnifying Maxwell fisheye lenses, which are made of two half-lenses of different radii, have been fabricated and characterized. The lens action is based on control of polarization-dependent effective refractive index in a lithographically formed tapered waveguide. We have studied wavelength and [...] Read more.
Recently suggested magnifying Maxwell fisheye lenses, which are made of two half-lenses of different radii, have been fabricated and characterized. The lens action is based on control of polarization-dependent effective refractive index in a lithographically formed tapered waveguide. We have studied wavelength and polarization dependent performance of the lenses, and their potential applications in waveguide mode sorting. Full article
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Open AccessCommunication
Efficient Disinfection of Tap and Surface Water with Single High Power 285 nm LED and Square Quartz Tube
Photonics 2016, 3(1), 7; https://doi.org/10.3390/photonics3010007 - 27 Jan 2016
Cited by 3 | Viewed by 5420
Abstract
A small water disinfection system based on the combination of a strong single 25 mW LED with a wavelength of 285 nm and a short quartz tube with an outer rectangular cross section is presented. For the disinfection tests clear tap water and [...] Read more.
A small water disinfection system based on the combination of a strong single 25 mW LED with a wavelength of 285 nm and a short quartz tube with an outer rectangular cross section is presented. For the disinfection tests clear tap water and slightly turbid and yellow pond water are contaminated with high concentrations of Escherichia coli bacteria. These water samples are exposed to the germicidal 285 nm LED radiation while they flow through the quartz tube. The portion of surviving germs is determined by membrane filtration for different water qualities and flow rates. For clear tap water the bacteria concentration can be reduced by at least three orders of magnitude up to flow rates of about 20 L/h. In pond water the maximum flow rate for such a reduction is less than 3 L/h. These high disinfection capabilities and the small size of this system, allow its integration in medical systems for point of use disinfection or even its application in the Third World for decentralized water disinfection powered by small solar cells, because this disinfection capacity should be sufficient for small groups or families. Full article
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Open AccessEditorial
Acknowledgement to Reviewers of Photonics in 2015
Photonics 2016, 3(1), 6; https://doi.org/10.3390/photonics3010006 - 21 Jan 2016
Viewed by 1094
Abstract
The editors of Photonics would like to express their sincere gratitude to the following reviewers for assessing manuscripts in 2015. [...] Full article
Open AccessArticle
Modeling of the Interminiband Absorption Coefficient in InGaN Quantum Dot Superlattices
Photonics 2016, 3(1), 5; https://doi.org/10.3390/photonics3010005 - 13 Jan 2016
Cited by 5 | Viewed by 1943
Abstract
In this paper, a model to estimate minibands and theinterminiband absorption coefficient for a wurtzite (WZ) indium gallium nitride (InGaN) self-assembled quantum dot superlattice (QDSL) is developed. It considers a simplified cuboid shape for quantum dots (QDs). The semi-analytical investigation starts from evaluation [...] Read more.
In this paper, a model to estimate minibands and theinterminiband absorption coefficient for a wurtzite (WZ) indium gallium nitride (InGaN) self-assembled quantum dot superlattice (QDSL) is developed. It considers a simplified cuboid shape for quantum dots (QDs). The semi-analytical investigation starts from evaluation through the three-dimensional (3D) finite element method (FEM) simulations of crystal mechanical deformation derived from heterostructure lattice mismatch under spontaneous and piezoelectric polarization effects. From these results, mean values in QDs and barrier regions of charge carriers’ electric potentials and effective masses for the conduction band (CB) and three valence sub-bands for each direction are evaluated. For the minibands’ investigation, the single-particle time-independent Schrödinger equation in effective mass approximation is decoupled in three directions and resolved using the one-dimensional (1D) Kronig–Penney model. The built-in electric field is also considered along the polar axis direction, obtaining Wannier–Stark ladders. Then, theinterminiband absorption coefficient in thermal equilibrium for transverse electric (TE) and magnetic (TM) incident light polarization is calculated using Fermi’s golden rule implementation based on a numerical integration into the first Brillouin zone. For more detailed results, an absorption coefficient component related to superlattice free excitons is also introduced. Finally, some simulation results, observations and comments are given. Full article
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Open AccessArticle
A Single-Element Plane Grating Monochromator
Photonics 2016, 3(1), 3; https://doi.org/10.3390/photonics3010003 - 11 Jan 2016
Cited by 3 | Viewed by 2763
Abstract
Concerted rotations of a self-focused varied line-space diffraction grating about its groove axis and surface normal define a new geometric class of monochromator. Defocusing is canceled, while the scanned wavelength is reinforced at fixed conjugate distances and horizontal deviation angle. This enables high [...] Read more.
Concerted rotations of a self-focused varied line-space diffraction grating about its groove axis and surface normal define a new geometric class of monochromator. Defocusing is canceled, while the scanned wavelength is reinforced at fixed conjugate distances and horizontal deviation angle. This enables high spectral resolution over a wide band, and is of particular advantage at grazing reflection angles. A new, rigorous light-path formulation employs non-paraxial reference points to isolate the lateral ray aberrations, with those of power-sum ≤ 3 explicitly expanded for a plane grating. Each of these 14 Fermat equations agrees precisely with the value extracted from numerical raytrace simulations. An example soft X-ray design (6° deviation angle and 2 × 4 mrad aperture) attains a resolving power > 25,000 over a three octave scan range. The proposed rotation scheme is not limited to plane surfaces or monochromators, providing a new degree of freedom in optical design. Grating rotation about its third (meridional) axis may be employed to cancel vertical deflection of the diffracted beam while maintaining the above aberration correction. This enables a simpler (pure rotary) motion for the exit slit and a fixed beam direction both horizontally and vertically. Full article
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Open AccessArticle
Design and Analysis of Enhanced Modulation Response in Integrated Coupled Cavities DBR Lasers Using Photon-Photon Resonance
Photonics 2016, 3(1), 4; https://doi.org/10.3390/photonics3010004 - 08 Jan 2016
Cited by 5 | Viewed by 1992
Abstract
In the last few decades, various solutions have been proposed to increase the modulation bandwidth and, consequently, the transmission bit-rate of semiconductor lasers. In this manuscript, we discuss a design procedure for a recently proposed laser cavity realized with the monolithic integration of [...] Read more.
In the last few decades, various solutions have been proposed to increase the modulation bandwidth and, consequently, the transmission bit-rate of semiconductor lasers. In this manuscript, we discuss a design procedure for a recently proposed laser cavity realized with the monolithic integration of two distributed Bragg reflector (DBR) lasers allowing one to extend the modulation bandwidth. Such an extension is obtained introducing in the dynamic response a photon-photon resonance (PPR) at a frequency higher than the modulation bandwidth of the corresponding single-section laser. Design guidelines will be proposed, and dynamic small and large signal simulations results, calculated using a finite difference traveling wave (FDTW) numerical simulator, will be discussed to confirm the design results. The effectiveness of the design procedure is verified in a structure with PPR frequency at 35 GHz allowing one to obtain an open eye diagram for a non-return-to-zero (NRZ) digital signal up to 80 GHz . Furthermore, the investigation of the rich dynamics of this structure shows that with proper bias conditions, it is possible to obtain also a tunable self-pulsating signal in a frequency range related to the PPR design. Full article
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Open AccessArticle
Numerical Study of Light Transport in Apple Models Based on Monte Carlo Simulations
Photonics 2016, 3(1), 2; https://doi.org/10.3390/photonics3010002 - 26 Dec 2015
Cited by 7 | Viewed by 2392
Abstract
This paper reports on the quantification of light transport in apple models using Monte Carlo simulations. To this end, apple was modeled as a two-layer spherical model including skin and flesh bulk tissues. The optical properties of both tissue types used to generate [...] Read more.
This paper reports on the quantification of light transport in apple models using Monte Carlo simulations. To this end, apple was modeled as a two-layer spherical model including skin and flesh bulk tissues. The optical properties of both tissue types used to generate Monte Carlo data were collected from the literature, and selected to cover a range of values related to three apple varieties. Two different imaging-tissue setups were simulated in order to show the role of the skin on steady-state backscattering images, spatially-resolved reflectance profiles, and assessment of flesh optical properties using an inverse nonlinear least squares fitting algorithm. Simulation results suggest that apple skin cannot be ignored when a Visible/Near-Infrared (Vis/NIR) steady-state imaging setup is used for investigating quality attributes of apples. They also help to improve optical inspection techniques in the horticultural products. Full article
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Open AccessArticle
PLAT4M: Progressing Silicon Photonics in Europe
Photonics 2016, 3(1), 1; https://doi.org/10.3390/photonics3010001 - 24 Dec 2015
Cited by 3 | Viewed by 2730
Abstract
Photonic integration is an appealing technology for emerging applications in communications, medical diagnostics and sensing. Silicon Photonics presents a highly attractive solution for large-scale photonic integration, principally because it is based on well-established CMOS-fabrication technologies. However, Silicon photonics can be difficult and expensive [...] Read more.
Photonic integration is an appealing technology for emerging applications in communications, medical diagnostics and sensing. Silicon Photonics presents a highly attractive solution for large-scale photonic integration, principally because it is based on well-established CMOS-fabrication technologies. However, Silicon photonics can be difficult and expensive to implement, as it requires complex device design, fabrication and packaging capabilities. Photonic Libraries And Technology for Manufacturing (PLAT4M) is a major European project that brings together the key capabilities required to develop solutions for a range of Silicon photonic-based applications. This paper will present an overview of the PLAT4M project. It will present, in detail, a key application demonstrator (Coherent Beam Combiner), highlighting the ability of the project team to develop an integrated Silicon Photonic sub-system, from design, through to device fabrication, packaging and final test. The paper also highlights the need to consider additional capabilities besides device fabrication, such as packaging, which are critical to achieving fully operational sub-systems. Full article
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