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Photonics, Volume 4, Issue 4 (December 2017) – 7 articles

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2791 KiB  
Article
Extraordinary Light-Trapping Enhancement in Silicon Solar Cell Patterned with Graded Photonic Super-Crystals
by Safaa Hassan, David Lowell, Murthada Adewole, David George, Hualiang Zhang and Yuankun Lin
Photonics 2017, 4(4), 50; https://doi.org/10.3390/photonics4040050 - 20 Dec 2017
Cited by 11 | Viewed by 3875
Abstract
Light-trapping enhancement in newly discovered graded photonic super-crystals (GPSCs) with dual periodicity and dual basis is herein explored for the first time. Broadband, wide-incident-angle, and polarization-independent light-trapping enhancement was achieved in silicon solar cells patterned with these GPSCs. These super-crystals were designed by [...] Read more.
Light-trapping enhancement in newly discovered graded photonic super-crystals (GPSCs) with dual periodicity and dual basis is herein explored for the first time. Broadband, wide-incident-angle, and polarization-independent light-trapping enhancement was achieved in silicon solar cells patterned with these GPSCs. These super-crystals were designed by multi-beam interference, rendering them flexible and efficient. The optical response of the patterned silicon solar cell retained Bloch-mode resonance; however, light absorption was greatly enhanced in broadband wavelengths due to the graded, complex unit super-cell nanostructures, leading to the overlap of Bloch-mode resonances. The broadband, wide-angle light coupling and trapping enhancement mechanism are understood to be due to the spatial variance of the index of refraction, and this spatial variance is due to the varying filling fraction, the dual basis, and the varying lattice constants in different directions. Full article
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4068 KiB  
Review
Microwave Signal Processing over Multicore Fiber
by Sergi García, David Barrera, Javier Hervás, Salvador Sales and Ivana Gasulla
Photonics 2017, 4(4), 49; https://doi.org/10.3390/photonics4040049 - 08 Dec 2017
Cited by 8 | Viewed by 5361
Abstract
We review the introduction of the space dimension into fiber-based technologies to implement compact and versatile signal processing solutions for microwave and millimeter wave signals. Built upon multicore fiber links and devices, this approach allows the realization of fiber-distributed signal processing in the [...] Read more.
We review the introduction of the space dimension into fiber-based technologies to implement compact and versatile signal processing solutions for microwave and millimeter wave signals. Built upon multicore fiber links and devices, this approach allows the realization of fiber-distributed signal processing in the context of fiber-wireless communications, providing both radiofrequency access distribution and signal processing in the same fiber medium. We present different space-division multiplexing architectures to implement tunable true time delay lines that can be applied to a variety of microwave photonics functionalities, such as signal filtering, radio beamsteering in phased array antennas or optoelectronic oscillation. In particular, this paper gathers our latest work on the following multicore fiber technologies: dispersion-engineered heterogeneous multicore fiber links for distributed tunable true time delay line operation; multicavity devices built upon the selective inscription of gratings in homogenous multicore fibers for compact true time delay line operation; and multicavity optoelectronic oscillation over both homogeneous and heterogeneous multicore fibers. Full article
(This article belongs to the Special Issue Microwave Photonics 2017)
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315 KiB  
Article
Higher-Order Interactions in Quantum Optomechanics: Analytical Solution of Nonlinearity
by Sina Khorasani
Photonics 2017, 4(4), 48; https://doi.org/10.3390/photonics4040048 - 05 Dec 2017
Cited by 8 | Viewed by 3865
Abstract
A method is described to solve the nonlinear Langevin equations arising from quadratic interactions in quantum mechanics. While the zeroth order linearization approximation to the operators is normally used, here, first and second order truncation perturbation schemes are proposed. These schemes employ higher-order [...] Read more.
A method is described to solve the nonlinear Langevin equations arising from quadratic interactions in quantum mechanics. While the zeroth order linearization approximation to the operators is normally used, here, first and second order truncation perturbation schemes are proposed. These schemes employ higher-order system operators, and then approximate number operators with their corresponding mean boson numbers only where needed. Spectral densities of higher-order operators are derived, and an expression for the second-order correlation function at zero time-delay has been found, which reveals that the cavity photon occupation of an ideal laser at threshold reaches 6 2 , in good agreement with extensive numerical calculations. As further applications, analysis of the quantum anharmonic oscillator, calculation of Q-functions, analysis of quantum limited amplifiers, and nondemoliton measurements are provided. Full article
7108 KiB  
Article
Heat Dissipation Schemes in AlInAs/InGaAs/InP Quantum Cascade Lasers Monitored by CCD Thermoreflectance
by Dorota Pierścińska, Kamil Pierściński, Piotr Gutowski, Mikołaj Badura, Grzegorz Sobczak, Olga Serebrennikova, Beata Ściana, Marek Tłaczała, Grzegorz Sobczak and Maciej Bugajski
Photonics 2017, 4(4), 47; https://doi.org/10.3390/photonics4040047 - 03 Dec 2017
Cited by 15 | Viewed by 5149
Abstract
In this paper, we report on the experimental investigation of the thermal performance of lattice matched AlInAs/InGaAs/InP quantum cascade lasers. Investigated designs include double trench, single mesa, and buried heterostructures, which were grown by combined Molecular Beam Epitaxy (MBE) and Metal Organic Vapor [...] Read more.
In this paper, we report on the experimental investigation of the thermal performance of lattice matched AlInAs/InGaAs/InP quantum cascade lasers. Investigated designs include double trench, single mesa, and buried heterostructures, which were grown by combined Molecular Beam Epitaxy (MBE) and Metal Organic Vapor Phase Epitaxy (MOVPE) techniques. The thermal characteristics of lasers are investigated by Charge-Coupled Device CCD thermoreflectance. This method allows for the fast and accurate registration of high-resolution temperature maps of the whole device. We observe different heat dissipation mechanisms for investigated geometries of Quantum Cascade Lasers (QCLs). From the thermal point of view, the preferred design is the buried heterostructure. The buried heterostructures structure and epi-layer down mounting help dissipate the heat generated from active core of the QCL. The experimental results are in very good agreement with theoretical predictions of heat dissipation in various device constructions. Full article
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1995 KiB  
Review
Integrated Microwave Photonics for Wideband Signal Processing
by Xiaoke Yi, Suen Xin Chew, Shijie Song, Linh Nguyen and Robert Minasian
Photonics 2017, 4(4), 46; https://doi.org/10.3390/photonics4040046 - 30 Nov 2017
Cited by 33 | Viewed by 7075
Abstract
We describe recent progress in integrated microwave photonics in wideband signal processing applications with a focus on the key signal processing building blocks, the realization of monolithic integration, and cascaded photonic signal processing for analog radio frequency (RF) photonic links. New developments in [...] Read more.
We describe recent progress in integrated microwave photonics in wideband signal processing applications with a focus on the key signal processing building blocks, the realization of monolithic integration, and cascaded photonic signal processing for analog radio frequency (RF) photonic links. New developments in integration-based microwave photonic techniques, that have high potentialities to be used in a variety of sensing applications for enhanced resolution and speed are also presented. Full article
(This article belongs to the Special Issue Microwave Photonics 2017)
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4542 KiB  
Review
Tunable Multiband Microwave Photonic Filters
by Mable P. Fok and Jia Ge
Photonics 2017, 4(4), 45; https://doi.org/10.3390/photonics4040045 - 23 Nov 2017
Cited by 29 | Viewed by 7912
Abstract
The increasing demand for multifunctional devices, the use of cognitive wireless technology to solve the frequency resource shortage problem, as well as the capabilities and operational flexibility necessary to meet ever-changing environment result in an urgent need of multiband wireless communications. Spectral filter [...] Read more.
The increasing demand for multifunctional devices, the use of cognitive wireless technology to solve the frequency resource shortage problem, as well as the capabilities and operational flexibility necessary to meet ever-changing environment result in an urgent need of multiband wireless communications. Spectral filter is an essential part of any communication systems, and in the case of multiband wireless communications, tunable multiband RF filters are required for channel selection, noise/interference removal, and RF signal processing. Unfortunately, it is difficult for RF electronics to achieve both tunable and multiband spectral filtering. Recent advancements of microwave photonics have proven itself to be a promising candidate to solve various challenges in RF electronics including spectral filtering, however, the development of multiband microwave photonic filtering still faces lots of difficulties, due to the limited scalability and tunability of existing microwave photonic schemes. In this review paper, we first discuss the challenges that were facing by multiband microwave photonic filter, then we review recent techniques that have been developed to tackle the challenge and lead to promising developments of tunable microwave photonic multiband filters. The successful design and implementation of tunable microwave photonic multiband filter facilitate the vision of dynamic multiband wireless communications and radio frequency signal processing for commercial, defense, and civilian applications. Full article
(This article belongs to the Special Issue Microwave Photonics 2017)
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12019 KiB  
Review
Simultaneous Multi-Channel Microwave Photonic Signal Processing
by Lawrence R. Chen, Parisa Moslemi, Ming Ma and Rhys Adams
Photonics 2017, 4(4), 44; https://doi.org/10.3390/photonics4040044 - 17 Nov 2017
Cited by 5 | Viewed by 5977
Abstract
Microwave photonic (MWP) systems exploit the advantages of photonics, especially with regards to ultrabroad bandwidth and adaptability, features that are significantly more challenging to obtain in the electronic domain. Thus, MWP systems can be used to realize a number of microwave signal processing [...] Read more.
Microwave photonic (MWP) systems exploit the advantages of photonics, especially with regards to ultrabroad bandwidth and adaptability, features that are significantly more challenging to obtain in the electronic domain. Thus, MWP systems can be used to realize a number of microwave signal processing functions including, amongst others, waveform generation and radio-frequency spectrum analysis (RFSA). In this paper, we review recent results on fiber and integrated approaches for simultaneous generation of multiple chirped microwave waveforms as well as multi-channel RFSA of ultrahigh repetition optical rate pulse trains. Full article
(This article belongs to the Special Issue Microwave Photonics 2017)
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