| 41. |
- Qiu, Min, et al.
(författare)
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Wave propagation through a photonic crystal in a negative phase refractive-index region
- 2003
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Ingår i: IEEE Journal of Selected Topics in Quantum Electronics. - : Institute of Electrical and Electronics Engineers (IEEE). - 1077-260X .- 1558-4542. ; 9:1, s. 106-110
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Tidskriftsartikel (refereegranskat)abstract
- The wave propagation through a photonic crystal with a triangular lattice of air holes realized in the InP-InGaAsP heterostructure are studied theoretically for the transverse magnetic modes. The photonic crystal possesses a negative refractive index, and the self-focus of the beam is successfully observed. The weak side beams are observed due to high-order Bloch waves in the photonic crystal. The coupling efficiency for the outgoing waves to a waveguide is also studied.
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| 42. |
- Sehati, Parisa, et al.
(författare)
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Energy-Level Alignment at Metal-Organic and Organic-Organic Interfaces in Bulk-Heterojunction Solar Cells
- 2010
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Ingår i: IEEE Journal of Selected Topics in Quantum Electronics. - : Institute of Electrical and Electronics Engineers (IEEE). - 1077-260X .- 1558-4542. ; 16:6, s. 1718-1724
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Tidskriftsartikel (refereegranskat)abstract
- Ultraviolet photoelectron spectroscopy measurements in combination with the integer charge transfer (ICT) model is used to obtain the energy-level alignment diagrams for two common types of bulk-heterojunction solar cell devices based on poly(3-hexylthiophene) or poly(2-methoxy-5-(3,7 -dimethyloctyloxy)- 1,4-phenylene vinylene) as the donor polymer and (6,6)phenyl- C61-butric-acid as the acceptor molecule. A ground-state interface dipole at the donor/acceptor heterojunction is present for both systems, but the origin of the interface dipole differs, quadrupole-induced in the case of poly(2-methoxy-5-(3,7-dimethyl-octyloxy)-1,4-phenylene vinylene), and ICT state based for poly(3-hexylthiophene). The presence of bound electron-hole charge carriers (CT states) and/or interface dipoles are expected to enhance exciton dissociation into free charge carriers, thus reducing the probability that charges become trapped by Coulomb forces at the interface followed by recombination.
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| 43. |
- Sennaroglu, A., et al.
(författare)
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Introduction to the Special Issue on Solid-State Lasers
- 2018
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Ingår i: IEEE Journal of Selected Topics in Quantum Electronics. - : Institute of Electrical and Electronics Engineers (IEEE). - 1077-260X .- 1558-4542. ; 24:5
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Tidskriftsartikel (refereegranskat)
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| 44. |
- Sheng, Zhen, et al.
(författare)
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Comparative Study of Losses in Ultrasharp Silicon-on-Insulator Nanowire Bends
- 2009
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Ingår i: IEEE Journal of Selected Topics in Quantum Electronics. - 1077-260X .- 1558-4542. ; 15:5, s. 1406-1412
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Tidskriftsartikel (refereegranskat)abstract
- Ultrasharp silicon-on-insulator (SOI) nanowire bends (with a bending radius of R < 2 mu m) are analyzed numerically. It is shown that the calculated bending losses for ultrasharp bends are overestimated when using a modal analysis method based on finite-difference method. In this case, reliable estimation of the bending loss can be made with a 3-D finite-difference time-domain (3-D-FDTD) method. By using 3-D-FDTD simulation, the losses in SOI nanowire bends with different structures and parameters are studied. By increasing the core width or height of the waveguide, one can reduce the bending loss at longer wavelengths for TE mode while the bending performance at shorter wavelengths degrades due to the multimode effect. Increasing the core height is much more effective to reduce the bending loss of TM mode than increasing core width. The relationship between the intrinsic Q-factor of a microring resonator and the bending radius is also obtained.
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| 45. |
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| 46. |
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| 47. |
- Song, Jinxiang, 1995, et al.
(författare)
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Model-Based End-to-End Learning for WDM Systems With Transceiver Hardware Impairments
- 2022
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Ingår i: IEEE Journal of Selected Topics in Quantum Electronics. - 1558-4542 .- 1077-260X. ; 28:4
-
Tidskriftsartikel (refereegranskat)abstract
- We propose an AE-based transceiver for a WDM system impaired by hardware imperfections. We design our AE following the architecture of conventional communication systems. This enables to initialize the AE-based transceiver to have similar performance to its conventional counterpart prior to training and improves the training convergence rate. We first train the AE in a single-channel system, and show that it achieves performance improvements by putting energy outside the desired bandwidth, and therefore cannot be used for a WDM system. We then train the AE in a WDM setup. Simulation results show that the proposed AE significantly outperforms the conventional approach. More specifically, it increases the spectral efficiency of the considered system by reducing the guard band by 37% and 50% for a root-raised-cosine filter-based matched filter with 10% and 1% roll-off, respectively. An ablation study indicates that the performance gain can be ascribed to the optimization of the symbol mapper, the pulse-shaping filter, and the symbol demapper. Finally, we use reinforcement learning to learn the pulse-shaping filter under the assumption that the channel model is unknown. Simulation results show that the reinforcement-learning-based algorithm achieves similar performance to the standard supervised end-to-end learning approach assuming perfect channel knowledge.
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| 48. |
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| 49. |
- Sun, Xu, et al.
(författare)
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Nanoscale Surface Plasmon Polariton Disk Resonators, a Theoretical Analysis
- 2016
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Ingår i: IEEE Journal of Selected Topics in Quantum Electronics. - : IEEE. - 1077-260X .- 1558-4542. ; 22:2
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Tidskriftsartikel (refereegranskat)abstract
- We analyze whispering gallery-type disk resonators with radii down to 50 nm. Single interface waveguiding is accomplished by a plasmonic-dielectric interface operating near the surface plasmon polariton (SPP) resonance, employing a hypothetical material with lower loss than what is currently available in metals or negative permittivity media. The disk is immersed in a second dielectric, nonresonant to the plasmonic medium. Due to the high effective index of the disk mode and the concomitant low radiation losses, the quality (Q) values of the resonator are solely determined by material losses, in contrast to more conventional nanoscale resonators. We calculate the dependence of the effective indices of the guided mode, the Q values of absorption and radiation, and the Purcell factor on the deviation from the SPP resonance.
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| 50. |
- Tong, Zhi, 1977, et al.
(författare)
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Ultra-low-noise, Broadband Phase-Sensitive Optical Amplifiers and Their Applications
- 2012
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Ingår i: IEEE Journal of Selected Topics in Quantum Electronics. - 1558-4542 .- 1077-260X. ; 18:2, s. 1016-1032
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Forskningsöversikt (refereegranskat)abstract
- Frequency non-degenerate phase-sensitive amplifiers (PSAs) have the potential to realize broadband and noiseless amplification. However the rigorous requirement of phase- and wavelength-locking of the input waves has significantly hampered their progress. In this paper, we review recent research on this type of optical amplifier. This work is based on a copier-PSA scheme, which consists of a parametric phase-insensitive copier followed by one or more PSAs. Broadband gain and noise performance of a fiber-based non-degenerate PSA has been characterized, both theoretically and experimentally. A record-low 1.1 dB noise figure was measured at > 26 dB gain, and a clear phase dependent gain was observed. Moreover, potential applications including phase noise squeezing and ultra-low noise, multi-channel and modulation-format-transparent linear amplification with up to 6 dB link noise figure advantage over conventional EDFA-amplified links have been experimentally demonstrated. The prospects and practical challenges of this intriguing amplification technology are also discussed
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