2015
2015
-
Record 397 of
Title:Ultra-broadband and polarization-insensitive wide-angle terahertz metamaterial absorber
Author(s):Li, Xinwang(1); Liu, Hongjun(1); Sun, Qibing(1); Huang, Nan(1)Source: Photonics and Nanostructures - Fundamentals and Applications Volume: 15 Issue: DOI: 10.1016/j.photonics.2015.04.002 Published: June 1, 2015Abstract:In this paper, an ultra-broadband and polarization insensitive terahertz (THz) metamaterial absorber is presented and investigated. With the optimization of the structural parameters, resonant peaks are merged into a broadband absorption spectrum. The simulation results demonstrate that a wide bandwidth of 3.1 THz is obtained in the range from 2.6 to 5.7 THz, where the absorption is higher than 90% for the normal incident THz waves. The full width at half maximum (FWHM) of absorption spectrum is 95% with respect to central frequency (～4 THz), which is five times greater than the FWHM of a single layer structure. Furthermore, this structure can keep the absorption above 88% over a large frequency range (>2.5 THz) when the incident angle is smaller than 50°. This metamaterial absorber can find potential applications in terahertz imaging and stealth technology. ? 2015 Elsevier B.V. All rights reserved.Accession Number: 20151700778660 -
Record 398 of
Title:Bound-state fiber laser mode-locked by a graphene-nanotube saturable absorber
Author(s):Yang, H.R.(1); Chen, G.W.(1); Kong, Y.C.(1); Li, W.L.(1)Source: Laser Physics Volume: 25 Issue: 2 DOI: 10.1088/1054-660X/25/2/025101 Published: February 1, 2015Abstract:We have experimentally observed the multiple bound states in a linear-cavity fiber laser mode-locked by a mixture of graphene and single-walled carbon nanotubes. The proposed laser can deliver the fundamental frequency soliton as well as the two and three bound-state solitons at suitable conditions. The numerical simulations confirm the experimental observations. Both the theoretical predictions and experimental results reveal that the spectral filtering effect plays a key role on the lasers. ? 2015 Astro Ltd.Accession Number: 20150400457312 -
Record 399 of
Title:Single-beam phase retrieval with partially coherent light
Author(s):Zhou, Meiling(1); Min, Junwei(1); Gao, Peng(1); Liang, Yansheng(1); Lei, Ming(1); Yao, Baoli(1)Source: Digital Holography and Three-Dimensional Imaging, DH 2015 Volume: Issue: DOI: 10.1364/dh.2015.dw2a.28 Published: May 18, 2015Abstract:A single-beam iterative phase retrieval method with partially coherent beam is proposed. Reference-less system make it high immunity to environmental disturbance and partially coherent light improve the image quality with low coherent noise.Accession Number: 20152701006636 -
Record 400 of
Title:Single-beam phase retrieval with partially coherent light illumination
Author(s):Zhou, Meiling(1); Min, Junwei(1); Gao, Peng(1); Liang, Yansheng(1); Lei, Ming(1); Yao, Baoli(1)Source: Journal of Optics (United Kingdom) Volume: 18 Issue: 1 DOI: 10.1088/2040-8978/18/1/015701 Published: November 24, 2015Abstract:A single-beam phase retrieval method with partially coherent illumination is proposed. By using an obverse and reverse iterative (ORI) algorithm, objects can be reconstructed within less time by recording a sequence of diffraction patterns at different axial planes under partially coherent light illumination. Partially coherent light illumination reduces coherent noise and the number of diffraction patterns needed for reconstruction. Thus, the whole process is fast and has high immunity to external perturbation due to the reference-less configuration. Both simulation and experimental results are presented to demonstrate the feasibility of the proposed approach. ? 2016 IOP Publishing Ltd.Accession Number: 20155201732469 -
Record 401 of
Title:Switchable multi-wavelength and dual-scale soliton fiber laser incorporating cascaded chirped fiber Bragg gratings
Author(s):Zeng, C.(1); Cui, Y.D.(1)Source: Laser Physics Volume: 25 Issue: 4 DOI: 10.1088/1054-660X/25/4/045102 Published: April 1, 2015Abstract:A simple scheme of a switchable multi-wavelength and dual-scale soliton fiber laser is proposed by cascading three chirped fiber Bragg gratings (CFBGs). By managing the cavity dispersion and controlling the losses of attenuators, quadruple-wavelength switchable pulses are generated, including one dissipative soliton (DS) and three conventional solitons (CSs). The central wavelength of the DS is 1565 nm with a pulse duration of 12.5 ps which can be compressed to ～571 fs after a 70 m single mode fiber external to cavity. Three CSs are achieved at 1539.5, 1544.5, and 1549.5 nm with pulse durations of 9.6, 8.7, and 8.8 ps, corresponding to the CFBG-based comb spectral filtering. These results demonstrate that the proposed method offers potential opportunities to exploit the flexibly switchable multiwavelength CS/DS-pulse sources at picosecond and femtosecond scales. ? 2015 Astro Ltd.Accession Number: 20151400703809 -
Record 402 of
Title:Heterostructured cathode with graded bandgap window-layer for photon-enhanced thermionic emission solar energy converters
Author(s):Yang, Yang(1); Yang, Wenzheng(1); Sun, Chuandong(1)Source: Solar Energy Materials and Solar Cells Volume: 132 Issue: DOI: 10.1016/j.solmat.2014.09.027 Published: 2014Abstract:A heterostructured cathode having a graded bandgap window-layer is proposed in this study to improve the performance of photon-enhanced thermionic emission (PETE) solar energy converters. A model based on a one-dimensional steady-state equation is developed to analyze the characteristics of the proposed device. This model is used to calculate the conversion efficiency of a PETE device with an AlxGa1-xAs/GaAs cathode. The built-in electric field induced by the bandgap gradation in the window-layer is shown to improve the efficiency because of the reduction of contact surface recombination losses and efficient collection of photogenerated electrons. This field is unaffected by temperature variation, and the improvement of efficiency is sustained at elevated temperatures. The effect of window-layer parameters and cathode thickness on efficiency is discussed. We also show that the efficiency maximizes at lower temperatures for cathodes with lower electron affinities. Moreover an optimal value exists for anode work function at a given anode temperature, thus providing guidance for the optimum design of barrier conditions for both cathode and anode. ? 2014 Elsevier B.V. All rights reserved.Accession Number: 20144500158920 -
Record 403 of
Title:Nanotube-mode-locked fiber laser delivering dual-wavelength conventional and dissipative solitons
Author(s):Han, X.X.(1)Source: Laser Physics Volume: 25 Issue: 10 DOI: 10.1088/1054-660X/25/10/105101 Published: October 1, 2015Abstract:We propose a novel passively nanotube-mode-locked fiber laser, which consists of a linear oscillator generating conventional solitons (CSs) and a ring oscillator delivering dissipative solitons (DSs) simultaneously. The CSs exhibit distinct spectral sidebands with a bandwidth of ～0.53 nm and duration of ～5.47 ps, while the DSs have a quasi-rectangular spectral profile with a bandwidth of ～11.9 nm. The pulse duration of chirped DSs is ～5.30 ps and can be further compressed to ～0.55 ps external to the cavity. The experimental observations are well confirmed by numerical results. This compact all-fiber laser delivering two different types of ultrafast soliton simultaneously is quite cost-efficient for practical applications, such as optical communications, nonlinear optics and ultrafast optics. ? 2015 Astro Ltd.Accession Number: 20154201385781 -
Record 404 of
Title:Generation and three-dimensional characterization of complex nondiffracting optical beams
Author(s):Yu, Xiang-Hua(1); Yao, Bao-Li(1); Lei, Ming(1); Yan, Shao-Hui(1); Yang, Yan-Long(1); Li, Run-Ze(1); Cai, Ya-Nan(1)Source: Wuli Xuebao/Acta Physica Sinica Volume: 64 Issue: 24 DOI: 10.7498/aps.64.244203 Published: December 20, 2015Abstract:Nondiffracting optical beams play an important role in contemporary optics due to their special propagation characteristics, i.e., nondiffracting in a diffraction-free zone, shape recovering behind obstacles or self-healing property. Liquid crystal spatial light modulators (LC-SLM) are widely used for generating nondiffracting optical beams in virtue of programmable and dynamic features. In this paper, we propose a complex amplitude modulation technique that can encode any scalar complex fields for generating the complex nondiffracting beams. Before experiment, the phase modulation curve of the phase-only LC-SLM is optimized into being linear in a range of 0-2π by gamma correction in the way of variable binary phase gratings. Then, we experimentally generate the nonaccelerating beams, e.g., two zero-order Bessel beams with variable intensity distributions, and the nondiffracting petal-like beams generated by interfering with two coaxial Bessel beams. By scanning a reflection mirror near the focal region along the optical axis, a stack of two-dimensional images is acquired, and then a three-dimensional intensity profile of the beam is reconstructed with a software. We also experimentally demonstrate a new kind of multi-main-lobe accelerating beam with parabolic accelerating trajectory by modifying the spatial spectrum of classical Airy beam. Compared with the so-called vectorial accelerating beam with multiple main lobes in spheroidal coordinates, our generated two-main-lobe accelerating beam has a very high energy efficiency. The self-healing property of the two-main-lobe accelerating beam is also demonstrated. The presented technique can generate a variety of complex nondiffracting optical beams rapidly and obtain their threedimensional intensity distributions accurately, which has potential applications in the fields of optical microscope, optical date storage, optical trapping, optical micromachining, etc. ? 2015 Chinese Physical Society.Accession Number: 20160301816308 -
Record 405 of
Title:Accelerating nondiffracting beams
Author(s):Yan, Shaohui(1); Li, Manman(1); Yao, Baoli(1); Yu, Xianghua(1); Lei, Ming(1); Dan, Dan(1); Yang, Yanlong(1); Min, Junwei(1); Peng, Tong(1)Source: Physics Letters, Section A: General, Atomic and Solid State Physics Volume: Issue: DOI: 10.1016/j.physleta.2015.01.017 Published: December 03, 2014Abstract:We present a set of beams which combine the properties of accelerating beams and (conventional) diffraction-free beams. These beams can travel along a desired trajectory while keeping an approximately invariant transverse profile, which may be (higher-order) Bessel-, Mathieu- or parabolic-nondiffracting-like beams, depending on the initial complex amplitude distribution. A possible application of these beams presented here may be found in optical trapping field. For example, a higher-order Bessel-like beam, which has a hollow (transverse) pattern, is suitable for guiding low-refractive-index or metal particles along a curve. ? 2015 Elsevier B.V.Accession Number: 20202208734993 -
Record 406 of
Title:Metamaterial terahertz switch based on split-ring resonator embedded with photoconductive silicon
Author(s):Liu, Xinwang(1); Liu, Hongjun(1); Sun, Qibing(1); Huang, Nan(1)Source: Applied Optics Volume: 54 Issue: 12 DOI: 10.1364/AO.54.003478 Published: April 20, 2015Abstract:In this paper, a metamaterial terahertz (THz) switch based on a split-ring resonator embedded with photoconductive silicon is presented and numerically investigated. Simulation results show that the switch works at two different resonant modes with different pump light powers and that the response time of the switch is less than 1 ps. By defining the switching window as the frequency range where the transmission magnitude of the ON state is one order of magnitude higher than the OFF state, a switching window ranging from 1.26 to 1.49 THz is obtained. The large modulation depth of the switch is due to the large separations of the maximum and minimum transmissions, which are 0.89 and 0.01, respectively. Particularly, the switch is frequency tunable by changing the thickness and permittivity of the dielectric layer. ? 2015 Optical Society of America.Accession Number: 20153801292592 -
Record 407 of
Title:Coexistence of conventional solitons and stretched pulses in a fiber laser mode-locked by carbon nanotubes
Author(s):Li, W.L.(1); Kong, Y.C.(1); Chen, G.W.(1); Yang, H.R.(1)Source: Laser Physics Volume: 25 Issue: 4 DOI: 10.1088/1054-660X/25/4/045103 Published: April 1, 2015Abstract:We have proposed a nanotube-mode-locking fiber laser that can generate conventional solitons and stretched pulses in the same cavity. The net cavity dispersion of laser is slightly negative. The central wavelength and bandwidth of the conventional solitons are 1584.7 and 9.2 nm, respectively. The stretched pulse locates at 1572 nm with a bandwidth of 18.8 nm. The switchable mode-locking operation is mainly attributable to the bandwidth-dependent stretching factor that is tunable due to the spectral filtering effect induced by nonlinear polarization rotation. ? 2015 Astro Ltd.Accession Number: 20151400703810 -
Record 408 of
Title:Three types of pulses delivered from a nanotube-mode-locked fiber laser
Author(s):Yao, X.K.(1)Source: Laser Physics Volume: 25 Issue: 7 DOI: 10.1088/1054-660X/25/7/075101 Published: July 1, 2015Abstract:Three types of pulses are experimentally investigated in a switchable normal-dispersion nanotube-mode-locked fiber laser by adjusting polarizer controller and pump power. They are a standard dissipative-soliton (DS), conventional soliton (CS)-like pulse, and noiselike pulse, which correspond to three mode-locking states. The standard DS with a rectangular spectrum possesses a Gaussian-shape pulse. The CS-like operation has a Lorenz shape, and the spectrum involves several sidebands similar to the CS case. For the noiselike pulse with a bell-shaped spectrum, a 317 fs peak rides upon the 132.5 ps pedestal in the autocorrelation trace. The spectra of these three pulse operations are centered at three close wavelengths. The generation of three such different types of pulses in one identical normal- dispersion laser cavity may find an important application for the future of mode-locked laser research. ? 2015 Astro Ltd.Accession Number: 20152801019519