2019
2019
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Record 133 of
Title:Multiband phase-coded signal generation based on a simple photonic bi-phase modulator
Author(s):Gao, Yiran(1); Wu, Zhonghan(1); Dai, Jian(1,2); Xu, Kun(1)Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 11048 Issue: DOI: 10.1117/12.2518297 Published: 2019Abstract:A simple photonic approach for the multiband phase-coded microwave generation based on a dual-drive Mach-Zehnder modulator (DDMZM) is proposed. By injecting the 5-bit barker code sequence to the bias of DDMZM, the binary phase-coded microwave signal for multiband radar application is generated. A proof-of-concept experiment is performed. The generation of phase-coded signals tuning from 1 to 9 GHz with 1 to 20 Mbit/s coding rates is verified. ? 2019 SPIE.Accession Number: 20191006602278 -
Record 134 of
Title:Graphene Oxide Waveguide and Micro-Ring Resonator Polarizers
Author(s):Wu, Jiayang(1); Yang, Yunyi(1,2); Qu, Yang(1); Xu, Xingyuan(1); Liang, Yao(1); Chu, Sai Tak(3); Little, Brent E.(4); Morandotti, Roberto(5,6,7); Jia, Baohua(1,2); Moss, David J.(1)Source: Laser and Photonics Reviews Volume: 13 Issue: 9 DOI: 10.1002/lpor.201900056 Published: September 1, 2019Abstract:Integrated waveguide polarizers and polarization-selective micro-ring resonators (MRRs) incorporated with graphene oxide (GO) films are experimentally demonstrated. CMOS-compatible doped silica waveguides and MRRs with both uniformly coated and patterned GO films are fabricated based on a large-area, transfer-free, layer-by-layer GO coating method that yields precise control of the film thickness. Photolithography and lift-off processes are used to achieve photolithographic patterning of GO films with precise control of the placement and coating length. Detailed measurements are performed to characterize the performance of the devices versus GO film thickness and coating length as a function of polarization, wavelength and power. A high polarization dependent loss of ≈53.8?dB is achieved for the waveguide coated with 2-mm-long patterned GO films. It is found that intrinsic film material loss anisotropy dominates the performance for less than 20 layers whereas polarization-dependent mode overlap dominates for thicker layers. For the MRRs, the GO coating length is reduced to 50?μm, yielding a ≈8.3?dB polarization extinction ratio between transverse electric (TE) and transverse magnetic (TM) resonances. These results offer interesting physical insights and trends of the layered GO films and demonstrate the effectiveness of introducing GO films into photonic-integrated devices to realize high-performance polarization selective components. ? 2019 WILEY-VCH Verlag GmbH & Co. KGaA, WeinheimAccession Number: 20193407334319 -
Record 135 of
Title:Large-scale and uniform Raman substrate of coupled Ag grating with Ag triangle arrays
Author(s):Li, Kuanguo(1,2); Liu, Guangju(1); Ghafoor, Sonia(3); Dai, Yanqiu(3); Huang, Wanxia(1); Zhang, Fabao(1); Lu, Yonghua(3)Source: Journal of Optics (United Kingdom) Volume: 21 Issue: 3 DOI: 10.1088/2040-8986/ab0273 Published: February 14, 2019Abstract:Vertically coupled plasmonic structures have been widely used in optical applications due to its enhanced electromagnetic fields in the gaps between metallic nanostructures. In this paper, a large-scale vertically coupled structure composed of the Ag triangle array (AgTA) on Ag grating separated by a nanometric dielectric layer is fabricated by nanosphere lithography incorporated with photolithography. Thanks to the effective surface plasmon polaritons excitation on the Ag grating, a significant surface enhanced Raman spectroscopy (SERS) effect arises from a strongly enhanced local electric field within the tiny gaps between the AgTA and Ag grating, which is verified by experiment and theoretical simulations. The as-proposed SERS substrate exhibits a nice uniformity with the relative standard deviation of about 10.5%, leading to excellent reliability for Raman detection. The simple fabrication of the large-area, productive, and inexpensive vertically coupled plasmonic structure can be a potential candidate for SERS applications. ? 2019 IOP Publishing Ltd.Accession Number: 20191506771926 -
Record 136 of
Title:Nonlinear reconstruction of weak optical diffused images under turbid water
Author(s):Wang, Zhaolu(1); Liu, Hongjun(1,2); Huang, Nan(1); Zhang, Yongbin(1); Chi, Jiao(1)Source: Optics Letters Volume: 44 Issue: 14 DOI: 10.1364/OL.44.003502 Published: 2019Abstract:Forward scattering noise may degrade the imaging resolution and diffuse the image in turbid water. The reconstruction of diffused images hidden by forward scattering noise is crucial for underwater imaging. To overcome the limitation of forward scattering for optical imaging in turbid water, a nonlinear image reconstruction technology is proposed in the experiment. We experimentally demonstrated the reconstruction of the diffused images under turbid water via signal seeded incoherent modulation instability (MI) in a nonlinear photorefractive crystal. The reconstructed image with high quality and the minimum resolution of 28.51 lp/mm are observed in the experiment. This is the first time, to the best of our knowledge, that a spatial MI effect is used to process underwater weak optical diffused images in the experiment. ? 2019 Optical Society of America.Accession Number: 20193007222157 -
Record 137 of
Title:MAP Detection of Probabilistically Shaped Constellations in Optical Fiber Transmissions
Author(s):Hu, Shaohua(1); Zhang, Wenjing(1); Yi, Xingwen(2); Li, Zhaohui(2); Li, Fan(2); Huang, Xinning(3); Zhu, Mingyue(1); Jingzhang(1); Qiu, Kun(1)Source: 2019 Optical Fiber Communications Conference and Exhibition, OFC 2019 - Proceedings Volume: Issue: DOI: 10.1364/ofc.2019.w1d.3 Published: April 22, 2019Abstract:We present the theoretical analysis and experimental demonstration of MAP detection that outperforms the conventional detection for probabilistically shaped constellations in optical fiber transmissions. Larger BER improvements are observed for the stronger shaped constellations. ? 2019 OSA.Accession Number: 20192006917117 -
Record 138 of
Title:Design and magneto-optical characteristics of Ge–Sb–S–PbI2 chalcogenide glasses with a high Verdet constant
Author(s):Xu, Yantao(1,2); Guo, Haitao(1,2); Liu, Xiaogang(1); Cui, Jian(1,2); Xiao, Xusheng(1); Cui, Xiaoxia(1,2); Guo, Junjiang(1,2); She, Jiangbo(1,2); Lu, Min(1); Peng, Bo(1)Source: Journal of the American Ceramic Society Volume: 102 Issue: 11 DOI: 10.1111/jace.16551 Published: November 1, 2019Abstract:To develop high-performance magneto-optical chalcogenide glasses and clarify the mechanisms of the Verdet constant, a series of GeS2–Sb2S3–PbI2 chalcogenide glasses were designed and fabricated, and their Faraday effects were investigated at a wavelength of 980?nm. A new parameter, that is, average polarizability, was proposed, and the results show that the Verdet constant has a good linear relationship with average polarizability, meaning that the Verdet constant of a chalcogenide glass can be directly estimated by its chemical constituents. The Verdet constant is as large as 0.200?min?G?1?cm?1 at 980?nm for 22.5GeS2–67.5Sb2S3–10PbI2 composition glass, which is the largest value reported thus far for sulfide glasses; this glass also possesses good thermal and optical properties and therefore might be an attractive candidate for mid-infrared magneto-optical device applications. ? 2019 The American Ceramic SocietyAccession Number: 20193607408976 -
Record 139 of
Title:Semantic Descriptions of High-Resolution Remote Sensing Images
Author(s):Wang, Binqiang(1,2); Lu, Xiaoqiang(1); Zheng, Xiangtao(1); Li, Xuelong(3)Source: IEEE Geoscience and Remote Sensing Letters Volume: 16 Issue: 8 DOI: 10.1109/LGRS.2019.2893772 Published: August 2019Abstract:Image captioning has attracted more and more attention in remote sensing filed since it provides more specific information than traditional tasks, such as classification. Though image captioning has gained some developments in recent years, it is difficult to describe the image in one simple sentence. To relieve the limitation, a novel captioning task is proposed and a novel framework is proposed to solve the novel task. The proposed framework uses semantic embedding to measure the image representation and the sentence representation. The captioning performance is improved by a proposed sentence representation (collective representation). Experimental results and human evaluations on three captioning data sets in remote sensing field demonstrate that the proposed framework can lead to advancement in image captioning results. ? 2019 IEEE.Accession Number: 20193007231091 -
Record 140 of
Title:Sample and Structure-Guided Network for Road Crack Detection
Author(s):Wu, Siyuan(1); Fang, Jie(1,2); Zheng, Xiangtao(1); Li, Xijie(1)Source: IEEE Access Volume: 7 Issue: DOI: 10.1109/ACCESS.2019.2940767 Published: 2019Abstract:As an indispensable task for traffic management department, road maintenance has attracted much attention during the last decade due to the rapid development of traffic network. As is known, crack is the early form of many road damages, and repair it in time can significantly save the maintenance cost. In this case, how to detect crack regions quickly and accurately becomes a huge demand. Actually, many image processing technique based methods have been proposed for crack detection, but their performances can not meet our expectations. The reason is that, most of these methods use bottom features such as color and texture to detect the cracks, which are easily influenced by the varied conditions such as light and shadow. Inspired by the great successes of machine learning and artificial intelligence, this paper presents a sample and structure guided network for detecting road cracks. Specifically, the proposed network is based on U-Net architecture, which remains the details from input to output by using skip connection strategy. Then, because the scale of crack samples is much smaller than that of non-crack ones, directly using the conventional cross entropy loss can not optimize the network effectively. In this case, the Focal loss is utilized to address the model optimization problem. Additionally, we incorporate the self-attention strategy into the proposed network, which enhances its stability by encoding the 2-order information among different local regions into the final features. Finally, we test the proposed method on four datasets, three public ones with labels and a photographed one without labels, to validate its effectiveness. It is noteworthy that, for the photographed dataset, we design a series of image processing strategies such as contrast enhancement to improve the generalization capability of the proposed method. ? 2013 IEEE.Accession Number: 20200308030780 -
Record 141 of
Title:High performance photonic microwave filters based on a 50GHz optical soliton crystal Kerr micro-comb
Author(s):Xu, Xingyuan(1); Tan, Mengxi(1); Wu, Jiayang(1); Nguyen, Thach G.(2); Chu, Sai T.(3); Little, Brent E.(4); Morandotti, Roberto(5,6,7); Mitchell, Arnan(2); Moss, David J.(1)Source: arXiv Volume: Issue: DOI: 10.48550/arXiv.1903.08541 Published: February 21, 2019Abstract:We demonstrate a photonic radio frequency (RF) transversal filter based on an integrated optical micro-comb source featuring a record low free spectral range of 49 GHz yielding 80 micro-comb lines across the C-band. This record-high number of taps, or wavelengths for the transversal filter results in significantly increased performance including a QRF factor more than four times higher than previous results. Further, by employing both positive and negative taps, an improved out-of-band rejection of up to 48.9 dB is demonstrated using Gaussian apodization, together with a tunable centre frequency covering the RF spectra range, with a widely tunable 3-dB bandwidth and versatile dynamically adjustable filter shapes. Our experimental results match well with theory, showing that our transversal filter is a competitive solution to implement advanced adaptive RF filters with broad operational bandwidths, high frequency selectivity, high reconfigurability, and potentially reduced cost and footprint. This approach is promising for applications in modern radar and communications systems. Copyright ? 2019, The Authors. All rights reserved.Accession Number: 20200456016 -
Record 142 of
Title:Spatial structure preserving feature pyramid network for semantic image segmentation
Author(s):Yuan, Yuan(1); Fang, Jie(2,3); Lu, Xiaoqiang(3); Feng, Yachuang(3)Source: ACM Transactions on Multimedia Computing, Communications and Applications Volume: 15 Issue: 3 DOI: 10.1145/3321512 Published: August 2019Abstract:Recently, progress on semantic image segmentation is substantial, benefiting from the rapid development of Convolutional Neural Networks. Semantic image segmentation approaches proposed lately have been mostly based on Fully convolutional Networks (FCNs). However, these FCN-based methods use large receptive fields and too many pooling layers to depict the discriminative semantic information of the images. Specifically, on one hand, convolutional kernel with large receptive field smooth the detailed edges, since too much contexture information is used to depict the "center pixel." However, the pooling layer increases the receptive field through zooming out the latest feature maps, which loses many detailed information of the image, especially in the deeper layers of the network. These operations often cause low spatial resolution inside deep layers, which leads to spatially fragmented prediction. To address this problem, we exploit the inherent multi-scale and pyramidal hierarchy of deep convolutional networks to extract the feature maps with different resolutions and take full advantages of these feature maps via a gradually stacked fusing way. Specifically, for two adjacent convolutional layers, we upsample the features from deeper layer with stride of 2 and then stack them on the features from shallower layer. Then, a convolutional layer with kernels of 1 × 1 is followed to fuse these stacked features. The fused feature preserves the spatial structure information of the image; meanwhile, it owns strong discriminative capability for pixel classification. Additionally, to further preserve the spatial structure information and regional connectivity of the predicted category label map, we propose a novel loss term for the network. In detail, two graph model-based spatial affinity matrixes are proposed, which are used to depict the pixel-level relationships in the input image and predicted category label map respectively, and then their cosine distance is backward propagated to the network. The proposed architecture, called spatial structure preserving feature pyramid network, significantly improves the spatial resolution of the predicted category label map for semantic image segmentation. The proposed method achieves state-of-the-art results on three public and challenging datasets for semantic image segmentation. ? 2019 Association for Computing Machinery.Accession Number: 20193707423899 -
Record 143 of
Title:Microwave Q-band oscillator at 49GHz for broadband frequency conversion based on a Kerr optical soliton crystal micro-comb
Author(s):Xu, Xingyuan(1); Wu, Jiayang(1); Tan, Mengxi(1); Nguyen, Thach G.(2); Chu, Sai T.(3); Little, Brent E.(4); Morandotti, Roberto(5,6,7); Mitchell, Arnan(2); Moss, David J.(1)Source: arXiv Volume: Issue: DOI: null Published: July 21, 2019Abstract:We report a broadband microwave frequency converter based on a coherent Kerr optical micro-comb generated by an integrated micro-ring resonator. The coherent micro-comb displays features that are consistent with soliton crystal dynamics with an FSR of 48.9-GHz. We use this to demonstrate a high-performance millimeter-wave local oscillator at 48.9-GHz in the Q-band for microwave frequency conversion. We experimentally verify the microwave performance up to 40 GHz, achieving a ratio of ?6.8 dB between output RF power and IF power and a spurious suppression ratio of > 43.5 dB. The experimental results show good agreement with theory and verify the effectiveness of microwave frequency converters based on coherent optical micro-combs, with the ability to achieve reduced size, complexity, and potential cost. Copyright ? 2019, The Authors. All rights reserved.Accession Number: 20200461960 -
Record 144 of
Title:Speckle Effect on Active Illuminated Intensity Correlation Imaging
Author(s):Li, Chong(1); Gao, Xin(1); Qin, Xing(2,3); Li, Xi-Yu(1); Lu, Chang-Ming(1)Source: Guangzi Xuebao/Acta Photonica Sinica Volume: 48 Issue: 1 DOI: 10.3788/gzxb20194801.0111004 Published: January 1, 2019Abstract:The principle of intensity correlation imaging is demonstrated in this paper. Besides, the speckle effect of illumination laser is analyzed and the influence on spectral modulus induced by speckle effect is also analyzed with the aid of simulation. The digital micromirror array is used to design the experiment. Utilizing the wavefront data measured by the adaptive optical telescope, the rotational state of digital micromirror array can be set. Hence, the information of intensity fluctuation from different targets can be obtained. Then, the image restoration can be realized using prior information iteration algorithm. The results show that the intensity fluctuation of the target speckle light field obeys the negative exponential distribution. Apart from that, the speckle light field makes the error of the high frequency part of the target spectral modulus. Using the prior information iteration algorithm can recover the target image well, and the peak signal-to-noise ratio of the target recovery image can reach up to 29.87 dB. ? 2019, Science Press. All right reserved.Accession Number: 20191206655203