查看更多>>摘要：The length of an erbium-doped fiber laser is optimized to develop a dual-wavelength nonlinear polarization rotation mode-locked erbium-doped fiber laser. The mode-locked laser can emit two stable wavelengths of 1530 nm and 1558 nm with a fiber length of 570 cm. With the absorbed pump power of 150 mW, the maximum average output power of 19.2 mW with the repetition frequency of 11.95 MHz and pulse width of 389 fs is obtained.
查看更多>>摘要：The scattering and absorption of particles in underwater environment seriously affect the quality of underwater images, resulting in reduced contrast and imaging quality. In this work, the underwater active polarization dehazing imaging based on the deep learning model is studied. A modified lightweight dehazing convolutional neural network (CNN) model with four input channels is designed by combining both the advantages of the deep learning and polarization dehazing imaging technology. The lightweight CNN is trained and tested with the images of different polarization components (00, 450, 900 linear polarization and circular polarization) in different turbidity underwater environments. The experimental results show that this method can rapidly achieve the better dehazing imaging effect than that of conventional dehazing methods.
查看更多>>摘要：To improve the optical performance of the large-aperture optical antenna, the Cassegrain splicing receiving antenna consisting of spherical sub-mirrors with different curvatures is designed and optimized based on the three-dimensional (3-D) vector theory of rotation and reflection. Compared with the splicing antenna consisting of spherical sub-mirrors with the same curvatures, the antenna proposed in this paper can decrease the root mean square (RMS) of the spot radius at the receiving plane from 0.0202223 m to 0.0109724 m, and the spot size decreases 45.74%. Besides, the influence of on-axial defocusing and incident ray tilt on the performance of the optical antenna is analyzed. This paper provides not only a new antenna with better performance but also a new idea for designing large-aperture splicing optical antennas.
查看更多>>摘要：A high sensitive optical fiber refractive index (RI) sensor based on Mach-Zehnder interferometer (MZI) is proposed. The sensor consists of single mode fiber-multimode fiber-photonic crystal fiber-single mode fiber (SMPS) structure using fusion technology. The experimental results have shown that the RI sensitivity of the SMPS structure is as high as 342.78 nm/RIU in the range of 1.3330-1.3775. Meanwhile, the effects of different length of PCF on the RI are also investigated. It was found that the shorter the length of PCF, the higher the sensitivity. In addition, a temperature sensitivity of 16.37 pm/celcius for the sensor is achieved. The sensor has advantages of high fringe visibility over 20 dB and simple fabrication, which has displayed great potential in the field of RI measurement.
查看更多>>摘要：We study the effect of a three-dimensional extremely short optical pulse in a medium with chiral carbon nanotubes on the order parameter of this medium. The possibility of the appearance of a phase transition in such a medium is shown. We investigate the dependence of the pulse shape on the relaxation rate of the order parameter and on the parameter beta in the Landau expansion of free energy.
查看更多>>摘要：The Wigner distribution one of the most celebrated time-frequency tool for analyzing non-transient signals and has been widely employed in signal processing and other allied fields. In this article, we introduce a novel quadratic-phase Wigner distribution (QWD) by intervening the advantages of quadratic-phase Fourier transforms and Wigner distribution. We initiate our investigation by studying the fundamental properties of the proposed distribution, including the marginal, shifting, conjugate-symmetry, anti-derivative, Moyal's and inversion formulae by using the machinery of quadratic-phase Fourier transforms and operator theory. Moreover, the convolution and correlation theorems associated with QWD are derived. Finally, we broaden the scope of the proposed distribution by detecting the parameters of the linear frequency modulated signals.
Hegde, VinodKamath, Sudha D.Kebaili, ImenSayyed, M. I....
13页
查看更多>>摘要：In this study, highly Eu3+-doped (up to 5 mol%) 10ZnO-40Bi(2)O(3)-50B(2)O(3) glasses were prepared by melt quench process. The excitation and emission results of the prepared glasses were recorded in the visible region. The Judd-Ofelt intensity and CIE chromaticity parameters of the glasses were calculated and discussed. The nonlinear optical properties of glasses were studied at a pumping wavelength of 532 nm under a nanosecond regime utilizing the sensitive Z-scan technique. We investigated the linear attenuation coefficient (LAC) for the prepared glasses for energies ranging from 0.296 to 1.458 MeV. According to the Z(eff) results, 10ZnO-40Bi(2)O(3)-45B(2)O(3)-5Eu(2)O(3) exhibited good attenuation properties among the fabricated samples.
Ye, QingLiang, ZhenghaoZhong, HaoxinZhang, Yongmei...
14页
查看更多>>摘要：Aiming at the problem of confusion of recognition categories caused by insufficient feature information extraction and insufficient use of time correlation information between video frames in human behavior recognition, we propose a human behavior recognition algorithm based on time correlation sampling two-stream heterogeneous grafting network. In the video sampling, we adopt the time correlation sampling of video frames based on the TRN algorithm to remove redundant information in adjacent frames and make full use of the time correlation between different video stages. Based on their changes in the time dimension, many easily confused behaviors can be well distinguished. Due to the complexity and diversity of behavior feature information, we propose a two-stream heterogeneous network based on the basic structure of the traditional two-stream network. In order to improve the efficiency of network convolution kernel, filter weight grafting is carried out for invalid filters in DenseNet network and BNIception network based on filter grafting technology. It can effectively improve the network model's ability to express feature information. Then the improved DenseNet network and BNIception network are used to form a two-stream heterogeneous network to extract spatial and temporal information. The experimental results show that the accuracy of this method in UCF101 dataset and in KTH dataset are respectively 89.3% and 92.1%, which proves the effectiveness of the algorithm.
查看更多>>摘要：This work presents two 4-mode, broadband, low loss, compact, and fabrication tolerant (de) multiplexers comprised of a 1 x 4 mode converter-splitter, multimode interferometer MMI, and phase shifter devices. The first device is designed using conventional waveguides. The second one is built utilizing subwavelength grating technology introduced in the multimode section of the MMI coupler. To the best of our knowledge, this is the first demonstration of a 4 x 4 (de) multiplexer based on a SWG-MMI coupler. Both devices are built in a silicon-on-insulator (SOI) platform. In the operation of the designed devices, four input modes TE0, TE1, TE2, and TE3 are split and converted into a fundamental TE0 mode at the output end. 80 nm (1510-1590 nm) operating bandwidth, losses -15 dB are achieved from the conven-tional version of the (de)multiplexer, while 140 nm (1480-1620 nm), losses -0.5 dB, and crosstalk <-15 dB, are achieved from the subwavelength grating assisted device. The overall size of the designed devices is 4.5 x 173 mu m(2) and 4.5 x 123 mu m(2), for the conventional and sub-wavelength grating devices, respectively. Subwavelength grating technology offers flexibility in refractive index engineering for extra bandwidth (75% additional bandwidth) and compactness (30% size reduction) compared to the conventional counterpart.
查看更多>>摘要：SiO2 films were deposited on fused silica substrates by ALD technology. The properties of ALD SiO2 films irradiated by femtosecond laser were investigated. Raman spectra confirms the molecular structure of SiO2 films is identical to that of fused silica. The relative content of the three and four-membered ring of films irradiated is increased. Photoluminescence (PL) spectra shows that the defects of the films irradiated by laser of 10% power ratio are reduced. Indentation tests show that both hardness and elastic modulus are decreased by 1.8%, their standard deviations are decreased by 73.8% and 46.8% respectively. Scratch experiments exhibit that femtosecond irradiation improves the bonding performance of the films, and the critical load is increased by 10.8%. Meanwhile, the standard deviations of the lateral load and penetration depth are decreased on average from 0.0636 to 0.0336, from 8.3478 to 1.6747, individually. The plastic deformation ratio of the films are increased from 19.80% to 28.89%. The morphology and cross section of the scratches observed by optical microscopy and confocal laser microscopy suggest that the damage form of the films irradiated by laser is changed from the brittle fracture removal form to the mixed removal form of brittle fracture and plastic.
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Elsevier