查看更多>>摘要：The modulating retro-reflector (MRR) communication is developed to solve the problem of insufficient terminal power in underwater optical communication (UOC) where size, weight and power are severely restricted. Here, we propose a new MRR link scheme using the optical orbital angular momentum (OAM) for such scenarios to realize high-order coding. Furthermore, we simulate the OAM MRR link in the oceanic turbulence channel and use the convolutional neural network (CNN) to classify OAM patterns. The simulation results show that the OAM MRR link can realize error-free image transmission under weak turbulence strength of C-n(2)& nbsp;= 10(-15)K(2)m(-2/3) within 15 m distance using 8/16-ary OAM superposed modes, and with the increasing of the distance and the turbulence strength, the performance is decreasing, where the 16-ary format has a higher coding efficiency but lower performance than the 8-ary format. An experiment of the OAM MRR link using CNN to classify 16-ary OAM superposed modes is also demonstrated, where two space light modulators (SLMs) are used to simulate the short-distance oceanic turbulence channel and modulate the OAM beam, respectively. Our experiment result shows the recognition rate of 16-ary OAM set with different types of channel conditions. Our work may provide a novel way for high-order coding MRR links in underwater channels and hopefully increase the data rate of the MRR link in the future.
查看更多>>摘要：Wireless optical communication (WOC) through the atmosphere-ocean system is fundamentally complex because of the diversity, concentration, types and vertical thickness of the constituents and poses a major challenge from the optical characteristics of bubbles at the air-sea interface and water constituents (phytoplankton, suspended sediments, and dissolved organic matter), and stratification (medium inhomogeneity). The present study aims to analyse the effects of atmospheric aerosols (their intensity, diversity, and vertical thickness), waves/bubbles at the air-sea interface, seawater constituents (phytoplankton, suspended sediments, and dissolved organic matter), and medium inhomogeneity along the path between a laser transmitter in the airborne platform and a receiver in the underwater platform using Monte Carlo technique. For the first time, our analysis showed that for a homogeneous atmosphere-ocean channel (7 km in the atmosphere column and 42 m in the ocean medium), the estimated normalized received power reduced to 17 dB and the time delay spread increased to 1.01 ns (considering a receiver of 7 '' and an aperture FOV of 180 degrees) when compared to those values for a stratified atmosphere-ocean channel. The bubbles (both clean and coated) relative to the particulates in open oceanic water under high wind speeds have a significant impact on the spatio-temporal spread of the laser beam. There is also a well pronounced effect of coated bubbles on the received signal power in open ocean water. In contrast, the particulates have a higher impact on the received signal power than the clean/coated bubbles in turbid coastal water. These results suggest that the normalized received power when calculated for the cases of dense bubble populations under high wind speeds (at a wind speed 18 ms(-1)) reduced to 8-9 dB and increased to 0.0025 scintillation index. The coated bubbles at the air-water interface reduced the normalized received power by 1.41 dB compared to the clean bubbles. Further, our analysis indicated that the expansion of beam width and the reduction of beam divergence angle can be utilized to mitigate the performance degradation (power loss) caused by bubbles at the air-sea interface. These results and analyses will be helpful for a system designer to accurately define/decide the system parameters and build a functional communication system for the inhomogeneous atmosphere-ocean system.
查看更多>>摘要：This paper has investigated the transmission characteristics of inverse polarizing gratings with tapered slits in the deep ultraviolet band. It is demonstrated that the extraordinary suppressed transmission (EOST) of TM-polarized light can be boosted up by tapered slits. The exit and entrance aperture widths of the tapered slits play a crucial role in polarization transmission, not the taper angle. The TM transmission valley and extinction ratio peak appear about the same exit aperture width for different grating heights. The phenomenon can be partly explained as the exit aperture width satisfying the charge movement is in a low-frequency mode to suppress TM transmission further. The presented results provide the basis to quickly focus the structural parameters of grating with excellent polarization performance.
查看更多>>摘要：In this paper, a new design method of structural absorbers was proposed by frequency characteristic analysis of reflectivity function. A simplified Jaumann absorber is discussed, by taking derivation of the reflectivity function and monotonicity analyzing, the contribution of design parameters of the absorber to the reflectivity is determined. For a series of reflectivity targets, the value ranges of the thickness and permittivity of dielectric layer, and the square resistance of resistive layer were calculated. Physical samples were prepared for verification, with quartz plates as dielectric layers, and magnetron sputtered Ni-Cr film as resistance layer. Continuous effective bandwidths below -10 dB in 6.2~& nbsp;18 GHz band and below -15 dB in 8.2~& nbsp;16 GHz band were obtained respectively, and their frequency characteristics are consistent with the results of mathematical analysis.
查看更多>>摘要：We present a new type of polarization-maintaining supermode fiber which can separate adjacent modes from each other. The proposed polarization-maintaining supermode fiber features an octagonal core composed of multiple high-refractive-index circular holes. By using high refractive index cores and setting the angle subtly between the cores, the fiber proposed can support 22 modes with different polarization states under two parameters in the entire C-band. Through the finite element method simulation, we conducted simulation study to analyze the influence of the angle between the cores and the core diameter on the performance of the optical fiber. In addition, we analyzed effective refractive index difference (d(neff)) and effective modal area (A(eff)) of the fiber for each characteristic mode. The differential mode delay (DMD) under different cores angle is also calculated. Numerical results present that the minimum A neff of the octagonal polarization-maintaining supermode fiber in the entire C-band under the two parameters is greater than 1.1 x 10(-4). It was measured to have good tolerance under the condition of unsatisfactory structure. These results indicate that the proposed fiber is superior candidate for improving the optical transmission capacity in the transmission of the mode division multiplexing system.
查看更多>>摘要：Owe to the ability of supporting propagating surface plasmons, silver nanowire can be decent candidate as optical nanoantenna to modulate the polarization property of nano-emitters. Here, we created a quantum dots and silver nanowire coupling system to implement the controllable polarization dependence of this antenna effect. Several basic modes are mainly explored with both positive and negative excitation and observation directions. For the contrast excitation directions, both the center and the end fluorescence spots have reverse polarization dependence characterizations. While the controllable polarization dependence only appears at the center spot for the different observation angles. Based on these modes, diverse polarization dependence properties can be extended flexibly. The reasons for the phenomena are explained using the theoretical simulation. The numerical calculation shows the silver nanowire can act both optical receiving antenna and transmitting antenna in this process. Achieving on the controllable polarization dependence, our results are useful in the investigation about the coupling of nano-emitters and optical antenna.
Kazemzadeh, MohammadrahimHisey, Colin L.Zargar-Shoshtari, KamranXu, Weiliang...
9页
查看更多>>摘要：Machine learning has shown great potential for classifying diverse samples in biomedical applications based on their Raman spectra. However, the acquired spectra typically require several preprocessing steps before standard machine learning algorithms can accurately and reliably classify them. To simplify this workflow and enable future growth of this technology, we present a unified solution for classifying biological Raman spectra without any need of prepossessing, including denoising and baseline establishment. This method is developed based on a custom version of a convolutional neural network (CNN) elicited from ResNet architecture, combined with our proposed data augmentation technique. The superiority of this method compared to conventional classification techniques is shown by applying it to Raman spectra of different grades of bladder cancer tissue and surface enhanced Raman spectroscopy (SERS) spectra of various strains of E. Coli extracellular vesicles (EVs). These results demonstrate that our method is far more robust compared to its conventional counterparts when dealing with the various kinds of spectral baselines produced by different Raman spectrometers.
查看更多>>摘要：In this paper, we propose an augmented reality (AR) autostereoscopic three-dimensional (3D) display based on sparse reflection array (SRA). The proposed display consists of a transparent light-emitting diode (LED) display panel and a periodic SRA. Benefiting from the advantages that most areas of the LED display panel are transparent and the arrangement of the SRA is periodic, the proposed display can realize a good fusion of real 3D objects and virtual 3D images. In addition, the proposed display has a higher light transmittance of the real-world object than the traditional parallax barrier based autostereoscopic 3D display and has a thinner thickness than the traditional lenticular lens barrier based autostereoscopic 3D display. An optical experiment of the proposed display is developed, and the experimental results show that the proposed display has a better display performance compared with the conventional AR autostereoscopic 3D display. Moreover, the proposed display is simple, which is more conducive to achieving practical applications in large-scene AR exhibition systems, glass curtain walls, and outdoor advertisements.
查看更多>>摘要：We study theoretically and numerically the manipulation of Raman-induced frequency shift (RIFS) with chirped Airy pulse in the optical fiber. The results show that the blue-shift of Airy pulse increases with the increase of the positive chirp parameter and so the RIFS can be suppressed. The red-shift of Airy pulse increases with the increase of the truncation coefficient and so the RIFS can be enhanced. In addition, the effect of the initial pulse width on the RIFS is discussed. The results show that the larger the launched pulse width, the stronger the RIFS of the pulse. And it is more obvious to suppress the RIFS with the increase of the positive chirp. Therefore, the RIFS of Airy pulse can be controlled effectively by adjusting the chirp or the truncation coefficient with different initial pulse width.
查看更多>>摘要：In this paper, the pre-configured Kramers-Kronig (Pre-KK) scheme combined with the chromatic dispersion pre-compensation (CDPC) has been proposed and studied to reduce the complexity of DSP and hardware implementation at the optical network unit (ONU) side for passive optical network (PON), avoiding the use of KK receiver. For further analysis and verification, 100 Gb/s/lambda PON downstream transmissions with 4-level pulse amplitude modulation (PAM-4) signal based on the Pre-KK scheme and KK receiver have been implemented and compared on a unified optical system platform. The results show that the Pre-KK requires 1-bit resolution lower than KK receiver for ADC, and achieves a power budget of 29 dB after 20 km fiber transmission at the strong FEC threshold of 1 x 10(-2). By increasing the launch power, the maximum power budget of 33.2 dB can be achieved due to the fiber nonlinearity. The effectiveness of CDPC in Pre-KK scheme has also been investigated and demonstrated over 20 and 50 km transmission. Besides, the computational complexities of two schemes are analyzed and discussed in detail. Hence, the Pre-KK scheme joint with CDPC can be a promising solution for the high-speed PON downstream transmission.
NSTL
Elsevier