查看更多>>摘要：In this paper, an optical single-sideband (OSSB) modulation radio over fiber (RoF) link with tunable optical carrier-to-side-band ratio (OCSR) and simultaneous third-order intermodulation distortion (IMD3) and power fading suppression is proposed. In the proposed link, a phase-modulated signal and an optical carrier are polarization multiplexed using a Sagnac loop. The periodic power fading caused by chromatic dispersion is avoided by filtering the lower sideband. By adjusting the polarization state, the IMD3 is suppressed and a tunable OCSR can be achieved. Compared with the traditional Mach-Zehnder modulator (MZM) based link, the spurious free dynamic range (SFDR) of the proposed link is improved by more than 18 dB with different RF frequencies. In the broadband characteristic test, the proposed link exhibits lower error vector amplitude (EVM) and higher adjacent channel power ratio (ACPR) in a larger input RF power range.
查看更多>>摘要：In order to effectively improve the information carrying capacity of modern wireless communication systems, vortex beams with orbital angular momentum (OAM) have attracted extensive attention due to extending communication capacity through orthogonal channels with different OAM modes carrying different information. However, the reported studies are only concentrated on single-function vortex beam. Here, we propose a notched concave metasurface to generate for multifunctional vortex beams such as four vortex beams, focusing vortex beams, deviation focusing vortex beams, and multi-beam vortex beam under different polarization. The theoretical results show good agreements with the full-wave simulations. The designed metasurface enables diversified promising applications for flexible manipulation OAM and terahertz wave polarization detection in future terahertz wireless communication.
Nikitin, Andrey A.Ryabcev, Ilya A.Nikitin, Aleksei A.Kondrashov, Alexandr, V...
5页
查看更多>>摘要：The present work focuses on experimental investigations of a bistable silicon-on-insulator (SOI) microring resonator (MRR). The resonator exploits a continuous-wave operation of the carrier-induced bistability demonstrating a stable hysteresis response at the through and drop ports when the input power exceeds the threshold value. Flipping the optical input power provides a convenient mechanism for a switching of the MRR output characteristics between two steady states having a long holding time. The transition of the resonator output between these states is experimentally investigated. It is shown that the switching speed is limited by a low-to-high transition of 188 ns. Obtained results shows an application of the passive SOI MRR as an all-optical memory cell with two complementary outputs.
查看更多>>摘要：We demonstrate an all-fiberized ytterbium-doped fiber laser (YDFL) at 1104.9 nm with a high optical signalto-noise ratio (OSNR) by using ytterbium gain purely. The system is built based on FBG-based master oscillator power amplifier (MOPA) configuration, producing 1.5-kW power with a near-diffraction-limited beam quality (M-2-1.4) and a narrow spectral linewidth (FWHM-70 GHz). The OSNR is-33 dB. A theoretical model is developed to calculate the amplified spontaneous emission (ASE) in the final amplifier. Both the calculated and experimental results suggest that the ASE or even parasitic lasing is the primary limitation for further power scaling. To the best of our knowledge, in > 1100 nm wavelength range, this is the highest output power narrow spectral YDFL (with < 100 GHz 3-dB spectral width) by using FBG-based MOPA configuration.
查看更多>>摘要：In this paper, we investigate the physical layer security for a reconfigurable intelligent surface (RIS)-aided heterogeneous visible light communication (VLC) and radio-frequency (RF) network with two legitimate user equipments (UEs) in cooperative nonorthogonal multiple access (NOMA). An external eavesdropper (Eve) tries to eavesdrop the information from the cooperative channel. Since VLC is mainly available for line-of-sight path, and the UEs and Eve under the worktable cannot directly receive signals from the optical access point, a device is naturally employed to perform optical-electrical conversion and RF transmission. Further the device and RIS are jointly employed to eliminate blind spots and extend communication coverage. With these settings, the statistical characteristics of the VLC link and RF link are determined based on the feature of the optical channel and the RIS-aided wireless channel, respectively. The close-form expression of the secrecy outage probability for the proposed RIS-aided heterogeneous VLC-RF cooperative NOMA network is derived. Simulation results show the secrecy outage performance of the proposed network depends on not only the reflecting meta-surface number of the RIS, the power allocation based on NOMA, but also the tradeoff design between the optical and electrical parameters.
查看更多>>摘要：We experimentally demonstrated a high sensitivity chaotic correlation fiber loop ring down sensing based on U-shaped fiber optical sensor. The U-shaped fiber optical sensors with different bending diameters were spliced into fiber loops with different cavity lengths to study the influence of cavity length and bending diameter on detection sensitivity. The relationship between cavity length and sensitivity was investigated theoretically and experimentally. The limit of sensitivity was analyzed theoretically and the highest sensitivity of 2253.390 mu s-1RIU-1 in the refractive index range of 1.3347-1.3721 was realized experimentally. A handheld probe measuring device was obtained by combining short cavity fiber loop ring down and U-shaped fiber optical sensor, and the probe device can achieve the detection of hemoglobin level with the high sensitivity.
查看更多>>摘要：Plasmonic nanoantenna has received tremendous attention in various optoelectronic applications owing to their unique optical characteristics with strong localized electric field enhancement. However, the highly intrinsic dissipation losses of metallic nanoantennas limits its application development. Coupling anapole modes of dielectric nanostructure with plasmonic mode of metallic nanoantenna seems to provide a promising alternative to further boost the electric field intensity with low dissipation losses. Herein, we demonstrate that the electric field intensity from a metallic nanoantenna can be remarkably heightened through introducing a dielectric nanostructure to build hybrid dielectric-metal nanoantenna, where the hybrid nanoantenna is composed of a gold nanorod dimer and a slotted silicon nanodisk. Through rationally optimizing the structural parameters, the hybrid nanoantenna exhibits an intensified resonant electric field intensity (> 3700 folds) at the gap of the dimer nanoantenna, which exceeds 30 times higher than that of the individual dimer nanoantenna. The far-field scattering characteristics and the near-field electromagnetic field distributions are systematically investigated to elucidate the field enhancement mechanism via utilizing numerical simulations and multipole decomposition analysis. It can be confirmed that the highly electric field intensity can be primarily attributed to the mode coupling between plasmonic resonances of Au nanoantenna and the radiationless anapole modes supported by the slotted Si nanodisk. The proposed hybrid dielectric-metal nanoantenna can serve as an effective platform to amplify the radiative decay rate and Raman scattering intensity, which paves a prospective avenue in the field of single-molecule surface enhanced spectroscopy.
查看更多>>摘要：Ultrafast carrier dynamics and terahertz conductivity of intrinsic 6H-SiC are investigated by optical-pump terahertz-probe spectroscopy at room temperature. The amplitude of photoinduced absorption increases gradually and followed by a biexponential recovery with photogenerated carrier densities from 7.43 x 10(17) to 2.81 x 10(18) cm(-3) at 400 nm. With the increase of photogenerated carrier density, the fast decay time decreases may be due to higher order recombination (i.e., Auger recombination), and the slow one increases is related to the band-filling effect. The evolution of complex conductivity with photogenerated carrier density at the delay time of about 50 ps can be better fitted with Drude-Smith model than Drude-Lorenz model. The Drude-Smith scattering time T(DS)and Smith parameter c(1) increase with photogenerated carrier density implies carriers backscattering is dominant. Our analysis provides important basic data for research and improvement ultrafast semiconductor devices of intrinsic 6H-SiC.
查看更多>>摘要：Whisper gallery mode (WGM) resonances and the coupling of excitons and WGMs are measured from ZnO microrod cavity in the visible and ultraviolet spectral ranges. The coupling of excitons and WGMs leads to split modes which exhibit a clear spatial dependence due to the uneven field distribution of WGM on ZnO microrod surface. Polarization dependent behavior together with a blueshift of the upper polariton branch mode are observed owing to the transition polarization of different types of excitons in the ZnO microcavity. Numerical simulations are carried out using finite element method to support the experimental results. This work reveals the spatial and polarization dependent exciton-photon coupling in a ZnO microrod which implies promising applications in photonic polariton field ranging from ultraviolet lasers, high-sensitivity detectors to optoelectronic devices
查看更多>>摘要：We propose a joint monitoring scheme of optical signal-to-noise ratio (OSNR) and frequency offset (FO) based on the analysis of a quadrature phase-shift keying training sequence (QPSK-TS) spectrum for coherent optical fiber communication systems. In the proposed scheme, the FO estimation (FOE) consists of a coarse FOE stage and a fine FOE stage. Firstly, the coarse FOE stage is operated by searching for the peak of QPSK-TS spectrum. Then, after conducting coarse FO compensation (FOC) and down-sampling process to the QPSK-TS signal, the fine FOE stage can be realized by operating fast Fourier transform (FFT) to the 4th power of the signal. Compared with the traditional FOE scheme based on FFT with 4th-power operation, the FOE range of the proposed scheme can be extended to 3 times without losing the FOE resolution. After the FOC procedure with the proposed FOE scheme, OSNR can be monitored accurately by obtaining the whole in-band amplified spontaneous emission (ASE) noise from QPSK-TS spectrum. It is noteworthy that both the proposed FOE scheme and the OSNR monitoring scheme are insensitive to chromatic dispersion (CD) and intra-channel nonlinearity (NL). Simulation results for a 28 GBaud system with 2400 km transmission length show that when the OSNR range is 10 & SIM;28 dB and FO is 10.25 GHz, the mean OSNR estimated error is < 0.9 dB and the standard deviation is < 0.3 dB. Furthermore, the back-to-back (B2B) experiment results with 20 GBaud show that when the OSNR range is 10 & SIM;26 dB and FO is 7 GHz, the mean OSNR estimated error is < 0.8 dB and the standard deviation is also < 0.3 dB.
NSTL
Elsevier