查看更多>>摘要：The influence of extrusion on the properties of chalcogenide glasses and fibers was investigated systematically via measuring and analyzing their structural and physical properties of Ge10As22Se68 and As2S3. The experimental results showed that the extrusion processing has an insignificant effect on the glass network, crystallization, and compositions, but does have an influence on the glass transmission rate, refractive index and density. Meanwhile, the fiber loss after extrusion processing was greatly improved with 57.65% or 71.43%, corresponding to Ge10As22Se68 or As2S3 fiber, respectively.
查看更多>>摘要：We present a demonstration of flash resonance Raman lidar for leak detection of SO2 gas. An optical parametric oscillator (OPO) with a deep UV tuning range around 217.0 nm corresponding to an electronic absorption band of SO2 gas has been utilized to monitor the 3D leakage of SO(2 )gas occurring 2 m away and to explore the wavelength dependence of the resonance Raman effect for SO2 gas. We believe this new efficient gas sensing technique provides an attractive alternative to conventional 3D lidar sensing based on the mechanical scan.
查看更多>>摘要：In this paper, we investigate the system model of intensity modulation with direct detection (IM/DD)-based high-speed short-reach link with directly modulation laser (DML) and bandwidth-limitation optics devices. And, based on this model, we propose a modified Volterra equalizer to compensate distortion by constructing second-order feature vectors for support vector machine (SVM) trainer in this high-capacity and limited bandwidth system. Owing to high-dimensional mapping characteristics of SVM, for our scheme, only a single classification hyperplane is needed to be trained to achieve satisfactory equalization performance for the multi classification tasks of PAM-M, which would reduce the calculation complexity. Moreover, the 80-Gb/s PAM-4 per wavelength transmission experiment with 10-G optics in 20-km standard single mode fiber (SSMF) DML system is conducted and utilized to manifest the feasibility and effectiveness of our scheme. The results show that our scheme can reach the HD-FEC threshold and achieve outstanding performance than commonly used equalizers.
查看更多>>摘要：Long-distance coupling between two optical cavities is enabled through a taper fiber. Phase shift and loss induced by the taper lead to complex coupling strength and hence observation of various distinctive coupling conditions like exceptional points, bound state in the continuum, and dissipative coupling with optothermal effect. Large tunability of coupling conditions is demonstrated via controlling the translation stage, as manifested in the transmission spectrum. Theoretical prediction and simulation coincide well with experimental measurement. Lastly, we propose to advance the role of taper for application in taper-based sensing and optomechanics.
查看更多>>摘要：An all fiber temperature compensated curvature sensor with insensitive axial strain is proposed and experimentally demonstrated. The sensor is fabricated by a 2 cm ring core fiber (RCF) which is spliced between single mode fibers (SMFs) with two up-tapers, and a Mach-Zehnder Interferometer (MZI) is formed. The simulation results show that the first up-taper scatters a portion of the input light that should be in the ring core into the outer cladding, and then the ring core modes interfere with the cladding modes distributed in both inner cladding and outer cladding. The interference dips of this structure respond differently to curvature and temperature, so a calibration matrix can be established to implement temperature compensation. Experimental results show that this structure offers a maximum curvature sensitivity of -3.504 nm/m(-1) in the range from 1.316 m(-1) to 2.372 m(-1) with a high linear regression coefficient value of 0.9971, and a maximum temperature sensitivity of 59.42 pm/degrees C is obtained in the range from 25 degrees C to 60 degrees C. We also test the axial strain characteristics of this structure and the results imply a minimum cross sensitivity of 8.086 x 10(-5) m(-1)/mu epsilon which is extremely low. This indicates that our sensor has axial strain insensitivity which will improve its measurement accuracy.
查看更多>>摘要：Light-matter interaction at the nanoscale is of particular interest for future photonic integrated circuits and devices with applications ranging from communication to sensing and imaging. In this letter, we proposed a plasmon modulator to enhance the Light-matter interaction by dynamically controlling the spatial distribution of carrier density at the nanoscale, which is demonstrated by a hybrid graphene-dielectric-grating structure. The numerical results show that both the applied voltage and the grating period can be utilized to modulate the surface plasmon polaritons (SPPs) effectively. The modulator can also work on an ultra-wideband in theory as the scattering effect is independent of the wavelength. Compared with the modulator via changing the whole carrier density, the modulation depth by controlling the spatial distribution of carrier density at the nanoscale has improved about 18.6 dB at the working wavelength of 12.4 mu m. This plasmon modulator triggers an approach for the enhancement of Light-matter interaction at the nanoscale and improves the modulation depth significantly, which will have a potential application in the fields of optical switches, sensor and photo-detection.
查看更多>>摘要：Optical frequency comb (OFC) based on mode-locked fiber lasers has abstracted extensive interest in the field of laser ranging and precision spectroscopy with its extremely high time-frequency accuracy. Therefore, the repetition rate stabilization plays a notably key role in OFC. Mechanical motion is generally used to change the geometric length of the laser cavity to stabilize the repetition rate. However, this method has some disadvantages such as high feedback voltage and mechanical disturbance caused by the characteristics of the piezoelectric ceramic transducer (PZT). To overcome these problems, the refractive index of the gain fiber can be regulated via controlling the pump power, thereby optically stabilizing the repetition rate. In this study, we reported the optical repetition rate stabilization via regulating the nonlinear refractive index of Er-fiber in an all-polarization-maintaining (PM) figure-of-nine laser cavity. The repetition rate reached 80.1 MHz and was stabilized for more than 1 h. The standard deviation (SD) was 178 mu Hz within 1-s gate time. As far as we know, in terms of optical repetition rate stabilization, the mode-locked Er-fiber laser achieved the highest repetition rate.
查看更多>>摘要：Phoxonic crystal is a kind of artificial periodic structure which can manipulate light and sound in the same time and space domain. It has good application prospect in optical communication system and opto-mechnical sensor. In this paper, a two-dimensional silicon phoxonic crystal slab structure is proposed, which can exhibit large phononic and photonic bandgaps simultaneously. Then a periodic cylindrical structure is introduced on the side surface of the slab. The effects of the height and radius of the cylinder on the side surface wave modes are analyzed. On this basis, a phoxonic crystal hetero-structure cavity composed of cylinders with different radii and heights is constructed, which can simultaneously confine the acoustic and optical modes because of mode gap effect. Seven phononic cavity modes and two photonic cavity modes are obtained. The two photonic cavity modes are called dielectric mode and air mode respectively. Further, the acousto-optical coupling rates between the seven phononic cavity modes and dielectric mode are calculated. Finally, a gap is etched on each cylinder in hetero-structure cavity, which can increase the surface area of the cavity by 23%. Then two phononic cavity modes and photonic dielectric mode with higher coupling rates are considered. The results show that etching the z-direction gap in the center of the cylinder can effectively increase the acousto-optical coupling rates.
查看更多>>摘要：This paper proposes and experimentally demonstrates a passive beamformer based remote beamforming scheme for millimeter-wave band radio-over-fiber systems. The proposed scheme can control the beam direction of remote radio units (RRUs) from the central station (CS); it yields extremely simple RRUs for flexible and cost-effective deployment. The proposed scheme sets a passive beamformer such as beamforming network, reflector, or lens in the RRU and different wavelengths are assigned to each input port of the passive beamformer. This configuration offers remote beam switching by just carrier wavelength switching at CS. Multi beam operation can be also realized simply by using multiple wavelengths simultaneously. Experiments on a 28 GHz band reflectarray are conducted. The feasibility of remote beam switching by wavelength switching is confirmed. 5G signal transmission over 20 km of single-mode fiber and 6.3 m air link is successfully achieved with error vector magnitude values of 2.71-3.55%, which satisfies the 3GPP requirements of 8%.
Avramov-Zamurovic, SvetlanaNelson, CharlesEsposito, Joel M.
9页
查看更多>>摘要：Optical communication links constructed using orthogonal basis beams have the potential to significantly increase data bandwidth through the use of a complex set of alphabet symbols decoded at the receiver by a machine learning-based classifier. Vortex beams theoretically have the capability to mitigate some of the deleterious effects of optical turbulence. Our research objective is to study Laguerre-Gaussian (LG) single mode basis beams under the assumption that the superimposed beams will maintain a more robust vortex structure on propagation through optical turbulence. If the vortex structure is preserved then the feature diversity of the symbols will allow effective machine learning classification. To better understand the primary drivers influencing vortex robustness, we experimentally measured the scintillation and vortex structure of zero-order LG beams through strong underwater optical turbulence as a function of topological charge ranging from one to nine. We conclude that LG beams with higher topological charges appear to distort less upon propagation, suggesting their suitability as basis beams for easier classification by machine learning techniques.
NSTL
Elsevier