Flynnnyholm1329

Our work opens a simple but efficient approach for transmission enhancement, that may find practical applications in transparent electrodes and tunneling WiFi signals through walls of buildings.In this work, a silicon-integrated edge coupler supporting dual-mode fiber-to-chip coupling was designed and fabricated on 220-nm-thick SOI wafer with standard CMOS-compatible fabrication process. The proposed low-complexity structure consists of a multimode interference and triple-tip inverse taper. Both LP01 and LP11 modes in the few mode fiber (FMF) can be stimulated simultaneously by the edge coupler from TE0 and TE1 modes in silicon waveguide. Such a design is compatible with broadband wavelength division multiplexing and can be scaled up to 4-polarization-mode coupling as well. Using the proposed edge coupler, 2×100-Gbps/lambda PAM4 multimode interface through dual-mode fiber was demonstrated successfully.Structured light is an optical 3D surface measurement technique with the merits of high speed and high robustness. However, the huge size of traditional digital light processing (DLP) projectors limits its convenience in numerous applications. In this paper, a one-axis MEMS mirror is used as the structured light projector in 3D modeling systems, and has the advantages of small volume and low cost. check details Limited by the inability to project orthogonal patterns and projection distortion, it is difficult for the one-axis MEMS mirror based 3D modeling system to obtain high accuracy through existing calibration methods. This paper proposed a calibration method for structured light 3D modeling systems that can only project stripes in one direction with projection distortion. A curved surface equation called curved light surface model was proposed to replace the ideal plane equation as the mathematic model of the projected structured light stripes. Experiment results verified that this method can significantly reduce the effect of projection distortion and an accuracy of 0.11 mm was achieved when measuring a standard dumbbell-shaped object with 201.10 mm center-to-center distance.After electrons tunnel out of a laser-Coulomb-formed barrier, the movement of the tunneling electron can be affected by the Coulomb potential. We show that this Coulomb effect induces a large time difference (longer than a hundred attoseconds) between the tunneling-out time at which the electron exits the barrier and the ionization time at which the electron is free. This large time difference has important influences on strong-field processes such as above-threshold ionization and high-harmonic generation, with remarkably changing time-frequency properties of electron trajectories. Some semi-quantitative evaluations on these influences are addressed, which provide new insight into strong-field processes and give suggestions on attosecond measurements.The optoelectronic oscillator (OEO) has been widely investigated to generate ultra-pure single-frequency microwave signals. In this study, we propose and experimentally demonstrate an active mode-locking optoelectronic oscillator (AML-OEO), which can generate broadband microwave frequency comb (MFC) signals. An additional intensity modulator is inserted into the OEO as an active mode-locking device for loss modulation to realize phase-locking between adjacent oscillation modes. Through the active mode-locking technique, steady multi-mode oscillation is achieved, which is difficult to realize in a conventional OEO due to the mode-competition effect. By tuning the frequency of the active modulation signal (AMS), both fundamental and harmonic AML-OEOs can be established. In the experiments, MFC signals with a frequency spacing of 195 kHz and 50.115/100.035 MHz are generated with fundamental and harmonic AML-OEOs.In this paper, the polar coded probabilistic amplitude shaping (PC-PAS) is investigated in a free space optical (FSO) communication system to combat the fading induced by turbulence. The achievable rate of multiple level coding (MLC) and bit-interleaved coded modulation (BICM) schemes with different distributions are studied in turbulence channels, which proves that the non-uniform distribution can achieve larger achievable rates than the uniform distribution in the FSO turbulence channel. And the PC-PAS techniques based on MLC and BICM are both investigated. For MLC-based PC-PAS, the dynamically frozen bits scheme is adopted and the modification to the labeling rule is proposed to label the non-negative constellation points. For the BICM-based PC-PAS, the exchange scheme is proposed to combine the polar codes and PAS technique. The Block error rate (BLER) is evaluated by the Monte Carlo simulation method. From the results, both the MLC-based and the BICM-based PC-PAS can improve the performance compared to the uniform distribution. And the PC-PAS based on MLC outperforms the PC-PAS based on BICM in the same turbulence condition.Owing to the omnidirectional perfect transmission and omnidirectional zero phase accumulation properties, S-type optical nihility media (ONM) have been utilized to design hyperlenses, optical waveguides, field concentrators and field rotators. Under the multiple interference mechanism, for conventional all-dielectric one-dimensional photonic crystals (1DPCs), all the transmittance peaks within the passband will shift towards short wavelengths (blueshift) with the increase in incident angle. Therefore, effective ONM cannot be realized in all-dielectric 1DPCs because the perfect transmission and zero phase accumulation conditions at the wavelength of the transmittance peak can only be satisfied at a specific incident angle. However, in a 1DPC composed of alternating dielectric and hyperbolic metamaterial (HMM) layers, one can realize a stopband of which one band edge is redshifted. At the same time, a transmittance peak in the passband is blueshifted. Therefore, between the redshift band edge and the blueshift transmittance peak, one can obtain an angle-independent transmittance peak. The HMM layer is mimicked by a dielectric/doped semiconductor multilayer. At the wavelength of the angle-independent transmittance peak, perfect transmission and zero phase accumulation conditions can be satisfied at any incident angle. Our work provides a route, under the current experimental conditions, to realize an effective S-type ONM by a simple one-dimensional structure in the near-infrared range.Photonic bandgap fibers have a critical constraint determined by wavelength. The principle of scale invariance requires that features remain unchanged even as the scale of an object changes. This paper introduces a new concept for fractal photonic crystal fibers integrating these two. Our simulation confirmed single-mode transmission is possible for a fiber whose core diameter exceeds 35 times the wavelength.We theoretically analyze directional surface electromagnetic waves supported at an interface between an isotropic medium and anisotropic metal with effective uniaxial negative permittivity. We identify two types of surface wave solutions, resulting in unique hyperbolic dispersion in the wavevector space. Such anisotropic metal can be realized by alternating dielectric and metallic layers with deep subwavelength thicknesses or metallic nanowires in dielectric host. Such systems serve as a platform for many applications in nanophotonics.The operational MEdium Resolution Imaging Spectrometer (MERIS) daily mean photosynthetically available radiation (PAR) product generated by the NASA Ocean Biology Processing Group (OBPG) was evaluated in clear sky conditions against in-situ measurements at various sites in the northwestern Mediterranean Sea (BOUSSOLE buoy), the northwestern Pacific (CCE-1 and -2 moorings), and the northeastern Atlantic (COVE platform). The measurements were first checked and corrected for calibration errors and uncertainties in data processing by comparing daily means for clear days (i.e., no clouds from sunrise to sunset and low aerosol abundance) with theoretical values from an accurate Monte Carlo radiative transfer code. The OBPG algorithm performed well when sky was completely cloudless during daytime, with a bias of 0.26 E/m2/d (0.6%) and a RMS difference of 1.7 E/m2/d (4.0%). Using satellite-derived aerosol optical thickness (AOT) and Angström coefficient instead of climatology slightly degraded the results, which was PAR estimates in such situations does not reside so much in improving the radiative transfer treatment or specifying more accurately aerosol properties, but rather in accounting properly for the diurnal variability of cloudiness. To this end, a methodology that utilized Modern Era Retrospective Reanalysis for Research and Applications, Version 2 (MERRA-2) hourly cloud data (fractional coverage, optical thickness) was proposed and tested, reducing the bias to 1.6 E/m2/d (4.2%). Improvement was not sufficient in some situations, due to the coarse resolution and uncertainties of the MERRA-2 products, which could not describe properly the cloud properties at the local scale (MERIS pixel). The treatment is applicable to any cloud situation and should be considered in a future version of the of OBPG PAR algorithm. This would require, however, refreshing the standard OBPG PAR products generated as part of the ocean-color processing line according to MERRA-2 data availability.Accurate image reconstruction in color lens-free imaging has proven challenging. The color image reconstruction of a sample is impacted not only by how strongly the illumination intensity is absorbed at a given spectral range, but also by the lack of phase information recorded on the image sensor. We present a compact and cost-effective approach of addressing the need for phase retrieval to enable robust color image reconstruction in lens-free imaging. The amplitude images obtained at transparent wavelength bands are used to estimate the phase in highly absorbed wavelength bands. The accurate phase information, obtained through our iterative algorithm, removes the color artefacts due to twin-image noise in the reconstructed image and improves image reconstruction quality to allow accurate color reconstruction. This could enable the technique to be applied for imaging of stained pathology slides, an important tool in medical diagnostics.Dihedral corner reflector arrays (DCRAs) are imaging devices that form real images and are used in a variety of applications, including floating virtual touchscreens and image presentation around physical objects. However, they induce several types of degradations to floating images. It is desirable to suppress these degradations to provide better viewing experiences. This paper proposes a method of suppressing degradations which appear as high-frequency noise by using mechanical vibration. The effects of vibrating the DCRA were confirmed through an analysis of the floating image quality in the frequency domain.We experimentally study the radiation direction and relaxation rate of quantum emitters (QEs) coupled with a plasmonic waveguide integrated with a V-shaped traveling wave antenna. The plasmonic waveguide couples the excitation energy of the nearby QEs into surface plasmons and the connected V-shaped traveling wave antenna converts them into highly directional radiation. The directivity of the radiation depends on the shape of the antenna. The half-power beam widths of the radiation with respect to the azimuthal and polar angles are as small as 15.1° and 13.1°, respectively, when the antenna has a 144° intersection angle. The relaxation rates of the QEs are enhanced up to 33.04 times relative to the intrinsic emission rate. The method to control the fluorescence of QEs is of great significance for optical devices, nanoscale light sources, and integrated optics.