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Toward quantitative electric structure inside tiny platinum nanoclusters.
We describe curved-mirror Fabry-Perot cavities with embedded silicon nitride membranes, fabricated using a monolithic surface-micromachining process. The presence of the suspended membranes was confirmed by confocal microscopy, and their properties were verified through optical studies and thermomechanical calibration of mechanical/vibrational noise spectra measured at room temperature and atmospheric pressure. The cavities exhibit reflectance-limited finesse (F ∼ 103) and wavelength-scale mode volumes (VM ∼ 10·λ3). The short cavity length (L ∼ 2·λ) results in large optomechanical coupling, which is desirable for numerous applications in sensing and quantum information.In general, the functions of most metalenses cannot be adjusted dynamically after being fabricated. Here, we theoretically propose an electrically tunable metalens composed of single-layered and non-structured doped graphene loaded with ribbon-shaped metallic strip arrays with varied widths and gaps. The combination of the different widths and gaps can provide full phase coverage from 0 to 2π, which is necessary for a plane wave to be focused. The metalens exhibits obvious tunability of focal length and focal intensity as we varied the Fermi levels of the doped graphene at 10 THz. The focus is able to be shifted within 90.4 µm (∼3λ), with maximum focusing efficiency up to 61.62%. The tunable metalens can also be expanded to other operation frequencies from mid-infrared to terahertz range by properly designing structural parameters. The metalens consisting of nanostructured metal and non-structured graphene utilizes mature metal nanostructure preparation process and avoids the graphene processing, which consequently facilitates the fabrication and promotes the application.The three-channel spectral sensitivity of a trichromatic camera represents the characteristics of system color space. It is a mapping bridge from the spectral information of a scene to the response value of a camera. In this paper, we propose an estimation method for three-channel spectral sensitivity of a trichromatic camera. It includes calibration experiment by orthogonal test design and the data processing by window filtering. The calibration experiment was first designed by an orthogonal table of the 9-level and 3-factor. A rough estimation model of spectral sensitivity is established on the data pairs of the system input and output in calibration experiments. The data of rough estimation is then modulated by two window filters on frequency and spatial domain. find more The Luther-Ives condition and the smoothness condition are introduced to design the window, and help to achieve the optimal estimation of the system spectral sensitivity. Finally, the proposed method is verified by some comparison experiments. The results show that the estimated spectral sensitivity is basically consistent with the measured results of the monochromator experiments, the relative full-scale errors of the RGB three-channel is obviously lower than the Wiener filtering method and the Fourier band-limitedness method. The proposed method can estimate the spectral sensitivity of the trichromatic digital camera very well, which is of great significance for the colorimetric characterization and evaluation of imaging systems.Mie theory is widely used for the simulation and characterization of optical interaction with scattering media, such atmospheric pollutants. The complex refractive index of particle plays an important role in determining the scattering and absorption of light. Complex optical fields, such as vortex beams, will interact with scattering particulates differently to plane wave or Gaussian optical fields. By considering the three typical aerosol particles compositions that lead to haze in the atmosphere, distinctive scattering dynamic were identified for vortex beams as compared to Gaussian beams. Using parameters similar to real world atmospheric conditions, a new aerosol particle model is proposed to efficiently and concisely describe the aerosol scattering. Numerical simulations indicate unique signatures in the scattering dynamics of the vortex beams that can indicate particles composition and also suggest that potentially there is higher optical transmission of vortex beams propagating in certain hazy environments.Behaviors of platonic bacteria individuals are profoundly influenced by their interplay. However, probing such interplay still remains a challenge since identification and tracking of bacterial individuals becomes difficult as they come close and interact with each other. Herein, we report 3D tracking of the motions of multiple bacteria by using digital holographic microscopy (DHM), where the subtle 3D behaviors can be characterized as bacteria approach and run away from each other. An algorithm was developed to identify and recover the gap between 3D trajectory segments raising by the interruption from other bacteria through lateral image recognition and axial loalization utilizing cost function. We value the performance of the algorithm in terms of the statistics in trajectory length and correct rate. The study clearly shows how the interplaying Escherichia coli alter their motions.In this paper, a received signal strength assisted perspective-three-point positioning algorithm (R-P3P) is proposed for visible light positioning (VLP) systems. Due to the directional propagation of visible light, the orientations of light-emitting diodes (LEDs) and receivers can affect the positioning accuracy seriously. To circumvent this challenge, R-P3P is proposed to mitigate the limitation on LEDs' and receiver's orientation in VLP systems. The basic idea of R-P3P is to jointly utilize visual and strength information to estimate the receiver position using 3 LEDs regardless of the orientations of LEDs and receivers. Simulation results show that R-P3P can achieve positioning accuracy within 10 cm over 70% of an indoor area with low complexity.We systematically study the stable-, period-N- and multiple-soliton regimes in an Erbium-doped fiber laser effectively mode-locked by nonlinear polarization rotation technique. In the stable mode-locked regime, an invariant soliton with 497 fs pulse duration and 6.9 nm optical spectrum are obtained. With a larger pump power of 180 mW, the period-N state (in which the pulse intensity returns to its original value after N cavity-roundtrips) emerges, accompanied by sub-sideband generation on the first Kelly sideband and spectrum shift. Considering the inconsistent central wavelengths between gain and polarization-dependent isolator (PD-ISO) firstly, to our knowledge, the numerical results are in good agreement with the experiment and reveal the composite filtering of gain and PD-ISO takes major responsibility for spectrum shift, which causes group velocity offset simultaneously. Further study shows the continued increase of pump power can lead to the laser operating in the unstable multi-pulse state and the narrow spectral width contributes to stabilizing the multi-pulse state.
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