Optical edge detection, a part of image processing, plays an important role in extracting image information used in optical analog computation. In this Letter, we raise a new way to realize optical edge detection. This design is based on two liquid crystal polarization gratings with a period of 2.2 mm, which function as a spatial differentiator. We experimentally demonstrate broadband optical detection and real-time adjustable resolution. The proposed method takes advantage of the convenience to use, simple fabrication process, and real-time tunable resolution. It may guide more significant applications in the optical field and other practical scenarios like machine vision in computers.

Image sticking in liquid crystal display (LCD) is related to the residual direct current (DC) voltage (RDCV) on the cell and the dynamic response of the liquid crystal materials. According to the capacitance change of the liquid crystal cell under the DC bias, the saturated RDCV (SRDCV) can be obtained. The response time can be obtained by testing the optical dynamic response of the liquid crystal cell, thereby evaluating the image sticking problem. Based on this, the image sticking of vertical aligned nematic (VAN) LCD (VAN-LCD) with different cell thicknesses (3.8 μm and 11.5 μm) and different concentrations of γ-Fe2O3 nanoparticles (0.017 wt.%, 0.034 wt.%, 0.051 wt.%, 0.068 wt.%, 0.136 wt.%, 0.204 wt.%, and 0.272 wt.%) was evaluated, and the effect of nano-doping was analyzed. It is found that the SRDCV and response time decrease firstly and then increase with the increase of the doping concentration of γ-Fe2O3 nanoparticles in the VAN cell. When the doping concentration is 0.034 wt.%, the γ-Fe2O3 nanoparticles can adsorb most of the free impurity ions in liquid crystal materials, resulting in 70% reduction in the SRDCV, 8.11% decrease in the decay time, and 15.49% reduction in the rise time. The results show that the doping of γ-Fe2O3 nanoparticles can effectively improve the image sticking of VAN-LCD and provide useful guidance for improving the display quality.

We propose and demonstrate single fiber dual-functionality optical tweezers based on a graded-index multimode fiber. By using the multi-angle fiber grinding and polishing technology, we fabricate the multimode fiber tip to be a special tapered shape, contributing to focus the outgoing beam with a large intensity gradient for the first functionality—three-dimensional contactless trapping of a microparticle. By adjusting the radial direction offset between the lead-in single mode fiber and the graded-index multimode fiber, we perform the second functionality—axial shift of the trapped microparticle with respect to the fiber tip without need of moving the fiber probe itself. It is convenient for practical applications. The theoretical and experimental results about the relationship between the radial offset and the equilibrium positions of the microparticle have the good consistency. Tailoring the trap and axial shift of the microparticle based on the graded-index multimode fiber provides convenient avenues for fiber optical tweezers applied in practical researches.

For better night-vision applications using the low-light-level visible and infrared imaging, a fusion framework for night-vision context enhancement (FNCE) method is proposed. An adaptive brightness stretching method is first proposed for enhancing the visible image. Then, a hybrid multi-scale decomposition with edge-preserving filtering is proposed to decompose the source images. Finally, the fused result is obtained via a combination of the decomposed images in three different rules. Experimental results demonstrate that the FNCE method has better performance on the details (edges), the contrast, the sharpness, and the human visual perception. Therefore, better results for the night-vision context enhancement can be achieved.

The authors would like to apologize for an error in the paper Chinese Optics Letters vol. 15, no. 3, page 030010. On page 030010-3, the caption for Figs. 5 (a)–(c) should read “2 μm silica” (not 3 μm polystyrene).

As perovskite solar cells show tremendous potential for widespread applications, we find that adding inorganic thermal-stable cesium ions into MAPbI3 results in significantly improves thermal stability. For un-encapsulated perovskite devices, the energy conversion efficiency maintains about 75% of its original value (over 15%) in the MA0.85Cs0.05PbI3 device under 80 min of heating at 140°C in a dry atmosphere (RH≤30%). With significantly improved thermal stability achieved by a convenient process, it is expected that this type of mixed-cation perovskites can further facilitate large scale applications.

Polymethyl methacrylate (PMMA) plate luminescent solar concentrators with a bottom-mounted (BM-LSCs) photovoltaic (PV) cell are fabricated by using a mixture of Lumogen Red 305 and Yellow 083 fluorescent dyes and a commercial monocrystalline silicon cell. The fabricated LSC with dye concentrations of 40 ppm has the highest power gain of 1.50, which is the highest value reported for the dye-doped PMMA plate LSCs. The power gain of the LSC comes from three parts: the waveguide light, the transmitted light, and the reflected light from a white reflector, and their contributions are analyzed quantitatively. The results suggest that the BM-LSCs have great potential for future low-cost PV devices in building integrated PV applications.

The authors would like to apologize for an error in our paper in Chin. Opt. Lett. 15(10), 100604 (2017).

In this letter, we introduce the project of multilayer dielectric film based on conventional optics to design laser-protective coating. A desired material with an ideal refractive index is used to optimize the design results. Two film-thickness masks are designed to improve the uniformity of large-size coatings. Experimental results show that the average spectral transmittance from 400 to 1000 nm is higher than 85%, the attenuation of high-energy laser at both 532 and 1064 nm is larger than 98% in the range of ±20° and the film uniformity of large area is more than 98.2%. The coating performance observed meets the requirements of both utilization of solar energy and laser protection.

A novel method for preparing a luminescent solar concentrator (LSC) with fluorescent aqueous layer sandwiched between two pieces of flat glass is developed. By this method, an aqueous layer concentrator with a size of 78×78×7 (mm) is fabricated. After coupled with silicon solar cell, the concentrator shows a power conversion efficiency of 3.9%, about 30% higher than that of the same sized laminated glass concentrator employing the same dyes. Furthermore, the measured efficiency almost reaches the calculated limit of the aqueous layer LSC. This kind of aqueous layer LSC offers a potential application in the building-integrated photovoltaics.

This letter presents an approach based on differential evolution (DE) algorithm for determining the solar cell model parameters from current-voltage (I-V) characteristics. The validity of this approach has been confirmed with experimental and simulated I-V data. It was demonstrated that the I-V curve derived from the parameters extracted by the DE approach is in good agreement with the experimental or simulated I-V data. A low objective function value as well as a high parameter precision can be obtained by the DE algorithm.

We develop a phenomenological model to investigate dynamics of ionization-induced injection. In the "bubble" regime of laser wakefield acceleration (LWFA), it is found that there is an upper limit for laser intensity of ionization-induced injection. In the plane perpendicular to the laser polarization, when the laser pulse is linearly polarized, ionization-induced injected electrons exhibit a filamented structure and semi-coherent betatron oscillation.

We experimentally demonstrate the generation of an array of optical bottle beams by employing multiple self-accelerating Airy beams. This kind of optical bottle array is created by superimposing eight Airy beams along a circle, all with inward acceleration directed towards the center. In addition, we demonstrate stable trapping of multiple absorbing glassy carbon particles using the proposedoptical bottle array.

We present three possible design options of laser plasma acceleration (LPA) for reaching a 100-GeV level energy by means of a multi-petawatt laser such as the 3.5-kJ, 500-fs PETawatt Aquitane Laser (PETAL) at French Alternative Energies and Atomic Energy Commission (CEA). Based on scaling of laser wakefield acceleration in the quasi-linear regime with the normalized vector potential a0 = 1.4(1.6), acceleration to 100 (130) GeV requires a 30-m-long plasma waveguide operated at the plasma density ne \approx 7 \times 10^{15} cm^{ 3} with a channel depth \Delta n/ne=20%, while a nonlinear laser wakefield accelerator in the bubble regime with a0 \geq 2 can reach 100 GeV approximately in a 36/a0-m-long plasma through self-guiding. The third option is a hybrid concept that employs a ponderomotive channel created by a long leading pulse for guiding a short trailing driving laser pulse. The detail parameters for three options are evaluated, optimizing the operating plasma density at which a given energy gain is obtained over the dephasing length and the matched conditions for propagation of relativistic laser pulses in plasma channels, including the self-guiding. For the production of high-quality beams with 1%-level energy spread and a 1\pi-mm-mradlevel transverse normalized emittance at 100-MeV energy, a simple scheme based on the ionization-induced injection mechanism may be conceived. We investigate electron beam dynamics and effects of synchrotron radiation due to betatron motion by solving the beam dynamics equations on energy and beam radius numerically. For the bubble regime case with a0=4, radiative energy loss becomes 10% at the maximum energy of 90 GeV.

An electron beam is obtained using laser wakefield electron accelerator, and converted into a \gamma-ray source after undergoing bremsstrahlung radiation in a dense material. A quasi-monoenergetic structure is observed when the length of the plasma channel was modified. The structure has a 58-MeV peak energy, 15-mrad (full-width at half-maximum) divergence angle, and 340-pC charge. The \gamma-ray source generated by this high-quality electron beam is brighter and has higher spatial and temporal resolutions than other conventional sources. A \gamma-ray radiography demonstrational experiment is performed. Pictures of a ball with different layers made of different materials are taken. The results show a clear structure and density resolution.