Optimization of coating uniformity in a simple rotation system by using a rotating shadow mask.

A theoretically designed rotating shadow mask is proposed to optimize the uniformity of a simple rotation system, which makes full use of the width of the coating chamber. This method can fabricate a large-aperture optical component, the diameter of which is more than half the width of the coating machine. The rotating shadow mask is applied to correct the film thickness uniformity near the center point of simple plane substrate. The factors influencing the effect of the rotating shadow mask are simulated and discussed. Then the shape of the rotating shadow mask is theoretically designed, and the uniformity within a corresponding radius is well corrected. After determining the shape of the rotating shadow mask, an additional fixed shadow mask is calculated and used to improve the uniformity of the entire substrate. Through the application of the two shadow masks together, uniformity about 99.5% is obtained in the diameter of 640 mm on a 1100 mm coating machine.

Experimental study on imaging and image deconvolution of a diffractive telescope system.

Diffractive telescopes are one of the most promising solutions to build lightweight space telescopes with a diameter over 10 m. However, the performance of the imaging systems is inevitably degraded by the high-order diffractive light from the diffractive system. To address this problem, in this paper we mathematically deduce the imaging model, including multiple-order diffraction, by the scalar diffraction theory. After the imaging characteristics analysis, an adaptive Wiener filtering algorithm based on the principal component analysis method is proposed. The broadband imaging and deconvolution experiments are performed by the 80 mm diffractive optical telescope systems. Results demonstrate that this method increases the average gradient by at least 8.2 times and improves imaging quality and contrast. It could be a useful exploration for high-performance imaging of large-aperture and lightweight telescopes.

Application of first-order nonparaxial scalar theory to determine surface scattering intensity of multilayer optical coatings.

A novel first-order nonparaxial scalar theory for calculating the angular scattering that is caused by the interface roughness in an optical multilayer was proposed. As in the case that the interface roughness is moderate, the analytic expressions of angular-resolved scattering for a typical p-layer design were derived. Notably, these formulas are general because they do not depend on the prior restrictive hypothesis for the correlation degree of the various interfaces in a stack. In order to verify the theory, the formulas in the case of single-surface are presented and are exactly identical to those of the generalized Harvey-Shack theory. Also, their smooth-surface approximations are the same in form as those given by the typical first-order vector perturbation theories and are validated by numerically comparing with the typical vector theory for three representative multilayer design types with slightly rough interfaces. In addition, the usability of the novel theory in the case of moderate roughness is discussed by comparing this theory to the typical theories for optical coatings at different roughness levels.

Self-assembly of high-index faceted gold nanocrystals to fabricate tunable coupled plasmonic superlattices.

Herein, we present an effective bottom-up strategy to fabricate unprecedented macroscopic two-dimensional (2D) plasmonic gold superlattices composed of high-index faceted gold nanocrystal building blocks (NBBs) at the air-liquid interface. In this approach, a synergistic electrostatic and layered self-assembly technique was executed using unique icosidodecahedral gold nanocrystals. It showed that centimeter-squared areas of close-packed monolayer films were formed, and the interparticle spacing of neighbouring Au NBBs could be facilely manipulated from hundreds to several nanometers. Optical characterization demonstrated that particular plasmonic coupling could occur and enhance in a wide spectral range (visible and near-IR) as the self-assembled Au superlattices were tuned for an appropriate gap distance and specific NBB size; however, the orientation of individual NBBs remained somewhat unorganized. Thus, the well pronounced shift of localized surface plasmon resonances (LSPR) and the in-depth resonance splitting behaviors were presented in our investigations. Furthermore, corresponding electromagnetic simulations showed good agreement with the experimental results; this indicated that a new class of tunable coupled plasmonic Au superlattices was realized. This study complements the insights into the plasmonic coupling of layered Au superlattices and enables the colloidal self-assembly to extend to unconventional NBBs; thus, it may facilitate the design of novel plasmonic metamaterials or other superstructures for desired functionalities and applications in the future.

First-order nonparaxial scalar theory of surface and bulk scattering for high-quality optical coatings.

A novel nonparaxial scalar theory is presented to calculate the angular scattering that is due to interface roughnesses or bulk inhomogeneities in a high-quality optical coating. Based on the empirically modified Beckmann-Kirchhoff surface scatter model, this theory in surface scattering and bulk scattering predicts similar formulas for the angular scattered intensity, and at the same time provides new understanding and insight into multilayer scattering phenomena. It is worth noting that the derived expressions are in the same form as those given by the typical vector methods. Based on comparisons of the surface and bulk models with the corresponding typical models for several multilayer designs, the novel theory is demonstrated to be valid for multilayer coatings even with large incident and scattering angles.

First on-sky demonstration of the piezoelectric adaptive secondary mirror.

We propose using a piezoelectric adaptive secondary mirror (PASM) in the medium-sized adaptive telescopes with a 2-4 m aperture for structure and control simplification by utilizing the piezoelectric actuators in contrast with the voice-coil adaptive secondary mirror. A closed-loop experimental setup was built for on-sky demonstration of the 73-element PASM developed by our laboratory. In this Letter, the PASM and the closed-loop adaptive optics system are introduced. High-resolution stellar images were obtained by using the PASM to correct high-order wavefront errors in May 2016. To the best of our knowledge, this is the first successful on-sky demonstration of the PASM. The results show that with the PASM as the deformable mirror, the angular resolution of the 1.8 m telescope can be effectively improved.

Facile large-area uniform photolithography of membrane diffractive lens based on vacuum assisted self contact method.

Optical polyimide (PI) membrane is a promising substrate material for diffractive lens applied in future large-aperture space based imaging system because of its light weight, environmental adaptability and deployable feature. In this letter, we put forward a facile large-area uniform photolithography technique using vacuum assisted self contact method to fabricate large-aperture membrane diffractive lens. We fabricated a φ 400 mm aperture membrane off-axis 2-levels Fresnel Zone Lens (FZL) based on the method and achieved uniformly distributed photoresist morphology as well as over 36.6% average diffraction efficiency in full aperture. The results demonstrated that vacuum assisted self contact method effectively eliminates considerable air gaps caused by unevenness of large area photomask and substrate, thus facilitates uniform light field distribution in photoresist. This work provides reference to fabrication techniques of large aperture membrane diffractive lens, and offers feasible methods for future large area flexible electronics manufacturing.

Decoupling algorithm of a double-layer bimorph deformable mirror: analysis and experimental test.

With the increasing requirements on spatial resolution and actuator pitch, multilayer bimorph deformable mirrors are coming into wider application in adaptive optics. This paper discusses the coupling of actuators of multilayer bimorph deformable mirrors. A decoupling algorithm based on controlling gradients directly is presented. And a closed-loop adaptive optics system, which consists of a double-layer bimorph deformable mirror and a Shack-Hartmann wavefront sensor, is set up to validate this decoupling algorithm. Experimental results show that the intensity distribution at the image plane of the distorted wavefront is effectively improved when the modified closed-loop control is on. Besides, the experimental results fit well with the conclusion of numerical simulation.

Facile Film-Nanoctahedron Assembly Route to Plasmonic Metamaterial Absorbers at Visible Frequencies.

Plasmonic metamaterial absorbers (MAs) with broadband and near-perfect absorption properties in the visible region were successfully fabricated via a facile film-colloidal nanoparticle (NP) assembly method. In this approach, colloidal octahedral Au NPs were employed as the surface meta-atoms of MAs, whereas nanoscale-thick SiO2 and Al films were used as the dielectric spacer and reflector, respectively. It is worth noting that the Au nanoctahedra were randomly assembled onto the Al-SiO2 films, and no effort was made to precisely control their spatial arrangements. The optical characterization showed that the as-prepared MAs exhibited broadband high absorption (average absorptivity above 85%) within the whole visible spectrum for a broad range of incident angles (0°-60°). In particular, two polarization-independent near-perfect absorption peaks (absorptance above 99%) were recorded near 540 and 727 nm, respectively. Moreover, the absorption properties of the MAs can be effectively controlled and tailored by varying the geometry (the thickness of the dielectric spacer and the surface coverages of the Au nanoctahedra). Electromagnetic simulations further demonstrated that enhanced Mie resonances and strong plasmonic coupling effects were critical for the designed MAs. This work here may provide an efficient and alternative route for the design of scalable visible light absorbers for applications such as solar cells, photothermalvoltaics, and biochemical sensors.

[Impact of a reservoir project on schistosomiasis transmission in lake region].

OBJECTIVE: To determine the impact of a project of building dike for storing water on schistosomiasis transmission in Junshan Lake. METHODS: Junshan Lake in Jinxian County of Jiangxi Province was selected as survey pilot. Data on snail distribution and historical prevalence of schistosomiasis before building dike were collected. The water level inside and outside of the dike was recorded from 1995 to 2002, and the relationship between the water level and snail population at the inside of the dike was analyzed. Survey was made in a natural endemic village to confirm the current endemicity of schistosomiasis. RESULTS: In the selected area of Junshan lake, schistosomiasis was prevalent in 6 villages of 3 townships, with a snail area of 1,394,030 m2 (2,090 Chinese Mu). Snails distributed mainly in the marshland at an elevation of 16.6-17.2 m, and the average infection rate of schistosomiasis in the residents was 12.5% in 1958 before the dike project. In 1960, two years after the dike was built, no living snails were found on the marshland, and the infection rate of schistosomiasis in the residents reduced remarkably. Currently, no schistosomiasis cases were found in human being and cattle in the surveyed village. CONCLUSION: The reservoir project had helped the elimination of snails and interrupted schistosomiasis transmission.

[Effect of straw return to field and fertilization in autumn on dryland corn growth and on water and fertilizer efficiency].

A ten years location experiment of various kinds straw return to field and deep fertilization in autumn was conducted in Shouyang dryland experimental area of Shanxi Province to study their effect on the growth and yield of dryland corn, the use efficency of soil water and fertilizer, and the changes of soil fertility. The results showed that this kind of experimental method could better solve the contradiction of deep fertilization with maintaining soil moisture and keeping a full stand of seedlings in spring, and the competition of water and fertilizer between the degradation of crop remains and the seedlings. What is more, the abundant resources of crop remains were used more sufficiently, the activity of soil microorganisms was more active, and soil fertility was obviously improved, which was proved by the complete and strong seedlings and developed roots, the photosynthesis and transpiration rates were enhanced, the water use efficiency (WUE) was increased by 3.26 - 3.51 kg x hm(-2) x mm(-1), and the accumulated water consumption was decreased by 8.1 - 264.5 mm. During plant growth period, the utilization rate of fertilizer N and P could increase 3.9% - 13.9% and 3.0% - 9.1%, respectively, and the use efficiency of water and fertilizer was higher. The ten years accumulated yield increased 12.10 - 17.27 t x hm(-2), a rise of 25.6% - 36.5%, and in the meantime, higher soil fertility and productivity were maintained.