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In the current solution for multiwavelength achromatic flat lenses, a one-to-one correspondence exists between the number of writing phase distributions and the number of achromatic wavelengths. Breaking this correspondence requires a complex phase design and parameter optimization. Here, we show that a dual-layer cascade liquid crystal Pancharatnam-Berry lens (CLCPBL) with two writing phase distributions and a specific coupled phase distribution between the layers can achieve three wavelength achromaticity without any parameter optimization process. Similarly, in a three-layer cascade, the number of achromatic wavelengths increases to seven through the permutations of the layers, with adjustable amplitude factors. We fabricate a three-layer CLCPBL with the design wavelengths of 396.8 nm, 1064 nm, and 1550 nm, which theoretically allows the light at 632.8, 532.8, 3383 and 450 nm to form a common focus, and test such structure. Our CLCPBL enables a wider range of applications than conventional achromatic flat lenses. Metalenses are lightweight and compact alternative to achromatic lens assemblies, but they usually fulfill the focusing requirements for a single wavelength. The authors design and fabricate a cascade liquid crystal Pancharatnam-Berry lens that enables a seven-wavelength achromatic focusing in a broad range of frequencies. [ABSTRACT FROM AUTHOR]

Mentions how a Co/Sb multilayer shows the theoretical reflectance of 62% at a photoenergy of 528 eV and the grazing angle of 10.3°. How the measured reflectance is very low, which is considered to result from the low energy resolution of the incidence light; Investigation of the effect of the energy resolution of the incidence light on the measured reflectance; Reference to a new method how to calculate the reflectance of non-monochromatic light; Trend for the calculated data to show that the reflectance of Co/Sb multilayer is very sensitive to the effect of the energy resolution of the incidence light; Findings for it to be very low unless the energy resolution of the incidence light is high enough; Use of a method which gives the fitted result of the reflectance spectrum; Consistency of the fitted result with the measured reflectance spectrum.

Large-scale layers peeling after the laser irradiation of dual ion beam sputtering coatings is discovered and a model is established to explain it. The laser damage morphologies relate to the laser fluence, showing thermomechanical coupling failure at low energy and coating layers separation at high energy. High-pressure gradients appear in the interaction between laser and coatings, resulting in large-scale layer separation. A two-step laser damage model including defect-induced damage process and ionized air wave damage process is proposed to explain the two phenomena at different energy. At relatively high energies (higher than 20 J/cm2), ionization of the air can be initiated, leading to a peeling off effect. The peeling effect is related to the thermomechanical properties of the coating materials. [ABSTRACT FROM AUTHOR]

A broadband metamaterial absorber (MA) based on the titanium nitride (TiN) nano-disk array is studied using finite difference time domain simulations. The semiconducting indium tin oxide (ITO) thin film is introduced as the space layer in this sandwiched structure. Utilizing the symmetrical geometry of the MA structure, polarization insensitivity of the broadband absorption was gained. The absorber with TiN nano-disk array shows a peak absorbance of 99 % and larger than 98 % from 560 to 675 nm by numerical simulation. This compact design may have potential applications in the plasmonic sensing and photovoltaic devices. [ABSTRACT FROM AUTHOR]

Metal multi-layer dielectric gratings (MMDG) for pulse compressors in high-energy laser systems should provide broad bandwidth as well as high laser-induced damage thresholds. The non-uniform optical near-field distribution of MMDG is an important factor that limits damage resistant capabilities. MMDG for pulse compressors operating at 800 nm with a corrugated SiO layer are designed by using a genetic algorithm and the Fourier mode method. The diffraction efficiency, bandwidth, and near-field distribution of the MMDG are theoretically investigated. For the single dielectric match layer grating, the bandwidth is 140 nm, if the thickness and refractive index of the match layer are changed, the maximum electric field in the grating ridge, match layer, and metal layer of the grating increases with the decrease in grating diffraction efficiency. For the multi-dielectric match layer grating, the bandwidth and the maximum electric field in the metal layer decrease with the increase in high- and low-index material pairs, and the maximum electric field in the grating ridge and match layer initially decreases and then increases. Over a wide wavelength range, the maximum electric field in the grating ridge, match layer, and metal layer is minimal near the central wavelength. Moreover, MMDG should be used at larger incident angles while keeping enough bandwidth to reduce the electric field in the grating. [ABSTRACT FROM AUTHOR]

In this paper, nanostructured ZrO films were prepared by electron beam evaporation with the glancing angle deposition (GLAD) technique. Columnar films with voids in between formed owing to the self-shadowing effect and the limited diffusion of deposited atoms. The microstructure evolves from slanted columnar structure to helical and pillar structures as the substrate rotational speed increases. The diameter of the columns is in the range of 30-50 nm. A higher rotational speed favors a larger nodule size and a greater surface roughness. Due to the porous structure, the refractive index n of GLAD ZrO films varies from 1.75 to 1.80, lower than that of bulk material. A maximum value of birefringence (Δ n=0.03) is obtained in a slanted columnar structure, and the relationship between birefringence and microstructure orientation is discussed. Our results demonstrate that glancing angle deposition is a feasible approach for designing the nanostructure and optical properties of thin films. [ABSTRACT FROM AUTHOR]