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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]

Atmospheric-pressure plasma processing (APPP) is an important method for the fabrication of high-precision optics because it involves highly efficient and nondamaging material removal based on its pure chemical etching mechanism. However, owing to the heat accumulation phenomenon caused by the jet heat flux, the nonlinearity of the material removal rate in APPP is inevitable, making it difficult to achieve deterministic optical surfacing. To bridge this gap, this study focused on analyzing the nonlinear relationship between the material removal rate and heat accumulation. The simulation results indicated that when the sliding distance increased from 10 to 50 mm, the surface temperature of the workpiece increased from 387.3 to 419.5 K, an increase of more than 8%. When the dwell time increased from 0.33 to 2 s, the surface temperature of the workpiece increased from 348.1 to 419.5 K (including the effect of sliding distance), an increase of more than 21%. A novel algorithm that simultaneously considers dwell time and sliding distance was proposed based on the results. A threshold parameter tq was introduced to determine whether to correct the deviation caused by the sliding distance. With the proposed algorithm, the matching residual surface root-mean-square (RMS) error decreased from 97.5 to 39.6 nm. The RMS deviation error of the matching residual surface error converged from 11.6 to 4.7% after surface-figuring experiments. The proposed algorithm is expected to provide a promising solution for future deterministic optical surfacing. [ABSTRACT FROM AUTHOR]

Compressing high-energy laser pulses to a single-cycle and realizing the "λ3 laser concept", where λ is the wavelength of the laser, will break the current limitation of super-scale projects and contribute to the future 100-petawatt and even Exawatt lasers. Here, we have realized ultra-broadband gold gratings, core optics in the chirped pulse amplification, in the 750–1150 nm spectral range with a > 90% −1 order diffraction efficiency for near single-cycle pulse stretching and compression. The grating is also compatible with azimuthal angles from −15° to 15°, making it possible to design a three-dimensional compressor. In developing and manufacturing processes, a crucial grating profile with large base width and sharp ridge is carefully optimized and controlled to dramatically broaden the high diffraction efficiency bandwidth from the current 100–200 nm to over 400 nm. This work has removed a key obstacle to achieving the near single-cycle 100-PW lasers in the future. Gratings are used for pulse compression and stretching in chirped pulse amplification (CPA) or optical parametric CPA methods. Here the authors demonstrate ultra-broadband gold gratings that can compress single-cycle pulses with powers around 100 petawatts. [ABSTRACT FROM AUTHOR]

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]

Axially coordinated metal-porphyrin-functionalized multi-walled carbon nanotube (MWCNT) nanohybrids were prepared via two different synthetic approaches (a one-pot 1,3-dipolar cycloaddition reaction and a stepwise approach that involved 1,3-dipolar cycloaddition followed by nucleophilic substitution), and characterized through spectroscopic techniques. Attachment of the tin porphyrins to the surface of the MWCNTs significantly improves their solubility and ease of processing. These axially coordinated (5,10,15,20-tetraphenylporphyrinato)tin(IV) (SnTPP)-MWCNTs exhibit significant fluorescence quenching. The third-order nonlinear optical properties of the resultant nanohybrids were studied by using the Z-scan technique at 532 nm with both nanosecond and picosecond laser pulses. The results show that the nanohybrids exhibit significant reverse saturable absorption or saturable absorption when nanosecond or picosecond pulses, respectively, are employed. Improvement in the nanosecond regime nonlinear absorption is observed on proceeding to the nanohybrids and is ascribed to a combination of the outstanding properties of MWCNTs and the chemically attached metal-porphyrins. [Figure not available: see fulltext.] [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]

In general, the propagating behavior of extraordinary wave in anisotropic materials is different from that in isotropic materials. With the tangential continuity of Maxwell’s equations, the electromagnetic propagating behaviors have been investigated at the incident and exit interfaces of the uniaxial anisotropic thin film. The emphasis was placed on two interesting optical phenomena such as homolateral refraction behavior and wide-angle Brewster’s phenomenon, which occurred at the interfaces of uniaxial anisotropic thin film. [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.

Multilayers always dissolve some gas atoms during sputtering. In this paper, we develop a new method to study the effect of gas atoms on X-ray reflectance of the multilayer. Our theoretical analysis shows that this effect depends not only on the content of gas atom but also on the wavelength and the grazing angle. The shorter the wavelength and the bigger the grazing angle, the stronger this effect of gas atoms. We fabricated Mo/Si multilayers under various sputtering pressures and measured their small angle X-ray diffraction spectra. The measured results coincide with those calculated by our method. [ABSTRACT FROM AUTHOR]

1 064 nm, 532 nm frequency-doubled antireflection (AR) coatings with buffer layer of SiO between the coating and the substrate were fabricated by the electron beam evaporation technology on the substrate of lithium triborate (LiBO or LBO) crystals. The residual reflectance of the sample is 0.07% and 0.11% at 1 064 nm and 532 nm, respectively. The adhesion and the laser-induced damage threshold (LIDT) of the sample are greater than 200 mN and 18.6 J/cm. The strengthening mechanism of adhesion and LIDT of the buffer layer of SiO were discussed by considering full plastic indentation and shear theory, and spallation of a plated film induced by thermal shock stress, respectively. [ABSTRACT FROM AUTHOR]

Frequency-doubled antireflection coatings simultaneously effective at 1064 nm and 532 nm were deposited on the lithium triborate (LiB3O5 or LBO) crystals using the electron beam evaporation method. Comparing with the sample without buffer layer, it is found that the adhesion of the sample with buffer layer of SiO2 between coating and LBO substrate is improved significantly from 137.4 mN to greater than 200 mN. And the laser-induced damage threshold is increased by 20% from 15.1 J/cm2 to 18.6 J/cm2. The strengthening mechanism of adhesion of the buffer layer of SiO2 is discussed by considering full plastic indentation and shear theory. [ABSTRACT FROM AUTHOR]