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Cadmium oxide (CdO) has recently attracted attention as a material with controllable properties tailored for optoelectronic and nanophotonic devices due to its superior mobility. However, its potential application in near-infrared (NIR) remains to be explored. In this work, we demonstrate that the epsilon-near-zero (ENZ) wavelength and nonlinear optical properties of CdO films can be effectively tuned by Mo doping. The results show that Mo doping increases the electron concentration as well as improve the crystalline quality of CdO. With increasing Mo doping, we achieve blueshifts of the ENZ wavelength from 2.89 to 1.56 μm. The nonlinear absorption (NLA) behavior at 1550 nm changes from reverse saturable absorption to saturable absorption with increasing Mo content. Moreover, significant improvement in NLA performance with nonlinear absorption coefficient β = −72 cm/GW is observed at the highest doping content. Our work shows that doped CdO films with tunable optoelectrical and nonlinear optical properties can be an ideal candidate for optoelectronic and nanophotonic application in the NIR region. [ABSTRACT FROM AUTHOR]

The laser-induced damage (LID) response of multilayer dielectric gratings (MDGs) to transverse magnetic (TM) and transverse electric polarization was investigated based on polarized-independent MDGs. It was found that TM-polarized MDGs have the superiority of a high LID threshold, low sensitivity to laser excitation strength, low response to damaged structure, and reduced LID growth speed and dynamics. These results provide a strong motive to preferentially develop and mount TM-polarized MDGs in the next generation of high-intensity picosecond-petawatt laser systems. [ABSTRACT FROM AUTHOR]

Laser polishing efficiently reduces the surface roughness of die steel, but at the same time, residual tensile stress is induced on the surface, leading to crack initiation and propagation. The present study induces residual compressive stress on the laser-polished surface of Cr12 steel by laser shock peening. The surface residual stress of samples, which underwent different treatments, is measured and compared. The experimental results show that laser shock peening effectively eliminates the residual tensile stress generated by laser polishing. The compressive residual stresses of the laser-polished samples subjected to laser shock peening with 3, 6, and 9 J energies are 114.5, −138.5, and −209.5 MPa, respectively. Moreover, the surface roughness, microhardness, and microstructure evolution of the laser-polished surface with laser shock peening are investigated. [ABSTRACT FROM AUTHOR]

In this paper, we present a glass-based double-side cascade film stack structure for visible-infrared ultrabroadband absorption. The proposed structure demonstrates an average absorption as high as ∼95% over an ultrawide range of wavelengths from 0.4 μm to 20 μm. The high absorption feature of the different bandgap materials is applied in this absorption device to realize the ultrabroadband absorption, combining with the metal-dielectric-like configuration for those unmatched-admittance wavelengths and the graded index profile arrangement for the 0.4–2.5 μm band. The proposed ultrabroadband absorber shows a great angular tolerance up to 60° with the average absorption of 90% remaining. The proposed approach can have tremendous potential in fields of optical sensing, camouflage, optical imaging, passive cooling, and sustainable power generation, profiting from the good mechanical characteristics of this compact multilayer film structure and the low manufacture costs with the simple physical vapor deposition. [ABSTRACT FROM AUTHOR]

TiO2 films are deposited by electron beam evaporation as a function of oxygen partial pressure. The packing density, refractive index, and extinction coefficient all decrease with the increase of pressure, which also induces the change of the film’s microstructure, such as the increase of voids and H2O concentration in the film. The laser-induced damage threshold (LIDT) of the film increases monotonically with the rise of pressure in this experiment. The porous structure and low nonstoichiometric defects absorption contribute to the film’s high LIDT. The films prepared at the lowest and the highest pressure show nonstoichiometric and surface-defects-induced damage features, respectively. [ABSTRACT FROM AUTHOR]

This paper presents a simple system capable of detecting wavefront information in the wavelength range of 488–1064 nm based on an interferometric system consisting of a ball lens and an aspheric collimator. The design is conducive to short-distance Gaussian beam expansion and collimation at multiple wavelengths. The design principles and performance of the system are described in detail; the measurement precision of the system is verified experimentally by measuring the surface profile of a piece of uncoated N-BK7 glass at various test wavelengths with the proposed setup and with a digital 4D FizCam 2000 interferometer. The highly consistent measurement results of the two methods reveal that the proposed system operates precisely and effectively at various wavelengths. Subsequently, the system is applied to measure the transmitted-wavefront error of a solar filter at a wavelength of 808.0 nm; the measurement results show superb repeatability. The proposed technique avoids the shortcomings of conventional single-working-wavelength interferometric systems, which can neither work in a wide spectrum with high precision nor measure the wavefront properties of many optical bandpass elements in one device; this technique also provides technical support for future applications of high-precision and low-cost wavelength-switchable laser interferometers. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) diffraction gratings have been developed rapidly in several growing areas of research, but most of them were polarization sensitive with limitations toward practical applications. We report a 2D diffraction grating solution for achieving polarization-independent high efficiency property. The grating was designed and fabricated based on thin-film coatings, orthogonally lithography, and ion-beam etching technology. The measured average (−1, 0) order reflective diffraction efficiency (DE) is 74.8% (p-polarization) and 68.2% (s-polarization) from 770 nm to 790 nm and the lowest difference of DE between two polarizations is 0.593% at 785.5 nm incident wavelength of our sample. [ABSTRACT FROM AUTHOR]

The measurement of the spectral diffraction efficiencies of a diffraction grating is essential for improving the manufacturing technique and for assessing the grating’s function in practical applications. The drawback of the currently popular measurement technique is its slow speed due to the hundreds of repetitions of two kinds of time-consuming mechanical movements during the measuring process (i.e., the rotation of the mechanical arm to capture the light beam and the mechanical variation of the output wavelength of the grating monochromator). This limitation greatly restricts the usage of this technique in dynamic measurement. In this manuscript, we present a motionless and fast measurement technique for obtaining the spectral diffraction efficiencies of a plane grating, effectively eliminating the aforementioned two kinds of mechanical movements. Herein, the proposed solution for removing the first kind of mechanical movement is tested, and the experimental result shows that the proposed method can be successfully used to measure the plane transmission grating’s spectral diffraction efficiencies in the wavelength range of 550-750 nm. The method for eliminating the second kind of mechanical movement is not verified in this manuscript; however, we think that it is very straightforward and commercially available. We estimate that the spectral measurement can be achieved on a millisecond time scale by combining the two solutions. Our motionless and fast measuring technique will find broad applications in dynamic measurement environments and mass industrial testing. [ABSTRACT FROM AUTHOR]

An in situ multi-beam optical sensor system was used to monitor and analyze the force per unit width (F/w) and stress evolution during several stages in magnetron-sputtered SiO2 and SiNx films. Stress was observed to relieve quickly after interrupt and recover rapidly after growth resumption in both films. Stress relief was reversible in SiO2 film but partial reversible in SiNx film. Stress relief results from both physical and chemical adsorption. Stress recovery is caused by physical desorption. And chemical adsorption results in an irreversible stress relief component. No chemical adsorption occurs in SiO2 film because of the stable chemical structure. The relationship between adsorption kinetics and films' mechanical behavior is revealed. [ABSTRACT FROM AUTHOR]