Newton's Rings Research Articles

Towards a more practical analysis of Newton's rings using deep learning.

As a typical form of optical fringes with a quadratic phase, Newton's ring patterns play an important role in spherical measurements and optical interferometry. A variety of methods have been used to analyze Newton's ring patterns. However, it is still rather challenging to fulfill the analysis. We present a deep-learning-based method to estimate the parameters of Newton's ring patterns and fulfill the analysis accordingly. The experimental results indicate the excellent accuracy, noise robustness, and demodulation efficiency of our method. It provides another applicable approach to analyzing Newton's ring patterns and brings insights into fringe analysis and interferometry-based measurements.

Transient ablation topography of a thin chromium film after ultrashort pulsed laser irradiation in the spallation and phase explosion regime

Time-resolved imaging pump–probe reflectometry is an established technique to characterize the dynamic processes occurring during the material ablation upon ultrashort pulsed laser irradiation. In the phase explosion regime, however, the presence of an expanding liquid–vapor mixture on top of the ablated material makes an unambiguous determination of the transient ablation topography almost impossible, especially when only front-side pump–probe reflectometry is used. To circumvent this limitation, the front-side reflectometry was complemented by rear-side reflectometry, where the probe radiation does not interact with the liquid–vapor mixture, and the underneath ablation kinetics of the material becomes observable. To interpret the measured front- and rear-side reflectances, an optical multilayer model of the ablation process was developed. Its applicability is demonstrated on a thin chromium film that was ablated by a single pump pulse. The optical model replicates the Newton rings measured during spallation and phase explosion very well, which allows the reconstruction of the transient ablation topography. The combination of the front- and rear-side reflectometry with modeling offers a valuable tool for studying the ablation processes in thin metal films, because it overcomes the challenges of the phase explosion regime, and thus enhances the understanding of material dynamics upon laser irradiation.

Metasurface-enhanced Newton's rings interferometer-enabled local curvature detection

Curvature detection can reveal significant characteristics of target areas, playing a pivotal role in micro–nano fabrication. The Newton's rings experiment is one of the classical methods for detecting curvature; however, it has several limitations. First, stress-induced deformation damages the convex lens. Second, its applicability is restricted to spherical surfaces. Here, a flexible and low-damage metasurface-enhanced Newton's rings interferometer is proposed to enable the local curvature detection within a micrometer range. Since the metasurface performs differential operation on the pattern of Newton's rings, the three-dimensional local surface of convex lens is directly obtained by bias imaging. As a result, we can calculate the curvature of the target curve on the surface with an error of 2.1 %. Furthermore, such approach was also experimentally demonstrated to realize local curvature detection of aspherical objects such as transparent liquids. It is believed that the proposed scheme can open up more possibilities for applications involving metasurfaces.

Ultraflat Graphene Oxide Membranes with Newton-Ring Prepared by Vortex Shear Field for Ion Sieving.

The wrinkles on graphene oxide (GO) membranes have unique properties; however, they interfere with the mass transfer of interlayer channels, posing a major challenge in the development of wrinkle-free GO membranes with smooth channels. In this study, the wrinkles on GO were flattened using vortex shear to tightly stack them into ultraflat GO membranes with Newton's ring interference pattern, causing hydrolysis of the lipid bonds in the wrinkles and an increase in the number of oxygen-containing groups. With increasing flatness, the interlayer spacing of the GO membranes decreased, improving the stability of the interlayer structure, the flow resistance of water through the ultraflat interlayer decreased, and the water flux increased 3-fold. Importantly, the selectivity for K+/Mg2+ reached approximately 379.17 in a real salt lake. A novel concept is proposed for the development of new membrane preparation methods. Our findings provide insights into the use of vortex shearing to flatten GO.

Newton ring interferometry application for 2D lens array alignment with micrometer accuracy.

The dense packing of two-dimensional (2D) lens arrays with high tilt and decentration accuracies is a technological challenge in coherent beam combining, as the collimator lens parameters and 2D lens array alignment must satisfy stringent requirements. A method for 2D lens array alignment based on Newton ring interferometry (NRI) is proposed. The analytical model and the algorithm presented in this study enabled the estimation of alignment sensitivity. An optical setup for alignment tests using NRI was developed and experimentally verified, and micrometer sensitivity was demonstrated. Analytical and experimental results showed that micrometer accuracy was achieved. Its limitations and prospects for improvement are also discussed.

Electrical and Structural Analysis of β‐Ga2O3/GaN Wafer‐Bonded Heterojunctions with a ZnO Interlayer

AbstractWafer bonding of β‐Ga2O3 and N‐polar GaN single crystal substrates is demonstrated by adding ZnO as a “glue” interlayer. The wafers are fully bonded such that Newton rings are not observed. Temperature‐dependent current‐voltage (I–V) measurements are conducted on the as‐bonded Ga2O3/ZnO/N‐polar GaN test structure and after annealing at 600 °C and 1100 °C. The impact of post‐annealing temperature on the electrical and structural characteristics of the bonded samples is investigated. A consistently ohmic‐like characteristic is obtained by annealing the bonded wafers at 1100 °C in N2, which is in part due to crystallization of ZnO and diffusion of Ga into ZnO which makes it n‐type doped. The wafer bonding of β‐Ga2O3 and GaN achieved in this work is promising to combine the material merits of both GaN and Ga2O3 targeting breakthrough high‐frequency and high‐power device performances.

Electron affinity measurement of hydrogen negative ion

Photodetachment Microscopy experiment was first carried out in the presence of an electric field by Blondel et al in 1996 for Bromine negative ion. It measures the spatial distribution of ejected electrons on the detector screen which is a direct view of the spatial structure of the wave function of an atomic electron in the form of a ring pattern. From a semi-classical point of view, this ring pattern is formed because of the interference between two electron waves; one is direct while the other is reflected from an electric field. Following Blondel's photodetachment microscopy experiment, a formula that displays the Newton Rings is derived using a theoretical imaging technique or hydrogen negative ion near a plane interface. The interface means an elastic plane in the vicinity of the source of photoelectrons. The direct and reflected electron waves in this formula generate quantum interference in the form of Newton Rings. It is found that the number of rings increases as we increase the photon energy of the laser light. This finding is in accordance with the very well-known Einstein photoelectric effect which finally provides help to find the electron affinity of the hydrogen negative ion very accurately.

Phase transition and birefringence studies on some ferroelectric liquid crystals

In the present studies the homologous series of hydroxy phenylamino methyl phenoxy benzoate liquid crystals (n = 8,9 and m = 6) are used. The temperature variation of density is measured. Using density data the phase variants in the compounds are identified. All the compounds exhibit first-order phase transitions. By Newton rings method the birefringence is measured directly in smectic and nematic phases. The advantages of the newton ring technique are presented over the conventional methods for the determination of orientational order parameter. The orientational order parameter attained by the newton rings scheme is equated through the literature data, the results are discussed.

Improved Frft Method Based on Triangle Shrinkage Estimating the Physical Parameters from Newton's Rings

Improved Frft Method Based on Triangle Shrinkage Estimating the Physical Parameters from Newton's Rings

Light-Induced Raman Spectra Oscillations and Macroscopic Propulsion of Graphene Bubbles

Atomically thin graphene bubbles can form on a flat substrate due to trapped substances between graphene and the substrate, providing an impressive case to study the intriguing properties of graphene with a nanoscale curvature. The energy balance between the van der Waals interaction of graphene to the substrate and the elastic energy required to deform graphene determines the shape, size, and internal pressure of the graphene bubble. In this work, light interference-induced Newton rings were clearly resolved not only in optical microscopy images but also in Raman spectroscopy maps of the graphene bubble, which originated from the optical standing waves formed in the graphene/SiO2/Si microcavity. Importantly, for the first time, such optical standing waves were directly visualized by imaging the spatial temperature distribution of laser-irradiated graphene bubbles through Raman scan mapping. Raman spectra oscillations can be explained by the laser-induced local heating effect and nonuniform temperature on the surface of the graphene bubble. Furthermore, with a higher laser power of illumination, a direct light propulsion of the bubble was observed on a macroscopic scale. The trajectory of the graphene bubble movement can be effectively manipulated by controlling the position and travel direction of the laser beam. These results offer an exciting opportunity to tune the optoelectronic properties of graphene and other two-dimensional materials at nanoscale confinement and to achieve the direct light manipulation of matter.

Nanocracks in nature and industry.

Nanocracks in nature and industry.

Bilayer-film-decorated microsphere with suppressed interface reflection for enhanced nano-imaging.

Microspheres as special optical lenses have extensive applications due to their super-focusing ability and outstanding resolving power on imaging. The interface reflection between the microsphere and sample surface significantly affects nano-imaging as exhibited in the form of the Newton's rings pattern in virtual images. In this work, a new scheme of decorating the microsphere with a dielectric bilayer thin film is proposed to suppress the interface reflection and thus enhance the imaging performance. The particle swarm optimization algorithm is performed with a full-wave simulation to refine the bilayer thin film decorated microsphere design, which is successfully realized via a novel fabrication strategy. Experimental imaging results demonstrate that the Newton's rings pattern in virtual images is substantially diminished. Both the imaging contrast and effective field-of-view of the microsphere nano-imaging are improved via this effective light manipulation scheme, which is also applicable to promoting the performance of the microsphere in other optical applications.

Effects of Electrode Combinations on RSW of 5182-O/AlSi10MnMg Aluminum

Aluminum is a key lightweight material for reducing vehicle weight and improving fuel efficiency and is used in wrought, extruded, and cast forms. There is little research on resistance spot welding (RSW) of wrought-to-cast dissimilar aluminum alloys. For this paper, two types of electrodes were developed, and 2.3-mm 5182-O wrought and 4-mm AlSi10MnMg die cast sheets were welded by RSW with different electrode combinations. The results demonstrate that electrode geometry significantly influences the weld nugget morphology, weld performance, and failure mode. The proprietary Newton ring electrode produces the largest weld nugget size and consistent weld performance. Through the optimized electrode combination, severe weld nugget migration problems can be addressed for RSW of dissimilar aluminum alloys. Furthermore, the fracture crack under the tensile shear load always starts from the AlSi10MnMg side but not on the 5182-O side due to work hardening and concentration of stress regardless of whether the welds failed in the interfacial failure or pullout failure modes.

Features of Glass Plate Hardening by the Ion Exchange Method

In this work various methods of glass plate hardening are considered. These plates are used to protect defense devices. As a glass was used system R2O-B2O3-SiO2. The method of thermal hardening was considered. Technological disadvantages of this method were discovered by analyzing Newton's rings and a polarizing plate. The use of chemical hardening has shown its advantages over the thermal method. The essence of the method is the ion exchange of alkali metals between glass plates and the chemical mixture melt. The operating principle of the chemical hardening equipment and its technology were considered. As a result, hardened glass plates with preservation of planar geometry were obtained.

Evidence of flexoelectricity in graphene nanobubbles created by tip induced electric field

Strain engineering in graphene nanobubbles (GNB) has made significant progress in recent years opening new possibilities to observe quantum phenomena such as Newton's ring oscillation and generation of pseudomagnetic field. Here, we demonstrated that controlled formation of graphene nanobubbles is possible on transferred graphene on standard SiO2/Si substrate by the application of external electric field through the tip of piezoelectric force microscope (PFM). We manipulated their dimensional attributes (height, area and volume) by varying tip ramp voltage and tip distance. Prominent out-of-plane piezo-response (flexoelectricity) was observed using PFM in the newly created nanobubbles due to the presence of non-uniform strain gradients in the nanobubbles. Moreover, we found quadratic dependence of the effective piezoelectric coefficient proportional to the increasing bubble creation ramp voltage. Our work motivates the exploration of flexoelectric properties and related applications with 2D nanobubbles on different substrates.

Radius of curvature of spherical wave measurement based on vortex beam interference

We proposed a new method for the radius of curvature (ROC) of spherical wave measurement based on vortex beam interference and Fermat's spiral fitting, which can not only provide a large measurement range but also have high precision. Theoretical analysis showed that the maximum distribution of the interference light intensity is in accordance with the Fermat's spiral, and the spiral coefficient is proportional to the ROC of spherical wave. For a concave spherical mirror with a ROC of 899.89mm and a convex spherical lens with a ROC of 59.99mm, the average measurement error of five measurements are 0.080% and 0.083%, respectively. Controlled experiments showed that, our proposed method has a higher measurement accuracy and a larger measurement range than Newton's rings method, it has almost equal measurement accuracy for large and small ROC. This research provides a theoretical basis for the development of a ROC measurement system with large measurement range and high precision.

Improving mechanical properties and electrode life for joining aluminum alloys with innovatively designated Newton ring electrode

Abstract Aluminum alloys are critical lightweight materials in the automotive industry, which can significantly reduce vehicle weight and improve vehicle fuel efficiency. However, resistance spot welding, as one of key joining approaches, faces the challenges of short electrode life and unstable weld quality when welding aluminum alloy. A novel electrode named as Newton Ring (NTR) electrode was developed to address these issues. The mechanical property, nugget evolution and electrode degradation during continuous welding of aluminum alloy with NTR electrode were investigated and compared with the typical spherical electrode. Results indicate that the mechanical property, electrode life and surface quality of the weld fabricated by NTR electrode were much better than typical one. The improvement in the weld quality with NTR electrode stems from its unique surface morphology, which changes the current density distribution during welding and creates a ring-shaped nucleation process of the nugget. Therefore, the shape and size of the nugget are more stable, and the nugget does not cause serious offset in the continuous welding test. Additionally, the wear of the NTR electrode gradually grows from concentric rings to the base ring, avoiding the random and rapid wear on the electrode weld face, thus improving the surface quality of the weld.

Electron interference in atomic ionization by two crossing polarized ultrashort pulses

Formation of geometrically regular interference patterns in the photoelectron momentum distributions (PMDs) corresponding to the photoionization of atoms by two single-color, crossing ultrashort pulses is investigated both analytically and numerically. It is shown that, in contrast to the photoionization by monochromatic pulses, PMDs for the ionization by crossing and co-propagating broadband pulses are essentially different (unless both pulses are linearly polarized), namely, when one pulse is linearly polarized along the propagation direction, $\stackrel{\ifmmode \hat{}\else \^{}\fi{}}{\mathbf{k}}$, of the circularly polarized (CP) pulse, then interference maxima (minima) of the ionization probability have the form of three-dimensional single-arm regular spirals which are wound along $\stackrel{\ifmmode \hat{}\else \^{}\fi{}}{\mathbf{k}}$. Next, the interference maxima (minima) of the ionization probability by a pair of crossing elliptically polarized pulses have the form of either Newton's rings or two-arm Fermat's spirals, depending on the position of a detection plane. Remarkably, these regular patterns occur only for certain values of the pulse ellipticities, and they become distorted for CP pulses. For both above-mentioned pulse configurations, the features of interference patterns depend on the time delay between pulses, their relative electric field amplitude, and relative carrier-envelope phase. Our predictions, illustrated by the numerical results for the ionization of H and He atoms by two orthogonal pulses, are quite general and we expect them to be valid for the ionization of any randomly oriented atomic or molecular target.

Laser thermal lens measurement based on Newton ring interferometry

Thermal lens technology has attracted much attention because of its high sensitivity, low detection limit and being suitable for the analyses of minute samples. Thermal lens technology has been widely used in many fields, such as chemistry, physics, environmental monitoring, electronics, material science and life science. In this paper, the laser thermal lens measurement is studied based on Newton’s ring interferometry, especially for the case of low-power laser. The application of this method in the measurement of small samples is also discussed. It is helpful to study the micro deformation of thin film and lens under low power laser at room temperature. The results are very important for the future research on the micro deformation of optical elements.

Cell-Like Behaviors of Dynamic Graphene Bubbles with Fast Water Transport.

Ultrafast water transport in graphitic nanoenvironment is fundamentally important in the research of biomimetic membranes for potential applications in separation and energy. Yet, the form of graphitic nanostructures has not been fully explored with only carbon nanotubes and graphene nanochannels reported. Here, we fabricated dynamic graphene bubbles via strain engineering of chemical vapor deposition (CVD)-grown graphene on metal substrates. These graphene bubbles could switch between an inflated state and a deflated state continuously with the control of environmental moisture flow. It is demonstrated that water vapors transport through graphene wrinkles and condense inside graphene bubbles. The water transport rates across these graphene bubbles were calculated via dynamic Newton rings, which is comparable to that of carbon nanotubes and aquaporin. The discovery of dynamic graphene bubbles hosting the ability of fast water transport is helpful for an advanced understanding of the nanofluidic phenomenon and its future applications.