Praseodymium (Pr) and Bismuth (Bi) co-doped Yttrium Iron Garnet (PrxBiY2-xFe?O??, where x = 0.1, 0.25, 0.5, and 1.0) nanoparticles were synthesized via a self-combustion-assisted sol-gel method. Structural analysis confirmed the formation of a pure cubic Y?Fe?O?? (YIG) phase without any secondary phases. Morphological characterization and energy dispersive spectroscopy (EDS) confirmed the successful incorporation of Pr³? and Bi3+ ions into the YIG ferrite structure. Optical measurements showed a decreased optical band gap attributed to new energy levels introduced by Pr³? doping. Magnetic characterization exhibited typical ferrimagnetic behaviour, with reduced saturation magnetization, coercive field, and anisotropy constant as Pr³? content increased, indicating disruption in magnetic alignment. While challenges remain in balancing enhanced dielectric properties with reduced magnetic alignment and ensuring stability for practical applications, the composition with x = 0.25 demonstrated balanced magneto-dielectric properties. This makes it a promising candidate for multifunctional microwave applications such as filters and resonators

Ferroelectric thin?film capacitors are of interest for energy storage due to their high charge/discharge rates, essential for compact electronics. As alternatives to Pb?based materials, environmentally friendly barium titanate–based systems show great energy?storage potential. Herein, Ba0.7Sr0.3TiO3 (BST7)/Ba0.6Sr0.4TiO3 (BST6) thin films altering the layer structure are designed and constructed on boron?doped Si <100> substrates by solution?based spin?coating method. The structural and electric properties of trilayer thin films are investigated, and the results are compared with those of monolayer thin films such as BST7 and BST6. An enhanced polarization and improved breakdown strength are simultaneously achieved in the BST767 (Ba0.7Sr0.3TiO3/Ba0.6Sr0.4TiO3/Ba0.7Sr0.3TiO3) trilayer thin film caused by the interfacial effect, which leads to an ultrahigh energy?storage density (Wrec) of ?56.9Jcm?3 accompanying an efficiency (?) of ?72%. The BST767 trilayer capacitor processes a fast charging/discharging speed and a giant power density of 0.72MWcm?3. These thin?film capacitors exhibit a relatively high resistive switching behavior with an improved on–off ratio compared to ceramic capacitors. The mechanisms underlying current conduction are thoroughly analyzed. Such performance makes them suitable for future portable electronics, hybrid vehicles, and aerospace applications

Smart manufacturing, or Industry 4.0, integrates technologies such as the Internet of Things (IoT), artificial intelligence (AI), and cloud computing to transform production, enhancing productivity and flexibility. However, IoT devices often rely on conventional batteries, which have drawbacks like toxicity, short lifespan, and the need for frequent replacement. Magneto-mechano-electric (MME) generators offer a sustainable alternative for powering IoT devices and wearable electronics by harvesting energy from stray magnetic fields. Recent advancements in MME generators include the use of multiferroic composites in cantilever structures, combining magnetostrictive, piezoelectric, and triboelectric materials with permanent magnets. These innovations focus on optimizing crystallographic orientation, minimizing energy conversion losses, and utilizing flexible micro-fiber materials and magnetic flux concentration. Hybrid energy conversion principles and magnetic shape memory alloys, which deform under magnetic fields, further enhance energy harvesting capabilities. This review explores the design and development of MME generators, emphasizing strategies to improve efficiency and integrate hybrid energy harvesting technologies. It also highlights challenges and future prospects for achieving self-powered IoT sensors and wearable devices.

The study introduces a novel asymmetric optical cryptosystem that utilizes bright C-point polarization singularity speckle (BCPSS) patterns as security keys while offering multiuser capabilities. The C-point singular beams, with spatially varying polarization distributions, are created by superposing optical vortex modes of different magnitudes into an orthogonal polarization basis. This complex light beam is then scattered through a rough surface to generate the BCPSS patterns. These generated speckle patterns inherit some unique properties due to the vectorial light field and the randomness of the rough surface, which make them nearly impossible to duplicate. To generate a complex image, the BCPSS phase mask is used to further modify the original image after it has been phase encoded. The final encrypted image is then obtained by processing the intermediate complex image using two-dimensional non-separable linear canonical transform (2D-NS-LCT) and polar decomposition. The 2D-NS-LCT has ten independent parameters which expends the key space, improving its resistance to various attacks. The implementation of polar decomposition in the proposed cryptosystem enables us to have two private keys, helping in multiuser functionality. The proposed method is also validated by testing it against various potential attacks, including contamination and plaintext attacks. Numerical simulations confirm the authenticity and reliability of the proposed cryptosystem

Energy harvesting transduces untapped ambient energy into electrical power, supporting autonomous, sustainable devices. Magneto-mechano-piezoelectric nanogenerators (MMPNGs) leverage magnetic torque-induced mechanical strain to activate the piezoelectric mechanism, efficiently converting mechanical energy into electrical energy and driving innovation in energy-harvesting systems for next-generation applications. This work aims to designate flexible and biocompatible PNGs and MMPNG from the site-engineered BCZT-based ceramics synthesized through the solid-state reaction method with the thermal quenching process. The PNG was initially designated and tested for its energy harvesting properties under biomechanical tapping, yielding the power characteristics of 7.8 V/164.4 nA (corresponding peak power density of 711.1 µW cm?3). The designated MMPNG, under an alternating current magnetic field of 6 Oe, generated an open-circuit peak-to-peak voltage (V p-p) and a short-circuit current of 4.4 V and 202 nA, respectively. The harvesting device also exhibits a maximum root mean square power output of 4.4 nW, equivalent to a power density of 395 nW cm?3. These energy harvesters demonstrated the ability to maintain consistent performance over 50000 operational cycles without significant degradation in output. These findings reveal strong potential for powering autonomous miniature electronics, paving the way for sustainable and efficient compact energy solutions

It is well known that the coherence vortices are robust against atmospheric turbulence and can be effectively utilized for communication and imaging applications. In this paper, we study, both theoretically and experimentally, the generation of coherence vortices by the cross-correlation between two scattered optical vortices with different topological orders and how the orders of the input fields affect the size of the generated coherence vortices. We have analyzed the size by considering the coherence vortex at a given plane as a ring with inner and outer radii. The inner and outer radii vary linearly with order and the propagation distance. The slope of radius vs. propagation distance is considered as the divergence by which one will be able to find the order. All the theoretical predictions have been validated with the experimental results. It is also observed that the propagation characteristics are similar to the coherent optical vortices

The topological charge (TC) of optical vortex beams can be measured using various interferometric and non-interferometric techniques in both coherent and partially coherent domains. However, these methods are not suitable for obstructed vortex beams, also known as open optical vortex (OOV) beams. Recently, several methods for studying open optical vortex (OOV) beams, have recently been proposed and demonstrated based on interferometry, phase retrieval, spatial coherence analysis, which limit their applicability in the presence of significant perturbations or long-distance propagation. In this study, we propose and experimentally demonstrate an efficient method for measuring both the magnitude and sign of the topological charge (TC) of OOV beams using the auto-correlation distribution after scattering through a rough surface. We generated the OOV beams using partially blocked computer-generated holograms. Although the rings or zero points present in the auto-correlation are broken, the number of rings is equal to the TC. Further, we have utilized the radius of the first ring and its divergence with propagation distance, which can be easily observed for all orders, for finding the TC of higher orders. We can measure the sign of the topological charge solely through intensity measurements using the rotation of the autocorrelation profile with the help of blocking parameter. Furthermore, we demonstrate that the characteristics of OOV beams derived from our proposed method align well with the propagation characteristics of unobstructed OV beams. The results confirm the efficacy of optical vortex beams for free-space optical communication

The properties of lead-free piezoelectric K0.5Na0.5NbO3 (KNN) were enhanced by antimony (Sb) doping on the B-site using a solid-state reaction method. XRD and Raman analysis confirmed phase purity, showing an orthorhombic structure. X-ray diffraction patterns were fitted using FullProf to determine lattice parameters, revealing reduced bond angles and lengths in Sb-doped KNN (KNNS). The dielectric properties showed a phase transition in pure KNN at 185 °C (orthorhombic to tetragonal) and 380 °C (tetragonal to cubic), while KNNS exhibited relaxer ferroelectric behaviour. KNNS displayed enhanced ferroelectricity (2Ps=26.2 ?C/cm2) and low leakage current (4.17 nA-cm?2). KNNS also demonstrated superior energy harvesting, producing 25.2 V and a power density of 7.71 mW-cm?2 under finger tapping, a 280% improvement over pure KNN. The study highlights the benefits of Sb doping in improving the electrical properties and Curie temperature of KNN, as well as its successful application in energy harvesting and ultrasonic testing of aluminium alloy specimens

We propose an optical asymmetric phase image encryption method in which the vectorial light field is used to encode the data. In transverse plane, the vectorial light field has spatially varying polarization distributions where we are allowed to have a greater number of degrees of freedom. In this scheme, the input image is first phase encoded and then modulated by a phase encrypting key, synthesized from the speckles obtained by the scattering of Hermite–Gaussian beams. The modulated image is further processed using fractional Fourier transform with a specific order (?). A pixel scrambling operator is utilized to increase the randomness to further enhance the security and singular value decomposition approach is employed to add the nonlinearity in the encryption process. Now, the stokes parameters, i.e. S1 and S2 are calculated using the light intensities correspond to different polarizations. S1 is used as the encrypted image for transmission and S2 is reserved as one of the private decryption keys. The robustness of the proposed technique is tested against various existing attacks, such as known plaintext attack, chosen plaintext attack, and contamination attacks. Numerically simulated results validate the effectiveness and efficiency of the proposed method

This paper introduces a robust and automated method for detecting grain boundaries and estimating particle sizes in microstructural images using OpenCV-based image processing techniques. The approach leverages high-resolution image analysis to enhance clarity and precision in boundary detection through a series of preprocessing steps, including image format conversion, cropping, brightness/contrast adjustments, and sharpening. Following this, Gaussian blurring and thresholding are applied to separate particles, with contour detection used to accurately identify grain boundaries. Particle sizes are then calculated by converting pixel dimensions to micrometers, enabling precise measurements. To improve the reliability of the results, statistical techniques like outlier removal and clustering are employed to refine the size distribution. Additionally, texture analysis is performed using the Gray Level Co-occurrence Matrix (GLCM), and k-means clustering is applied to segment regions based on texture similarity. This comprehensive method provides material scientists with a highly accurate, efficient tool for grain size analysis and boundary detection, offering significant improvements in both speed and precision compared to traditional manual techniques

Data protection via encryption continues to be a key concern in the constantly changing field of digital security. This study investigates a novel method of pixel displacement picture encryption via a modified Caesar cipher algorithm. The proposed method ensures enhanced security by shifting pixel values according to a random key matrix, obscuring image content from unauthorized access. Unlike traditional Caesar cipher applications, which are often criticized for their simplicity and vulnerability, this pixel-wise encryption method leverages the power of modular arithmetic to transform grayscale image data into a format resilient to common cryptographic attacks and concerns. Since the encryption strength is largely dependent on the key's unpredictability and secrecy, key management is essential to this strategy. This technique offers a trivial alternative suitable for specific low resource applications where efficiency is Paramount. The paper also discusses the implications of this method in the broader context of confidentiality, data integrity, and authentication, which are crucial elements in the modern digital security paradigm

A new nonlinear optical multi-image authentication scheme is proposed based on Kramers-Kronig digital holography and orthogonal triangular decomposition or QR decomposition. Here, the complex light field carrying the information of multiple images is modulated by random phase masks and propagated at certain distance. Afterwards, the QR decomposition is applied to the complex wavefront to generate the private keys and to add the non-linearity in the scheme. Next, the product of orthogonal matrix and upper triangular matrix is processed further. The obtained output is modulated by different phase masks and interfered with reference beam to record the encrypted image. For decryption, the Kramer-Kronig relation is utilized to extract the plaintext images directly with only the positive frequency part. A series of numerical simulations are conducted to validate the efficacy and robustness of proposed image authentication scheme.

Computational methods have been established as cornerstones in optical imaging and holography in recent years. Every year, the dependence of optical imaging and holography on computational methods is increasing significantly to the extent that optical methods and components are being completely and efficiently replaced with computational methods at low cost. This roadmap reviews the current scenario in four major areas namely incoherent digital holography, quantitative phase imaging, imaging through scattering layers, and super-resolution imaging. In addition to registering the perspectives of the modern-day architects of the above research areas, the roadmap also reports some of the latest studies on the topic. Computational codes and pseudocodes are presented for computational methods in a plug-and-play fashion for readers to not only read and understand but also practice the latest algorithms with their data. We believe that this roadmap will be a valuable tool for analyzing the current trends in computational methods to predict and prepare the future of computational methods in optical imaging and holography. © The Author(s) 2024.

Piezoelectric energy harvesting has recently gained attention due to its high power density and potential for self-powered sensor networks. This study investigates the effects of dopants on Ba0.85Ca0.15Zr0.1Ti0.9O3 (BCZT) ceramics, examining Strontium (Sr2+), Zinc (Zn2+), and praseodymium (Pr3+/4+) ions at different sites and their impact on structural, dielectric, and electrical properties. X-ray diffraction and Rietveld analysis reveal a coexistence of tetragonal and rhombohedral/orthorhombic phases, with a predominant tetragonal phase, confirmed by Raman analysis. Energy-dispersive X-ray spectroscopy ensures chemical homogeneity. The density measurements indicate a dense microstructure with a relative density of 90–95 %. Dielectric analysis shows a relaxor-like behavior in AB-site doped BCZT ceramics, validated by polarization-electric field hysteresis loops. B-site doped BCZT ceramics exhibit ultra-low leakage currents, approximately 103 times lower than undoped BCZT. An optimized biocompatible flexible film-based energy harvester, incorporating A-site doped BCZT ceramic particles, demonstrated impressive energy harvesting capabilities. A simple finger tapping generated ?80.2 V and ?18.2 nA, with an average peak-to-peak power density of 7.6 µW-cm?3. These results highlight the significant potential of dopant inclusion in BCZT ceramics, marking a major advancement in doping strategies for piezoelectric energy harvesting in miniature electronics. © 2024 Elsevier Ltd

We propose a new asymmetric optical cryptosystem for phase image encoding with the utilization of speckles generated by scattering the Hermite Gaussian beams (HGBs) through a rough surface. These speckle patterns are unique and almost impossible to clone as one cannot mimic the physical process. The generalized Schur decomposition, named as, QZ decomposition, approach is used to generate unique private keys for decrypting the encoded data. The plaintext image is first phase-encoded and then modulated with the pattern obtained by the convolution of HGBs and random phase masks. The modulated image is then Fresnel propagated for a distance of z, and the QZ decomposition operation is performed on the complex wavefront to generate the private keys. Afterward, the gyrator transforms with a rotational angle (?), and the phase truncation is used to further process the information. The phase truncation and phase reservation (PT/PR) will result in another phase private key, which will be utilized for decryption. A non-linear power function is introduced to modify the amplitude part after PT/PR operation and the resultant is modulated using an HGB amplitude mask to get an intermediate wavefront. Finally, the encrypted image is obtained by Fresnel propagating the intermediate wavefront with a distance of z. The effectiveness and validity of the proposed method are tested and verified through numerical simulations. A series of potential attacks such as contamination and plaintext attacks have been tried and tested to further check the robustness of the proposed method. The results confirm the efficacy of the proposed method.

Extracting the grain size from the microscopic images is a rigorous task involving much human expertise and manual effort. While calculating the grain size, we will be utilizing a finite number of particles which may lead to an uncertainty in the measurement. To avoid this difficulty, we utilize a simple mathematical tool, the auto-correlation function, to determine the grain size. The random particle distribution and the finite width Gaussian histogram of particle size has motivated us to utilize the auto-correlation function, which has been extensively studied for finding the size of random optical patterns. The finite width of the correlation function provides the grain size, and the difference in correlation length along two mutually independent directions provides information about the asymmetry present in the particle distribution, i.e., the deviation from a spherical shape. The results may find applications in material, pharmaceutical, chemical, and biological studies where extracting the grain size is essential.

Piezoelectric materials play a crucial role in energy harvesting applications, efficiently capturing renewable energy from sources like human activities and vibrations. Oxygen vacancies, common imperfections in these materials, significantly influence their overall effectiveness. In our study, Ba 0.85 Ca 0.15 Zr 0.1 Ti 0.9 O 3 (BCZT) powder was calcined under different conditions (air and vacuum) to investigate their impact on crystal structure, microstructure, electrical properties, and energy harvesting performance. X-ray diffraction (XRD) and Rietveld analysis confirmed varied phases in vacuum calcined BCZT with a smaller particle size. X-ray photoelectron spectroscopy (XPS) revealed lower oxygen vacancy concentration for vacuum-calcined samples. The vacuum calcined BCZT ceramics demonstrated a remarkable 580% enhancement in the figure of merit (FOM) when contrasted with traditional ceramics, highlighting superior dielectric and piezoelectric characteristics. In mechanical energy harvesting, BCZT ceramics, protected by polyimide with Cu/Ag electrodes, outperformed conventional ceramics, generating a higher open-circuit voltage (10.61?V) and peak-to-peak power (1.510?mW/cm 3 ). This energy harvester maintained stable output through 7000 cycles, suggesting its potential for powering miniature electronics.

In the modern era, the secure transmission and storage of information are among the utmost priorities. Optical security protocols have demonstrated significant advantages over digital counterparts, i.e., a high speed, a complex degree of freedom, physical parameters as keys (i.e., phase, wavelength, polarization, quantum properties of photons, multiplexing, etc.) and multi-dimension processing capabilities. This paper provides a comprehensive overview of optical cryptosystems developed over the years. We have also analyzed the trend in the growth of optical image encryption methods since their inception in 1995 based on the data collected from various literature libraries such as Google Scholar, IEEE Library and Science Direct Database. The security algorithms developed in the literature are focused on two major aspects, i.e., symmetric and asymmetric cryptosystems. A summary of state-of-the-art works is described based on these two aspects. Current challenges and future perspectives of the field are also discussed.

Pulsed power and power electronics systems used in electric vehicles (EVs) demand high-speed charging and discharging capabilities, as well as a long lifespan for energy storage. To meet these requirements, ferroelectric dielectric capacitors are essential. We prepared lead-free ferroelectric ceramics with varying compositions of (1 ? x)BaSrTiO–(x)BiMgTiO (BST–BMT) (x = 0, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1) using a solid-state-reaction method. To analyze the crystallinity and structural parameters, we examined the X-ray diffraction (XRD) patterns using the pseudo-Voigt function in the FullProf software. Additionally, Raman spectrum analysis confirmed the presence of ceramic structural distortion caused by microstrain and doping. Microstructure images of the ceramic samples showed an increase in grain size from 1 to 2.4 ?m and an improved distribution of grain sizes with increasing doping levels. We investigated the dielectric properties of the BST–BMT ceramic capacitors across a wide range of frequencies and temperatures. Interestingly, as the BMT content increased, the previously saturated ferroelectric (FE) curve for x = 0.01 gradually shifted towards a narrower relaxor ferroelectric (RFE) curve for x = 0.1. The most favorable effective energy storage density was observed with a BMT doping concentration of x = 0.04, which coincided with exceptionally high-energy efficiency (? ~ 91%) under a field strength of 50 kV/cm and a relatively high dielectric normalized energy storage density of 3.71 µJV cm due to structural modifications that causes relaxor ferroelectric behavior. More interestingly, the energy storage performance of 0.96BST–0.04BMT displays a fatigue free characteristic enduring through numerous switching cycles. We also calculated the optical bandgap (E) values from UV–Vis spectra and compared them with the increase in BMT concentration. The E value for all ceramics was approximately 3.2 eV, similar to the pure BST ceramic sample. Additionally, the resistive switching behavior demonstrated by our bulk ceramic capacitors is not commonly observed in other bulk ceramics.

There has been considerable interest in the nonlinear optical phenomenon in recent years, particularly in two-dimensional materials. Here, we study the optical polarization quantities namely ellipticity and Faraday rotation for the monolayer 1T -WTe two-dimensional (2D) material. We develop a new general approach based on many-body perturbation theory to compute polarization quantities via the second harmonic susceptibility of the material. We find that the nonlinear second-harmonic longitudinal and transverse responses are tunable with the inclination angle made by the out-of-plane field with an axis vertical to the 2D plane. This field breaks the inversion symmetry of the system which is an essential condition for the behavior of the second harmonic susceptibility. Such tunable behavior gives significant variation to the Faraday rotation and ellipticity. Our findings provide valuable information for future experiments on the optical phenomenon in 2D materials.

Magneto-mechano-electric (MME) generators efficiently harness ubiquitous stray magnetic fields and convert them into electricity, capturing significant attention for powering innumerable wireless sensors. In this study, lead-free 0-3 particulate magnetoelectric (ME) nano-composite ceramics, specifically x(Ba 0.85 Ca 0.15 Zr 0.1 Ti 0.9 O 3 )-(1-x)Ni 0.5 Zn 0.5 Fe 2 O 4 [x(BCT-BZT)–(1-x)NZFO], were synthesized using the sol-gel method. Subsequently, a flexible MME generator was designed, incorporating the optimized ME composite. Structural parameter calculations indicated higher tetragonal distortion of 0.4% in 0.4(BCT-BZT)-0.6NZFO, possibly due to uniform particulate distribution. The ME composites displayed uniform dual-phase microstructures, with 0.4(BCT-BZT)-0.6NZFO showing a higher NZFO concentration. The maximum values of the magnetodielectric (MD) and ME coupling coefficients have been determined to be -3.6% and 2.55 mV cm -1  Oe -1, respectively, for an x = 0.4 composite. The MME generator is designed using an optimized 0.4(BCT-BZT)-0.6NZFO ME composite with film thickness of 34 ?m. This MME generator harvests a sinusoidal wave with a maximum output peak-to-peak voltage of 4.1 V when exposed to a weak AC magnetic field of 10 Oe at a frequency of 50 Hz. Additionally, the device demonstrates an exceptional optimal DC power density of 3.89 ?W cm -3. The lead-free 0-3 particulate ME composite enables effective magnetic energy harnessing. As a result, it holds great promise as an efficient autonomous power supply for various Internet of Things based applications.

The integration of magnetoelectric (ME) principles using magneto-mechano-electrical (MME) generators enables the construction of self-powered wireless sensor networks (WSNs) for mechanical energy harvesting. In this study, we propose a lead-free, flexible MME generator that incorporates poly(vinylidene fluoride) (PVDF)/BaCaTiZrO (BCZT) fiber composites and Metglas. This generator produces a robust output voltage even in the presence of stray magnetic fields, without requiring a magnetic bias field. We prepared flexible PVDF/BCZT fiber composites by electrospinning the components at various proportions, and a magnetostrictive Metglas layer was incorporated during the ME composite fabrication process. Under resonance conditions (50 Hz), the optimized ME composition yielded a maximum ME voltage of 472 V cm Oe without a magnetic DC bias field. This significant improvement is attributed to the interfacial interactions between the surface of inorganic BCZT nanoparticles and dipoles within the PVDF polymer matrix, as well as the high permeability of Metglas. Additionally, the flexible MME generator proposed in this study produced an open-circuit voltage of 14.8 V and an approximate power density of 4.7 µW cm under an AC magnetic field of 10 Oe with a frequency of 50 Hz. We demonstrate that our MME device can be used to monitor the health of a muffle furnace by tapping into the magnetic field noise coming from its electronic cables. The as-developed lead-free flexible MME generator shows potential for advanced applications in self-powered WSN and energy harvesting technologies.

Many researchers have been interested in finding elements that help in calculating the orbital angular momentum (OAM) of perturbed vortex beams i.e., after propagating through turbulence in recent years. In this work, we realized a method that utilizes the area of spatial auto-correlation function of scattered optical vortices for finding the topological charge. We have also established an analogy between the area of the intensity auto-correlation profile of the partially coherent vortices and the radii of the related coherent ring-shaped vortex beam transverse profiles which helps us finding the topological charge in a simpler way. This method is independent of the beam waist of Gaussian laser beam for generating the vortex beams. Our experimental results are in good agreement with the theoretically obtained results. These results may find applications in free space optical communication and ghost imaging with vortex beams.

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We propose a new asymmetric cryptosystem for phase image encryption, using the physically unclonable functions (PUFs) as security keys. For encryption, the original amplitude image is first converted into a phase image and modulated with a PUF to obtain a complex image. This complex image is then illuminated with a plane wave, and the complex wavefront at a distance d is recorded. The real part of the complex wavefront is further processed to obtain the encrypted image and the imaginary part is kept as the private key. The polar decomposition approach is utilized to generate two more private security keys and to enable the multi-user capability in the cryptosystem. Numerical simulations confirm the feasibility of the proposed method.

Interferenceless coded aperture correlation holography (I-COACH) is one of the simplest incoherent holography techniques. In I-COACH, the light from an object is modulated by a coded mask, and the resulting intensity distribution is recorded. The 3D image of the object is reconstructed by processing the object intensity distribution with the pre-recorded 3D point spread intensity distributions. The first version of I-COACH was implemented using a scattering phase mask, which makes its implementation challenging in light-sensitive experiments. The I-COACH technique gradually evolved with the advancement in the engineering of coded phase masks that retain randomness but improve the concentration of light in smaller areas in the image sensor. In this direction, I-COACH was demonstrated using weakly scattered intensity patterns, dot patterns and recently using accelerating Airy patterns, and the case with accelerating Airy patterns exhibited the highest SNR. In this study, we propose and demonstrate I-COACH with an ensemble of self-rotating beams. Unlike accelerating Airy beams, self-rotating beams exhibit a better energy concentration. In the case of self-rotating beams, the uniqueness of the intensity distributions with depth is attributed to the rotation of the intensity pattern as opposed to the shifts of the Airy patterns, making the intensity distribution stable along depths. A significant improvement in SNR was observed in optical experiments.

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We propose a new multiuser nonlinear optical cryptosystem using fractional-order vortex speckle (FOVS) patterns as security keys. In conventional optical cryptosystems, mostly random phase masks are used as the security keys which are prone to various attacks such as brute force attack. In the current study, the FOVSs are generated optically by the scattering of the fractional-order vortex beam, known for azimuthal phase and helical wavefronts, through a ground glass diffuser. FOVSs have a remarkable property that makes them almost impossible to replicate. In the input plane, the amplitude image is first phase encoded and then modulated with the FOVS phase mask to obtain the complex image. This complex image is further processed to obtain the encrypted image using the proposed method. Two private security keys are obtained through polar decomposition which enables the multi-user capability in the cryptosystem. The robustness of the proposed method is tested against existing attacks such as the contamination attack and known-plaintext attack. Numerical simulations confirm the validity and feasibility of the proposed method.

Yttrium iron garnet (YIG; Y 3 Fe 5 O 12 ) is an important material in the field of electronics because of its unique magnetic properties. This makes it ideal for use in devices such as microwave filters, amplifiers, sensors, and even magnetic storage devices. It is also used in spintronics, which is the study of the spin of electrons and how it can be manipulated for storage and computation. Additionally, it is highly stable and has low losses when exposed to electromagnetic fields, making it useful in applications such as controlling electric properties with magnetic fields or vice-versa, and magnetic resonance imaging (MRI). Herein, we have prepared YIG and Bi-doped YIG (Bi: YIG: Y 2 Bi 1 Fe 5 O 12 ) nanoparticles (NPs) using the sol–gel auto-combustion method. The obtained garnet powders were sintered at 950 °C both in an air and vacuum environment. We have explored the structural, electrical, optical, magnetic, and magneto-electric (ME) properties of Bi-doped YIG sintered in a vacuum (YBIG-V) and compared it with YIG and Bi-doped YIG sintered in the air (YBIG-A). We found the enhancement in dielectric response, magnetic properties, and the reduction in leakage current for the YBIG-V ceramics than for YBIG-A, YIG ceramics. We have studied the magneto-electric (ME) coupling at room temperature and found that YBIG-V ceramics show the better coupling strength with a maximum coupling coefficient, ? ME of 354.3 mV/cm-Oe. The dielectric response of these samples significantly varies with the applied magnetic field, which will be positive in Bi-doped YIG ceramics and negative in pure YIG ceramics. Compared to YBIG-A, YBIG-V samples have better variation in dielectric response with the magnetic field, due to which they may be utilized for magnetic field sensing applications. We also observed that the resonance frequency varies with the applied magnetic field, which may be another parameter for field sensing applications. We attribute the enhancement of these properties in YBIG-V sample to the reduction in the average oxygen valency which is 1.63 for YBIG-A and 1.58 for YBIG-V. These values have been determined with the help of X-ray photoelectron emission spectroscopy data.

Mechanical energy harvesting and energy storage through lead-free piezoelectric materials is an inevitable source of eco-friendly sustainable powering of electronic devices. Herein, we have synthesized amphoteric rare-earth element praseodymium (Pr) modified Ba 0.85 Ca 0.15 Ti 0.9 Zr 0.1 O 3 (BCZT) ceramics, with a cost-effective solid-state-reaction based two-step sintering method for the controlled grain growth. Their crystalline structures and surface morphology were investigated by using X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The dielectric and ferroelectric properties of the ceramic capacitors were investigated and correlated with structural parameters. In the vicinity of the monotonic phase transition region, with the coexistence of orthorhombic and tetragonal symmetry, the Pr ion addition in BCZT improves the tetragonal phase, which widens its energy harvesting and storage arena. The appreciable energy harvesting ability was found for an optimized energy harvester with a composition of 0.04 wt% Pr added BCZT ceramic, with an open-circuit voltage of about 5.1 V (corresponding power density of 1.213 mW/cm 3 ) from a simple finger tapping and bring about output voltage stability with a maximum output voltage of about 9 V over 10,000 cycles when periodic force is applied by a machine tapping. Furthermore, this optimized Pr added BCZT ceramic capacitor is capable of storing a substantial recoverable energy density of 81.9 mJ/cm 3 with a considerable energy storage efficiency of 76.4%. These upshots offer a head start in implementing these ceramic capacitors for effective energy harvesting and energy storage applications for powering futuristic miniature electronics.

We introduce a modified sintering approach to investigate the microstructure, dielectric, and resistive switching (RS) properties of bulk BaSrTiO (BST) ceramics. The ceramics were prepared using a solid-state-reaction method, and then sintered using modified double-step sintering (DS) processes, as well as conventional single-step sintering (CSS) at different peak temperatures (1250°C and 1350°C). To find the phase purity, lattice parameters, and tetragonality of the samples, x-ray diffraction patterns were fitted with the pseudo-Voigt function in the FullProf software. With the help of the software, bond angles and bond lengths were found for all the ceramics. Furthermore, Raman spectrum analysis was performed to confirm the samples' structural variations. The microstructure images of the samples show that the grain size was reduced and the grain size distribution was improved for the DS-processed ceramics as compared to the CSS-processed ceramics. The dielectric properties of the BST ceramic capacitors were investigated in a wide range of frequencies and temperatures. All the BST ceramics displayed humps at near-room temperature, corresponding to tetragonal–cubic phase transitions, and a small shift in transition temperature towards higher temperature regions for the DS ceramics compared with the CSS ceramics was observed due to structural modification by a grain size effect. The metal–insulator–metal (MIM) structures, so-called memristors, were designed with these dielectric ceramics. A bipolar RS behavior was observed in these MIM structures which were confirmed through current–voltage (I–V) characteristics. The improved RS in these structures is the result of the migration and redistribution of cations, such as oxygen ions and oxygen vacancies ,as well as the ferroelectric domain orientation.

The vulnerability of Linear Canonical Transform (LCT)-based optical encryption system. One of the primary reasons for this is the predictable nature of the security keys (i.e., simulated random keys) used in the encryption process. To alleviate, in this work, we are presenting a Physically Unclonable Function (PUF) for producing a robust encryption key for the digital implementations of any optical encoding systems. We note a correlation function of the scattered perfect optical vortex (POV) beams is utilized to generate the encryption keys. To the best of our knowledge, this is the first report on properly utilizing a scattered POV for the optical encryption systems. To validate the generated keys, the standard Linear Canonical Transform-based Double Random Phase Encoding (LCT-DRPE) technique is used. Experimental and simulation result validates the proposed key generation method as an effective alternative to the digital encryption keys.

We have generated and propagated both diffracting and non-diffracting speckles using the scattering of perfect optical vortices. The diffracting speckles have been realized in the near field and non-diffracting speckles have been realized in the far field, i.e. after taking the Fourier transform of near-field speckles using a simple convex lens. We found that the experimental results are in good agreement with the theoretical results. These results may find applications in classical cryptography and communication as we have both varying and non-varying random field patterns with propagation distance.

We study correlations in the speckle patterns generated by the scattering of perfect optical vortex (POV) beams and use them to produce a new class of coherence functions, namely Bessel coherence functions. Higher (zeroth) order Bessel coherence functions have been realized in cross (auto)-correlation between the speckle patterns generated by the scattering of perfect vortex beams of different orders. We have also studied the propagation of produced Bessel coherence functions and characterized their divergence with respect to the radius of their first ring for different orders m = 0-4. We observe that the divergence varies linearly with the order of the coherence function. We provide the exact analytical expression for the auto-correlation, as well as cross-correlation functions for speckle patterns. Our experimental results are in good agreement with the analytical results.

Ruby is one of the best solids for generation of slow light at room temperature. Ultraslow light propagation to ? 2.8 m/s has been demonstrated experimentally in ruby rod of length 7.6 cm. The systematic variation of optical delay with the modulation frequency, laser power and depth of focus has been studied. Fine tuning from ? 12 ms to ? 20 ms has been achieved by using laser power and depth of focus as a knob, at a modulation frequency of 1.8 Hz. These studies suggest that ruby rod may find potential applications in developing the tunable optical delay-based devices.

Spatially incoherent light can result from nonlinear processes where a group of photons are emitted in entangled states of spatial modes, which results in an incoherent mixture of constituting spatial modes when the photons are assessed one by one. In this paper we explore a method which uses a tilted lens to probe the orbital angular momentum (OAM) spectrum of such a mixture. We examine the general case where the photons are in mixtures of both different OAM and radial modes, resulting in a 2-dimensional random distribution that creates a more difficult challenge compared to mixtures of OAM only.

Polarization speckle is a fine granular light pattern having spatially varying random polarization profile. We generate these speckle patterns by using the scattering of Poincaré beams, a special class of vector vortex beams, through a ground glass plate. Here, the Poincaré beams are generated using a polarization sensitive spatial light modulator displaying an on-axis hologram corresponding to an optical vortex phase profile. The different inhomogeneities of the rough surface experience different polarizations, which control the ability for scattered waves to interfere at the detection plane and causes a spatially varying polarization profile. We experimentally determined the spatial variation of local degree of polarization and orientation of the polarization ellipse for these speckle patterns from the Stokes analysis. We also determined the size of scalar speckles using the auto-correlation function of Stokes parameter S and the size of polarization speckles using the sum of auto-correlation functions of remaining three Stokes parameters. We found that the change in scalar speckle size with the index of the vector beam is very small and of the order of 1 pixel size of the camera but the size of polarization speckles decreases with the increase in index of the vector beam.