Search

We study, using micromagnetic simulations, the inelastic scattering of spin-wave beams on edge-localized spin-wave modes in a thin ferromagnetic film. In the splitting and confluence processes, the new spin-wave beams are generated with frequencies shifted by the edge-mode frequency. We report that inelastically scattered spin-wave beams in both processes not only change their direction of propagation but also undergo lateral shifts along the interface, analogous to the Goos–Hänchen effect known in optics. These shifts of inelastically scattered beams, for a few special cases described in the paper, can be in the range of several wavelengths, which is larger than the Goos–Hänchen shift of elastically reflected beam. Unexpectedly, at selected frequencies, we found a significant increase in the value of the lateral shifts of the scattered spin-wave beams formed in the confluence process. We show that this effect is associated with the cascading nonlinear processes taking place at the edge of the film and involving the primary edge spin wave. Our results make an important contribution to the understanding of the nonlinear nature of spin waves and provide a way to exploit it in signal processing with magnons. [ABSTRACT FROM AUTHOR]

Full-aperture continuous polishing is one of the key processes for polishing large flat optical elements. The surface figure of the optics polished by continuous polishing depends largely on the pitch polishing lap's surface shape, which is controlled by a large conditioner. The changing process of the surface shape of the viscoelastic pitch lap under the loading conditioner is extremely complicated and has not been fully understood. This paper focuses on the formation mechanism and changing principle of the dynamic shape of the pitch lap during polishing. Firstly, the viscoelastic properties of the pitch lap are analyzed, and a viscoelastic creep model of the pitch lap is established. Then, the dynamic alteration process of the surface shape of the pitch lap under the loading pressure of the conditioner is explored, and a solution model of the dynamic shape of the pitch lap at the polishing station is established. Finally, polishing experiments were conducted to verify the model. This paper for the first time reveals that the surface shape of the pitch lap presents a dynamic alteration, which lays a foundation for controlling the surface shape of the pitch lap. [ABSTRACT FROM AUTHOR]

In this paper, we present a method based on the conjugate image principle and micro-nano optics to detect tilt aberrations of a phased fiber laser array system. A co-aperture optics system was adapted to detect the tilt aberrations of a seven-element phased fiber laser array system simultaneously. A Kepler telescope was designed to construct the conjugate relation between the exit pupil of a fiber optic laser array system and a microlens array and also to match the size of the seven beams and the microlens array. The apochromatic theory was used to meet the multispectral (1064 ± 0.3 nm, 1030 ± 0.3 nm, and 633 ± 0.2 nm) detection needs. A far-field detection unit was also designed to evaluate beam quality. When the actual beam was offset by 1 pixel, the beam tilt was about 0.7 µrad. The maximum detection error of the seven-element system was about 7 µrad. It could not only directly detect the beam's tilt angle but also maintained detection accuracy while reducing the algorithm complexity. [ABSTRACT FROM AUTHOR]

With the development of the Internet of Things, cloud networking, and 4K/8K high-definition video, global internet traffic has seen a dramatic increase. This surge in traffic has placed higher demands on the performance of optical networks, featuring higher data rates, lower latency, and lower cost. The passive optical network (PON) is a representative scenario of optical access networks. Issues such as burst-mode detection in upstream PON scenarios, flexible rate allocation in downstream scenarios, and the simplification of hardware complexity at the optical network unit (ONU) side have attracted considerable attention. Compared to intensity modulation/direct detection (IM/DD), a recently proposed coherent PON incorporates a local oscillator laser at the receiver, enabling superior receiver sensitivity, spectrally efficient modulation, linear optical field recovery, and flexible channel selection. These features significantly enhance the flexibility and data rates of PON systems. This paper provides a comprehensive review of the development of coherent PONs, particularly in aspects of preamble design for burst-mode detection in upstream scenarios, the design of flexible rate PONs in downstream scenarios, and solutions for reducing hardware complexity at the ONU side. [ABSTRACT FROM AUTHOR]

Frustrated total internal reflection (FTIR) is analyzed from a novel perspective. Unlike similar works, the angle of incidence is used here as the experimental variable instead of the film thickness through which light tunnels. This method makes it possible to visualize not only the phenomenon of FTIR but also the resonance processes that occur for angles of incidence below the critical angle. An affordable straightforward experiment appropriate for undergraduates is presented. The experiment involves measuring the reflection and transmission of light through a pair of prisms separated by an air or water layer, and the results are in fair agreement with theory. Editor's Note: Total internal reflection occurs when light passes from one medium into another of lower refractive index at an angle greater than the so-called critical angle. However, the term is misleading; the field of the incident wave actually penetrates evanescently into the second medium to a depth of the order of a wavelength. This effect can be "frustrated" by introducing a third medium of refractive index greater than the lower-index medium close to the interface so that the low-index medium becomes an intermediate thin layer; in this case, the evanescent wave couples to the new medium and continues to propagate. In the experiment described in this paper, this effect is investigated by trapping a thin layer of air or water between two prisms and using a laser as the light source. In most such experiments, the width of the trapped layer is varied while the angle of incidence is kept fixed and transmitted/reflected intensities are measured. Adjusting the width is difficult, and the novel aspect here is that the thickness of the layer is fixed while the angle of incidence is varied. This allows the authors to investigate intensities at angles both above and below the critical angle. Results are in respectable accord with theory; the authors also discuss an analogy with quantum tunneling. Appropriate for upper-level optics/electromagnetic theory students. [ABSTRACT FROM AUTHOR]

This article addresses the issues related to the application of refractometry to determination of the optical properties of composite materials containing methacrylic monomers. Refractometric technologies yielding precise and highly informative data are promising for studies of multicomponent composites. The paper defines the purpose and tasks of the study. A block diagram of the investigation system developed here is provided and technical characteristics are given. Relationships between refractive index and increases in temperature are documented, and these produced the data required for finding the temperature coefficient of the refractive index of the samples under study. The results of linear interpolation n(T) were obtained and compared with experimental data. [ABSTRACT FROM AUTHOR]

The multi-dimensional Special Affine Fourier transform (MSAFT) is an intriguing new addition to the integral transform class, which generalizes several popular unitary transformations, signal processing transformations, and mathematical procedures linked to optics. Such as the multi-dimensional linear canonical transform, the multi-dimensional fractional Fourier transform, and so on. In this paper, we extend several quantum mechanical uncertainty principles (UPs), such as Classical Heisenberg’s UP, Nazarov’s UP, Hardy’s UP, Beurling’s UP, Logarithmic UP, and Entropic UP, which have already been thoroughly studied in the Fourier transform domain over the last few decades, to the MSAFT domain in a broader sense in order to characterize simultaneously local analysis of a signal and its multi-dimensional Special affine Fourier transform. [ABSTRACT FROM AUTHOR]

Many laboratories use two-photon microscopy through commercial suppliers, or homemade designs of considerable complexity. The integrated nature of these systems complicates customization, troubleshooting, and training on the principles of two-photon microscopy. Here, we present "Twinkle": a microscope for Two-photon Imaging in Neuroscience, and Kit for Learning and Education. It is a fully open, high performing and easy-to-set-up microscope that can effectively be used for both education and research. The instrument features a >1 mm field of view, using a modern objective with 3 mm working distance and 2 inch diameter optics combined with GaAsP photomultiplier tubes to maximize the fluorescence signal. We document our experiences using this system as a teaching tool in several two week long workshops, exemplify scientific use cases, and conclude with a broader note on the place of our work in the growing space of open scientific instrumentation. [ABSTRACT FROM AUTHOR]

The integration of organic components into inorganic silica systems through sol–gel synthesis has significantly expanded the potential applications of these materials by enhancing features such as transparency, crack resistance, flexibility, and the introduction of new functional groups. Understanding the influence of organic groups on the sol–gel process and exploring various approaches to crafting organic-inorganic hybrid (OIH) silica systems are essential endeavors. This review aims to provide a comprehensive guide, particularly targeted towards researchers new to OIH synthesis. It delineates the key parameters of the sol–gel process, presents five distinct synthesis strategies, and provides exemplary applications. Beyond traditional methods like co-condensation with organoalkoxysilanes and bridged-organoalkoxysilanes, alternative strategies are elucidated, including biopolymer functionalization, photopolymerization enabling 3D printing, and utilization of polyhedral oligomeric silsesquioxanes (POSS). Furthermore, recent literature exploration has uncovered promising optical applications for OIH materials. These materials serve as excellent hosts for luminophores due to their inherent transparency and the synergistic interactions between the organic functional groups and luminophores, which can enhance properties such as quantum yield, particularly with lanthanides, and even improve the photochromic performance of polyoxometalates. Consequently, OIH materials find extensive utilization in optical technologies, encompassing luminescent solar concentrators, light-emitting diodes, photochromism, random lasers, optical sensing, and various optical components, as we aim to demonstrate comprehensively herein. Highlights: Systematization of five synthesis strategies for synthesizing organic–inorganic hybrids silica systems. Systematization of strategies for employing organic-inorganic hybrids as luminophores host. Emerging optical applications using organic–inorganic hybrids. [ABSTRACT FROM AUTHOR]

Photoplethysmography is a widely used optical technique to extract physiological information non-invasively. Despite its large use and adoption, multiple factors influence the signal shape and quality, including the instrumentation used. This work analyzes the variability of the DC component of the PPG signal at three source–detector distances (6 mm, 9 mm, and 12 mm) using green, red, and infrared light and four photodiodes per distance. The coefficient of variation (CV) is proposed as a new signal quality index (SQI) to evaluate signal variabilities. This study first characterizes the PPG system, which is then used to acquire PPG signals in the chest of 14 healthy participants. Results show a great DC variability at 6 mm, homogenizing at 9 and 12 mm. This suggests that PPG systems are also sensitive to the near- and far-field effects commonly reported and studied in optics, which can impact the accuracy of physiological parameters dependent on the DC component, such as oxygen saturation (SpO2). [ABSTRACT FROM AUTHOR]

Conducting polymers represent a crucial class of functional materials with widespread applications in diverse fields. Among these, poly(3,4-ethylenedioxythiophene) (PEDOT) and its derivatives have garnered significant attention due to their distinctive optical, electronic, and magnetic properties, as well as their exceptional tunability. These properties often exhibit intricate interdependencies, manifesting as synergistic, concomitant, or antagonistic relationships. In optics, PEDOTs are renowned for their high transparency and unique photoelectric responses. From an electrical perspective, they display exceptional conductivity, thermoelectric, and piezoelectric performance, along with notable electrochemical activity and stability, enabling a wide array of electronic applications. In terms of magnetic properties, PEDOTs demonstrate outstanding electromagnetic shielding efficiency and microwave absorption capabilities. Moreover, these properties can be precisely tailored through molecular structure modifications, chemical doping, and composite formation to suit various application requirements. This review systematically examines the mechanisms underlying the optoelectromagnetic properties of PEDOTs, highlights their tunability, and outlines prospective research directions. By providing critical theoretical insights and technical references, this review aims to advance the application landscape of PEDOTs. [ABSTRACT FROM AUTHOR]

The Sweatt model has been extensively used to design optical systems containing diffractive optical elements (DOEs) because it captures the dispersive characteristics of DOEs. We introduce a new dispersive Sweatt model (DSM) that can describe meta-atom (MA) dispersion, which has material and geometric contributions in addition to diffraction. It uses a wavelength-dependent scalar coefficient to modify the diffractive dispersion and describe the dispersion of a given MA basis. This provides a robust framework to design systems containing metasurface (MS) elements while including their unique dispersive properties in the design optimization. Importantly, the DSM is based on ray optics and enables the design of MS-containing systems using conventional optical design software such as Zemax and Code V. We use the DSM to demonstrate the design of a hybrid refractive/MS achromatic doublet for the midwave infrared (MWIR) band. The design example includes multiple wavelengths and field angles during optimization and demonstrates excellent agreement between the DSM and real hybrid lens performance modeled using wave optics. We discuss the limits of the DSM and present a simple model to predict performance limits due to phase mismatch at Fresnel zone boundaries. [ABSTRACT FROM AUTHOR]

Acoustoplasmonic resonators, such as nanobars and crosses, are efficient acousto-optical transducers. The excitation of mechanical modes in these structures strongly depends on the spatial profile of the eigenmodes of the resonator. Using a system of two identical gold elongated bars placed on a silicon dioxide substrate, we examine how breaking mirror symmetries affects the optical and acoustic properties to provide insights in the design of acoustoplasmonic metasurfaces for nonsymmetric acousto-optical transducers. Our findings show that the absence of mirror symmetries affects differently the optical and nanomechanical response. Broken mirror symmetries not only couple nanomechanical modes existing in single bars but introduce new torsional resonant modes. [ABSTRACT FROM AUTHOR]