Search Results (5)

In this work, using a Richards-Wolf formalism, we derive explicit analytical relationships to describe vectors of the major and minor axes of polarization ellipses centered in the focal plane when focusing a cylindrical vector beam of integer order n. In these beams, the major axis of a polarization ellipse is found to lie in the focal plane, with the minor axis being perpendicular to the focal plane. This means that the polarization ellipse is perpendicular to the focal plane, with its polarization vector rotating either clockwise or anticlockwise and forming “photonic wheels”. Considering that the wave vector is also perpendicular to the focal plane, we conclude that the polarization ellipse and the wave vector are in the same plane, so that at some point these can coincide, which is uncharacteristic of transverse electromagnetic oscillations. In a cylindrical vector beam, the spin angular momentum vector lies in the focal plane, so when making a circle centered on the optical axis, at some sections, the handedness of the spin vector and circular motion are the same, being opposite elsewhere. This effect may be called an azimuthal transverse spin Hall effect, unlike the familiar longitudinal spin Hall effect found at the sharp focus. The longitudinal spin Hall effect occurs when opposite-sign longitudinal projections of the spin angular momentum vector are spatially separated in the focal plane. In this work, we show that for the latter, there are always an even number of spatially separated regions and that, when making an axis-centered circle, the major-axis vector of polarization ellipse forms a two-sided twisted surface with an even number of twists. Full article

Transverse spin angular momentum (SAM) of photon, also known as ‘photonic wheel’, has attracted much attention, owing to its extraordinary properties and broad application prospect. Thus, it is essential to flexibly manipulate the transverse SAM in order to satisfy different needs. In this article, we design and generate a new kind of symmetrically modulated hybridly polarized vector optical field (SM-HP-VOF), and pure transverse SAM can be achieved based on the tightly focused SM-HP-VOF. Through adjusting the parameters of the SM-HP-VOF, the shape, intensity, and symmetry of the transverse SAM can be modulated. Moreover, by adding a segmented vortex phase distribution to the SM-HP-VOF, the transverse SAM becomes more concentrated and stronger, indicating that the orbital angular momentum can be a catalyst in modulating transverse SAM. Such results can provide a new avenue in studying and modulating transverse SAM, which would have potential applications in various areas including chip optical circuitry, optical quantum computing, and optical trapping and manipulation. Full article

To protect the environment, the use of mercury tubes has been prohibited in Europe since 2000. As an alternative, phosphor-doped silicone resin wheels have been used to convert blue-ray laser diodes. However, high-temperature photonic decay and cracking on the lens surface significantly degrade transmission. Recent research has explored the possibility of replacing the silicone encapsulant material of the phosphor layer with glass. In this study, the thermal effects of a glass-based phosphor-converted color wheel (GP wheel) and a silicone-based phosphor-converted color wheel (SP wheel) were investigated using various parameters and geometries. A thermal-structural coupling finite element (FE) model of the color wheels was employed to simulate the thermal and stress distributions. To construct the FE model, experiments were conducted and the inverse engineering approach was employed to extract the optical-to-heat conversion coefficient and the heat convection coefficient. In addition, an arc-shaped moving input heat flux was used to simulate a moving laser input and reduce the calculation time of the FE model. Based on the numerical and experimental results, the FE model developed can simulate the steady/transient behavior of the resin and the GP wheel. In addition, the results reveal that thermal failures of the SP wheel are very likely to occur under all parameters employed in this study, whereas the maximum temperature of the GP wheel reaches only approximately 40% of the glass transition temperature. The numerical results indicate that the GP wheel may be useful for overcoming all of these thermal disadvantages in a high-power laser-lit projector. Full article

The purpose of this study is to show the effects of the direct fusion of raw materials used for vitrified grinding wheels by photonic interactions. The paper describes the construction of a sintering apparatus that employs a pulsed neodymium: yttrium aluminum garnet (Nd:YAG) laser to fuse a combination of raw materials such as ball clay, feldspar, and borax to form a partially-crystalline glass material. The experimental results show that lasers can replace traditional methods of glass frit formation by fusing raw materials used in the manufacture of glass bonds for vitrified grinding wheels. X-ray diffraction data shows that a glass with short range order has formed using the new method. The work described herein provides a new avenue for glass frit formation applied to grinding wheel manufacture. Full article

This paper presents the concept, structural design and implementation of components of a multifunctional sensory network, consisting of a Mobile Robotic Platform (MRP) and stationary multifunctional sensors, which are wirelessly communicating with the MRP. Each section provides the review of the principles of operation and the network components’ practical implementation. The analysis is focused on the structure of the robotic platform, sensory network and electronics and on the methods of the environment monitoring and data processing algorithms that provide maximal reliability, flexibility and stable operability of the system. The main aim of this project is the development of the Robotic Nurse (RN)—a 24/7 robotic helper for the hospital nurse personnel. To support long-lasting autonomic operation of the platform, all mechanical, electronic and photonic components were designed to provide minimal weight, size and power consumption, while still providing high operational efficiency, accuracy of measurements and adequateness of the sensor response. The stationary sensors serve as the remote “eyes, ears and noses” of the main MRP. After data acquisition, processing and analysing, the robot activates the mobile platform or specific sensors and cameras. The cross-use of data received from sensors of different types provides high reliability of the system. The key RN capabilities are simultaneous monitoring of physical conditions of a large number of patients and alarming in case of an emergency. The robotic platform Nav-2 exploits innovative principles of any-direction motion with omni-wheels, navigation and environment analysis. It includes an innovative mini-laser, the absorption spectrum analyser and a portable, extremely high signal-to-noise ratio spectrometer with two-dimensional detector array. Full article