Orbital Angular Momentum Waves: Generation, Detection and Emerging Applications

Orbital angular momentum (OAM) has aroused a widespread interest in many fields, especially in telecommunications due to its potential for unleashing new capacity in the severely congested spectrum of commercial communication systems. Beams carrying OAM have a helical phase front and a field strength with a singularity along the axial center, which can be used for information transmission, imaging and particle manipulation. The number of orthogonal OAM modes in a single beam is theoretically infinite and each mode is an element of a complete orthogonal basis that can be employed for multiplexing different signals, thus greatly improving the spectrum efficiency. In this paper, we comprehensively summarize and compare the methods for generation and detection of optical OAM, radio OAM and acoustic OAM. Then, we represent the applications and technical challenges of OAM in communications, including free-space optical communications, optical fiber communications, radio communications and acoustic communications. To complete our survey, we also discuss the state of art of particle manipulation and target imaging with OAM beams

Roadmap on multimode photonics

Multimode devices and components have attracted considerable attention in the last years, and different research topics and themes have emerged very recently. The multimodality can be seen as an additional degree of freedom in designing devices, thus allowing for the development of more complex and sophisticated components. The propagation of different modes can be used to increase the fiber optic capacity, but also to introduce novel intermodal interactions, as well as allowing for complex manipulation of optical modes for a variety of applications. In this roadmap we would like to give to the readers a comprehensive overview of the most recent developments in the field, presenting contributions coming from different research topics, including optical fiber technologies, integrated optics, basic physics and telecommunications

Mustang Daily, May 14, 1973

Student newspaper of California Polytechnic State University, San Luis Obispo, CA.https://digitalcommons.calpoly.edu/studentnewspaper/3010/thumbnail.jp

Lanthorn, vol. 30, no. 30, April 18, 1996

Lanthorn is Grand Valley State\u27s student newspaper, published from 1968 to the present

Investigation into the acupuncture and meridian system

The Meridian system conceived by the ancient Chinese has been described and referenced for more than a thousand years. The Meridians meaning paths are the main trunks that run longitudinally within the body. The Meridian system consists of about 400 acupuncture nodes and 20 Meridian channels connecting most of these points. It deals with the routing and distribution of certain signals that may affect physiological functions. It integrates meridians, tissues and organs into a complex system. Initially, modeling of the acupuncture system is investigated. The physical effect of injecting an acupuncture needle at a node is suggested by an equivalent model of a current (voltage) source based on a simple Faraday disk generator concept. The motion of the needle due to hand manipulation in the presence of Earth\u27s magnetic fields acts as a Faraday\u27s dynamo and causes accumulation of positive (negative) charges at the tip of the needle. Due to clockwise (counter clockwise) rotation, further increase of accumulated charges at the tip results in their release in the form of an equivalent current (voltage) source. This effect has been enhanced by connecting a variable frequency source on a needle inserted into one of the nodes of the meridian system. Voltage variations at the adjacent nodes along the same meridian are measured and the relative connectivity has been observed to verify the concept of a network. It is observed that the induced voltages are proportional to the corresponding path lengths, and further more, the existence paths are found to be frequency dependent. An equivalent transmission line model is suggested. The presence of minute electrical currents also suggests that there is magnetic field along the meridian and therefore the inclusion of series inductance is appropriate. This has already been confirmed by SQUID measurements carried out and reported by [Lo 2003]. The presence of the inductive (resistive) path suggests that capacitive effects due to accompanying electric fields have to be included as shunt capacitance in the equivalent model. It shows that distributed resistance and inductance plus the shunt capacitance perfectly simulate the equivalent transmission line that is essential for signal propagation along the meridians of the acupuncture system. Measurements carried out indicate the presence of lossy resistive paths along the meridian consisting of three nodes. This has been carried out in an acupuncture clinic and two human subjects are subjected to testing on three different occasions. Sinusoidal signals in the frequency range between 20 to 80 Hz are used with different amplitudes, and strengths of propagated signals are measured to verify the existence of the electrical transmission path along that meridian. Additional hypothesis is made suggesting that the cluster water wire can be used to model the pathways of the acupuncture system. One of the reasons for this approach is that cluster water wires are ideal to model tiny nano-size capillaries. They may be present but their presences have not been verified yet physically, even through the SQUID measurements confirm the flow of minute currents along the acupuncture meridians. Petri net formulation has been developed as an attractive alternative to model bionetwork consisting of acupuncture nodes and meridians. However, validating this assumption requires an extensive measurement to be carried out, which is beyond the currently available capabilities and resources. Future work includes much more accurate modeling of pathways and nodes on each meridian, their coupling with each other. Further frequency dependent system identification in terms of equivalent parameters and their coupling behavior in the complex network, i.e., Petri net formation is required to solve the unexplained acupuncture meridian system. The presence of 20 meridians involving more than 400 nodes suggests that the acupuncture system is ideal to model a biological network

Laser-induced forward transfer (LIFT) of water soluble polyvinyl alcohol (PVA) polymers for use as support material for 3D-printed structures

The additive microfabrication method of laser-induced forward transfer (LIFT) permits the creation of functional microstructures with feature sizes down to below a micrometre [1]. Compared to other additive manufacturing techniques, LIFT can be used to deposit a broad range of materials in a contactless fashion. LIFT features the possibility of building out of plane features, but is currently limited to 2D or 2½D structures [2–4]. That is because printing of 3D structures requires sophisticated printing strategies, such as mechanical support structures and post-processing, as the material to be printed is in the liquid phase. Therefore, we propose the use of water-soluble materials as a support (and sacrificial) material, which can be easily removed after printing, by submerging the printed structure in water, without exposing the sample to more aggressive solvents or sintering treatments. Here, we present studies on LIFT printing of polyvinyl alcohol (PVA) polymer thin films via a picosecond pulsed laser source. Glass carriers are coated with a solution of PVA (donor) and brought into proximity to a receiver substrate (glass, silicon) once dried. Focussing of a laser pulse with a beam radius of 2 µm at the interface of carrier and donor leads to the ejection of a small volume of PVA that is being deposited on a receiver substrate. The effect of laser pulse fluence , donor film thickness and receiver material on the morphology (shape and size) of the deposits are studied. Adhesion of the deposits on the receiver is verified via deposition on various receiver materials and via a tape test. The solubility of PVA after laser irradiation is confirmed via dissolution in de-ionised water. In our study, the feasibility of the concept of printing PVA with the help of LIFT is demonstrated. The transfer process maintains the ability of water solubility of the deposits allowing the use as support material in LIFT printing of complex 3D structures. Future studies will investigate the compatibility (i.e. adhesion) of PVA with relevant donor materials, such as metals and functional polymers. References: [1] A. Piqué and P. Serra (2018) Laser Printing of Functional Materials. Weinheim, Germany: Wiley-VCH Verlag GmbH & Co. KGaA. [2] R. C. Y. Auyeung, H. Kim, A. J. Birnbaum, M. Zalalutdinov, S. A. Mathews, and A. Piqué (2009) Laser decal transfer of freestanding microcantilevers and microbridges, Appl. Phys. A, vol. 97, no. 3, pp. 513–519. [3] C. W. Visser, R. Pohl, C. Sun, G.-W. Römer, B. Huis in ‘t Veld, and D. Lohse (2015) Toward 3D Printing of Pure Metals by Laser-Induced Forward Transfer, Adv. Mater., vol. 27, no. 27, pp. 4087–4092. [4] J. Luo et al. (2017) Printing Functional 3D Microdevices by Laser-Induced Forward Transfer, Small, vol. 13, no. 9, p. 1602553

February 7, 1991

The Breeze is the student newspaper of James Madison University in Harrisonburg, Virginia

High Energy Astronomy Observatory, Mission C, Phase A. Volume 2: Preliminary analyses and conceptual design

An analysis and conceptual design of a baseline mission and spacecraft are presented. Aspects of the HEAO-C discussed include: baseline experiments with X-ray observations of space, analysis of mission requirements, observatory design, structural analysis, thermal control, attitude sensing and control system, communication and data handling, and space shuttle launch and retrieval of HEAO-C

ASRDI oxygen technology survey, Volume 7: Characteristics of metals that influence system safety

A literature survey and analysis of the material and process factors affecting the safety of metals in oxygen systems is presented. In addition, the practices of those who specify, build, or use oxygen systems relative to the previous is summarized. Alloys based on iron, copper, nickel, and aluminum were investigated representing the bulk of metals found in oxygen systems. Safety-related characteristics of other miscellaneous metals are summarized. It was found that factors affecting the safety of metals in oxygen systems exit in all phases of the evolutionary process, from smelting and mill techniques through end-production fabrication. The safety of a given metal in an oxygen system was determined to be influenced by the particular service requirement. The metal characteristics should favorably influence fulfillment of these requirements. Thus, no singular metal or alloy could be classified as safest for all types of oxygen service