Transverse energy confinement and resonance suppression in SAW resonators using low-cut lithium tantalate

This paper discusses the applicability of double busbar design to surface acoustic wave (SAW) devices employing low-cut lithium tantalate (LT) with multi-layered structure. This design offers good energy confinement, scattering loss suppression and transverse mode suppression for a wide frequency range. In addition, the effectiveness of manipulating the slowness curve shape for transverse mode suppression is demonstrated. First, three different lateral edge designs are applied to the layered SAW configuration on low-cut LT, and their performances are compared using the periodic 3-dimensional finite-element method powered by the hierarchical cascading technique. Then, the discussion is extended to influence of the SAW slowness shape to the transverse mode suppression.

Er3+Incorporated Transparent Ternary Nanocomposite as Active Core Material in Polymer Optical Preform with Improved Photo-emission Performance

Background: A polymer as a host in the optical waveguide has many advantages and, when doped with rare-earth (RE) elements, offers an efficient connection, compared to its glass-based counterparts as an amplifier. However, a polymer matrix causes the concentration quenching effect of REs in the polymer matrix, making the fabrication of RE-doped polymer waveguides more complicated as compared to the fabrication of glass-based complements. Moreover, controlling scattering loss at the particle-polymer interface for maintaining the optical clarity of the composite is also a great challenge. Objective: The main aim of the present study was to optimize the synthesis of Er2O3grafted Polymethylmethacrylate (PMMA)-Polystyrene (PS) composite based transparent ternary nanocomposite and its characterization to implement them as a potential material for active core in Polymer Optical Preform (POP). Methods: Nano Erbium Oxide (Er2O3) was successfully synthesized by the wet-chemical method and encapsulated by a polymerizable surfactant, i.e., 3-Methacyloxypropyltrimethoxy silane (MPS). The encapsulated nanoparticles were further subjected to grafting with PMMA using in-situ polymerization of methyl methacrylate (MMA) followed by blending with PS via solvent mixing technique. Results: The optical transparency of the ternary composite was achieved by fine-tuning the diameter (15-20 nm) of the PMMA coated Er2O3. The crystallinity present in Er2O3 was significantly reduced after PMMA coating. The comparatively higher refractive index obtained at 589 nm wavelength for the synthesized material indicated its usability as active core material in the presence of a commercial acrylate cladding tube. A photoluminescence (Pl) study indicated that the technique might be used for a higher level of Er3+doping in polymer matrix without sacrificing its transparency. Conclusion: The obtained results indicated that the sample synthesized with the adopted technique gives better Pl intensity compared to the other methods of Er3+ incorporation in polymer optical preform (POP).

Diode pumped visible Dy3+-doped silica fiber laser: Ge-co-doping effects on lasing efficiency and photodarkening

We present the first demonstration of visible laser oscillation in the Dy3+-doped silica fiber pumped by a 451nm InGaN laser diode. It was found that Ge-co-doping plays the following important roles of laser oscillation: (1) to reduce the Rayleigh scattering loss, (2) to suppress the X-ray-induced and pump-induced photodarkening (PD), and (3) to increase lasing slope efficiency. In a fiber with 0.46wt% Dy, 1.8 wt% Ge, and 0.54wt% Al, the slope efficiency is 22.0 % at 582.5 nm, and the maximum output power is 18.4 mW.

Effect of optical fiber core diameter on Brillouin scattering loss

This paper reports the effect of core diameter of optical fiber cables on stimulated Brillouin scattering loss, which is one of the major loss characteristics of an optical fiber communication system. Analysis of this loss characteristic at three windows of the operating wavelength of a laser has been carried out through a numerical approach. Among different types of optical fiber cables, multi-mode step index silica fiber, multi-mode graded index silica fiber and plastic fibers have been considered for the numerical analysis. The numerical analysis has been performed using MATLAB in this research work. Through the comparative analysis, it has been ascertained that the Brillouin scattering loss is not only affected by the operating wavelength, but also by the core diameter of the different type of the cable. From the investigation of the comparative analysis, it is revealed that Brillouin scattering loss declines with the application of multi-mode graded index silica fiber. However, in the plastic fiber category, plastic step index fiber offers better performance.

Low Effective Material Loss TOPAS Based Single-Mode Photonic Crystal Fiber with High Core Power Fraction in the THz Waveguiding

In this study, five layers of hexagonal cladding and two elliptical air holes based on photonic crystal fiber are discussed highly for many communication areas by decreasing different types of losses such as effective material loss (EML), scattering loss, and confinement loss in the terahertz (THz) waveguiding. Our suggested fiber (H-PCF) and all simulation results are obtained with the finite element method (FEM) and the perfectly matched layer (PML) boundary conditions based COMSOL Multiphysics software have been used to design in the THz region. After investigating all the graphical results, this optical communication-related H-PCF fiber discloses an extremely low effective material loss (EML) of 0.0184 cm−1, with an effective area of 7.07×10-8 m2 and flow of power in the core region of 88% at 1 terahertz (THz). Here, other simulation parameters such as confinement loss, scattering loss, and V-parameter are also presented with a proper graph. So, we can easily say that the reported H-PCF fiber is strongly appropriate for different types of short and long-distance communication applications in the terahertz (THz) wave pulse region.

A Comprehensive Review of Micro/Nano Precision Glass Molding Molds and Their Fabrication Methods

Micro/nano-precision glass molding (MNPGM) is an efficient approach for manufacturing micro/nanostructured glass components with intricate geometry and a high-quality optical finish. In MNPGM, the mold, which directly imprints the desired pattern on the glass substrate, is a key component. To date, a wide variety of mold inserts have been utilized in MNPGM. The aim of this article is to review the latest advances in molds for MNPGM and their fabrication methods. Surface finishing is specifically addressed because molded glass is usually intended for optical applications in which the surface roughness should be lower than the wavelength of incident light to avoid scattering loss. The use of molds for a wide range of molding temperatures is also discussed in detail. Finally, a series of tables summarizing the mold fabrication methods, mold patterns and their dimensions, anti-adhesion coatings, molding conditions, molding methods, surface roughness values, glass substrates and their glass transition temperatures, and associated applications are presented. This review is intended as a roadmap for those interested in the glass molding field.

Discovery of proton hill in the phase space during interactions between ions and electromagnetic ion cyclotron waves

A study using Arase data gives the first observational evidence that the frequency drift of electromagnetic ion cyclotron (EMIC) waves is caused by cyclotron trapping. EMIC emissions play an important role in planetary magnetospheres, causing scattering loss of radiation belt relativistic electrons and energetic protons. EMIC waves frequently show nonlinear signatures that include frequency drift and amplitude enhancements. While nonlinear growth theory has suggested that the frequency change is caused by nonlinear resonant currents owing to cyclotron trapping of the particles, observational evidence for this has been elusive. We survey the wave data observed by Arase from March, 2017 to September 2019, and find the best falling tone emission event, one detected on 11th November, 2017, for the wave particle interaction analysis. Here, we show for the first time direct evidence of the formation of a proton hill in phase space indicating cyclotron trapping. The associated resonance currents and the wave growth of a falling tone EMIC wave are observed coincident with the hill, as theoretically predicted.

Design and Analysis of the Effect of Zeonex Based Octagonal Photonic Crystal Fiber for Different Types of Communication Applications

In this present work, a novel structure of octagonal cladding with two elliptical air holes based on photonic crystal fiber (O-PCF) has been presented for the application of different types of communication areas within the terahertz (THz) wave propagation. There are five layers of octagonal design shape of circular air holes (CAH) in cladding region with elliptical design shape of two air holes in core area has been reported in this research work. This O-PCF fiber has been investigated by the perfectly matched layers (PML) with the finite element method (FEM). After the simulation process, our proposed O-PCF fiber shows a low effective material loss (EML) of 0.0162 cm −1 , the larger effective area of 5.88×10-8 m2, the core power fraction (PF) of 80%, the scattering loss of 1.22×10 -10 dB/km, and the confinement loss of 3.33×10 -14 dB/m at the controlling region of 1 terahertz (THz). Due to its excellent characteristics, this proposed O-PCF fiber gives proficient transmission of broadband terahertz waves of signals. Moreover, for different kinds of optical communication applications and biomedical signals, our suggested O-PCF fiber will be highly perfect in the terahertz (THz) regions.