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Yttrium aluminosilicate glasses with 25–78 mol% silica were studied using molecular dynamics simulations to understand their structural and property changes. The results show that Al3+ ions primarily exist as four-fold coordinated, with <5% in higher-coordinated states that increase with decreasing silica content. The formation of significant concentrations (4–9%) of oxygen tri-clusters and small amounts of free oxygen were also observed, suggesting a perturbed glass network structure. An average Y-O bond distance of 2.26 Å and Y coordination number of 6.3 were found. The glass transition temperatures are relatively insensitive to composition, agreeing with experiments. A 16% and 30% increase in Young's and bulk moduli, respectively, was observed with decreasing silica contents which was explained by the strong Y-O bond and formation of oxygen tri-clusters that aggregate higher coordinated Al species. These results were discussed in the context of optical and acoustic properties of YAS optical fibers that exhibit reduced nonlinearities. 

Nearly a decade ago, transverse Anderson localization was observed for the first time in an optical fiber with a random transverse refractive index profile. This started the development of a whole new class of optical fibers that guide light, not in a conventional core-cladding setting based on total internal reflection, but utilizing Anderson localization, where light can guide at any location across the transverse profile of the fiber. These fibers have since been used successfully in high-quality endoscopic image transport. They also show interesting nonlinear and active (lasing) properties with promising applications. This review will cover a brief history of these fibers with personal accounts of the events that led to their development in our research groups. It will then follow with recent progress and future perspectives on science and applications of these fibers. 

We investigate and report the optical and laser characteristics of a ytterbium-doped transverse Anderson localizing optical fiber to develop a fundamental understanding of the light propagation, generation, and amplification processes in this novel fiber. Ultimately, the goal based on the measurements and calculations conducted herein is to design and build a random fiber laser with a highly directional beam. The measurements are based on certain observations of the laser pump propagation and amplified spontaneous emission generation in this fiber. Judicious approximations are used in the propagation equations to obtain the relevant desired parameters in simple theoretical fits to experimental observations, without resorting to speculations based on the intended construction from the fiber preform.

 

A detailed analysis of a novel Yb-doped silica transverse Anderson localizing optical fiber is performed. Comparisons between measurements and theory determine the parasitic attenuation, gain, saturation power, and the number of modes. 

In its 60 years of existence, the field of nonlinear optics has gained momentum especially over the past two decades thanks to major breakthroughs in material science and technology. In this article, we present a new set of data tables listing nonlinear-optical properties for different material categories as reported in the literature since 2000. The papers included in the data tables are representative experimental works on bulk materials, solvents, 0D–1D–2D materials, metamaterials, fiber waveguiding materials, on-chip waveguiding materials, hybrid waveguiding systems, and materials suitable for nonlinear optics at THz frequencies. In addition to the data tables, we also provide best practices for performing and reporting nonlinear-optical experiments. These best practices underpin the selection process that was used for including papers in the tables. While the tables indeed show strong advancements in the field over the past two decades, we encourage the nonlinear-optics community to implement the identified best practices in future works. This will allow a more adequate comparison, interpretation and use of the published parameters, and as such further stimulate the overall progress in nonlinear-optical science and applications.

 

Recently developed methods for high resolution birefringence measurement have been applied to distinguish between the surface and interior birefringence of silica glass fibers as a function of drawing temperature and initial surface condition for two types of silica glass with different water contents. Fibers were drawn in a water‐free argon environment using graphite heating elements. It was found that fibers drawn at lower temperatures resulted in greater, interior birefringence, in agreement with previous reports. Additionally, it was found that in the case of low‐water silica glass, flame polishing via oxygen–hydrogen mixture and drawn into fibers at lower temperature resulted in significant surface compressive stress upon drawing. This compressive stress may be the result of surface stress relaxation in silica glass that occurs in the presence of water during fiber drawing. In silica glass that contains greater internal hydroxyl impurity concentrations, the interior birefringence as well as the surface stress relaxation was significantly reduced under the same fiber drawing conditions. Characterization of such stress responses provides insight into the effects of common processing techniques as well as impresses the significance of preform processing for consistent fiber production.

 

An all-solid transverse Anderson localizing optical fiber (TALOF) was fabricated using a novel combination of the stack-and-draw and molten core methods. Strong Anderson localization is observed in multiple regions of the fiber cross section associated with the higher index strontium aluminosilicate phases randomly arranged within a pure silica matrix. Further, to the best of our knowledge, nonlinear four-wave mixing is reported for the first time in a TALOF.

 

Glass optical fibers have reached a scale and commercial maturity that few, if any, other material and form can claim. Furthermore, optical fibers not only enable a remarkably broad range of applications but are, themselves, unique tools for fundamental studies into light‐matter interactions. That said, despite such ubiquity and global impact, increasing demands from existing systems, coupled with new expectations from novel emerging technologies, are necessitating a remarkably creative renaissance in optical fiber materials, structures, and processing methodologies. This paper, a follow‐on to a previous historical retrospective [Ballato and Dragic, Int. J. Appl. Glass Sci. 7, 413 (2016)], discusses current and future trends, recent advances in optical fiber materials, processing and properties, and muses about their forthcoming prospects and areas for further study and development. Specifically, optical fibers employed in present and future communications, sensors, and laser systems are discussed along with material innovations that could yield revolutionary advances in performance or manufacturability.