Seed layer formation by deposition of microcrystallites on a revolving substrate: modeling of the effective linear elastic, piezoelectric, and dielectric coefficients.

Averaging of material coefficients of crystallites deposited at an angle to a rotating substrate is considered. A simple model is proposed, and applied to determine effective linear dielectric, piezoelectric, and elastic constants of all Laue groups. While these represent tensors of rank 2, 3, and 4, the method applies generally to tensors of any rank.

Toward optimizing gain in Er-Ba nanoparticle-doped optical fibers.

Modern commercial erbium-doped fibers are limited in their doping concentrations due to the tendency of Er ions to cluster in silicate glasses. Clustering inevitably leads to ion quenching, one major obstacle preventing erbium-doped fibers (EDFs) from scaling to higher laser power near 15XX nm. Here, we present a new, to our knowledge, method for doping erbium into fibers through the use of Er:BaF nanoparticle (NP) precursors.

Solid-state transverse Anderson localized fiber laser.

For the first time, to our knowledge, an all-solid transverse Anderson localizing optical fiber laser is demonstrated. A combination of the molten core and stack-and-draw fiber fabrication techniques is used to produce a 112 µm core diameter fiber that is a random array of Yb-doped high index and passive low index regions. A localized channel first assists in the guidance of amplified spontaneous emission before stimulating laser action, which occurs in the same channel via mixed Anderson localization and step index wave-guiding.

Versatile luminescence thermometry via intense green defect emission from an infrared-pumped fluorosilicate optical fiber.

An all-glass optical fiber capable of two distinct methods of optical thermometry is described. Specifically, a silica-clad, barium fluorosilicate glass core fiber, when pumped in the infrared, exhibits visibly intense green defect luminescence whose intensity and upper-state lifetime are strong functions of temperature. Intensity-based optical thermometry over the range from 25°C to 130°C is demonstrated, while a lifetime-based temperature sensitivity is shown from 25°C to 100°C.

High-efficiency radiation-balanced Yb-doped silica fiber laser with 200-mW output.

The focus of this study was the development of a second generation of fiber lasers internally cooled by anti-Stokes fluorescence. The laser consisted of a length of a single-mode fiber spliced to fiber Bragg gratings to form the optical resonator. The fiber was single-moded at the pump (1040 nm) and signal (1064 nm) wavelengths.

Virtual reality enabled asynchronous learning modules for fiber optic preform manufacturing education.

The demand for skilled workers and novel manufacturing training solutions has increased with the growing demand for fiber optic cables. Web-based simulations can be used for training, and this paper presents an approach for developing a fiber preform manufacturing browser-based VR simulation. Subsequently, a study was conducted to evaluate the effectiveness of the simulation based on learning gains and learner perception of ease of use, usefulness, intention of use, learning outcomes, and workload.

Raman amplification at 2.2 μm in silicon core fibers with prospects for extended mid-infrared source generation.

Raman scattering provides a convenient mechanism to generate or amplify light at wavelengths where gain is not otherwise available. When combined with recent advancements in high-power fiber lasers that operate at wavelengths ~2 μm, great opportunities exist for Raman systems that extend operation further into the mid-infrared regime for applications such as gas sensing, spectroscopy, and biomedical analyses. Here, a thulium-doped fiber laser is used to demonstrate Raman emission and amplification from a highly nonlinear silicon core fiber (SCF) platform at wavelengths beyond 2 μm.

Power scaling limits of diffraction-limited fiber amplifiers considering transverse mode instability.

An empirical TMI threshold formula is derived based on a recently developed model and used to analyze the power-scaling performance of ytterbium-doped silica glass and YAG (YAlO) and lutetia (LuO) single-crystalline fiber amplifiers. Overall, the single-crystalline fiber lasers are found to scale potentially to higher average powers due to their higher thermal conductivities compared to silica glass. This work serves as a useful extension to earlier works and shines significant new light on optimal fiber and amplifier designs for maximum average output power with TMI considered.

All-fibre heterogeneously-integrated frequency comb generation using silicon core fibre.

Originally developed for metrology, optical frequency combs are becoming increasingly pervasive in a wider range of research topics including optical communications, spectroscopy, and radio or microwave signal processing. However, application demands in these fields can be more challenging as they require compact sources with a high tolerance to temperature variations that are capable of delivering flat comb spectra, high power per tone, narrow linewidth and high optical signal-to-noise ratio. This work reports the generation of a flat, high power frequency comb in the telecom band using a 17 mm fully-integrated silicon core fibre as a parametric mixer.

Localised structuring of metal-semiconductor cores in silica clad fibres using laser-driven thermal gradients.

The molten core drawing method allows scalable fabrication of novel core fibres with kilometre lengths. With metal and semiconducting components combined in a glass-clad fibre, CO laser irradiation was used to write localised structures in the core materials. Thermal gradients in axial and transverse directions allowed the controlled introduction, segregation and chemical reaction of metal components within an initially pure silicon core, and restructuring of heterogeneous material.

Anti-Stokes fluorescence cooling of nanoparticle-doped silica fibers.

The first observation of cooling by anti-Stokes pumping in nanoparticle-doped silica fibers is reported. Four Yb-doped fibers fabricated using conventional modified chemical vapor deposition (MCVD) techniques were evaluated, namely, an aluminosilicate fiber and three fibers in which the Yb ions were encapsulated in CaF, SrF, or BaF nanoparticles. The nanoparticles, which oxidize during preform processing, provide a modified chemical environment for the Yb ions that is beneficial to cooling.

Raman enhanced four-wave mixing in silicon core fibers.

A strong Raman enhancement to the four-wave mixing (FWM) conversion efficiency is obtained in a silicon core fiber (SCF) when pumped with a continuous-wave (CW) source in the telecom band. By tapering the SCFs to alter the core diameter and length, the role of phase-matching on the conversion enhancement is investigated, with a maximum Raman enhancement of ∼15 dB obtained for an SCF with a zero dispersion wavelength close to the pump. Simulations show that by optimizing the tapered waist diameter to overlap the FWM phase-matching with the peak Raman gain, it is possible to obtain large Raman enhanced FWM conversion efficiencies of up to ∼2 dB using modest CW pump powers over wavelengths covering the extended telecom bands.

Semiconductor core fibres: materials science in a bottle.

Novel core fibers have a wide range of applications in optics, as sources, detectors and nonlinear response media. Optoelectronic, and even electronic device applications are now possible, due to the introduction of methods for drawing fibres with a semiconductor core. This review examines progress in the development of glass-clad, crystalline core fibres, with an emphasis on semiconducting cores.

All-optical high-speed modulation of THz transmission through silicon core optical fibers.

High speed optical modulation of THz radiation is of interest for information processing and communications applications. In this paper infrared femtosecond pulses are used to generate free carriers that reduce the THz transmission of silicon based waveguides over a broad spectral range. Up to 96% modulation is observed from 0.

Random lasing from optical fibers with phase separated glass cores.

A novel random laser, integrating a passive optical fiber with a phase separated aluminosilicate core-silica cladding as the feedback medium, is proposed and presented. The core exhibits greatly enhanced Rayleigh scattering, therefore requiring a significantly reduced length of scattering fiber (4 m) for lasing. With a Yb-doped fiber as the gain medium, the fiber laser operates at 1050 nm with low threshold power and possesses an output that can be amplified through conventional means.

Experimental comparison of silica fibers for laser cooling.

Laser cooling in silica has recently been demonstrated, but there is still a lack of understanding on how fiber composition, core size, and contamination influence cooling performance. In this work, six Yb-doped silica fibers were studied to illuminate the influence of these parameters. The best fiber cooled by -70 with only 170 mW/m of absorbed pump power at 1040 nm, which corresponds to twice as much heat extracted per unit length compared to the first reported laser cooling in silica.

Laser cooling in a silica optical fiber at atmospheric pressure.

For the first time, to the best of our knowledge, laser cooling is reported in a silica optical fiber. The fiber has a 21-µm diameter core doped with 2.06 wt.

Observation of optical nonlinearities in an all-solid transverse Anderson localizing optical fiber.

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.

Low-loss silicon core fibre platform for mid-infrared nonlinear photonics.

Broadband mid-infrared light sources are highly desired for wide-ranging applications that span free-space communications to spectroscopy. In recent years, silicon has attracted great interest as a platform for nonlinear optical wavelength conversion in this region, owing to its low losses (linear and nonlinear) and high stability. However, most research in this area has made use of small core waveguides fabricated from silicon-on-insulator platforms, which suffer from high absorption losses of the use of silica cladding, limiting their ability to generate light beyond 3 µm.

Insights and Aspects to the Modeling of the Molten Core Method for Optical Fiber Fabrication.

The molten core method (MCM) is a versatile technique to fabricate a wide variety of optical fiber core compositions ranging from novel glasses to crystalline semiconductors. One common feature of the MCM is an interaction between the molten core and softened glass cladding during the draw process, which often leads to compositional modification between the original preform and the drawn fiber. This causes the final fiber core diameter, core composition, and associated refractive index profile to vary over time and longitudinally along the fiber.

Laser restructuring and photoluminescence of glass-clad GaSb/Si-core optical fibres.

Semiconductor-core optical fibres have potential applications in photonics and optoelectronics due to large nonlinear optical coefficients and an extended transparency window. Laser processing can impose large temperature gradients, an ability that has been used to improve the uniformity of unary fibre cores, and to inscribe compositional variations in alloy systems. Interest in an integrated light-emitting element suggests a move from Group IV to III-V materials, or a core that contains both.