Orbital angular momentum (OAM) based photonics promises researchers and systems designers with a new degree of freedom whilst offering annular intensity distributions rather than Gaussian intensity distributions. However, absence of an optical fiber design that not only supports propagation of OAM signals and cylindrical vector modes but does so with a large design space for designers to adjust and tune the modal properties of the optical fiber supporting these OAM signals has hampered developments. Embodiments of the invention exploit photonic crystal fiber designs to support this design/manufacturing tunability whilst also supporting endlessly single-radial order modal regimes where the optical fiber is mono-annular over a wide range of optical wavelengths. Such optical fibers being able to support the transmission of a larger diversity of mono-annular modes (OAM or vector modes in nature, or otherwise) in a reliable manner and over a wider range of wavelengths than conventional silica optical fibers.

An Nd.sup.3+ optical fiber laser and amplifier operating in the wavelength range from 1300 to 1450 nm is described. The fiber includes a rare earth doped optical amplifier or laser operating within this wavelength band is based upon an optical fiber that guides light in this wavelength band. The waveguide structure attenuates light in the wavelength range from 850 nm to 950 nm and from 1050 nm to 1150 nm.

One aspect relates to a process for the preparation of a quartz glass body. The process includes providing a silicon dioxide granulate, making a glass melt out of the silicon dioxide granulate, and making a quartz glass body out of at least a part of the glass melt. In one aspect, providing a silicon dioxide granulate includes providing of a silicon dioxide powder and processing of the powder to obtain a silicon dioxide granulate including the spray drying of a silicon dioxide slurry using a nozzle. The nozzle has a contact surface to the slurry made of glass, plastic or a combination thereof. Furthermore, one aspect relates to a quartz glass body obtainable by this process. Furthermore, one aspect relates to the preparation of a silicon dioxide granulate. One aspect also relates to a light guide, an illuminant, and a formed body, made from processing of the quartz glass body.

Rare earth doped fiber lasers can be robust and efficient sources of high quality light, but are usually limited to the highest gain transitions of the active species. But rare earths typically possess a multitude of potentially useful transitions that might be accessed if the dominant transition can be suppressed. In fiber lasers this suppression is complicated by the very high net gain the dominant transitions exhibit; effective suppression requires some mechanism distributed along the length of the fiber. We have developed a novel waveguide with resonant leakage elements that frustrate guidance at well-defined and selectable wavelengths. Based on this waveguide, we have fabricated a Large Mode Area Neodymium doped fiber with suppression of the four-level transition around 1060 nm, and demonstrated lasing on the three-level transition at 930 nm with good efficiency.

Embodiments are directed to an optical fiber cable assembly. The optical fiber cable assembly is a polarization maintaining optical fiber assembly. The assembly includes an optical core located within a cladding. Also within the cladding is a stress rod. The stress rod can be centered within the cladding, with the optical fiber eccentrically located within the cladding. There can also be a second optical fiber eccentrically located within the cladding. The optical fiber can be centered within the cladding, with the stress rod eccentrically located within the cladding.

An optically active element, such as a photonic crystal, is formed by creating a matrix (1) in which an optically active material is dispersed, and generating one or more void structures (2, 3) in the matrix. The matrix (1) may comprise polymer dispersed liquid crystal. The void structures (2, 3) may be generated by laser ablation. Properties of the optically active element may be tuned by thermal effects, or via the application of electric, magnetic, or polarised electromagnetic fields. The element may be adapted for use in beam steering, fluid detection, tunable lasers, polarisation multiplexing, and optical switching.

A microstructured optical fiber has periodically arranged high-index rods embedded in a low-index background, a high-index ring surrounding the high-index rods, and a high-index core located at the center. The high-index rods and the low-index background forms a microstructured cladding region which supports the guidance of supermodes. The fundamental and the highest supermodes form a cladding-mode band, wherein at least the effective index of a core mode lies in the cladding-mode band. Also provided is

a technique for selectively filtering the fiber modes, to selectively filter out one or some of the high-order modes with the other modes still guided in the core with low loss. The cascade of optical fibers can filter out a group of fiber modes, marking guidance of a single high-order mode in a few-mode optical fiber possible.

An optical fiber mode stripper, a manufacturing method for an optical fiber mode stripper, and a laser are provided. The optical fiber mode stripper includes an optical fiber and fillers. The optical fiber is provided with a waveguide destruction region extending along a length direction of the optical fiber. A portion of the optical fiber in the waveguide destruction region includes a core and a cladding layer. The cladding layer is provided with recessed structures disposed at intervals along the length direction of the optical fiber and/or disposed at intervals circumferentially around the cladding layer. The fillers are filled in the recessed structures. The filler has a refractive index greater than a refractive index of the cladding layer.

One or more aspects of the present disclosure include coating the inside of an overmoded, smooth wall metallic waveguide with a thin dielectric layer. Coating the inside of a waveguide with a dielectric layer, as described in more detail herein, may result in similar boundary conditions to corrugated waveguides and may achieve extremely low transmission loss (e.g., propagating the HE11 mode). Such dielectric lined waveguides are an efficient (e.g., cost-effective) alternative to corrugated waveguides (e.g., for broadband microwave transmission, particularly at frequencies above 300 GHz). The systems and techniques described herein may improve hybrid electric mode purity (e.g., HE11 mode purity of approximately 98%). Dielectric lined waveguides described herein may have applications in many fields demanding low attenuation millimeter and terahertz transmission (e.g., such as radar, high-frequency communication systems, THz dynamic nuclear polarization, electron cyclotron heating in magnetically confined fusion experiments, etc.).