Various embodiments include large cores fibers that can propagate few modes or a single mode while introducing loss to higher order modes. Some of these fibers are holey fibers that comprising cladding features such as air-holes. Additional embodiments described herein include holey rods. The rods and fibers may be used in many optical systems including optical amplification systems, lasers, short pulse generators, Q-switched lasers, etc. and may be used for example for micromachining.

Single mode propagation in fibers and rods with large leakage channels

Embodiments of optical fiber may include cladding features that include a material (e.g., fluorine-doped silica glass) that may produce a very low relative refractive index difference with respect to cladding material in which the cladding features are disposed. This relative refractive index difference may be characterized by (ni-n2)/ni, where ni is the index of refraction of the cladding material in which the cladding features are included, and n2 is the index of refraction of the cladding features. In certain embodiments, the relative refractive index difference may be less than about 4.5 x 10'3. In various embodiments, the configuration of the cladding features including, for example, the size and spacing of the cladding features, can be selected to provide for confinement of the fundamental mode yet leakage for the second mode and higher modes, which may provide mode filtering, single mode propagation, and/or low bend loss.

Glass large-core optical fibers

An ytterbium-doped optical fiber of the present invention includes: a core which contains ytterbium, aluminum, and phosphorus and does not contain germanium; and a cladding which surrounds this core. The ytterbium concentration in the core in terms of ytterbium oxide is 0.09 to 0.68 mole percent. The molar ratio between the phosphorus concentration in the core in terms of diphosphorus pentoxide and the above ytterbium concentration in terms of ytterbium oxide is 3 to 30. The molar ratio between the aluminum concentration in the core in terms of aluminum oxide and the above ytterbium concentration in terms of ytterbium oxide is 3 to 32. The molar ratio between the above aluminum concentration in terms of aluminum oxide and the above phosphorus concentration in terms of diphosphorus pentoxide is 1 to 2.5.

Ytterbium-doped optical fiber, fiber laser, and fiber amplifier

According to one example of the invention an optical fiber comprises: (i) silica based, rare earth doped core having a first index of refraction n1; (ii) at least one silica based cladding surrounding the core and having a second index of refraction n2, such that n1> n2 with the following features, alone or in combination: said cladding includes 0.5 to 5 wt% F and 0.5 to 20 wt% B, said optical fiber has less than 8dB/km core background loss at a wavelength of 1280 nm. at least one of the core or cladding is doped with AI203 concentration is less than 2:1.

Optical fiber and method for making such fiber

Various embodiments described herein include rare earth doped glass compositions that may be used in optical fiber and rods having large core sizes. Such optical fibers and rods may be employed in fiber lasers and amplifiers. The index of refraction of the glass may be substantially uniform and may be close to that of silica in some embodiments. Possible advantages to such features include reduction of formation of additional waveguides within the core, which becomes increasingly a problem with larger core sizes.

Rare earth doped and large effective area optical fibers for fiber lasers and amplifiers

A method of producing an active optical waveguide having asymmetric polarisation, said method comprising the steps of (a) providin g an active optical waveguide (10) comprising: (i) a transverse refractive index profile (21) comprising a guiding region (11), an intermediate region (13), and a non-guiding region (12); (ii) a transverse photorefractive dopant profile (31) comprising a constant or graded photorefractive dopant concentration within at least one of the guiding, non-guiding and intermediate regions, except that the photorefractive dopant is not located solely in the guiding region; and (iii) exhibiting in said guiding region, intermediate region, or both, light guiding modes having different polarisations; and (b) exposing at least a part (10a, 10b) of the active optical waveguide to an effective transverse illumination of light (20) reacting with the photorefractive dopant and modifying said transverse refractive index profile; said part of the active optical waveguide being exposed to a fluence selectively suppressing the propagation of the light guiding modes having different polarisations so that the propagation of one mode is less suppressed than the propagation of the other mode(s). Such an active optical waveguide, single polarisation mode optical waveguide lasers and multi-wavelength single polarisation mode optical waveguide lasers comprising such an active optical waveguide, methods of their production, and their uses in telecommunications, in spectroscopy, in sensors and in absolute calibrated laser light sources.

Polarisation asymmetric active optical waveguide, method of its production, and its uses

The polarisation properties of a distributed feedback (DFB) fibre laser are investigated experimentally. A birefringent phase-shift is induced by side illumination of the centre part of the lasing structure with ultraviolet (UV) light and it is experimentally shown that the birefringence of the phase-shift is the dominating effect controlling the polarisation properties of the laser.

Polarisation control of DFB fibre laser using UV-induced birefringent phase-shift

The specification describes rare earth doped fiber amplifier devices for operation in the extended L-band, i.e. at wavelengths from 1565 nm to above 1610 nm. High efficiency and flat gain spectra are obtained using a high silica based fiber codoped with Er, Al, Ge, and P and an NA of at least 0.15.

Erbium doped fibers for extended l-band amplification

A fiber has been developed for use in extended L-band amplifiers, utilizing the wavelength range from 1565 to 1620 nm. The fiber is silica based and has low splice loss to standard telecommunication fiber. The quantum conversion efficiency is >60%.

Silica based erbium doped fiber extending the L-band to 1620+ nm

It has been demonstrated experimentally that the rate of homogeneous upconversion in erbium-doped fibres increases with increasing pump and signal power, even if the same degree of excitation is maintained. This is due to an increased redistribution of excitation energy among erbium ions by absorption and stimulated emission. A signal of 8.6 mW could more than double the upconversion rate in a densely doped fibre.

Bera Palsdottir

Papers

Polarisation asymmetric active optical waveguide, method of its production, and its uses

Polarisation control of DFB fibre laser using UV-induced birefringent phase-shift

Erbium doped fibers for extended l-band amplification

Silica based erbium doped fiber extending the L-band to 1620+ nm

Observation of energy-distribution-dependent homogeneous upconversion in erbium-doped silica glass fibres