Generation of pseudo-radially-polarized beams in a diode pumped solid-state laser

A simple technique for directly generating pseudo-radially-polarised or donut-shaped beams in a diode-pumped solid-state laser is presented. Preliminary results for a Nd:YAG laser are described and the further potential of this technique is discussed

High power radially-polarized Yb-doped fiber laser

A simple technique for directly generating a radially-polarized output beam from an ytterbium-doped fiber laser using an intracavity spatially-variant waveplate is reported. The laser yielded 32W of output with a corresponding slope efficiency of 65.8% in a radially-polarised beam with beam propagation factor ~2.1 and polarization purity >95%

Novel technique for the CO₂ laser fabrication of optical devices with sub-micrometer ablation depth precision

We present novel techniques for the processing of fibre end face and cladding surfaces using a 9.6 µm CO2 laser. We investigate the effects of pulse duration on process parameters

Direct generation of radially-polarized output from an Yb-doped fiber laser

A simple technique for directly generating a radially-polarized output beam from an ytterbium-doped fiber laser using an intracavity S-waveplate is reported. The laser yielded 7W of output with a corresponding slope efficiency of 67%

Novel technique for mode selection in a large-mode-area fiber laser

A novel method for selectively exciting a single-spatial-mode (fundamental or higher-order) in a high-power multi-mode fiber laser resonator is presented. Preliminary results for a cladding-pumped Tm-doped silica fiber laser are discussed

Extreme short wavelength operation (1.65 - 1.7 µm) of silica-based thulium-doped fiber amplifier

We report the first demonstration of silica-based thulium-doped fiber amplifier (TDFA) working in the 1.65 - 1.7 µm waveband. Up to 29 dB small signal gain and noise figure as low as 6.5 dB are achieved

Ultra-broadband wavelength swept Tm-doped fiber laser

Wavelength-swept laser sources with broad wavelength tunability and narrow instantaneous linewidth in the two-micron band have potential applications in a number of areas, including spectroscopic characterisation and optical coherence tomography (OCT). The use of OCT for non-invasive investigation of paintings to provide the information necessary for effective restoration and to aid conservation is one example of an emerging application where operation in two-micron band brings the advantage of increased penetration depth due to lower loss in commonly used pigments compared to the situation at near-infrared wavelengths. Tm-doped silica fibre lasers provide an efficient way to access the relevant wavelength region due to the wide emission line that extends from ~1700 nm to ~2100 nm. Unfortunately, wavelength tuning across the entire emission band with a single fibre gain stage is extremely difficult due to the combination of varying quasi-three-level character as a function of wavelength and gain saturation due to short wavelength amplified spontaneous emission. In order to access the full emission bandwidth potential of Tm-doped fibres, a different approach must be employed with two or more fibre gain stages and with each gain stage tailored to provide emission in complementary bands

Exploiting the short wavelength gain of silica-based thulium-doped fiber amplifiers

Short wavelength operation (1650-1800 nm) of silica-based thulium-doped fiber amplifiers (TDFAs) is investigated. We report the first demonstration of in-band diode-pumped silica-based TDFAs working in the 1700-1800 nm waveband. Up to 29 dB of small-signal gain is achieved in this spectral region, with an operation wavelength accessible by diode pumping as short as 1710 nm. Further gain extension toward shorter wavelengths is realized in a fiber laser pumped configuration. A silica-based TDFA working in the 1650-1700 nm range with up to 29 dB small-signal gain and noise figure as low as 6.5 dB is presented

Simple scheme for active mode selection in a multimode fibre oscillator

Operation of fibre lasers on individual higher order transverse modes has many attractions from a power scaling perspective. These include a higher threshold for unwanted nonlinear loss processes, reduced sensitivity to mode skew [1], as well as the prospect of improved energy extraction in pulsed systems. Moreover, it has also been shown that in some laser processing applications the use of doughnut-shaped beams or beams with a dynamically adaptable transverse profile can yield substantially higher processing speeds. However techniques for selecting individual higher order modes in multimode fibre oscillators are often quite difficult to implement and lack the flexibility to switch between modes to suit the application

Spatial mode switchable, wavelength tunable erbium doped fiber laser incorporating a spatial light modulator

We present a 2-mode group, switchable spatial mode erbium doped fiber laser incorporating a spatial light modulator. The laser wavelength can be tuned using an intra-cavity wavelength selective filter and provides >10dB extinction ratio between LP01/LP11 modes