Coherent beam combination of four holmium amplifiers with phase control via a direct digital synthesizer chip.

We present the coherent beam combination of four 2100 nm holmium amplifiers with their phase controlled through acousto-optic modulators driven by the RF output of direct digital synthesizer chips. Phase alignment was achieved through the use of a field programmable gate array based stochastic parallel gradient descent algorithm.

High power cryogenic Ho:YAG laser.

We have improved significantly the brightness of cryogenic Ho:YAG, reporting up to 65 W output power with a beam quality of M <1.3 and a slope efficiency of 71%. The laser emission was ~2 nm wide and centered at 2097.

CO laser-fabricated cladding light strippers for high-power fiber lasers and amplifiers.

We present and characterize a simple CO laser processing technique for the fabrication of compact all-glass optical fiber cladding light strippers. We investigate the cladding light loss as a function of radiation angle of incidence and demonstrate devices in a 400 μm diameter fiber with cladding losses of greater than 20 dB for a 7 cm device length. The core losses are also measured giving a loss of <0.

High precision 9.6 µm CO(2) laser end-face processing of optical fibres.

Reproducible, precise cleaving of optical fibres is of great importance to the fibre laser and telecommunications industries. We present a novel approach to the end-face processing of optical fibres using a 9.6 µm CO laser to produce flat, smooth and symmetric fibre end-face profiles with no rounding or melting at the edges of the fibre.

Tellurite microspheres for nanoparticle sensing and novel light sources.

High index Er-Yb codoped tellurite spheres with diameter of 9 μm and good sphericity were fabricated using a CO(2) laser. Upconversion modulated whispering gallery modes with a quality factor of 45,000 were observed in the sphere dipped in methanol. Refractometric sensing with detection sensitivity of 7.