Nikita Simakov

We describe the first power scalable, Q-switched, cryogenically cooled, resonantly pumped, Ho:YAG laser oscillator. The output energy was extracted from a confocal resonator with a single-pass pump geometry. Pulsed operation at higher average powers will be reported.

We will review recent progress in the area of average power and peak power scaling of sources based around thulium and holmium doped fibre lasers.

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 CO₂ laser to produce flat, smooth and symmetric fibre end-face profiles with no rounding or melting at the edges of the fibre. As a demonstration, precision cleaving of a 400 µm diameter optical fibre is reported. For this fibre a topographical profile height of 2 process that has generated a fibre end-face topography substantially smaller than a typical mechanical cleave. Highlighting the flexibility of this system, we have also demonstrated the generation of near arbitrary fiber end-face profiles such as discrete phase steps and non-spherical surface profiles.

We present a novel large-mode-area thulium-doped fibre with a large pedestal design. We discuss the advantages of this large pedestal fibre in the context of overcoming limitations imposed by cleaving and splicing tolerances. Finally we demonstrate the use of such a fibre in constructing monolithic fibre lasers operating at 1.95 µm with 170 W of output power, 0.1 nm line-width and a diffraction limited beam quality of M²_X,Y = 1.02, 1.03.

We present a tunable, high power cladding-pumped holmium doped fiber laser. The laser generated >15 W CW average power across a wavelength range of 2.043 – 2.171 μm, with a maximum output power of 29.7 W at 2.120 μm. The laser also produced 18.2 W when operating at 2.171 µm. To the best of our knowledge this is the highest power operation of a holmium doped laser at a wavelength >2.15 µm. We discuss the significance of background losses and fiber design for achieving efficient operation in holmium doped fibers.

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We present a monolithic, robustly polarised thulium fibre laser which produces pulses with 25 ns duration and energy of up to 35 µJ. A pulsed 1.55 μm source was used to gain switch the laser at repetition rates of up to 300 kHz, producing average powers of up to 8 W at 2.044 µm. To the best of our knowledge this is the highest power gain-switched thulium fibre laser and it is also the first with a linearly polarised output. The large repetition rate, pulse energy and average power will enable efficient energy extraction from a large mode-area, polarisation maintaining thulium fibre amplifier.