ABSTRACT
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.
ABSTRACT
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 M(2)(X,Y) = 1.02, 1.03.
ABSTRACT
We present the design of a polarisation maintaining, resonantly and cladding pumped, large mode area holmium-doped fibre. We describe the operation of this fibre in a pulsed amplifier configuration. The amplifier produced pulses with energy of 2.25 mJ and duration of 20 ns at a repetition rate of 20 kHz and average power of 45 W. The holmium-doped fibre provided >10 dB of gain at 2.09 µm and the polarisation extinction ratio was >11.5 dB. The beam quality of the output (M2) was 1.6. To the best of our knowledge this is the highest pulse energy achieved from any singly holmium-doped fibre by an order of magnitude.
ABSTRACT
We have demonstrated the highest reported output power from a mid-IR ZGP OPO. The laser is a cascaded hybrid system consisting of a thulium fibre laser, Ho:YAG solid state laser and a Zinc Germanium Phosphide parametric oscillator. The system produces 27 W of output power in the 3-5 µm wavelength range with an M(2) = 4.0 when operating in a repetitively q-switched mode, and a modulated peak output power of 99 W at a reduced duty cycle of 25%.
