Design, computation and characterization of thulium-doped photonic crystal fibre for emission around 1700 nm

We present a leaky thulium-doped photonic crystal fibre (PCF) design to down shift the thulium emission in the 1.7 - 1.8 mum band. The microstructured cladding structure manages confinement loss to counteract the thulium emission cross section. Thus, the fibre is considered as a distributed low pass filter along the fibre length. Computations on confinement loss show differential loss two orders of magnitude between 1.7 mum and 1.9 mum. We report on the fabrication and the linear characterization of the modelled fibre. A down shift around 1.75 mum of thulium fibre emission is experimentally demonstrated in single pass configuration.