Thermally resilient Tm-doped large mode area photonic crystal fiber with symmetry-free cladding.

The design of a Tm-doped photonic crystal fiber with ∼ 80 µm core diameter and robust single-mode guiding is proposed. State-of-art modal discrimination is obtained through the suppression of the inner cladding C(6ν) symmetry, which fosters the delocalization of the LP(11)-like mode. The effects of thermally-induced refractive index change are investigated by means of a computationally-efficient thermal model, and the possibility to obtain wide-band single-mode propagation and effective area exceeding 2500 µm(2) under a heat load of over 300 W/m is demonstrated.