Photonic crystal fibers design for 2 ?m wavelenght operation

New photonic crystal fiber designs are presented and numerically investigated in order to improve the state of art of high power fiber lasers. The focus of this work is targeted on the region of 2 ?m laser emission, which is of high interest due to its eye-safe nature and due to the large amount of applications permitted. Thulium doped fiber amplifiers are suitable for emitting in this region. Different fiber designs have been proposed, both flexible and rod-type, with the aim to enlarge mode area while maintaining robust single mode operation. The analysis of thermal effects, caused by the high thulium quantum defect, have been taken in consideration. Solutions to counteract issues derived by detrimental thermal effects have been implemented.