Patent ID: 7599404

Claim:
A composite optic fibre ( 1 ) for a laser, comprising: a core ( 2 ), the core ( 2 ) having a determined diameter and comprising a core material with additional doping elements which may be brought into at least one excited electronic state by absorbing energy from a pump optical signal of a first determined wavelength running through said core and capable of giving-back the former by de-energization in the form of an optical signal of a second determined wavelength; a pump guiding sheath ( 4 ) having a determined diameter surrounding and in contact with the core ( 2 ), the pump guiding sheath ( 4 ) being a photonic structure formed by a substantially regular matrix assembly of spaced capillaries arranged parallel to the core ( 2 ) in a pump guiding sheath material; a confinement sheath ( 5 ) around the pump guiding sheath ( 4 ), said confinement sheath ( 5 ) having an optical index smaller than an optical index of a material forming the pump guiding sheath ( 4 ); and a mechanical rigidification sheath ( 6 ) arranged around the confinement sheath ( 5 ), a material of the mechanical rigidification sheath ( 6 ) being glass or silica, the mechanical rigidification sheath ( 6 ) having a thickness of at least 2 mm, wherein the diameter of pump guiding sheath ( 4 ) is greater than the core diameter and smaller than or equal to four times the core diameter, the core diameter being greater than or equal to 35 micrometers, the fibre having a length less than 50 cm, and the fibre is straight and rigid.