The present invention concerns an optical guide (100) comprising an amplifier medium including:

• a core (10) in a main matrix of a transparent material, the main matrix containing particules (1, 2), each particule being formed of a submicronic matrix distinct from the main matrix and doped by an active metal element,
• an external guiding cladding (11) in contact with the core (10).
• The size of the particules (1, 2) is smaller than 20 nm.
• The present invention also concerns a method for producing this guide.