Laser device and method for manufacturing laser device

A laser device comprising:

• a laser unit that outputs laser light;
• an output end that launches the laser light;
• a first fusion splice portion;
• and
• a second fusion splice portion, wherein
• in each of the first fusion splice portion and the second fusion splice portion, two multi-mode fibers are fusion-spliced, wherein each of the two multi-mode fibers comprise a core through which the laser light propagates and a cladding that surrounds the core,
• the first fusion splice portion is disposed closer to the laser unit than is the second fusion splice portion,
• at least a part of the core in the first fusion splice portion contains a dopant that is the same type as a dopant contained in the cladding in the first fusion splice portion for decreasing a refractive index, and
• the core in the first fusion splice portion and the core in the second fusion splice portion have different refractive index profiles.