Optical part and semiconductor laser module

An optical part, comprising:

• an optical fiber having a core portion and a cladding portion that is formed around the core portion;
• a light absorber placed around the optical fiber;
• and
• an adhesive member that adheres the light absorber and the optical fiber to each other, wherein the cladding portion includes:
• a main portion extending along a longitudinal direction and having a main portion cladding diameter;
• and
• an input end portion positioned closer to a light input side with respect to the main portion,
• wherein:
• an input end face cladding diameter at an input end face of the input end portion is less than the main portion cladding diameter and is larger than a core diameter of the core portion,
• the core portion has a core diameter that is approximately constant in the longitudinal direction,
• the input end portion is tapered such that the input end portion changes in cladding diameter from the main portion cladding diameter to a diameter substantially equal to the input end face cladding diameter, and
• the input end face cladding diameter is 1.1 times the core diameter of the core portion or larger, and 1.4 times the core diameter or smaller such that a laser light beam propagated through the core portion does not reach an outer periphery of the cladding portion by seeping out to the cladding portion, and laser light beams incident on a tapered surface of the input end portion are reflected by the tapered surface of the input end portion or leak out of the cladding portion if the laser light beams are coupled into the cladding portion, wherein part of the input end portion of the cladding portion is coplanar with the input end face of the core portion.