▎ 摘　　要

NOVELTY - Saturable absorption body comprises optical fiber which includes the cladding and core, which includes the etching field in which a part of the cladding is etched. The material having the saturated absorption property is arranged in a part of the etching field. USE - Saturable absorption body. ADVANTAGE - The saturable absorption body has high damage threshold value and which easily controls the light interaction length. DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for a method for preparing saturable absorption body which involves: (A) etching the predefined domain of the optical fiber including the cladding and core so that a part of the cladding remains; and (B) coating the predefined domain of the optical fiber with the material having the saturated absorption property.