Optical amplifier, and a light source device

PROBLEM TO BE SOLVED: To provide an optical amplification device that can prevent incidence of return light to an optical amplification element and implement miniaturization and reduction of the cost, and a light source device using the same.SOLUTION: An optical amplification device includes a converter capable of converting a polarization state, a first optical element which has first and second incidence ports, and emits each of a first laser beam of a first polarization state incident to the first incidence port and a second laser beam of a second polarization state incident to the second incidence port to the converter, a second optical element capable of emitting the polarization-state-converted first laser beam as a laser beam of the second polarization state, and emitting the polarization-state-converted second laser beam to an output portion to the outside, and an optical amplifier for amplifying the first laser beam emitted as the laser beam of the second polarization state by the second optical element, and making the amplified first laser beam incident to the second incidence port of the first optical element as the second laser beam.SELECTED DRAWING: Figure 2