Optical amplification apparatus and optical amplification method

An optical amplification apparatus comprising:

• an optical amplification medium, having a gain in a wavelength band of signal light, configured to receive the signal light;
• an excitation light introduction unit configured to introduce, into the optical amplification medium, excitation light to excite the optical amplification medium;
• and
• a residual excitation light introduction unit configured to introduce, into the optical amplification medium, residual excitation light output from the optical amplification medium,
• the residual excitation light having a wavelength component of the excitation light, wherein the residual excitation light introduction unit includes:
• on a side of one end of the optical amplification medium, a residual excitation light multiplexing unit configured to multiplex the signal light and the residual excitation light,
• the optical amplification apparatus further comprising:
• a multiplexed light waveguide unit configured to guide the signal light and the residual excitation light multiplexed by the residual excitation light multiplexing unit;
• and
• a spatial light modulating unit, disposed on an output side of the residual excitation light multiplexing unit from which the residual excitation light is output, having a function of converting spatial intensity distribution of the residual excitation light, and
• the spatial light modulating unit converts the spatial intensity distribution in such a way that the residual excitation light is coupled to the multiplexed light waveguide unit.