Amplified spontaneous emission (ASE) ducts are disclosed for use with various gain media. An ASE duct may be configured and arranged to remove ASE from solid state or liquid gain media and transmit the ASE to an exterior optical medium. The refractive index of an ASE duct is selected as desired based on the refractive index of a gain medium and an exterior optical medium. An ASE duct may include first and second boundary surfaces joined at a vertex having an included angle that allows ASE (light) reflected off on one boundary surface to be incident on the another boundary surface at less than the critical angle and transmitted outside of the ASE duct. Laser systems using ASE ducts and methods of using and manufacturing ASE ducts are disclosed.