FLUORESCENT HANDPIECE

A handpiece can treat biological tissue using electromagnetic radiation, which can be substantially fluorescent light. The handpiece includes a source of electromagnetic radiation and a waveguide. The waveguide is adjacent the source, receives electromagnetic radiation from the source, and delivers the electromagnetic radiation to the biological tissue. The handpiece also includes a system for moving a fluorescent substance through the waveguide. The fluorescent substance includes a fluid base and a fluorescing agent and is capable of modulating at least one property of the electromagnetic radiation. A method is described for removing the fluorescing agent from the fluorescing substance and replacing it with a second, different fluorescing agent.