Fluorescent handpiece

A light-emitting, therapeutic system configured to treat biological tissue, comprising:

• a source of electromagnetic radiation;
• a waveguide positioned to receive electromagnetic radiation from the source, the waveguide comprising:
• first and second ends, and a wall extending therebetween, the wall configured to at least partially transmit the electromagnetic radiation therethrough, the wall defining a passage extending along a direction between said first and second ends;
• a fluorescent substance flowable within the passage, the fluorescent substance comprising a liquid base and a fluorescing agent;
• and
• an first port and an second port in fluid communication with the passage;
• an optical output element near one of the first and second ends of the waveguide;
• wherein the fluorescent substance is configured to absorb at least a portion of the electromagnetic radiation from the source through the wall and generate fluorescent light in response to the electromagnetic radiation, wherein the waveguide is configured to guide the fluorescent light emitted by the fluorescent substance towards the optical output element by internally reflecting at least a portion of the fluorescent light, and wherein the optical output element is configured to direct at least a portion of the fluorescent light towards biological tissue;
• a fluid conduit in fluid communication with the first and second ports and configured to carry the fluorescent substance between the waveguide's passage and a fluid moving system, the fluid moving system adapted to move the fluorescent substance from the first end to the second end through the passage and from the second end back to the first end through the fluid conduit;
• and
• a fluorescing agent removal device configured to be coupled to the fluid conduit and to remove the fluorescing agent from the fluorescent substance, the fluid conduit being configured to direct the fluorescent substance through the fluorescing agent removal device during a first mode of operation and to bypass the fluorescing agent removal device during a second mode of operation.