How 'random' lasers work: Natural cavities act like mirrors in light-emitting plastics

How 'random' lasers work: Natural cavities act like mirrors in light-emitting plastics: "When scientists discovered a new kind of laser that was generated by an electrically conducting plastic or polymer, no one could explain how it worked and some doubted it was real. Now, a decade later, researchers have found these 'random lasers' occur because of natural, mirror-like cavities in the polymers, and they say such lasers may prove useful for diagnosing cancer."