edible laser

...To prove his point, he suggested we try to obtain laser action from one of the colorful gelatin desserts popular with chidren. The next morning he arrived with a packet of 12 different flavors of Knox Jell-O. In our small dark room, we prepared two flavors according to the instructions by adding 16 ounces of hot water to the contents of one bag. We poured the liquid into clear plastic cups, where a colorful gel of normal food consistency formed after several hours. We then took these cups with their wobbly content to the nitrogen laser and focused the pump light from the top to a narrow line. Although we could see strong fluorescence, we did not observe any laser action. In resignation, Art took the obstinate experiment to his office and savored it as a snack. This ritual was repeated every morning until we had tried all 12 flavors without success. Not one to give up, Art pointed out that sodium fluorescein is almost non-toxic. So we mixed up some clear gelatin with a small amount of this dye, and we soon had a potent new laser material, although Art no longer insisted on eating it. The gelatin laser medium was rather soft for optical work, but could be cut with a knife into laser rods or other shapes. Later we explored the behavior of other laser dyes in gelatin. For rhodamine dyes we found a significant improvement in performance when we added some kitchen detergent (Pink Lotion Trend) to the mixture to prevent the dimerization of the dye molecules, even though the edibility of the laser medium was thus further compromised.

—Theodor W. Hänsch, "Edible Lasers and Other Delights of the 1970s," Optics and Photonics News, February 2005; via Prof. Siegman's awesome post in the thread "Lena's Birthday Question: Neatest Optical Hacks" on sci.optics; and via Everyday Scientist.

I especially like the phrase, "almost non-toxic"!