This was a fun little LCD project I spent an afternoon putting together. It’s based on a whole family of single button obstacle avoidance games. In short you move your helicopter up and down to avoid obstacles, scoring points for the distance travelled before inevitably crashing.
Update: Someone translated this post to Russian.
Update: I have confirmed that the output is still well within the spontaneous emission range and I am doubtful I can build an exciter with enough power. The paper uses a 532 nm Nd:YAG laser with a 7ns pulse duration and samples were performed at energies of 1.6mJ and 3.7mJ. This means that their source had an approximate power output between 229kW and 529kW.
There was an interesting article a while back over at new scientist describing research into a laser with a tunable output wavelength, after tracking down the original paper over at arXiv.org and looking at there experimental setup the I decided the device should be pretty straight forward to build.
The principal behind the design is you suspend a bunch of reflective balls in a laser dye and shake them really fast so the balls behave as though they are suspended. The laser dye is then excited by an external source and by changing the vibration frequency you can filter out different wavelengths of laser light emitted by the dye.