Baltimore citizens aren't just dealing drugs and installing wiretaps, some of them are busy using convex lenses to trap rainbows, which could be put to good use with optical computing—making hardware faster! Stronger! More powerful!
And pretty on the inside.
University professors coated one side of a 4.5 millimetre diameter lens with a 30 nanometre thick coat of gold film, which they then put on a sheet of glass also splashed with a helping of gold. After shining a laser beam at the space between the curved lens and the glass, a rainbow appeared trapped between the elements when looked down on with a microscope. No pot of gold appeared, but a little dancing McNulty, dressed in a leprechaun costume, could be seen under the rainbow. [Arxiv via New Scientist]
Image credit Carla216