Researchers have developed a microscopic lens with a focal length that can be controlled in less than a millisecond.

Controlling the focus of an optical lens is useful for microscopy and photography, but existing reconfigurable lenses are often bulky or slow to adjust. Romain Quidant and his colleagues at the Institute of Photonic Sciences in Barcelona, Spain, created a controllable lens by placing a disc of gold nanorods inside a thin chamber of water and putting it on top of a conventional lens.

They used a laser to excite the electrons in the nanorods, heating the water and changing its refractive index to create a lens-like effect. The team was able to vary the focal distance of the lens by tens of micrometres with sub-nanometre accuracy, and in only 200 microseconds.

ACS Photonics http://doi.org/2cd (2015)