Opt. Express 20, 5891–5895 (2012)

To operate a laser, its light-emitting gain medium needs to be excited by electrical or optical pulses designed to match the medium's excited energy states. For some applications it would be desirable if a laser could simply be powered by sunlight. However, the realization of solar-powered lasers is challenging as it requires the efficient conversion of the Sun's broad spectrum to light emission in the gain medium. Indeed, although solar-pumped crystal lasers were realized almost 50 years ago, extending this concept to more practical devices has proved difficult. However, Shintaro Mizuno and colleagues have now demonstrated the first solar-powered fibre laser. The laser is enabled by a Nd3+-doped glass that combines efficient light absorption in the visible region with strong light emission at the near-infrared laser wavelength of 1,053.7 nm. Lasing was demonstrated by focusing sunlight onto the fibre with a parabolic mirror, showing an overall laser energy-conversion efficiency of 1.76%. Such solar-powered lasers could be used for free-space communication tools, or to convert solar energy into other forms of energy.