New laser material combines high power with thermal tolerance

Materials capable of producing laser light need to have a variety of properties, related both to how their electrons behave and how they cope with the stresses of large amounts of energy passing through them. Researchers at the University of California San Diego have devised a method of combining alumina crystals with neodymium ions to produce a material that can deliver very short, high power pulses and is also tuneable across a range of light wavelengths and can resist thermal shock.

Both neodymium and alumina are common materials in solid-state lasers. The former is used to make high-power lasers; the latter, used as a matrix for metal ions that can emit light, makes lasers that emit short pulses and can withstand rapid changes of temperature and high heat loads. However, they are incompatible in size: alumina can only host small ions, and neodymium is large.

The San Diego team, led by mechanical engineer Javier Garay at the Jacobs School of Engineering, realised that the key to combining the two materials was in finessing the conditions in the material processing. Traditionally, alumina is doped – treated to disperse foreign ions within its structure – by melting two materials together and cooling them slowly so that the mixture crystallises. But if a molten mixture of alumina and neodymium is cooled too slowly, the neodymium crashes out of the solution. The first author of the team’s paper in the journal Light: Science & Applications, Elias Penilla, devised a new method based on speeding up both the heating and cooling steps fast enough to prevent neodymium ions escaping from the melt.