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It is reported that researchers at the University of California, San Diego (UCSD) have developed a new laser material-neodymium (Nd) doped alumina crystals, which can emit ultra-short (theoretically as low as 7.7 fs), high-power pulses, which can be used For the production of smaller, more powerful lasers with excellent thermal shock resistance.

To achieve this, engineers designed a new material processing strategy to dissolve high concentrations of neodymium ions into alumina crystals. The result is the first neodymium alumina laser gain medium in the field of laser materials research.

Nd (dopant) and alumina (host material) are the two most widely used components in today's most advanced solid-state laser materials. However, the combination of Nd and alumina to prepare laser media still faces great challenges: their sizes are not compatible. Alumina crystals often contain small ions such as titanium or chromium, while Nd ions are too large.

The key to preparing a neodymium alumina mixture is the rapid heating and cooling of two solids. Traditionally, researchers have doped alumina by melting it with another material, and then slowly cooling the mixture to crystallize it. "However, this process is too slow to use neodymium ions as dopants because they tend to be stripped from the alumina body during crystallization," said postdoctoral researcher Elias Penilla. So his solution was to speed up the heating and cooling steps To prevent neodymium ions from escaping.

The new method involves rapidly heating a pressurized mixture of alumina and neodymium powder at a rate of 300 ° C / minute until it reaches 1260 ° C. This temperature is sufficient to dissolve high concentrations of neodymium into the alumina lattice. The solid solution was kept at this temperature for 5 minutes, and then also rapidly cooled at a rate of 300 ° C / minute. The researchers used X-ray diffraction and electron microscopy to characterize the atomic structure of neodymium alumina crystals. To demonstrate its laser capabilities, the researchers also optically pumped the crystal with infrared light at 806 nm. This material can emit amplified light with a wavelength of 1064nm.

Through testing, the researchers also showed that the thermal shock resistance of neodymium alumina is 24 times higher than that of the leading solid-state laser gain material Nd: YAG. "This means we can pump this material with more energy before it breaks, so we can use it to make more powerful lasers," said Javier Garay, a professor of mechanical engineering.