工程師用釹(Nd)離子摻雜氧化鋁(Al2O3)晶體,開發(fā)出能夠發(fā)射超短脈沖高功率脈沖的新型激光材料。他們的材料加工方法產(chǎn)生了Nd-Al2O3激光增益介質(zhì),其抗熱沖擊性能比領先的固態(tài)激光增益材料高24倍。
Nd and Al2O3 are two of the most widely used components in today’s solid-state laser materials. However, alumina crystals typically host small ions like titanium or chromium. Neodymium ions are too big — they are normally hosted inside a yttrium aluminum garnet (YAG) crystal.
Nd和Al2O3是當今固態(tài)激光材料中使用最廣泛的兩種元件。 然而,氧化鋁晶體通常容納小的離子,如鈦或鉻。 釹離子太大,它們通常位于釔鋁石榴石(YAG)晶體內(nèi)。
To address this issue, the team from the University of California, San Diego tailored the crystallite size to other important length scales, i.e., the wavelength of light and interatomic dopant distances, which minimized optical losses and allowed successful Nd doping.
The new process involves rapidly heating a pressurized mixture of Al2O3 and Nd powders at a rate of 300 °C per minute until the mixture reaches 1260 °C. This is hot enough to dissolve a high concentration of Nd into the Al2O3 lattice. The solid solution is held at that temperature for five minutes and then rapidly cooled, also at a rate of 300 °C per minute.
The team characterized the atomic structure of the Nd-Al2O3 crystals using x-ray diffraction and electron microscopy. To demonstrate lasing capability, researchers optically pumped the crystals with IR light (806 nm). The material emitted amplified light (gain) at a lower frequency IR light at 1064 nm.
In tests, researchers showed that Nd-Al2O3 has 24× higher thermal shock resistance than Nd-YAG, one of the leading solid-state laser gain materials.
“This means we can pump this material with more energy before it cracks, which is why we can use it to make a more powerful laser,” said professor Javier Garay.
Traditionally, alumina is doped by melting it with another material and then cooling the mixture slowly so that it crystallizes.
傳統(tǒng)上,氧化鋁通過用另一種材料熔化而摻雜,然后緩慢冷卻混合物使其結晶。
“However, this process is too slow to work with neodymium ions as the dopant — they would essentially get kicked out of the alumina host as it crystallizes,” said researcher Elias Penilla.
The team speeded up the heating and cooling steps enough to prevent neodymium ions from escaping. The Nd-Al2O3 hybrid was made by rapidly heating and cooling the two solids together.
“Until now, it has been impossible to dope sufficient amounts of neodymium into an alumina matrix," Garay said. "We figured out a way to create a neodymium-alumina laser material that combines the best of both worlds: high power density, ultrashort pulses, and superior thermal shock resistance.”
The team is working on building a laser with their new material.
“That will take more engineering work," Garay said. "Our experiments show that the material will work as a laser and the fundamental physics is all there.”
“這將需要更多的工程工作,”Garay說。“我們的實驗表明,這種材料可以用作激光,基礎物理學就擺在那。”
The successful demonstration of gain and high bandwidth in a medium with superior Rs could lead to the development of lasers with previously unobtainable high-peak powers, short pulses, tunability, and high-duty cycles.
在具有優(yōu)越Rs的介質(zhì)中成功演示增益和高帶寬可能會推動激光器的發(fā)展到具有先前無法達到的高峰值功率、短脈沖、可調(diào)諧性和高占空比。
轉(zhuǎn)載請注明出處。