Engineers doped alumina (Al2O3) crystals with neodymium (Nd) ions to develop a new laser material capable of emitting ultrashort, high-power pulses. Their approach to materials processing resulted in a Nd-Al2O3 laser gain medium that has 24× higher thermal shock resistance than one of the leading solid-state laser gain materials.
工程師用釹（Nd）離子摻雜氧化鋁（Al2O3）晶體，開發出能夠發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生了Nd-Al2O3激光增益介質，其抗熱沖擊性能比領先的固態激光增益材料高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。
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.
為了解決這個問題，來自加利福尼亞大學圣地亞哥分校的團隊將微晶尺寸調整為其他重要的長度尺度，即光的波長和原子間摻雜劑距離，這使光學損耗最小化并允許成功的Nd摻雜。
By doping alumina crystals with neodymium ions, engineers at the University of California, San Diego have developed a laser material capable of emitting ultrashort, high-power pulses — a combination that could potentially yield smaller, more powerful lasers with superior thermal shock resistance, broad tunability, and high-duty cycles. Courtesy of Elias Penilla.
加州大學圣地亞哥分校的工程師通過摻雜釹離子的氧化鋁晶體開發出一種能夠發射超短脈沖、高功率脈沖的激光材料 – 這種組合可以產生更小、更強大的激光器，具有優異的抗熱震性、寬泛的可調性和高占空比。
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.
該新方法包括以300℃/分鐘的速率快速加熱Al2O3和Nd粉末的加壓混合物，直至混合物溫度達到1260℃，這溫度足以將高濃度的Nd溶解到Al2O3晶格中。將固溶體在該溫度下保持5分鐘，然后以300℃/分鐘的速率快速冷卻。
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.
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.
該團隊使用X射線衍射和電子顯微鏡表征了Nd-Al2O3晶體的原子結構。為了證明發射激光的能力，研究人員用紅外光（806 nm）光學泵浦晶體，該材料在1064nm的較低頻率紅外光下發射放大的光（增益）。
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.
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.
在測試中，研究人員表明，Nd-Al2O3的抗熱震性比Nd-YAG高24倍，而Nd-YAG是領先的固態激光增益材料之一。
“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.
“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.
“這意味著我們可以在其破裂之前用更多的能量泵浦這種材料，這就是為什么我們可以用它來制造更強大的激光，”Javier Garay教授說。
Traditionally, alumina is doped by melting it with another material and then cooling the mixture slowly so that it crystallizes.
傳統上，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。
Traditionally, alumina is doped by melting it with another material and then cooling the mixture slowly so that it crystallizes.
傳統上，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.
“然而，這個過程太慢了以至于不能使用釹離子作為摻雜劑 – 它們在結晶時基本上會從氧化鋁主體中被排斥出來，”研究人員Elias Penilla說。
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.
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.
該團隊加快了加熱和冷卻步驟，以防止釹離子逸出。 通過將兩種固體快速加熱和冷卻在一起制備Nd-Al 2 O 3雜化物。
Neodymium-alumina (left) shows no signs of cracking at 40 W with applied optical pumping at 808 nm, while neodymium-YAG (right) cracks at 25 W. Courtesy of Elias Penilla.
在808nm施加光泵浦時，釹 - 氧化鋁（左）在40W時沒有顯示出裂紋的跡象，而釹-YAG（右）在25W就已裂開。
“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.”
“在此之前，將足夠量的釹摻入氧化鋁基質中都是不可能的，”Garay說。“我們找到了一種方法來制造釹 - 氧化鋁激光材料，結合了兩者的優點：高功率密度、超短脈沖和卓越的抗熱沖擊性。“
The team is working on building a laser with their new material.
The team is working on building a laser with their new material.
該團隊正在研究用新材料制造激光器。
“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.
在具有優越Rs的介質中成功演示增益和高帶寬可能會推動激光器的發展到具有先前無法達到的高峰值功率、短脈沖、可調諧性和高占空比。
“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.
在具有優越Rs的介質中成功演示增益和高帶寬可能會推動激光器的發展到具有先前無法達到的高峰值功率、短脈沖、可調諧性和高占空比。
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