Room-temperature solid-state maser
Room-temperature solid-state maser
复制标题
DOI：
10.1038/nature11339
复制
发表时间：
2012-08-16
期刊：
影响因子：
64.8
通讯作者：
Alford, Neil M.
中科院分区：
文献类型：
--
作者：
Oxborrow, Mark;Breeze, Jonathan D.;Alford, Neil M.
激光的发明带来了许多创新，这种设备已经变得无处不在。然而，放大微波辐射而不是可见光的微波激射器并没有产生如此大的影响，尽管它对激光的诞生起到了重要作用[1，2]。脉泽的相对默默无闻主要是由于其各种实现所需的操作条件的不便：原子(3)和自由电子(4)脉泽需要真空室和抽气；而固态脉泽(5)，尽管它们作为低噪声放大器(6)出类拔萃，偶尔也被集成到超稳定振荡器(7，8)中，但通常需要低温制冷。大多数脉泽的实现还需要强大的磁铁、磁屏蔽或两者兼而有之。克服这些障碍将为改进铺平道路，例如更灵敏的化学分析，更精确的生物分子结构和功能测定，以及基于包含脉泽放大器和振荡器的增强型磁共振光谱仪(9)的更准确的医疗诊断(包括断层成像)。本文报道了室温脉冲式固体脉塞的实验演示。它工作在实验室的工作台上，在空气中，在地面磁场中，放大约1.45千兆赫。与低温红宝石脉泽(6)不同的是，在我们的脉泽中，增益介质是有机混合分子晶体，对-三苯基掺杂并五苯，后者被黄光激发。脉泽的泵浦机制利用自旋选择性分子系间交叉(10)进入并五苯的三重基态(11，12)。当配置为振荡器时，固态脉泽的测量输出功率约为-10分贝毫瓦，大约是以类似频率(约1.42千兆赫)振荡的原子氢脉泽(3)的1亿倍。通过利用光激发的并五苯和其他芳香族分子的系间交叉容易产生的高水平自旋极化，这种新型脉泽似乎能够在远低于室温的残余噪声温度下进行放大。
The invention of the laser has resulted in many innovations, and the device has become ubiquitous. However, the maser, which amplifies microwave radiation rather than visible light, has not had as large an impact, despite being instrumental in the laser's birth(1,2). The maser's relative obscurity has mainly been due to the inconvenience of the operating conditions needed for its various realizations: atomic(3) and free-electron(4) masers require vacuum chambers and pumping; and solid-state masers(5), although they excel as low-noise amplifiers(6) and are occasionally incorporated in ultrastable oscillators(7,8), typically require cryogenic refrigeration. Most realizations of masers also require strong magnets, magnetic shielding or both. Overcoming these various obstacles would pave the way for improvements such as more-sensitive chemical assays, more-precise determinations of biomolecular structure and function, and more-accurate medical diagnostics (including tomography) based on enhanced magnetic resonance spectrometers(9) incorporating maser amplifiers and oscillators. Here we report the experimental demonstration of a solid-state maser operating at room temperature in pulsed mode. It works on a laboratory bench, in air, in the terrestrial magnetic field and amplifies at around 1.45 gigahertz. In contrast to the cryogenic ruby maser(6), in our maser the gain medium is an organic mixed molecular crystal, p-terphenyl doped with pentacene, the latter being photo-excited by yellow light. The maser's pumping mechanism exploits spin-selective molecular intersystem crossing(10) into pentacene's triplet ground state(11,12). When configured as an oscillator, the solid-state maser's measured output power of around -10 decibel milliwatts is approximately 100 million times greater than that of an atomic hydrogen maser(3), which oscillates at a similar frequency (about 1.42 gigahertz). By exploiting the high levels of spin polarization readily generated by intersystem crossing in photo-excited pentacene and other aromatic molecules, this new type of maser seems to be capable of amplifying with a residual noise temperature far below room temperature.