Room Temperature, Earth's Field MASER

我们在这项研究中提出的工作是构建一种可以在室温和地球磁场中工作的微波激光器。微波激光器(通过辐射的受激辐射进行微波放大)实际上是激光的先驱，大约50年前由汤斯、巴索夫和普罗霍罗夫发现，他们因这项工作而分享了1964年的诺贝尔物理学奖。激光可以简单地被认为是与紫外线或可见光光谱中的高频光子一起工作的脉泽，而脉泽则工作在微波频率。这两个系统都依赖于一种化学物种，其激发的能级群体被激发到较低的能级，要么是受到光子的刺激，要么是受到与其他物种的碰撞。然后，除了进入系统的原始光子外，原子或分子还会发射光子。进入该系统的光子刺激发射出更多相同频率的光子，这意味着会产生一束强烈的单色辐射。最初，激光被认为是一个寻找应用的好主意。它们是小批量制造的，美国政府一度下令，出于军事和安全目的，每台激光都应该印上一个数字--当大量设备的市场潜力变得明显时，这个想法很快就失去了吸引力。如今，激光的产量以数十亿计，并已进入从DVD播放机到激光眼科手术的所有工业部门的应用。另一方面，脉泽仅用于非常特殊的应用，如原子钟和射频望远镜中的放大器。旅行者号航天器发出的令人惊叹的太阳系图像是由脉泽卫星拍摄的。那么，为什么脉泽没有得到广泛应用呢？有两个关键原因。首先，脉泽需要低温，这意味着要么使用低温液体，要么使用特殊的冰箱。其次，它们需要高磁场，这意味着使用需要高功率的大磁铁，如果是电磁铁，通常用水冷却；如果是超导磁铁，用氦冷却。这项研究的目的是制造一种在室温和地球磁场中工作的微波激射器。这当然是一个非常雄心勃勃的项目，但它是通过对一些将在该项目中使用的材料的研究而得到的，这些材料是非常高Q的谐振器。该小组对高Q谐振器的研究已经进行了几年，现在似乎可以使用高Q谐振器和相当低的功率来制造固态脉泽。我们的初步探测实验表明，在室温和地磁场脉冲模式下实现磁化确实是可能的。即将开展的研究将探索新材料，使微波激射器微型化，并需要非常低的功率才能达到微波激射所需的阈值。

The work we propose in this research is to construct a MASER that can work at room temperature and in the Earth's magnetic field.The MASER (Microwave amplification by the stimulated emission of radiation) is in fact the forerunner of the LASER and was discovered around 50 years ago by Townes, Basov, and Prokhorov who shared the 1964 Nobel Prize in Physics for this work. A LASER can be thought of simply as MASER that works with higher frequency photons in the ultraviolet or visible light spectrum whereas a maser works at microwave frequencies. Both systems rely on a chemical species with an excited energy-level population being stimulated into lower energy levels, either by photons or collisions with other species. Photons are then emitted by the atom or molecule, in addition to the original photons that entered the system. The photons entering the system stimulate the emission of further photons of the same frequency, meaning that a strong beam of monochromatic radiation is produced. Originally the laser was seen as a good idea looking for an application. They were made in small numbers and at one point the US government decreed that every laser should be stamped with a number for military and security purposes - an idea that soon lost its appeal when the market potential for the quantities of the devices became apparent. Today lasers are made in their billions and have found their way into applications in all sectors of industry from DVD players to laser eye surgery. Masers on the other hand are used only in very specialised applications such as atomic clocks and as amplifiers in radiofrequency telescopes. Masers were responsible for the stunning images of the solar system sent by the Voyager spacecraft. So why have masers not been widely applied? There are two key reasons. First masers need cryogenic temperatures and this means the use of either cryogenic liquids or special fridges. Second, they need high magnetic fields and this means the use of bulky magnets that need high power and usually cooling with water, if an electromagnet, or with helium, if a superconducting magnet. This research is aimed at producing a maser that will operate at room temperature and in the earth's magnetic field. This is of course an extremely ambitious project but it is borne out of research in some of the materials that will be used in the project and these are the very high Q resonators. Work on high Q resonators has been carried out by the group for several years and now it appears that a solid state maser can be made using a high Q resonator and quite a low power. Our initial scouting experiments have shown that it is indeed possible to achieve masing at room temperature and earth's field in pulsed mode. The research that will be carried out will explore new materials that will miniaturise the maser and require very low power to achieve the threshold required for masing.