CAREER: Finessing Optical Frequency Combs for Direct Cooling and Trapping of Molecules

虽然激光通常被认为是用来加热它们所照射的物体，但它们也被常规地用于科学实验室，使物体变得极冷。激光冷却能够将原子蒸气冷却到绝对零度以上几度，在那里它们的行为受量子物理学的控制。在过去的三十年里，科学家们将这些冷原子蒸汽作为学习量子机制的科学平台，该领域已经诞生了原子钟和传感器等应用。然而，可以用这种方法研究的化学物质受到可用激光颜色的限制。将激光冷却扩展到更广泛的原子和分子阵列是理想的，以了解这些物种以及它们如何在室温下不可能实现的细节水平上相互作用。这个项目支持的研究小组将研究一种不同类型的激光的应用，以冷却这些困难的物种。这些所谓的“超快”激光器可以一次发射出整个彩虹的颜色，这个项目将研究如何巧妙地将这些光源转化为激光，冷却更广泛的原子和分子。成功地将激光冷却扩展到这些物种，有望在下一代传感器、计算机和平台上为未来的科学找到用途。使用光学频率梳的直接激光冷却和捕获有可能将激光冷却扩展到比目前更多样化的原子和分子。这种潜力的产生是由于它们的实用性，在连续波激光器无法实现的部分光谱中平行产生许多光学频率，例如深紫外。锁模激光器可以通过非线性过程驱动双光子跃迁或转换为所需波长，从而提高效率，即使只使用一个齿，也可以利用梳中的全部功率，使该过程高效。具体来说，该项目支持的研究人员将使用皮秒锁模光学频率梳对双光子跃迁（铷、氮）上的原子进行直接激光冷却和磁光捕获，并对双原子分子（氢化锶）进行单光子激光冷却。梳子的时间依赖扫描也将作为一种光束减速和陷阱捕获的方法进行研究，这种方法将适用于比塞曼减速更广泛的物种，如双原子。开发一种广泛适用的分子冷却技术将会带来回报，包括解决偶极量子气体、量子模拟、受控化学和量子计算领域的重大未知问题的能力。

While lasers are typically thought of as heating objects they shine upon, they have also come to be routinely used in scientific laboratories to make things extremely cold. Laser cooling is capable of refrigerating vapors of atoms to fractions of a degree above absolute zero, where their behavior is governed by quantum physics. In the past three decades, scientists have used these cold atomic vapors as a scientific platform for learning about this quantum regime, and the field has given birth to applications such as atomic clocks and sensors. The chemicals that can be investigated in this way, however, are limited to only a handful by the laser colors available. Extending laser cooling to a broader array of atoms and molecules is desirable for learning about these species and how they interact at a level of detail not possible at room temperature. The research team supported by this program will be studying the application of a different type of laser to cool these difficult species. These so-called "ultrafast" lasers can be made to emit an entire rainbow of colors at once, and this program will study how to finesse these sources into laser cooling a wider array of atoms and molecules. Successful extension of laser cooling to these species is expected to find use in the next generation of sensors, computers, and platforms for future science.Direct laser cooling and trapping using optical frequency combs has the potential to extend laser cooling to more diverse species of atoms and molecules than are currently accessible. This potential arises due to their utility in creating many optical frequencies in parallel in parts of the optical spectrum where doing this with continuous-wave lasers is impractical, such as the deep ultraviolet. The enhanced efficiency with which mode-locked lasers can drive two-photon transitions or be converted to desired wavelengths via nonlinear processes results in utilization of the full power in the comb even if only one tooth is used, making this process efficient. Specifically, researchers supported by this program will use picosecond mode-locked optical frequency combs for direct laser cooling and magneto-optical trapping of atoms on two-photon transitions (rubidium, nitrogen) and single-photon laser cooling of diatomic molecules (Strontium Hydride). Time-dependent sweeps of the comb will also be investigated as a method for beam slowing and trap capture that would be applicable to a wider array of species than Zeeman slowing, such as diatomics. Development of a widely-applicable technique for cooling of molecules would have payoffs, including the ability to address significant unknowns in the fields of dipolar quantum gases, quantum simulations, controlled chemistry, and quantum computing.