Fiber Mirror Facility Upgrade for Quantum Optics and Sensing

光腔极大地增强了光与物质的相互作用，使它们成为光学、量子光学和传感领域普遍存在的工具。最近，微观“光纤腔”出现了，提供了明显更高的带宽和更严格的限制，从而进一步促进了这些相互作用。因此，现在我们的六个核心研究方向中有五个依赖于光纤腔技术。所需的光纤镜像基板在麦吉尔大学的共享设备中进行激光加工，虽然该系统使我们的研究在几个领域处于领先地位，但其低公差和缺乏灵活性现在威胁到进一步的进展。因此，我们要求升级，以提高精度，设计灵活性和吞吐量。每个研究领域都将从中受益，但最近的两个突破提供了特别的机会，促使其立即升级。首先，在光力学领域，我们成功地实现了一个由光纤腔内的超低噪声“蹦床”微机械传感器组成的系统，该系统的运动将由量子辐射压力波动在前所未有的频率范围内主导。这种量子主导的体制预示着“压缩”光的产生，这对超越“标准量子极限”和通过反馈制备任意运动量子态很有用，可以进行量子坍缩（例如，由于引力）的基本测试，以及用于暗物质搜索和力显微镜的量子增强传感器。然而，这些令人兴奋的机会需要显著改进的光纤反射镜来有效地耦合量子光：我们需要精确定位，超光滑和接近平坦的表面，我们目前无法制造。其次，在辐射剂量学领域，我们最近申请了一种以水为活性介质的组织等效体内纤维腔剂量计的专利。我们与Enger教授（MUHC）的合作现在已经在自由空间水中观察到有希望的信号，验证了我们的镜面涂层的辐射硬度，并开发了实现最佳剂量计的技术和详细理论。我们知道，目标灵敏度需要比我们现有设施的曲率半径大得多的反射镜。提议的升级——主要利用了几乎所有现有的基础设施——解决了上述所有问题，同时提高了可靠性和吞吐量。它包括用于在多个光纤尖端上进行任意形状的多次烧蚀的电动阶段，烧蚀期间和烧蚀后的自动烧蚀，具有业界领先的角度公差的光纤切割器，以消除有害的不对准，以及所有必要的集成硬件。除此之外，我们的设施还为哈佛大学、丹麦工业大学、高丽大学和阿尔伯塔大学的研究人员提供纤维。这里所要求的基础设施将提高产量、灵活性和可靠性，从而使该社区得以扩展。

Optical cavities vastly enhance light-matter interactions, making them a ubiquitous tool in optics, quantum optics, and sensing. Recently, microscopic "fiber cavities" have emerged, offering significantly higher bandwidth and tighter confinement, thereby boosting these interactions even further. As a result, five of our six core research directions now rely on fiber cavity technology. The requisite fiber mirror substrates are laser-machined in a shared facility at McGill, and, while this system has vaulted our research to the leading edge of several fields, its low tolerances and lack of flexibility now threaten to halt further progress. As such, we request an upgrade that will improve precision, design flexibility, and throughput. Each research area will greatly benefit from this, but two recent breakthroughs in particular present extraordinary opportunities that prompt an immediate upgrade. First, in the field of optomechanics, we have successfully realized a system comprising an ultralow-noise "trampoline" micromechanical sensor within a fiber cavity, whose motion will be dominated by quantum radiation pressure fluctuations over an unprecedented band of frequencies. This quantum-dominated regime heralds the generation of "squeezed" light useful for surpassing the "standard quantum limit" and preparing arbitrary motional quantum states via feedback, enabling fundamental tests of quantum collapse (e.g. due to gravity), and quantum-enhanced sensors for dark matter searches and force microscopy. However, these exciting opportunities require significantly improved fiber mirrors to efficiently out-couple quantum light: we need precisely positioned, ultrasmooth, and near-flat surfaces that we cannot currently fabricate. Second, in the field of radiation dosimetry, we recently patented a tissue-equivalent in vivo fiber-cavity dosimeter with water as the active medium. Our collaboration with Prof. Enger (MUHC) has now observed promising signals in free space water, verified the radiation hardness of our mirror coatings, and developed techniques and a detailed theory for realizing the optimal dosimeter. We know that the targeted sensitivities require mirrors with much larger radius of curvature than is possible in our existing facility. The proposed upgrade -- which notably utilizes almost all of the existing infrastructure -- addresses all of the above issues, while increasing reliability and throughput. It includes motorized stages for multi-shot ablation of arbitrary profiles on multiple fiber tips and automatic profiling during and after ablation, a fiber cleaver with industry-leading angular tolerances to eliminate detrimental misalignment, and all necessary integration hardware. Beyond this, our facility provides fibers to researchers at Harvard, TU Denmark, Korea University, and Alberta. The infrastructure requested here will increase production, flexibility, and reliability, allowing this community to expand.