TICTAC: Turnkey, Inexpensive and Compact Ti:sapphire Astrocomb Concept

1929年，埃德温·哈勃报告说，来自更远星系的光谱发生了更大的红移，为宇宙的扩张提供了基础证据。近100年后，光学天文学中一些最令人兴奋的科学案例依赖于光谱学，包括对类地系外行星的探测和表征，以及桑达奇测试，其目的是通过星系外来源红移的时间变化直接测量宇宙膨胀的加速度。天文学家使用高分辨率光谱仪来记录从遥远物体接收到的颜色的模式，但这些仪器的波长轴可以随着时间的推移略有移动。因此，必须定期使用外部参考光源进行校准，以确保观测之间的一致性。几十年来，产生数百条窄原子发射线的灯一直被用作校准源，但系外行星和宇宙学观测所要求的高精度和精确度现在已经超出了它们的能力范围。作为回应，天文学界转向了天体梳，这是一种激光技术，可以在5-50 GHz的可选栅格间距上提供一系列超窄、无漂移、规则分布的光学频率。参考GPS时间，星梳提供原子可追踪的光学频率，精度在10^-12级。目前的星梳是复杂而昂贵的系统，通常耗资200万欧元，其有限的可靠性需要博士级别的工作人员定期进行维护。我们的建议旨在通过开发基于二极管泵浦的钛蓝宝石的新的、简单而坚固的激光平台来解决这些问题。ESO以及HARPS3和ANDES仪器集团的支持信强调了这一概念的及时性。从Heriot-Watt目前的STFC财团拨款中产生的前景看好的概念验证钛宝石激光器将首先被系统地优化，以产生星梳系统所需的功率和脉冲持续时间。使用Heriot-Watt开发的新的对准和安装技术，它将被开发成一个交钥匙装置，其中形成激光腔的光学元件将直接结合到一个公共基板上，消除与光机械安装相关的漂移和不稳定。外部合作伙伴将为该项目提供最先进的非线性波导其设计可在开发的激光系统驱动下产生宽带可见光。使用光子锁定和过滤方法，我们将把这种光配置成天文梳子所需的格式。该项目的最后一年将把这些不同的元素集成到一个单一的天体梳子系统中，首先在Heriot-Watt.的高分辨率梳子模式分辨率光谱仪上对其进行测试。我们将在10米长的SALT望远镜上开展活动，在实验室外验证该系统，作为实现商业化和建立社区对这一颠覆性天文梳子概念性能的信心的关键一步。在项目期间将采取商业化的步骤，适当的包括：申请专利保护，剥离公司成立，制定许可协议，以及来自商业发展顾问的意见。该项目提供了极高的性价比，我们合作伙伴提供的GB 187K实物支持和Heriot-Watt提供的GB 120K现金(20%FEC)高度利用了STFC的GB 477K成本。

In 1929, Edwin Hubble reported that spectra from further away galaxies were more redshifted, providing foundational evidence for the expansion of the universe.Almost 100 years later, some of the most exciting science cases for optical astronomy rely on spectroscopy, including the detection and characterisation of Earth-like exoplanets, and the Sandage Test, which aims to directly measure the acceleration in the expansion of the universe from the temporal variation of the redshift of extra-galactic sources.Astronomers use high resolution spectrographs to record the pattern of colours received from distant objects, but the wavelength axes of these instruments can shift slightly over time, and so must be regularly calibrated with an external reference light source to ensure consistency between observations.For several decades, lamps producing hundreds of narrow atomic emission lines have been used as calibration sources, but the high precision and accuracy demanded by exoplanet and cosmological observations now exceeds their capabilities.In response, the astronomy community is turning to astrocombs, a laser technology giving a sequence of ultra-narrow, drift-free, regularly spaced optical frequencies on a selectable grid spacing of 5-50 GHz. When referenced to GPS time, astrocombs provide atomically traceable optical frequencies with a precision at the 10^-12 level.Current astrocombs are complex and expensive systems, typically costing >2 million EUR, and their limited reliability requires regular maintenance visits by PhD-level staff.Our proposal seeks to address these issues by developing a new, simple and robust laser platform based on diode-pumped Ti:sapphire. The timeliness of this concept is emphasised by letters of support from ESO, and from the HARPS3 and ANDES instrument consortia.A promising proof-of-concept Ti:sapphire laser emerging from Heriot-Watt's current STFC consortium grant will first be systematically optimised to produce the powers and pulse durations needed for an astrocomb system.Using new alignment and mounting techniques developed at Heriot-Watt it will then be developed into a turnkey device, in which the optical elements forming the laser cavity will be bonded directly to a common baseplate, eliminating the drift and instability associated with optomechanical mounts.External partners will provide state-of-the-art nonlinear waveguides to the project, with designs tailored to generate broadband visible light when driven by the developed laser system. Using photonic locking and filtering methods, we will configure this light into the format needed for an astrocomb. The final year of the project will integrate these diverse elements into a single astrocomb system, testing it first on a high resolution comb-mode-resolving spectrograph at Heriot-Watt.We will conclude the project with a campaign at the 10-metre SALT telescope, validating the system outside the lab, as a key step to commercialisation and building community confidence in the performance of this disruptive astrocomb concept.Steps towards commercialisation will be taken during the project including, where appropriate: filing of patent protection, spin-out company incorporation, development of licensing agreements, and input from business development advisors.The project offers excellent value for money, with the £477K cost to STFC being highly leveraged by £187K in-kind support from our partners and £120K cash (20% FEC) from Heriot-Watt.