Low line density, high efficiency, volume phase holographic gratings for the Extremely Large Telescope's HARMONI spectrograph

Harmoni是超大型望远镜(ELT)的首批光学仪器之一。它是一种整体场光谱仪(也称为高光谱成像仪)，可以在天空的二维视场中的每个点的近红外波长上同时拍摄光谱。与自适应光学系统相结合，Harmoni能够通过ELT获得尽可能高的空间分辨率。精致的空间分辨率，加上ELT巨大的收集面积，意味着Harmoni可以用光谱详细地研究微弱的物体，例如宇宙历史早期的遥远星系。我们希望通过进一步发展最先进的衍射栅制造来增强Harmoni的能力。该方案的目标是扩展现有的制造技术，以生产低线密度、高吞吐量、高均匀性、体位相全息光栅。在Harmoni中使用这些光栅将使仪器的瞬时波长覆盖范围增加到原来的两倍，使我们能够在一次观测中观测到更多来自天文目标的发射和吸收谱线。这提高了我们的观测效率，最大限度地利用了宝贵的望远镜时间，也让我们能够研究我们无法顺序观测的时变现象。作为这项提议的一部分，我们正在组建一个实验装置来量化这些新开发的光栅的性能，测试以确保它们在近红外波长的一致性和高吞吐量。该装置将向来自英国所有学科的其他研究小组的研究人员开放，从而增强英国在物理和天文学方面的仪器能力。

HARMONI is one of the first-light instruments for the Extremely Large Telescope (ELT). It is an integral field spectrograph (also called hyper-spectral imager) that takes simultaneous spectra at near-infrared wavelengths of every point in a two-dimensional field of view on the sky. Coupled with an adaptive optics system, HARMONI is able to achieve the highest spatial resolution possible with the ELT. The exquisite spatial resolution, coupled with the huge collecting area of the ELT, means that HARMONI can spectroscopically study faint objects in detail, such as distant galaxies at early times in the history of the Universe.We are looking to enhance HARMONI's capability by furthering the state-of-the-art in the manufacture of diffraction gratings. The goal of this proposal is to extend current manufacturing techniques to produce low line density, high throughput, high uniformity, volume phase holographic gratings. Use of these gratings in HARMONI will increase the instantaneous wavelength coverage of the instrument by a factor of two, allowing us to observe many more emission and absorption spectral lines from astronomical targets in a single observation. This increases our observing efficiency, making best use of precious telescope time, but also allows us to study time variable phenomenon that we cannot observe in a sequential fashion. As part of this proposal, we are assembling an experimental set-up to quantify the performance of these newly developed gratings, testing to ensure their uniformity and high throughput at near-infrared wavelengths. The set-up will be available to researchers from other research groups in all disciplines across the U.K., thus enhancing the country's instrumentation capabilities for physics and astronomy.