Applications of Integrated Photonic Spectrographs in astronomy
Applications of Integrated Photonic Spectrographs in astronomy
复制标题
集成光子摄谱仪在天文学中的应用
DOI：
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发表时间：
2012
期刊：
影响因子：
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通讯作者：
J. Allington
中科院分区：
文献类型：
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作者：
Robert J. Harris;J. Allington
生产超大型望远镜（ELT）仪器的问题之一是它们的尺寸（以及成本）随着望远镜孔径的变化而迅速变化。为了尝试打破这种关系，人们提出了替代新技术，例如使用集成光子摄谱仪（IPS）。由于其衍射极限特性，IPS 据称可以克服传统仪器中严格的缩放定律。与光子应用相反，天文学设备通常不在衍射极限下使用。因此，为了保留吞吐量和空间信息，IPS 需要光子灯 (PL) 将输入的多模光分解为单模。然后将其馈送到众多阵列波导光栅 (AWG) 或传统的摄谱仪中。
我们研究了使用 IPS 代替传统单片光学器件的潜在优势，以实现 8 m 望远镜上的现有仪器和其他计划用于 ELT 的仪器所代表的各种功能。为此，我们构建了不同版本 IPS 的玩具模型，并计算了相对仪器尺寸和所需的探测器像素数量。这使我们能够量化针对不同科学要求的仪器的相对尺寸/成本优势。我们证明，完整的 IPS 仪器相当于图像切片机。如前所述，图像切片对于 ELT 来说是一种有益的策略。然而，在许多情况下，将输入光分解为各个模式的要求在组件和探测器像素的数量方面强加了冗余，这抵消了光子组件小尺寸的优势。然而，在某些特定应用中，IPS 具有我们所描述的潜在优势。此外，IPS 方法具有最小化或消除体光学器件的潜在优势。我们表明，从 PL 接收多个单模输入的 AWG 需要相对庞大的辅助光学器件和 2D 探测器阵列，这显着增加了仪器的尺寸。一个更有吸引力的选择是结合许多 AWG 的输出，以便可以使用一维探测器来大大减少所需的探测器像素数量，并提供对弯曲输出焦面的有效适应。
One of the problems of producing instruments for extremely large telescopes (ELTs) is that their size (and hence cost) scales rapidly with telescope aperture. To try to break this relation alternative new technologies have been proposed, such as the use of the Integrated Photonic Spectrograph (IPS). Due to their diffraction-limited nature, the IPS is claimed to defeat the harsh scaling law applying to conventional instruments. In contrast to photonic applications, devices for astronomy are not usually used at the diffraction limit. Therefore, to retain throughput and spatial information, the IPS requires a photonic lantern (PL) to decompose the input multi-mode light into single modes. This is then fed into either numerous arrayed waveguide gratings (AWGs) or a conventional spectrograph.
We investigate the potential advantage of using an IPS instead of conventional monolithic optics for a variety of capabilities represented by existing instruments on 8 m telescopes and others planned for ELTs. To do this, we have constructed toy models of different versions of the IPS and calculated the relative instrument sizes and the number of detector pixels required. This allows us to quantify the relative size/cost advantage for instruments aimed at different science requirements. We show that a full IPS instrument is equivalent to an image slicer. Image slicing is a beneficial strategy for ELTs as previously demonstrated. However, the requirement to decompose the input light into individual modes imposes a redundancy in terms of the numbers of components and detector pixels in many cases which acts to cancel out the advantage of the small size of the photonic components. However, there are specific applications where an IPS gives a potential advantage which we describe. Furthermore, the IPS approach has the potential advantage of minimizing or eliminating bulk optics. We show that AWGs fed with multiple single-mode inputs from an PL require relatively bulky auxiliary optics and a 2D detector array which significantly increases the size of the instrument. A more attractive option is to combine the outputs of many AWGs so that a 1D detector can be used to greatly reduce the number of detector pixels required and provide efficient adaptation to the curved output focal surface.