“MODAL NOISE” IN SINGLE-MODE FIBERS: A CAUTIONARY NOTE FOR HIGH PRECISION RADIAL VELOCITY INSTRUMENTS
“MODAL NOISE” IN SINGLE-MODE FIBERS: A CAUTIONARY NOTE FOR HIGH PRECISION RADIAL VELOCITY INSTRUMENTS
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单模光纤中的“模态噪声”：高精度径向速度仪器的警告
DOI：
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发表时间：
2015
期刊：
影响因子：
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通讯作者：
C. Schwab
中科院分区：
文献类型：
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作者：
S. Halverson;Arpita Roy;S. Mahadevan;C. Schwab
自从大口径望远镜上出现衍射极限自适应光学系统以来，探索单模光纤 (SMF) 在高精度多普勒光谱仪中的使用变得越来越有吸引力。使用这些光纤的光谱仪可以比典型的“视见受限”仪器小得多，从而大大降低成本和整体复杂性。重要的是，使用 SMF 可以缓解与多模光纤相关的经典模式干扰和散斑问题（也称为“模态噪声”），同时还可以提供完美的径向和方位图像加扰。然而，SMF 确实支持多种偏振模式，鉴于传播模式数量众多，对于大芯光纤来说，这个问题通常会被忽略。由于大多数高分辨率天文仪器中使用的衍射光栅具有对入射偏振变化敏感的色散特性，因此光纤中的任何双折射变化都会导致效率分布的变化，从而降低照明稳定性。在此，我们提出一个警告，概述了 SMF 的偏振特性如何影响高分辨率摄谱仪的径向速度 (RV) 测量精度。这项工作与快速扩展的衍射极限、极高精度 RV 摄谱仪领域直接相关，目前许多小组正在设计和建造这些摄谱仪。
Exploring the use of single-mode fibers (SMFs) in high precision Doppler spectrometers has become increasingly attractive since the advent of diffraction-limited adaptive optics systems on large-aperture telescopes. Spectrometers fed with these fibers can be made significantly smaller than typical “seeing-limited” instruments, greatly reducing cost and overall complexity. Importantly, classical mode interference and speckle issues associated with multi-mode fibers, also known as “modal noise,” are mitigated when using SMFs, which also provide perfect radial and azimuthal image scrambling. However, SMFs do support multiple polarization modes, an issue that is generally ignored for larger-core fibers given the large number of propagation modes. Since diffraction gratings used in most high resolution astronomical instruments have dispersive properties that are sensitive to incident polarization changes, any birefringence variations in the fiber can cause variations in the efficiency profile, degrading illumination stability. Here we present a cautionary note outlining how the polarization properties of SMFs can affect the radial velocity (RV) measurement precision of high resolution spectrographs. This work is immediately relevant to the rapidly expanding field of diffraction-limited, extreme precision RV spectrographs that are currently being designed and built by a number of groups.
CARMENES 仪器概述
DOI：
10.1117/12.2056453
发表时间：
2014
期刊：
影响因子：
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作者：
Quirrenbach
通讯作者：
Quirrenbach