AI 中文总结
研究对用于甚大望远镜干涉仪的诺特中红外芯片进行低温特性研究，利用测试台和低温恒温器将芯片冷却至约138K并表征，得到宽带对比度等数据，为后续通过抗反射涂层提高通量奠定基础。
AI 中文摘要
诺特是甚大望远镜干涉仪（VLTI）新访客仪器套件阿斯加德的一部分，是南半球首个将投入使用的长基线消零干涉仪。它是L'波段（3.5 - 4μm）仪器，专为成像热的系外黄道尘埃和围绕附近主序星雪线运行的年轻巨行星而优化。L'波段在行星成像中有优势，能放宽恒星与行星对比度要求至约10⁻⁵，同时限制背景噪声水平。诺特使用由硫化镓镧（GLS）制成的光子光束组合器，已在室温下进行了表征。利用鲁汶大学组装的诺特仪器测试台及其测试低温恒温器，成功将芯片冷却至约138K并在低温下首次表征。结果显示原始宽带对比度约为1%，与室温下先前测量相似。不同耦合器的分光比在低温下也保持稳定，与室温测量相比不确定性小于约2%。当前芯片最大通量估计约为37%。未来工作将研究抗反射涂层以减少菲涅尔损耗并将通量提高至约50%。
英文摘要
NOTT is part of the new visitor instrument suite Asgard for the Very Large Telescope Interferometer (VLTI), and the first long-baseline nulling interferometer that will be operational in the southern hemisphere. It is an L'-band (3.5-4$\,μ$m) instrument optimized for imaging hot exozodiacal dust and young giant planets orbiting around the snowline of nearby main-sequence stars. For planet imaging, the L' band has the advantage of relaxing the requirements on the star-planet contrast to $\sim 10^{-5}$ while limiting the level of background noise compared with longer wavelengths. Nulling interferometry in the L'-band was made possible by the development of mid-infrared integrated optics with high throughput. NOTT uses a photonic beam combiner made of Gallium Lanthanum Sulfide (GLS), manufactured at Macquarie University and characterized at ambient temperatures at Universität zu Köln. This first characterization showed that the chip could achieve the broadband contrast requirement for exoplanet imaging. Using the test bench of the NOTT instrument assembled at KU Leuven, and its test cryostat, we successfully cooled the chip down to $\sim 138\,$K and performed its first characterization at cryogenic temperatures. The results show a raw broadband contrast of $\sim1\,\%$, similar to the previous measurements done at ambient temperatures. The splitting ratios of the different couplers are also shown to remain stable at cryogenic temperatures, with less than $\sim 2\,\%$ uncertainty compared to ambient measurements. These results thus show that the beam-combining properties and splitting ratios are behaving as expected at 138$\,$K. The current maximum throughput of the chip is estimated at $\sim37\,\%$. Future work will investigate an anti-reflection coating to reduce its Fresnel losses and increase its throughput to $\sim50\,\%$.
Comments13 pages (incl. 10 figures); Proc. SPIE Astronomical Telescopes + Instrumentation 2026 (Copenhagen; Denmark), Optical and Infrared Interferometry and Imaging X
