The number of terrestrial exoplanets accessible to high-contrast coronagraphic imaging with large telescopes is limited by the smallest angular offset from bright stars at which coronagraphs can observe. However, it is possible to reach inside a telescopes coronagraphic regime by employing nulling interferometry across a telescopes pupil. Indeed, cross-aperture nulling interferometry can observe significantly closer to stars than typical coronagraphs, enabling observations even within the stellar diffraction core. Identifying an optimal nulling coronagraph, i.e., one with both a very small IWA and a high throughput for exoplanet light, would thus be of great interest. A systematic examination of available nulling options has therefore been carried out, which has led to three things. The first is a topological overview that unites both multi-aperture nulling interferometers and single-aperture phase coronagraphs into a common geometrical framework. The second is a new type of phase-mask coronagraph that has emerged from a gap in this framework, called here the split-ring coronagraph. The third is a clear identification of the optimal configuration for a nulling coronagraph, which turned out to be an aperture-plane phase knife, i.e., an achromatic pi-radian phase shift applied to half the telescope pupil prior to focusing the telescopes point spread function into a single-mode fiber. The theoretical peak efficiency of the phase-knife fiber coronagraph, 35.2 percent for a circular telescope aperture, is found to be almost twice that of the next most efficient case, the vortex fiber nuller, at 19.0 percent.
The Nulling Interferometry Cryogenic Experiment (NICE): Architecture, requirements, and preliminary warm precursor results
ETH Zürich, Institute for Particle Physics & Astrophysics（苏黎世联邦理工学院，粒子物理与天体物理研究所）；ETH Zürich, Department of Earth and Planetary Sciences（苏黎世联邦理工学院，地球与行星科学系）
Seidr update: photonic 'black magic' for high-contrast interferometry using kernel-nulling and photonic lanterns
University of Sydney（悉尼大学）；Observatoire de la Cote d’Azur, Université Côte d’Azur（蔚蓝海岸天文台，蔚蓝海岸大学）；Australian National University（澳大利亚国立大学）；University of Exeter（埃克塞特大学）；Leiden University（莱顿大学）
Asgard/NOTT: L-band nulling interferometry at the VLTI -- III. The mid-infrared integrated optics beam combiner for NOTT
I. Physikalisches Institut der Universität zu Köln（科隆大学第一物理研究所）；Department of Physics & Astronomy, University of California, Los Angeles（加州大学洛杉矶分校物理与天文学系）；Institute of Astronomy, KU Leuven（鲁汶大学天体物理研究所）
Nulling at short wavelengths: theoretical performance constraints and a demonstration of faint companion detection inside the diffraction limit with a rotating-baseline interferometer
Palomar Fiber Nuller（PFN）是一种双基线调零干涉仪，可实现全方位覆盖的高精度近红外（NIR）调零观测。为了实现几× 10-4的近红外零深精度，PFN使用共模光学系统来提供高度对称性，单模光纤光束组合来降低对指向和波前误差的敏感度，极端自适应光学来稳定光纤耦合和交叉孔径条纹相位，快速信号校准和相机读出来最小化时间效应，以及统计零深度波动分析以放松相位稳定要求。在这里，我们描述了PFN的最终设计和性能，并提供了一个演示的微弱同伴检测的归零基线旋转的手段，最初设想的天基归零干涉。具体来说，在光谱双星eta Peg上测量的KS波段零深度旋转曲线反映了一颗与主星一样明亮的1.08 +/- 0.06 x 10-2的次级星，以及由于主星的大小而导致的4.8 +/- 1.6 x 10-4的零深度贡献。在30质量分离的时候，eta Peg B正好在望远镜衍射极限光束直径（88质量）和典型的日冕内部工作角内。最后，我们讨论了潜在的改进，可以使一些小角度调零观测较大的望远镜。
Tricouplers for nulling interferometry with photonic integrated circuits
California Institute of Technology（加州理工学院）；Astrophotonics Australia（天文光子学澳大利亚）；University of California, Los Angeles（加利福尼亚大学洛杉矶分校）；NASA Jet Propulsion Laboratory（美国国家航空航天局喷气推进实验室）；University of Maryland（马里兰大学）
Tri-coupler geometries for achromatic nulling interferometry in the near-infrared
Astrophotonics Australia；Department of Astronomy, California Institute of Technology（加州理工学院天文学系）；Physics & Astronomy Department, University of California, Los Angeles（加州大学洛杉矶分校物理与天文系）
Technologies and novel components for broadband splitting and coupling in pairwise and nulling interferometry
Astrophotonics Australia, Monash（蒙纳士大学天体光子学澳大利亚）；Department of Astronomy, California Institute of Technology（加州理工学院天文系）；Physics & Astronomy Department, University of California, Los Angeles（加州大学洛杉矶分校物理与天文系）；LIRA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Université de Paris（巴黎天文台LIRA实验室，巴黎文理研究大学，法国国家科学研究中心，索邦大学，巴黎大学）；Commissariat à l’Energie Atomique, Leti（法国原子能和替代能源委员会LETI实验室）；Astralis-AITC, Research School of Astronomy and Astrophysics, Australian National University（澳大利亚国立大学天文与天体物理研究学院）；Department of Quantum Science, Research School of Physics, Australian National University（澳大利亚国立大学量子科学系，物理研究学院）
The PLACID active coronagraphic imager instrument: commissioning status
University of Bern（伯尔尼大学）；Türkiye National Observatories, Atatürk University（土耳其国家天文台，阿塔图尔克大学）；LIRA, Université Paris Cité, Observatoire de Paris, Université PSL, Sorbonne Université, CNRS（拉伊拉实验室，巴黎西岱大学，巴黎天文台，巴黎文理研究大学，索邦大学，法国国家科学研究中心）；University of Applied Sciences HEIG-VD（沃州高等艺术学院）
Demonstrating the integration of a photonic lantern with an all-fiber-based nulling interferometer
Univ. of California, Santa Cruz（加州大学圣克鲁兹分校）；Univ. of California, Los Angeles（加州大学洛杉矶分校）；NASA Ames Research Center（NASA艾姆斯研究中心）；NASA Glenn Research Center（NASA格伦研究中心）；Univ. of Central Florida（中佛罗里达大学）
Large Interferometer For Exoplanets (LIFE): VII. Practical implementation of a five-telescope kernel-nulling beam combiner with a discussion on instrumental uncertainties and redundancy benefits
Achieving efficient broadband spatial filtering for LIFE: status and plan
ETH Zürich（苏黎世联邦理工学院）；Leiden Observatory, Leiden University（莱顿大学莱顿天文台）；Sydney Institute for Astronomy, School of Physics, University of Sydney（悉尼大学物理学院天体物理研究所）；Research School of Astronomy & Astrophysics, Australian National University（澳大利亚国立大学天文与天体物理研究学院）
Single-aperture spectro-interferometry in the visible at the Subaru telescope with FIRST: First on-sky demonstration on Keho'oea (α Lyrae) and Hokulei (α Aurigae)
