Photonic lantern nulling (PLN) is a method for enabling the detection and characterization of close-in exoplanets by exploiting the symmetries of the ports of a mode-selective photonic lantern (MSPL) to cancel out starlight. A six-port MSPL provides four ports where on-axis starlight is suppressed, while off-axis planet light is coupled with efficiencies that vary as a function of the planet’s spatial position. We characterize the properties of a six-port MSPL in the laboratory and perform the first testbed demonstration of the PLN in monochromatic light (1569 nm) and in broadband light (1450 to 1625 nm), each using two orthogonal polarizations. We compare the measured spatial throughput maps with those predicted by simulations using the lantern’s modes. We find that the morphologies of the measured throughput maps are reproduced by the simulations, though the real lantern is lossy and has lower throughputs overall. The measured ratios of on-axis stellar leakage to peak off-axis throughput are around 10−2, likely limited by testbed wavefront errors. These null-depths are already sufficient for observing young gas giants at the diffraction limit using ground-based observatories. Future work includes using wavefront control to further improve the nulls, as well as testing and validating the PLN on-sky.

中文翻译：

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单色光和宽带光下光子灯笼消零器的实验室演示

光子灯笼归零 (PLN) 是一种通过利用模式选择性光子灯笼 (MSPL) 端口的对称性来抵消星光来检测和表征近距离系外行星的方法。六端口 MSPL 提供四个端口，轴上星光受到抑制，而离轴行星光的效率随行星空间位置的变化而变化。我们在实验室中表征了六端口 MSPL 的特性，并在单色光（1569 nm）和宽带光（1450 至 1625 nm）下进行了 PLN 的首次测试台演示，每种光均使用两个正交偏振。我们将测量的空间吞吐量图与使用灯笼模式进行模拟预测的空间吞吐量图进行比较。我们发现，尽管真实的灯笼是有损的并且总体吞吐量较低，但测量的吞吐量图的形态是通过模拟再现的。测得的轴上恒星泄漏与峰值离轴吞吐量之比约为 10−2，可能受到测试台波前误差的限制。这些零深度已经足以使用地面天文台在衍射极限下观察年轻的气态巨行星。未来的工作包括使用波前控制来进一步改善零点，以及测试和验证天空中的 PLN。