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1. The Photonic Lantern Nuller: from concept to laboratory and on-sky demonstrations

   https://doi.org/10.1117/12.3103386  

   Xin, Yinzi; Jovanovic, Nemanja; Mawet, Dimitri; Echeverri, Daniel; Kim, Yoo Jung; Lin, Jonathan; Lozi, Julien; Vievard, Sébastien; Guyon, Olivier; Piroscia, Grace; et al (August 2026, SPIE)

   Rau, Gioia; Sanchez-Bermudez, Joel; Kammerer, Jens (Ed.)

   Not AvailableThis thesis work presents the conceptual design and experimental characterization of the Photonic Lantern Nuller instrument, which uses a multimode-to-single-mode demultiplexing waveguide to cancel out starlight while maintaining planet light, allowing for the direct characterization of planets at a telescope's diffraction limit. The PLN was experimentally characterized in the lab, where it was further enhanced using common-path wavefront sensing and control techniques, and then demonstrated on sky at the Subaru Telescope. Highlights include measured in-lab null-depths of ∼10−4 in three out of four ports simultaneously and on-sky null-depths of approximately ∼10−1 (limited by jitter and atmospheric residuals). We provide an overview of these results and discuss avenues for future work. 

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2. FIRST-PL: commissioning the first visible photonic lantern spectrograph for sub-diffraction-limit astronomy on Subaru/SCExAO

   https://doi.org/10.1117/12.3104134  

   Vievard, S; Huby, E; Lacour, S; Guyon, O; Lallement, M; Nowak, M; Kim, Y-J; Walk, A; Sarrazin, J; Leon-Saval, S; et al (August 2026, SPIE)

   Rau, Gioia; Sanchez-Bermudez, Joel; Kammerer, Jens (Ed.)

   FIRST-PL (Fibered Imager foR a Single Telescope - Photonic Lantern) is a newly commissioned visible-light instrument on Subaru/SCExAO achieving spectroscopy below the diffraction limit. The instrument uses a Photonic Lantern (PL)-converting multimode fiber into 19 single-mode outputs-feeding a mid-resolution spectrograph (R 3000, 630-790 nm). On-sky performance demonstrates 40% injection efficiency at 680 nm (Strehl 30%) and 12x throughput improvement over single-mode fibers. Three operational modes enable spectro-astrometry (50 microarcseconds precision demonstrated on beta-CMi), image reconstruction, and high-contrast imaging. FIRST-PL represents a significant advancement in high-throughput photonic instrumentation. 

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3. Focal-plane wavefront sensing with photonic lanterns II: numerical characterization and optimization

   https://doi.org/10.1364/JOSAB.502962  

   Lin, Jonathan; Fitzgerald, Michael P.; Xin, Yinzi; Kim, Yoo Jung; Guyon, Olivier; Leon-Saval, Sergio G.; Norris, Barnaby; Jovanovic, Nemanja (January 2023, Journal of the Optical Society of America B)

   We present numerical characterizations of the wavefront sensing performance for few-mode photonic lantern wavefront sensors (PLWFSs). These characterizations include calculations of the throughput, control space, sensor linearity, and an estimate of the maximum linear reconstruction range for standard and hybrid lanterns with between 3 and 19 ports, atλ=1550nm. We additionally consider the impact of beam-shaping optics and a charge-1 vortex mask placed in the pupil plane. The former is motivated by the application of PLs to high-resolution spectroscopy, which could enable efficient injection into the spectrometer along with simultaneous focal-plane wavefront sensing; similarly, the latter is motivated by the application of PLs to vortex fiber nulling (VFN), which can simultaneously enable wavefront sensing and the nulling of on-axis starlight. Overall, we find that the PLWFS setups tested in this work exhibit good linearity out to ∼0.25−0.5 radians of RMS wavefront error (WFE). Meanwhile, we estimate the maximum amount of WFE that can be handled by these sensors to be around ∼1−2 radians RMS before the sensor response becomes degenerate. In the future, we expect these limits can be pushed further by increasing the number of degrees of freedom, either by adopting higher mode-count lanterns, dispersing lantern outputs, or separating polarizations. Finally, we consider optimization strategies for the design of the PLWFS, which involve both modification of the lantern itself and the use of pre- and post-lantern optics like phase masks and interferometric beam recombiners. 

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4. Focal-plane wavefront sensing with photonic lanterns: theoretical framework

   https://doi.org/10.1364/JOSAB.466227  

   Lin, Jonathan; Fitzgerald, Michael P.; Xin, Yinzi; Guyon, Olivier; Leon-Saval, Sergio; Norris, Barnaby; Jovanovic, Nemanja (January 2022, Journal of the Optical Society of America B)

   The photonic lantern (PL) is a tapered waveguide that can efficiently couple light into multiple single-mode optical fibers. Such devices are currently being considered for a number of tasks, including the coupling of telescopes and high-resolution, fiber-fed spectrometers, coherent detection, nulling interferometry, and vortex-fiber nulling. In conjunction with these use cases, PLs can simultaneously perform low-order focal-plane wavefront sensing. In this work, we provide a mathematical framework for the analysis of a PL wavefront sensor (PLWFS), deriving linear and higher-order reconstruction models as well as metrics through which sensing performance—in both the linear and nonlinear regimes—can be quantified. This framework can be extended to account for additional optics such as beam-shaping optics and vortex masks, and can be generalized for other wavefront sensing architectures. Finally, we provide initial numerical verification of our mathematical models by simulating a six-port PLWFS. In a forthcoming companion paper (Lin and Fitzgerald), we provide a more comprehensive numerical characterization of few-port PLWFSs, and consider how the sensing properties of these devices can be controlled and optimized. 

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5. Experimental measurements of AO-Fed photonic lantern coupling efficiencies

   https://doi.org/10.1117/12.2630608  

   Lin, Jonathan; Vievard, Sébastien B.; Jovanovic, Nemanja; Norris, Barnaby R.; Fitzgerald, Michael P.; Betters, Christopher H.; Gatkine, Pradip R.; Guyon, Olivier; Kim, Yoo Jung; Leon-Saval, Sergio G.; et al (August 2022, Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation V)

   Geyl, Roland; Navarro, Ramón (Ed.)

   Efficiently coupling light from large telescopes to photonic devices is challenging. However, overcoming this challenge would enable diffraction-limited instruments, which offer significant miniaturization and advantages in thermo-mechanical stability. By coupling photonic lanterns with high performance adaptive optics systems, we recently demonstrated through simulation that high throughput diffraction-limited instruments are possible (Lin et al., Applied Optics, 2021). Here we build on that work and present initial results from validation experiments in the near-infrared to corroborate those simulations in the laboratory. Our experiments are conducted using a 19-port photonic lantern coupled to the state-of-the-art SCExAO instrument at the Subaru Telescope. The SCExAO instrument allows us to vary the alignment and focal ratio of the lantern injection, as well as the Strehl ratio and amount of tip/tilt jitter in the beam. In this work, we present experimental characterizations against the aforementioned parameters, in order to compare with previous simulations and elucidate optimal architectures for lantern-fed spectrographs. 

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