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Adaptive optics (AO) systems are critical in any application where highly resolved imaging or beam control must be performed through a dynamic medium. Such applications include astronomy and free-space optical communications, where light propagates through the atmosphere, as well as medical microscopy and vision science, where light propagates through biological tissues. Recent works have demonstrated common-path wavefront sensors (WFSs) for adaptive optics using the photonic lantern (PL), a slowly varying waveguide that can efficiently couple multi-moded light into single-mode fibers (SMFs). We use the SCExAO astrophotonics platform at the 8 m Subaru Telescope to show that spectral dispersion of lantern outputs can improve correction fidelity, culminating with an on-sky demonstration of real-time wavefront control. This is the first, to the best of our knowledge, result for either a spectrally dispersed or a photonic lantern wavefront sensor. Combined with the benefits offered by lanterns in precision spectroscopy, our results suggest the future possibility of a unified wavefront sensing spectrograph using compact photonic devices. 

Abstract MagAO-X is a recently commissioned extreme adaptive optics instrument for the Magellan Clay 6.5 m telescope at Las Campanas Observatory in Chile. MagAO-X had first light in 2019 and subsequent commissioning observations in 2022 and 2023. An essential step for the commissioning of any new instrument is the calibration of the conversion of detector coordinates to angular sky coordinates, which we accomplish with observations of HD 165054. The background stars adjacent to HD 165054 in Baade’s Window are in a fortuitous configuration for the astrometric calibration of natural-guide-star high-contrast imaging instruments. We extend past work to connect these stars’ positions to absolute astrometry for HD 165054 itself using Gaia Data Release 3 data, and bootstrap the creation of an astrometric solution for our new high-contrast imaging instrument. Through Markov Chain Monte Carlo analysis of the historical data and position measurements from MagAO-X, we obtain updated astrometric parameters for the seven background stars and an astrometric calibration of the MagAO-X science cameras. 

Abstract 2MASS J16120668–3010270 (hereafter 2MJ1612) is a young M0 star that hosts a protoplanetary disk in the Upper Scorpius star-forming region. Recent Atacama Large Millimeter/submillimeter Array (ALMA) observations of 2MJ1612 show a mildly inclined disk (i = 37°) with a large dust-depleted gap (R_cav ≈ 0 $\stackrel{\text{″}}{.}$4 or 53 au). We present high-contrast Hαobservations from MagAO-X on the 6.5 m Magellan telescope and new high-resolution submillimeter dust continuum observations with ALMA of 2MJ1612. On both 2025 April 13 and 16, we recovered a point source with Hαexcess with a signal-to-noise ratio ≳5 within the disk gap in our MagAO-X angular and spectral differential images at a separation of 141.96 ± 2.10 mas (23.45 ± 0.29 au deprojected) from the star and a position angle ​​​​​of 159 $\stackrel{\text{°}}{.}$00 ± 0 $\stackrel{\text{°}}{.}$55. Furthermore, this Hαsource is within close proximity to aK-band point source in the SPHERE/IRDIS observation taken on 2023 July 21. The astrometric offset between theKband and Hαsource can be explained by orbital motion of a bound companion. Thus, our observations can be best explained by the discovery of an accreting protoplanet, 2MJ1612 b, with an estimated mass of 4M_Jupand a Hαline flux ranging from (29.7 ± 7.5) × 10⁻¹⁶erg s cm²to (8.2 ± 3.4) × 10⁻¹⁶erg s cm². 2MJ1612 b is likely the third example of an accreting Hαprotoplanet responsible for carving the gap in its host disk, joining PDS 70 b and c. Further study is necessary to confirm and characterize this protoplanet candidate and to identify any additional protoplanets that may also play a role in shaping the gap. 

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. 

Abstract We present 3 yr of high-contrast imaging of the PDS 70 b and c accreting protoplanets with the new extreme AO system MagAO-X as part of the MaxProtoPlanetS survey of Hαprotoplanets. In 2023 and 2024, our sharp (25–27 mas FWHM), well-AO-corrected (20%–26% Strehl), deep (2–3.6 hr) images detected compact (r∼ 30 mas;r∼ 3 au) circumplanetary disks (CPDs) surrounding both protoplanets. Starlight scattering off the front edge of these dusty CPDs is the likely source of the bright compact continuum light detected within ∼30 mas of both planets in our simultaneously obtained continuum 668 nm filter images. After subtraction of contaminating continuum and point-spread function residuals withpyKLIPangular differential imaging and spectral differential imaging, we obtained high-contrast ASDI Hαimages of both planets in 2022, 2023, and 2024. We find the Hαline flux of planet b fell by (8.1 ± 1.6) × 10⁻¹⁶erg s⁻¹cm⁻², a factor of 4.6 drop in flux from 2022 to 2023. In 2024 March, planet b continued to be faint with just a slight 1.6× rise to an Hαline flux of (3.64 ± 0.87) × 10⁻¹⁶erg s⁻¹cm⁻². For c, we measure a significant increase of (2.74 ± 0.51) × 10⁻¹⁶erg s⁻¹cm⁻²from 2023 to 2024, which is a factor of 2.3 increase. So both protoplanets have recently experienced significant Hαvariability with ∼1 yr sampling. In 2024, planet c is brighter than b: as c is brightening and b generally fading. We also tentatively detect one new point source “CC3” inside the inner disk (∼49 mas; at PA ∼ 295°; 2024) with orbital motion roughly consistent with a ∼5.6 au orbit. 

Abstract The direct imaging of an Earth-like exoplanet will require sub-nanometric wave-front control across large light-collecting apertures to reject host starlight and detect the faint planetary signal. Current adaptive optics systems, which use wave-front sensors that reimage the telescope pupil, face two challenges that prevent this level of control: non-common-path aberrations, caused by differences between the sensing and science arms of the instrument; and petaling modes: discontinuous phase aberrations caused by pupil fragmentation, especially relevant for the upcoming 30 m class telescopes. Such aberrations drastically impact the capabilities of high-contrast instruments. To address these issues, we can add a second-stage wave-front sensor to the science focal plane. One promising architecture uses the photonic lantern (PL): a waveguide that efficiently couples aberrated light into single-mode fibers (SMFs). In turn, SMF-confined light can be stably injected into high-resolution spectrographs, enabling direct exoplanet characterization and precision radial velocity measurements; simultaneously, the PL can be used for focal-plane wave-front sensing. We present a real-time experimental demonstration of the PL wave-front sensor on the Subaru/SCExAO testbed. Our system is stable out to around ±400 nm of low-order Zernike wave-front error and can correct petaling modes. When injecting ∼30 nm rms of low-order time-varying error, we achieve ∼10× rejection at 1 s timescales; further refinements to the control law and lantern fabrication process should make sub-nanometric wave-front control possible. In the future, novel sensors like the PL wave-front sensor may prove to be critical in resolving the wave-front control challenges posed by exoplanet direct imaging. 

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. 

Inner working angle is a key parameter for enabling scientific discovery in direct exoplanet imaging and characterization. Approaches to improving the inner working angle to reach the diffraction limit center on the sensing and control of wavefront errors, starlight suppression via coronagraphy, and differential techniques applied in post-processing. These approaches are ultimately limited by the shot noise of the residual starlight, placing a premium on the ability of the adaptive optics system to sense and control wavefront errors so that the coronagraph can effectively suppress starlight reaching the science focal plane. Photonic lanterns are attractive for use in the science focal plane because of their ability to spatially filter light using a finite basis of accepted modes and effectively couple the results to diffraction-limited spectrometers, providing a compact and cost-effective means to implement post-processing based on spectral diversity. We aim to characterize the ability of photonic lanterns to serve as focal-plane wavefront sensors, allowing the adaptive optics system to control aberrations affecting the science focal plane and reject additional stellar photon noise. By serving as focal-plane wavefront sensors, photonic lanterns can improve sensitivity to exoplanets through both direct and coronagraphic observations. We have studied the sensing capabilities of photonic lanterns in the linear and quadratic regimes with analytical and numerical treatments for different lantern geometries (including non-mode-selective, mode-selective, and hybrid geometries) as a function of port number. In this presentation we report on the sensitivity of such lanterns and comment on the relative suitability and sensitivity impacts of different lantern geometries for focal-plane wavefront sensing. 

A focal plane wavefront sensor offers major advantages to adaptive optics, including removal of non-commonpath error and providing sensitivity to blind modes (such as petalling). But simply using the observed point spread function (PSF) is not sufficient for wavefront correction, as only the intensity, not phase, is measured. Here we demonstrate the use of a multimode fiber mode converter (photonic lantern) to directly measure the wavefront phase and amplitude at the focal plane. Starlight is injected into a multimode fiber at the image plane, with the combination of modes excited within the fiber a function of the phase and amplitude of the incident wavefront. The fiber undergoes an adiabatic transition into a set of multiple, single-mode outputs, such that the distribution of intensities between them encodes the incident wavefront. The mapping (which may be strongly non-linear) between spatial modes in the PSF and the outputs is stable but must be learned. This is done by a deep neural network, trained by applying random combinations of spatial modes to the deformable mirror. Once trained, the neural network can instantaneously predict the incident wavefront for any set of output intensities. We demonstrate the successful reconstruction of wavefronts produced in the laboratory with low-wind-effect, and an on-sky demonstration of reconstruction of low-order modes consistent with those measured by the existing pyramid wavefront sensor, using SCExAO observations at the Subaru Telescope.