Showing papers by "Simon Gross published in 2021"

Scalable photonic-based nulling interferometry with the dispersed multi-baseline GLINT instrument.

Abstract: Characterisation of exoplanets is key to understanding their formation, composition and potential for life. Nulling interferometry, combined with extreme adaptive optics, is among the most promising techniques to advance this goal. We present an integrated-optic nuller whose design is directly scalable to future science-ready interferometric nullers: the Guided-Light Interferometric Nulling Technology, deployed at the Subaru Telescope. It combines four beams and delivers spatial and spectral information. We demonstrate the capability of the instrument, achieving a null depth better than 10−3 with a precision of 10−4 for all baselines, in laboratory conditions with simulated seeing applied. On sky, the instrument delivered angular diameter measurements of stars that were 2.5 times smaller than the diffraction limit of the telescope. These successes pave the way for future design enhancements: scaling to more baselines, improved photonic component and handling low-order atmospheric aberration within the instrument, all of which will contribute to enhance sensitivity and precision. Nulling interferometry is a technique combining lights from different telescopes or apertures to observe weak sources nearby bright ones. The authors report the first nulling interferometer implemented in a photonic chip doing spectrally dispersed nulling on several baselines, simultaneously.

Achromatic photonic tricouplers for application in nulling interferometry.

Abstract: Integrated-optic components are being increasingly used in astrophysics, mainly where accuracy and precision are paramount. One such emerging technology is nulling interferometry that targets high contrast and high angular resolution. Two of the most critical limitations encountered by nullers are rapid phase fluctuations in the incoming light causing instability in the interference and chromaticity of the directional couplers that prevent a deep broadband interferometric null. We explore the use of a tricoupler designed by ultrafast laser inscription that solves both issues. Simulations of a tricoupler, incorporated into a nuller, result in an order of a magnitude improvement in null depth.

Very high resolution spectro-interferometry with wavefront sensing capabilities on Subaru/SCExAO using photonics

Abstract: Post Extreme Adaptive-Optics (ExAO) spectro-interferometers design allows high contrast imaging with an inner working angle down to half the theoretical angular resolution of the telescope. This regime, out of reach for conventional ExAO imaging systems, is obtained thanks to the interferometric recombination of multiple sub-apertures of a single telescope, using single mode waveguides to remove speckle noise. The SCExAO platform at the Subaru telescope hosts two instruments with such design, coupled with a spectrograph. The FIRST instrument operates in the Visible (600-800nm, R~400) and is based on pupil remapping using single-mode fibers. The GLINT instrument works in the NIR (1450-1650nm, R~160) and is based on nulling interferometry. We present here how these photonic instruments have the unique capability to simultaneously do high contrast imaging and be included in the wavefront sensing architecture of SCExAO.

A micro-optical module for multi-wavelength addressing of trapped ions

Abstract: Microfabricated devices for trapping atomic particles have created new opportunities for exploiting quantum phenomena in fundamental science, engineering and computing. While microfabricated ion traps have advanced considerably, the development of accompanying micro-optical systems for controlling arrays of trapped ions has lagged. Most present systems rely on bulk optics, which limits the number of trapping sites that can be optically addressed in a device. To enable experimental systems of increased complexity, and aid the translation to quantum technology applications, micro-optical systems are required for parallel addressing of multiple trapping sites. Photonic devices with micro-optical elements have been reported for coupling laser radiation to trapped ions, however these are restricted in their efficiency, operating wavelength range and polarisation versatility. Here we report a novel micro-optical assembly that irradiates two spatially separate points, each with a set of three blue (422 nm) and two infrared (1033 nm and 1092 nm) laser beams. A 1D array of ten fibre inputs is remapped by a laser-written waveguide chip to two sets of five outputs. These match a 2D array of diffractive microlenses which focus each beam to its intersection point with a unique k-vector. The device has average insertion losses of 8 dB across all channels and typical relative crosstalk intensities of <2×10^-3 at 422 nm. Realisation of this device required the first demonstration of laser-written waveguides that route blue wavelengths in three-dimensions. The material system enables operation over a wide wavelength range; while designed for 88Sr+ transitions, the principle is applicable to other species.

Achromatic photonic tricouplers for application in nulling interferometry

Abstract: Integrated-optic components are being increasingly used in astrophysics, mainly where accuracy and precision are paramount. One such emerging technology is nulling interferometry that targets high contrast and high angular resolution. Two of the most critical limitations encountered by nullers are rapid phase fluctuations in the incoming light causing instability in the interference and chromaticity of the directional couplers that prevent a deep broadband interferometric null. We explore the use of a tricoupler designed by ultrafast laser inscription that solves both issues. Simulations of a tricoupler, incorporated into a nuller, result in order of a magnitude improvement in null depth.

Building hybridized 28-baseline pupil-remapping photonic interferometers for future high resolution imaging

Abstract: One key advantage of single-mode photonic technologies for interferometric use is their ability to easily scale to an ever increasing number of inputs without a major increase in the overall device size, compared to traditional bulk optics. This is particularly important for the upcoming ELT generation of telescopes currently under construction. We demonstrate the fabrication and characterization of a novel hybridized photonic interferometer, with 8 simultaneous inputs, forming 28 baselines, the largest amount to-date. Utilizing different photonic fabrication technologies, we combine a 3D pupil remapper with a planar 8-port ABCD pairwise beam combiner, along with the injection optics necessary for telescope use, into a single integrated monolithic device. We successfully realized a combined device called Dragonfly, which demonstrates a raw instrumental closure-phase stability down to $0.9^{\circ}$ over $8\pi$ phase piston error, relating to a detection contrast of $\sim6.5\times 10^{-4}$ on an Adaptive-Optics corrected 8-m telescope. This prototype successfully demonstrates advanced hybridization and packaging techniques necessary for on-sky use for high-contrast detection at small inner working angles, ideally complementing what can currently be achieved using coronagraphs.

Building hybridized 28-baseline pupil-remapping photonic interferometers for future high-resolution imaging.

Abstract: One key advantage of single-mode photonic technologies for interferometric use is their ability to easily scale to an ever-increasing number of inputs without a major increase in the overall device size, compared to traditional bulk optics. This is particularly important for the upcoming extremely large telescope (ELT) generation of telescopes currently under construction. We demonstrate the fabrication and characterization of a hybridized photonic interferometer, with eight simultaneous inputs, forming 28 baselines, which is the largest amount to date, to the best of our knowledge. Using different photonic fabrication technologies, we combine a 3D pupil remapper with a planar eight-port ABCD pairwise beam combiner, along with the injection optics necessary for telescope use, into a single integrated monolithic device. We successfully realized a combined device called Dragonfly, which demonstrates a raw instrumental closure-phase stability down to 0.9° over $8\pi$ phase piston error, relating to a detection contrast of ${\sim}6.5 \times {10^{- 4}}$ on an adaptive-optics-corrected 8 m telescope. This prototype successfully demonstrates advanced hybridization and packaging techniques necessary for on-sky use for high-contrast detection at small inner working angles, ideally complementing what can currently be achieved using coronagraphs.

The GLINT South testbed for nulling interferometry with photonics: Design and on-sky results at the Anglo-Australian Telescope

Abstract: In 1978, Bracewell suggested the technique of nulling interferometry to directly image exoplanets which would enable characterisation of their surfaces, atmospheres, weather, and possibly determine their capacity to host life. The contrast needed to discriminate starlight reflected by a terrestrial-type planet from the glare of its host star lies at or beyond a forbidding for an exo-Earth in the habitable zone around a Sun-like star at near-infrared wavelengths, necessitating instrumentation with extremely precise control of the light. Guided Light Interferometric Nulling Technology (GLINT) is a testbed for new photonic devices conceived to overcome the challenges posed by nulling interferometry. At its heart, GLINT employs a single-mode nulling photonic chip fabricated by direct-write technology to coherently combine starlight from an arbitrarily large telescope at 1 550 nm. It operates in combination with an actuated segmented mirror in a closed-loop control system, to produce and sustain a deep null throughout observations. The GLINT South prototype interfaces the 3.9-m Anglo-Australian Telescope and was tested on a sample of bright Mira variable stars. Successful and continuous starlight injection into the photonic chip was achieved. A statistical model of the data was constructed, enabling a data reduction algorithm to retrieve contrast ratios of about . As a byproduct of this analysis, stellar angular diameters that were below the telescope diffraction limit ( 100 mas) were recovered with 1 accuracy and shown to be in agreement with literature values despite working in the seeing-limited regime. GLINT South serves as a demonstration of the capability of direct-write photonic technology for achieving coherent, stable nulling of starlight, which will encourage further technological developments towards the goal of directly imaging exoplanets with future large ground based and space telescopes.

A micro-optical module for multi-wavelength addressing of trapped ions

Abstract: The control of large-scale quantum information processors based on arrays of trapped ions requires a means to route and focus multiple laser beams to each of many trapping sites in parallel. Here, we combine arrays of fibres, 3D laser-written waveguides and diffractive microlenses to demonstrate the principle of a micro-optic interconnect suited to this task. The module is intended for use with an ion microtrap of 3D electrode geometry. It guides ten independent laser beams with unique trajectories to illuminate a pair of spatially separated target points. Three blue and two infrared beams converge to overlap precisely at each desired position. Typical relative crosstalk intensities in the blue are $3.6 \times 10^{-3}$ and the average insertion loss across all channels is $8~$dB. The module occupies $\sim 10^4$ times less volume than a conventional bulk-optic equivalent and is suited to different ion species.