Starlight demonstration of the Dragonfly instrument: an integrated photonic pupil-remapping interferometer for high-contrast imaging

Abstract

In the two decades since the first extra‐solar planet was discovered, the detection and characterization of extra‐solar planets has become one of the key endeavours in all of modern science. Recently, direct detection techniques such as interferometry or coronagraphy have received growing attention because they reveal the population of exoplanets inaccessible to Doppler or transit techniques, and moreover they allow the faint signal from the planet itself to be investigated. Next‐generation stellar interferometers are increasingly incorporating photonic technologies due to the increase in fidelity of the data generated. Here, we report the design, construction and commissioning of a new high‐contrast imager, the integrated pupil‐remapping interferometer, an instrument we expect will find application in the detection of young faint companions in the nearest star‐forming regions. The laboratory characterization of the instrument demonstrated high‐visibility fringes on all interferometer baselines in addition to stable closure phase signals. We also report the first successful on‐sky experiments with the prototype instrument at the 3.9‐m Anglo‐Australian Telescope. Performance metrics recovered were consistent with ideal device behaviour after accounting for expected levels of decoherence and signal loss from the uncompensated seeing. The prospect of complete Fourier coverage coupled with the current performance metrics means that this photonically enhanced instrument is well positioned to contribute to the science of high‐contrast companions.

Ultrafast-laser-inscribed 3D integrated photonics: challenges and emerging applications

“…The algorithm takes the limitation of the fabrication process such as accessible vertical real-estate, bends losses as well as minimum distance between waveguide to mitigate cross-coupling into account and creates an optimised waveguide layout with path length matching to within 100 nm [127]. Whilst the first generation of pupil remapping chips suffered from low throughput caused by bend losses [10], improved fabrication exploiting thermal annealing [67] vastly increased the transmission as well as closure phase stability [126].…”

“…A 3D waveguide architecture benefiting from the inherent stability of the in-bulk embedded waveguides created by ultrafast laser inscription is an elegant solution for this challenge. An instrument called DRAGONFLY was first to use the 3D waveguide approach and was also the first demonstration of stellar light captured by an astronomical telescope (3.9 m Anglo Australian Telescope) being injected into an ultrafast-laserinscribed optical chip [10]. The 3D waveguide chip contained eight waveguides to sample the telescope's pupil and remap the light via a side step into a linear array at the output, as shown in Figure 8.…”

“…Demonstrations of 3D photonic circuits include three-port couplers [4], 2D waveguide arrays [5], photonic lanterns [6], orbital angular momentum state generators [7] and quantum random walks [8]. With respect to a photon's higher degrees of freedom listed earlier, there have been reports of polarisation-encoded qubits [9], optical remapping and phase control aimed at stellar interferometry [10] and spatial mode conversion on a chip aimed at addressing future telecommunications needs [11], all of which exploit 3D photonic designs. This paper reviews the fabrication technology and challenges associated with ultrafast laser inscription, in particular the fabrication of 3D lightwave circuits.…”

Efficient photonic reformatting of celestial light for diffraction-limited spectroscopy

“…The device, which was fully fabricated using an advanced laser manufacturing technique known as ultrafast laser inscription (ULI) (Davis et al 1996;Jovanovic et al 2012), seamlessly and monolithically integrated a photonic lantern transition with a spatial reformatting section. The device was tested on-sky by feeding the photonic dicer with H-band (1450-1610 nm) stellar light directly from CANARY, and was found to exhibit an on-sky throughput of 20 per cent (Harris et al 2015), somewhat less than the 65 per cent measured in the laboratory due to suboptimal input coupling.…”

Low bend loss waveguides and photonic bandgaps enabled by high index contrast modifications

“…We have successfully applied this fabrication process to significantly increase the throughputs of a 3D astrophotonic device known as a 'pupil-remapper' (details in [6]). The chip contains 8 pathlength-matched waveguides with bend radii of 23 to 35 mm to remap the light from a 2D input plane into a linear array at the output.…”