A Multi-Core Fibre Photonic Lantern-Based Spectrograph for Raman Spectroscopy

Betters, Christopher H.; Bland-Hawthorn, Joss; Sukkarieh, Salah; Gris-Sánchez, Itandehui; Leon-Saval, Sergio G.

doi:10.1109/lpt.2020.2976599

Cited by 7 publications

(3 citation statements)

References 14 publications

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“…Optionally, a low-dispersion prism can be inserted to allow low-resolution spectral information to be obtained, potentially useful for more advanced wavefront control and telemetry algorithms, as well as science. The output of the MCF can be spectrally dispersed with no additional reformatting or slit, using the so-called photonic ‘TIGER’ configuration 35 – 37 . The output of this camera is then fed to the real-time computer of the adaptive optics system, where the incident wavefront error is inferred (using a simple neural network) and the appropriate correction applied to the DM.…”

Section: Resultsmentioning

confidence: 99%

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An all-photonic focal-plane wavefront sensor

et al. 2020

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Adaptive optics (AO) is critical in astronomy, optical communications and remote sensing to deal with the rapid blurring caused by the Earth’s turbulent atmosphere. But current AO systems are limited by their wavefront sensors, which need to be in an optical plane non-common to the science image and are insensitive to certain wavefront-error modes. Here we present a wavefront sensor based on a photonic lantern fibre-mode-converter and deep learning, which can be placed at the same focal plane as the science image, and is optimal for single-mode fibre injection. By measuring the intensities of an array of single-mode outputs, both phase and amplitude information on the incident wavefront can be reconstructed. We demonstrate the concept with simulations and an experimental realisation wherein Zernike wavefront errors are recovered from focal-plane measurements to a precision of 5.1 × 10−3 π radians root-mean-squared-error.

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Section: Resultsmentioning

confidence: 99%

“… 44 – 46 ). Furthermore this technique has been successfully employed in other light-starved applications with high-stability requirements, such as Raman spectroscopy 37 .…”

Section: Resultsmentioning

confidence: 99%

An all-photonic focal-plane wavefront sensor

et al. 2020

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show abstract

“…Optionally, a low-dispersion prism can be inserted to allow low-resolution spectral information to be obtained, potentially useful for more advanced wavefront control and telemetry algorithms, as well as science. The output of the MCF can be spectrally dispersed with no additional reformatting or slit, using the so-called 'TIGER' configuration (Leon-Saval et al 2012;Betters et al 2014Betters et al , 2020. The output of this camera is then fed to the real-time computer of the adaptive optics system, where the incident wavefront error is inferred (using a simple neural network) and the appropriate correction applied to the deformable mirror.…”

Section: On Sky Applicationmentioning

confidence: 99%

An all-photonic focal-plane wavefront sensor

Norris,

Wei,

Betters

et al. 2020

Preprint

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Adaptive optics (AO) is critical in modern astronomy, as well as in optical communications and remote sensing, to deal with the rapid blurring caused by the Earth's turbulent atmosphere. But even the best AO systems are limited by their wavefront sensors, which need to be in an optical plane non-common to the science image, unavoidably leading to errors that limit the reach of current astronomy. They are also insensitive to certain wavefront-error modes, and are poorly suited to injecting light into single-mode optical fibres, important for applications such as high-resolution spectroscopy of extra-solar planets. Here we present a new type of wavefront sensor based on a photonic lantern fibre-mode-converter and deep learning. This new wavefront sensor can be placed at the same focal plane as the science image, and is also optimal for single-mode fibre injection. By only measuring the intensities of an array of single-mode outputs, both phase and amplitude information on the incident wavefront can be reconstructed. We demonstrate the concept with both simulations and an experimental realisation of this novel wavefront sensor, wherein Zernike wavefront errors are recovered from focal-plane measurements to a precision of 2.6 × 10 −5 radians mean-squared-error.

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Modal noise mitigation for high-precision spectroscopy using a photonic reformatter

Pike

Benoît

MacLachlan

et al. 2020

Monthly Notices of the Royal Astronomical Society

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Abstract Recently, we demonstrated how an astrophotonic light reformatting device, based on a multicore fibre photonic lantern and a three-dimensional waveguide component, can be used to efficiently reformat the point spread function of a telescope to a diffraction-limited pseudo-slit. Here, we demonstrate how such a device can also efficiently mitigate modal noise – a potential source of instability in high resolution multi-mode fibre-fed spectrographs. To investigate the modal noise performance of the photonic reformatter, we have used it to feed light into a bench-top near-infrared spectrograph (R ≈ 7,000, λ ≈ 1550 nm). One approach to quantifying the modal noise involved the use of broadband excitation light and a statistical analysis of how the overall measured spectrum was affected by variations in the input coupling conditions. This approach indicated that the photonic reformatter could reduce modal noise by a factor of six when compared to a multi-mode fibre with a similar number of guided modes. Another approach to quantifying the modal noise involved the use of multiple spectrally narrow lines, and an analysis of how the measured barycentres of these lines were affected by variations in the input coupling. Using this approach, the photonic reformatter was observed to suppress modal noise to the level necessary to obtain spectra with stability close to that observed when using a single mode fibre feed. These results demonstrate the potential of using photonic reformatters to enable efficient multi-mode spectrographs that operate at the diffraction-limit and are free of modal noise, with potential applications including radial velocity measurements of M-dwarfs.

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A Multi-Core Fibre Photonic Lantern-Based Spectrograph for Raman Spectroscopy

Cited by 7 publications

References 14 publications

An all-photonic focal-plane wavefront sensor

An all-photonic focal-plane wavefront sensor

An all-photonic focal-plane wavefront sensor

Modal noise mitigation for high-precision spectroscopy using a photonic reformatter

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