MacLachlan, D. G. and Harris, R. J. and Gris-Sánchez, I. and Morris, T. J. and Choudhury, D. and Gendron, E. and Basden, A. G. and Spaleniak, I. and Arriola, A. and Birks, T. A. and Allington-Smith, J. R. and Thomson, R. R. (2017) 'Efficient photonic reformatting of celestial light for diffraction-limited spectroscopy.', Monthly notices of the Royal Astronomical Society., 464 (4). pp. 4950-4957.
The spectral resolution of a dispersive astronomical spectrograph is limited by the trade-off between throughput and the width of the entrance slit. Photonic guided wave transitions have been proposed as a route to bypass this trade-off, by enabling the efficient reformatting of incoherent seeing-limited light collected by the telescope into a linear array of single modes: a pseudo-slit which is highly multimode in one axis but diffraction-limited in the dispersion axis of the spectrograph. It is anticipated that the size of a single-object spectrograph fed with light in this manner would be essentially independent of the telescope aperture size. A further anticipated benefit is that such spectrographs would be free of ‘modal noise’, a phenomenon that occurs in high-resolution multimode fibre-fed spectrographs due to the coherent nature of the telescope point spread function (PSF). We seek to address these aspects by integrating a multicore fibre photonic lantern with an ultrafast laser inscribed three-dimensional waveguide interconnect to spatially reformat the modes within the PSF into a diffraction-limited pseudo-slit. Using the CANARY adaptive optics (AO) demonstrator on the William Herschel Telescope, and 1530 ± 80 nm stellar light, the device exhibits a transmission of 47–53 per cent depending upon the mode of AO correction applied. We also show the advantage of using AO to couple light into such a device by sampling only the core of the CANARY PSF. This result underscores the possibility that a fully optimized guided-wave device can be used with AO to provide efficient spectroscopy at high spectral resolution.
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|Publisher Web site:||https://doi.org/10.1093/mnras/stw2558|
|Publisher statement:||This article has been accepted for publication in Monthly notices of the Royal Astronomical Society ©: 2016 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.|
|Date accepted:||06 October 2016|
|Date deposited:||26 July 2017|
|Date of first online publication:||06 October 2016|
|Date first made open access:||26 July 2017|
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