Astrophotonics: molding the flow of light in astronomical instruments [Invited]

Abstract

Since its emergence two decades ago, astrophotonics has found broad application in scientific instruments at many institutions worldwide. The case for astrophotonics becomes more compelling as telescopes push for AO-assisted, diffraction-limited performance, a mode of observing that is central to the next-generation of extremely large telescopes (ELTs). Even AO systems are beginning to incorporate advanced photonic principles as the community pushes for higher performance and more complex guide-star configurations. Photonic instruments like Gravity on the Very Large Telescope achieve milliarcsec resolution at 2000 nm which would be very difficult to achieve with conventional optics. While space photonics is not reviewed here, we foresee that remote sensing platforms will become a major beneficiary of astrophotonic components in the years ahead. The field has 'given back' with the development of new technologies (e.g. photonic lantern, large area multi-core fibres) already finding widespread use in other fields; Google Scholar lists more than 400 research papers making reference to this technology. This short review covers representative key developments since the 2009 Focus issue on Astrophotonics.

Astrophotonics: astronomy and modern optics

“…As opposed to other overviews of the field (e.g., Bland-Hawthorn and Kern 2009;Bland-Hawthorn and Leon-Saval 2017), this paper incorporates different branches of astrophotonics that are usually addressed separately, as for instance spectroscopy, interferometry/high-contrast imaging, and calibration of instrumentation. Additionally, we give an introduction to the physics underlying the function of photonic technologies, through an introductory section on optical modes and in the description of the instruments.…”

Development of an integrated near-IR astrophotonic spectrograph

“…The photonic platform of guided light in fibers and waveguides has opened the doors to next-generation instrumentation for both ground-and space-based telescopes in optical and near/mid-IR bands, particularly for the upcoming extremely large telescopes (ELTs). [1][2][3][4][5] The key idea here is to leverage the ability of guiding the light in waveguides (using total internal reflection) to collapse the conventional optical setups into 2D "optical circuits". These optical circuits make use of single-mode waveguides or fibers, which are equivalent to diffractionlimited operation.…”

Towards a multi-input astrophotonic AWG spectrograph

“…The photonic approach is geared to solve to some of the major challenges in observational astronomy. [1][2][3] As larger and larger ground-and space-based telescopes are being proposed and built, the volume, mass, and cost of the associated conventional optical instruments scale roughly as the cube of the diameter of the telescope. 1 Maintaining the mechanical and thermal stability over such large volumes and across different optical elements of an instrument is challenging.…”

“…The astrophotonic devices are miniaturized and hence, reduce the size and mass of astronomical instrumentation by several orders of magnitude while keeping the costs substantially lower. 2,4,5 Further author information: (Send correspondence to P. Gatkine) E-mail: pgatkine@astro.umd.edu…”

“…The power of guiding the light and manipulating it on a micro/nano scale in photonics has imparted immense flexibility to a wide variety of astronomical instruments. 2,3 These instruments include spectrographs, [6][7][8][9] spatial/spectral filters 10 , Bragg gratings, 11,12 precision wavelength calibrators, 13 interferometers, 14 nullers, 15 beam combiners etc. Along with these instruments, the technology of coupling the inherently multi-mode astronomical light into these primarily single-mode photonic devices has taken a quantum leap.…”