Integrated photonic building blocks for next-generation astronomical instrumentation I: the multimode waveguide

Abstract

We report on the fabrication and characterization of composite multimode waveguide structures that consist of a stack of single-mode waveguides fabricated by ultrafast laser inscription. We explore 2 types of composite structures; those that consist of overlapping single-mode waveguides which offer the maximum effective index contrast and non overlapped structures which support multiple modes via strong evanescent coupling. We demonstrate that both types of waveguides have negligible propagation losses (to within experimental uncertainty) for light injected with focal ratios >8, which corresponds to the cutoff of the waveguides. We also show that right below cutoff, there is a narrow region where the injected focal ratio is preserved (to within experimental uncertainty) at the output. Finally, we outline the major application of these highly efficient waveguides; in a device that is used to reformat the light in the focal plane of a telescope to a slit, in order to feed a diffraction-limited spectrograph.

15 pages, 11 figures, accepted to Optics Express

References in corpus (3)

• An integrated optics beam combiner for the second generation VLTI instruments
• Astrophotonics: a new era for astronomical instruments
• Developing arrayed waveguide grating spectrographs for multi-object astronomical spectroscopy

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• Multiband processing of multimode light: combining 3D photonic lanterns with waveguide Bragg gratings
• Engineering integrated photonics for heralded quantum gates
• Design of Optically Path Length Matched, Three-Dimensional Photonic Circuits Comprising Uniquely Routed Waveguides
• Modal noise in an integrated photonic lantern fed diffraction-limited spectrograph
• Multicore fibre technology - the road to multimode photonics
• Astrophotonics -- current capabilities and the road ahead