Photonic reformatting can be defined as an instrumental technique that utilizes photonic components to improve performance through a spatial rearrangement – or reformatting – of the distribution of starlight collected by an astronomical telescope, either in the pupil or in the image plane.
In its simplest form, a reformatter is a network of waveguides or fibers used to remap the spatial arrangement of input ports into an equivalent number of output ports. Examples are fiber networks used in multiple-object spectroscopy or integral field spectroscopy to reformat the fibers sampling the focal plane of the telescope into a pseudo-slit feeding the spectrograph. Photonic lanterns are more advanced forms of reformatters, which are tapered multi-waveguide/fiber devices, that transform an N-modes multi-mode waveguide/fiber into N output single-mode waveguides/fibers with minimal light losses.
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Schematic design of the photonic dicer. A multi-mode input fiber converts to several single mode fibers as photonic lantern and then spatially reformates the fibers to a 1-dimensional pseudo-slit. |
A two-telescope prototype integrated optics beam combiner inscribed into Gallium Lanthanum Sulfide (GLS) by Ultrafast laser inscription. The coupler relies on evanescent coupling and creates two pi-phase shifted interferometric output signals. The coupler comprises a set of 20 couplers, slightly visible as fine lines. The enlarged superposed blue sketch depicts the layout of the inscribed evanescent couplers. |
Applications of photonic reformatters can be broadly classified according to the coherent or incoherent level of optical field detection required at the output of the device. In this context, incoherent reformatting implies that only the light intensity of the collected signal is measured, whereas coherent reformatting implies that both the amplitude and phase are the measurable quantities.
Our research focusses on the development of these devices and the technologies surrounding them, for both regimes.
