Described herein is a photonic spectrograph (1) for accurately measuring and displaying spectra from radiation signals received from a telescope (3). One embodiment provides a photonic imaging device, in the form of a spectrograph (1), including a plurality of input ports in the form of multi-mode optical fibres (5). The optical fibres (5) are adapted for receiving an arbitrary incident electromagnetic radiation field (7) containing one or more spatial propagation modes such as an optical signal from a telescope (3). The spectrograph (1) includes a coupling device in the form of a photonic lantern (9) attached to the multi- mode optical fibre (5) for efficiently coupling the incident electromagnetic radiation field into an arbitrary plurality (hereinafter denoted N) of single-mode optical fibres (11) for diffraction-limited single-mode propagation. The plurality, N, of single-mode fibres (11) is greater than or equal to the number of spatial modes supported in the incident radiation field such that efficient coupling is achieved. The single-mode optical signals output from the single-mode fibres (11) are received by an optical manipulation device in the form of an array waveguide grating (13) which selectively combines the single-mode signals into a continuous optical spectrum. An optical detector (15) is provided for detecting the continuous optical spectrum output from the array waveguide grating (13).
展开▼
