We demonstrate a new approach to classical fiber-fed spectroscopy. Our methodis to use a photonic lantern that converts an arbitrary (e.g. incoherent) inputbeam into N diffraction-limited outputs. For the highest throughput, the numberof outputs must be matched to the total number of unpolarized spatial modes oninput. This approach has many advantages: (i) after the lantern, the instrumentis constructed from 'commercial off the shelf' components; (ii) the instrumentis the minimum size and mass configuration at a fixed resolving power andspectral order (~shoebox sized in this case); (iii) the throughput is betterthan 60% (slit to detector, including detector QE of ~80%); (iv) the scatteredlight at the detector can be less than 0.1% (total power). Our firstimplementation operates over 1545-1555 nm (limited by the detector, a640$\times$512 array with 20$\mu$m pitch) with a spectral resolution of 0.055nm(R~30,000) using a 1$\times$7 (1 multi-mode input to 7 single-mode outputs)photonic lantern. This approach is a first step towards a fully integrated,multimode photonic microspectrograph.
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