Transparent microslices IFUs: From 200,000 to 5 millions spectra at once

The present design of IFUs typically gives a few hundred to a few thousand spectra. The new concept of transparent microslice IFUs permits 2-3 orders of magnitude more spatial elements at a reasonable cost. This idea was first applied to the feasibility studies of the spectrographs MEIFUS for the VLT and MEIFUS for Extremely Large Telescopes (ELTs). However, the design can also be applied to existing spectrographs. A design with a field of 3′ × 3′ with 400,000 elements for the IMACS spectrograph on Magellan is described as an example of application. The microslice IFUs are made of four cylindrical microlens arrays.