Modelling the application of integrated photonic spectrographs to astronomy

摘要

One of the well-known problems of producing instruments for Extremely Large Telescopes is that theirsize (and hence cost) scales rapidly with telescope aperture. To try to break this relation alternative newtechnologies have been proposed, such as the use of the Integrated Photonic Spectrograph (IPS). Due totheir diraction limited nature the IPS is claimed to defeat the harsh scaling law applying to conventionalinstruments. The problem with astronomical applications is that unlike conventional photonics, they are notusually fed by diraction limited sources. This means in order to retain throughput and spatial informationthe IPS will require multiple Arrayed Waveguide Gratings (AWGs) and a photonic lantern. We investigatethe implications of these extra components on the size of the instrument. We also investigate the potentialsize advantage of using an IPS as opposed to conventional monolithic optics. To do this, we have constructedtoy models of IPS and conventional image sliced spectrographs to calculate the relative instrument sizes andtheir requirements in terms of numbers of detector pixels. Using these models we can quantify the relativesize/cost advantage for dierent types of instrument, by varying dierent parameters e.g. multiplex gain andspectral resolution. This is accompanied by an assessment of the uncertainties in these predictions, whichmay prove crucial for the planning of future instrumentation for highly-multiplexed spectroscopy.© (2012) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.