KIDSpec: An MKID-Based Medium-Resolution, Integral Field Spectrograph

KIDSpec, the Kinetic Inductance Detector Spectrograph, is a concept for a highly sensitive, medium-spectral-resolution optical through near-IR spectrograph. It uses the intrinsic-energy-resolving capability of an array of optical/IR-sensitive MKIDs to distinguish multiple orders from a low-resolution grating. By acting as an ‘order resolver,’ the MKID array replaces the cross-disperser in an echelle spectrograph. This greatly simplifies the optical layout of the spectrograph and enables longer slits than are possible with cross-dispersed instruments (to improve sky subtraction). KIDSpec would have similar capabilities to ESO’s highly successful X-shooter instrument. It would provide an R = 4000–10,000 spectrum covering the optical and near-IR spectral range (0.4–1.5 µm). As well as a ‘long-slit’ mode, the IFU would provide a small ($$\sim 50\hbox { spaxel}$$∼50spaxel) field of view for spatially resolved sources. In addition, the photon-counting operation of MKIDs and their photon-energy-resolving ability enable a read-noise-free spectrum with perfect cosmic ray removal. The spectral resolution would be sufficient to remove the bright night-sky lines without the additional pixel noise, making the instrument more sensitive than an equivalent semiconductor-based instrument. KIDSpec would enhance many existing high-profile science cases, including transient (GRB, SNe, etc.) follow-up, redshift determination of faint objects and transit spectroscopy of exoplanets. In addition, it will enable unique science cases, such as dynamical mass estimates of the compact objects in ultra-compact binaries.