  Single-photon imaging spectrometers of high quantum efficiency in the
infrared to ultraviolet wavelength range, with good timing resolution and with
a vanishing dark count rate are on top of the wish list in earth-bound
astronomy, material and medical sciences, or quantum information technologies.
We review and present improved operation of a cryogenic detector system
potentially offering all these qualities. It is based on a superconducting
absorber strip read out with superconducting tunnel junctions. The detector
performance is discussed in terms of responsivity, noise properties, energy and
position resolution. Dynamic processes involved in the signal creation and
detection are investigated for a basic understanding of the physics, and for
possible application-specific modifications of device characteristics.
