  Wavelength-shifting (WLS) materials contain molecules that absorb light and
reemit at longer wavelengths. They can be used for light detection because they
provide a large effective area for low cost and they are able to efficiently
trap and guide light because of total internal reflection processes. We are
currently developing such a WLS detector, considering two main designs: A
single-shift design with one wavelength shift (tile) and a double-shift design
with two wavelength shifts (tile and fiber). As photodetectors we use small
Silicon photomultipliers (SiPMs) with a high photon detection efficiency (PDE)
and single-photon sensitivity. The double-shift layout goes at the expense of
detection efficiency. In this design however, light is channeled to the two
ends of a fiber, thus requiring a reduced photosensitive area compared to the
single-shift layout. We will present the results of our measurements and show
that light traps and SiPMs together represent a promising alternative to PMTs
in case of a non-focused light beam. For the special case of SWGO, the
application of light traps is also motivated by a possible improvement of the
gamma/hadron separation, using a one-chamber tank with an array of
wavelength-shifting light traps instead of a (two-chamber) tank with PMTs.
Besides SWGO, new WLS detectors could also constitute useful and cheap
technology for other experiments and use cases. The contribution summarizes our
motivation and efforts to build a light trap detection module and to
characterize its properties in terms of costs, temporal performance and
detection efficiency.
