  A new concept for the simultaneous detection of primary and secondary
scintillation in time projection chambers is proposed. Its core element is a
type of very-thick GEM structure supplied with transparent electrodes and
machined from a polyethylene naphthalate plate, a natural wavelength-shifter.
Such a device has good prospects for scalability and, by virtue of its genuine
optical properties, it can improve on the light collection efficiency, energy
threshold and resolution of conventional micropattern gas detectors. This,
together with the intrinsic radiopurity of its constituting elements, offers
advantages for noble gas and liquid based time projection chambers, used for
dark matter searches and neutrino experiments. Production, optical and
electrical characterization, and first measurements performed with the new
device are reported.
