  Natural photosynthetic photonic nanostructures can show sophisticated light
matter-interactions including enhanced light absorption by slow light even for
highly pigmented systems. Beyond fundamental biology aspects these natural
nanostructures are very attractive as blueprints for advanced photonic devices.
But the soft-matter biomimetic implementations of such nanostructures is
challenging due to the low refractive index contrast of most organic photonic
structures. Excitonic organic material with near zero index (NZI) optical
properties allow overcoming these bottlenecks. Here we demonstrate that the
combination of NZI thin films into photonic multilayers like the ones found in
nature enables broadband tuneable strong reflectance as well as slow light
absorption enhancement and tailored photoluminescence properties in the full
VIS spectrum. Moreover, it is shown that this complex optical response is
tuneable, paving the way towards the development of active devices based on all
polymer and near zero index materials photonic structures.
