Edge-addressed holograms-a novel approach towards narrow bandwidth filters

The authors outline a novel approach towards achieving the properties of an extremely thick reflection hologram (≳500 microns) i.e. high angular and spectral selectivity, from a comparatively thin film of holographic material (≈100 microns). The method involves fabricating a conventional `thin´ transmission hologram and interrogating this via an exposed edge of the film using a focussed Gaussian laser beam. Such holograms offer the potential of extremely narrow spectral bandwidths and their use is suggested as filters in single mode fibre de-multiplexing systems