Double-layer method for increasing the bandwidth of UV spectrally responsive holograms in dichromated gelatin

We present a method for increasing the bandwidth of reflection holograms in dichromated gelatin. The recording plate has two dichromated-gelatin layers of different hardness so that their shrinkage at the end of processing is different. We use this method for doubling the bandwidth of holographic mirrors that are designed for solar UV energy concentration. We also study the superposition of two double-layer holograms, which results in UV holographic mirrors with a bandwidth of 60 nm.