In this paper, Volume Holographic Optical Elements (V-HOEs), such as holographic gratings and spherical lenses, are designed and fabricated by using a prototype of photopolymer. The recording process of V-HOEs and their appropriate characterization are described. Moreover, V-HOEs possible applications as solar concentrator are investigated and results are discussed. Finally, a system that allows passive solar tracking is proposed and preliminary results are reported.

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Volume Holographic Gratings is designed and fabricated to obtain a simple, lightweight and cheap light deflector. The entire process, starting from the chemical preparation of the photosensitive material, to the recording of Volume Holographic Gratings and their appropriate characterization, is reported. The recording material was a new photopolymer sensitive to light at 532nm.Results showed that the recorded Volume Holographic Grating presents a very high value of the diffraction efficiency, up to 94%.In addition, a flexible material is used to write Volume Holographic Gratings.

Sensor holograms utilize the diffraction principle of transmitting volume holographic grating (VHG) recorded within a photopolymer appositely functionalized to detect a specific stimulus or analyte.A change in the swelling or shrinking state or cross-linking density of the polymer can be caused by the hologram interaction with an analyte. This leads to a change in the recorded hologram sensor and thus, considering an incident monochromatic light and the VHG angular selectivity, to an angle shift of the diffracted maximum intensity.In this work, two new photopolymers based on a sol-gel matrix opportunely functionalized to be sensitive to transition metals or heavy metals were used as sensitive material to record VHGs. An interferometric set up with a laser source at 532nm was used to record VHGs and gratings of 1000 lines/mm were realized. When exposed to a solution of water and lead, an angle shift of about 3° of the first order diffraction of the grating was measured, demonstrating its capability to reveal the presence of heavy metal in water.