**Author details**

isopropanol and then was inserted in a chamber connected with a turbo pump variation. The chamber was also connected to a residual gas analyzer (RGA) consisting of a mass spectrometer. Two tests were performed at different pressures. The first one had a base pressure of 2 × 10−8 mbar after 6 days of pumping at room temperature. The results, acquired with a mass spectrometer, reported the presence only of main gas species known that are the contaminants

The second test had a base pressure 7 × 10−8 mbar after 3 days of pumping at room temperature. Results acquired with the mass spectrometer highlighted the presence of unknown main gas species, with atomic mass units (AMU) up to 100. However, the intensity of the unknown gas is very small and comparable with the contaminants of the same chamber of

Finally, the behaviour of the focal length for different incident wavelengths reported in **Figure 7** can be useful in aerospace application. Indeed, considering that in the infrared region the focal length is very far by the focal length in the visible region (where the PV cell will be placed), the thermal overheating of the photovoltaic cell due to the absorption of infrared radiation is avoided, reducing cooling requirements. All these results confirmed the possibility to use this

In this chapter, we experimentally demonstrated that a new photosensitive material can be

Two configurations of holographic lenses were investigated: spherical in-line lenses and cylindrical off-axis lenses. The chromatic aberration of the spherical lens was characterized, proving a decrease of the focal length as the incident wavelength increases. Furthermore, the beam profile was characterized for both the proposed holographic lens in their focus. Performances of holographic lenses were compared to those of conventional optics. Some lower performances of holographic lens highlighted with respect to conventional optics, such as higher axial chromatic aberration and lower ability to concentrate light in the focus, are rewarded with a lower size, lower weight and lower cost. However, chromatic aberration can be useful to reduce cooling requirements. Indeed, considering that the PV cell will be placed at the focal length in the visible region, the infrared region will be focalized very far, avoiding the thermal overheating of the photovoltaic cell due to the absorption of infra-

Finally, a preliminary study of the influence of the thermal stress and the behaviour of the photopolymer in the absence of pressure (space conditions) revealed that the proposed photosensitive material could be suitable in space environment. Therefore, we are quite optimistic that our experimental results can open the way to the fabrication of efficient, cheap

and lightweight holographic solar compatible with space applications.

based on the chamber.

44 Holographic Materials and Optical Systems

photopolymer in spatial applications.

used to realize holographic solar concentrators.

the test.

**7. Conclusions**

red radiation.

Maria Antonietta Ferrara1\*, Gaetano Bianco1 , Fabio Borbone2 , Roberto Centore2 , Valerio Striano3 and Giuseppe Coppola1

\*Address all correspondence to: antonella.ferrara@na.imm.cnr.it

