The strong change of transparency in the visible and the modulation of the refractive index in the NIR which accompanies the photoreaction in P-type photochromic materials can be exploited to obtain amplitude and phase holographic optical elements, respectively. In this background, we developed a series of photochromic polyurethanes based onto dithienylethene and dithiazolethene derivatives. The different polymers in thin films show an optical density (OD) modulation in the visible of the order of 1-3. The change in the refractive index in the NIR have been determined by ellipsometry showing changes larger than 0.01, depending on the absorption properties of the different polymers. Examples of devices based on these photochromic polyurethanes will be described.
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