1. Chemistry Department and Center for Nanoscience (CeNS), University of Munich, Butenandtstrasse 11, 81377 Munich, Germany
2. Organic and Macromolecular Chemistry, University of Jena, Humboldtstrasse 10, 07743 Jena, Germany
3. Stratingh Institute and Materials Science Center, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
4. Present address: Physical Chemistry Department, University of Cologne, Luxemburgerstrasse 116, 50939 Cologne, Germany.

Correspondence to: Klaus Meerholz^1,2 Correspondence and requests for materials should be addressed to K.M. (e-mail: Email: klaus.meerholz@uni-koeln.de).

Abstract

Among the various applications for reversible holographic storage media^{1, 2}, a particularly interesting one is time-gated holographic imaging (TGHI)^{3, 4, 5}. This technique could provide a noninvasive medical diagnosis tool, related to optical coherence tomography^{6, 7}. In this technique, biological samples are illuminated within their transparency window with near-infrared light, and information about subsurface features is obtained by a detection method that distinguishes between reflected photons originating from a certain depth and those scattered from various depths. Such an application requires reversible holographic storage media with very high sensitivity in the near-infrared. Photorefractive materials, in particular certain amorphous organic systems, are in principle promising candidate media, but their sensitivity has so far been too low, mainly owing to their long response times in the near-infrared. Here we introduce an organic photorefractive material—a composite based on the poly(arylene vinylene) copolymer TPD-PPV⁸—that exhibits favourable near-infrared characteristics. We show that pre-illumination of this material at a shorter wavelength before holographic recording improves the response time by a factor of 40. This process was found to be reversible. We demonstrate multiple holographic recording with this technique at video rate under practical conditions.