Mecher Erwin, Gallego-Gómez Francisco, Tillmann Hartwig, Hörhold Hans-Heinrich, Hummelen Jan C, Meerholz Klaus
Chemistry Department and Center for Nanoscience (CeNS), University of Munich, Butenandtstrasse 11, 81377 Munich, Germany.
Nature. 2002 Aug 29;418(6901):959-64. doi: 10.1038/nature00975.
Among the various applications for reversible holographic storage media, a particularly interesting one is time-gated holographic imaging (TGHI). This technique could provide a noninvasive medical diagnosis tool, related to optical coherence tomography. 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-PPV -- 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.
在可逆全息存储介质的各种应用中，一种特别有趣的应用是时间门控全息成像（TGHI）。这项技术可以提供一种与光学相干断层扫描相关的非侵入性医学诊断工具。在这项技术中，生物样品在其透明窗口内用近红外光照射，并且通过一种检测方法获得有关亚表面特征的信息，该方法能够区分来自特定深度的反射光子和从不同深度散射的光子。这样的应用需要在近红外具有非常高灵敏度的可逆全息存储介质。光折变材料，特别是某些非晶有机体系，原则上是有前景的候选介质，但到目前为止它们的灵敏度太低，主要是由于它们在近红外的响应时间很长。在这里，我们介绍一种有机光折变材料——一种基于聚（亚芳基乙烯撑）共聚物TPD-PPV的复合材料——它具有良好的近红外特性。我们表明，在全息记录之前，用较短波长对该材料进行预照明可将响应时间提高40倍。发现这个过程是可逆的。我们在实际条件下以视频速率用该技术演示了多重全息记录。
