High density optical data storage using a medium which has photonic crystal structures

三维光存储由于能够克服光波的衍射所决定的密度极限，已经被许多研究者开发出来。为了提高轴向的密度，我们研制了一种光敏薄膜和非光敏透明薄膜交替堆叠的多层记录介质。由于光敏薄膜比记录光束的焦深薄，记录比特的空间频率分布沿轴向扩展。为了获得更高的分辨率和对比度，我们开发了在记录介质中制造光子晶体结构，在记录以六角阵列的形式排列的情况下，结构介质中记录比特的形状由聚焦光束的平方强度和图案化介质的结构的乘积确定。它的频率分布是由平方光斑强度的频率分布与图案化介质的频率分布卷积得到的。结果，图案化介质中的每个单独比特包含较高的空间频率分量。我们成功地记录了特定平面内间隔为0.5μm，连续层之间间隔为2.0μm的比特。因此，获得了2.0Tbit/cm3的存储密度。

Three-dimensional optical memory has been developed by many researchers because it can overcome the density limit determined by the diffraction of light wave. In order to increase the density in the axial direction, we have developed a mltilayered recording medium in which photosensitive thin films and nonphotosensitive transparent films were stacked alternately. Since the photosensitive films were thinner than the depth of focus of the recording beam, the spatial frequency distribution of the recorded bit was extended in the axial direction. We have developed the fabrication of photonic crystal structures in the recording medium to achieve higher resolution and contrast.In the case of recording are arranged in the form of hexagonal arrays, the shape of a recorded bit in a structured medium is determined by the products of squared intensity of the focused beam and the structure of the patterned medium. Its frequency distribution is given by convolution of the frequency distribution of the squared spot intensity and that of the patterned medium. As a result, each individual bit in the patterned media contains higher spatial frequency components. We succeeded in recording bits with a 0.5μm interval in particular plane and 2.0μm interval between successive layers. Thus, storage density of 2.0Tbits/cm3 is achieved.