Abstract

Two-photon absorption based three-dimensional (3-D) memories have been investigated and demonstrated over the last years, providing potentials for high memory densities and parallel access for fast data rates. Figure 1 illustrates the basic principle by which information is stored and retrieved in these 3-D memories. Two photons with appropriate combined energy (for example, λ = 1064 and 532 nm) are introduced into the memory and are absorbed simultaneously by the memory material which consists of spirobenzopyran (SP) in a PMMA host matrix).¹ The simultaneous absorption of the two photons by the photochromic molecule results in a bond dissociation transforming it into a new form with different properties, including the absorption spectrum as shown in Fig. 1. These two different molecular forms are defined as the non-written and written forms of the memory. When properly excited, the new molecular form emits fluorescence which can be detected during the read-out process. The peak fluorescence occurs at 660 nm.

© 1995 Optical Society of America