Characterization of phenanthrenequinone-doped poly(methyl methacrylate) for holographic memory

Abstract

The holographic recording characteristics of phenanthrenequinone-(PQ-) doped poly(methyl methacrylate) are investigated. The exposure sensitivity is characterized for single-hologram recording, and the M͞# is measured for samples as thick as 3 mm. Optically induced birefringence is observed in this material. © 1998 Optical Society of America OCIS codes: 090.2900, 090.4220, 210.2860.The characterization of phenanthrenequinone-(PQ-) doped poly(methyl methacrylate) 1,2 (PMMA) as a recording material for holographic memories is described in this Letter. This material consists of the polymer host matrix with added PQ molecules as photosensitive dopant. High-optical-quality samples of this material were made with variable thicknesses of up to 5 mm and in a variety of shapes. This material does not shrink after exposure and is lightweight, inexpensive, and durable, making it an attractive candidate for disk-based holographic memory systems.Sample preparation consists of dissolving PQ molecules in liquid methyl methacrylate together with a polymerization initiator. This solution is then poured into molds and allowed to polymerize in a pressure chamber at an elevated temperature. The molding process allows samples to be fabricated in a variety of geometries. Disks ranging from 2.5 to 10 cm in diameter with 1 -5-mm thickness were made. For a 1-mm-thick sample doped with a concentration of 0.7% of PQ molecules before exposure, the absorption reaches a maximum of 98.8% at 445 nm and is 58% for the 488-nm line of an argon laser, which was used in all experiments described in this Letter.A hologram was recorded by a pair of 488-nm beams, each incident upon the material at an outside angle of 21.5 ± . We monitored the growth of the hologram during recording by probing the sample with a Bragg-matched He-Ne laser beam. Figure 1 shows the diffraction eff iciency (diffracted power divided by the incident power) during recording in 1-mm-thick material. The diffraction eff iciency reached a maximum of 4.3% for an exposure energy of 2.5 J͞cm 2 . If exposure was allowed to continue, the diffraction eff iciency began to drop. After 20 J͞cm 2 of exposure with a single beam the hologram decayed to approximately 0.1%. At this point the material was completely exposed, and no more holograms could be recorded.We recorded permanent holograms that do not decay with subsequent illumination by stopping the exposure before saturation was reached and then baking the sample. Figure 2 shows the strength of a hologram as a function of baking time at a temperature of 55 ± C. The diffraction efficiency reached a maximum after 12 days and remained steady with continued baking. Figure 3 shows the selectivity curves for a weak and a strong hologram (2% and 35% diffraction eff iciency, respectively). The 2% hologram has a sinc-squared selectivity curve as expected for a 1-mm-thick hologram. The stronger hologram, on the other hand, has a selectivity curve that is distorted and shifted. For a holographic memory the diffraction eff iciency is relatively sma...

A photopolymerizable glass with diffraction efficiency near 100% for holographic storage

“…To our knowledge, these values of ⌬n, S, and S* are the highest reported to date in a photopolymerizable material of similar thickness. 3,[20][21][22] In the angular selectivity experiment ϭ10 mrad was measured, yielding an effective grating thickness of 941 m. This shows that the grating was recorded practically in entire depth of the monolith. We also recorded gratings in films of 260 m thickness with photoinitiator content of 0.8 wt %.…”

All optical three dimensional spatio-temporal correlator for automatic event recognition using a multiphoton atomic system

“…In order to realize this approach it is necessary to make holographic video discs with a thickness of 1 cm. One material suitable for realizing such a disc is made of PMMA (polymethyl methalycrate), doped with the dye called phenanthren-quinone 36,37,38,39,40,41,42,43,44 .…”

Light-Sensitive Media-Composites for Recording Volume Holograms Based on Porous Glass and Polymer

“…The hologram recorded, the particles, unbound to the framework (free), diffuse with the passage of time, spreading uniformly across the sample bulk and causing the supplementary grating to degrade and the photoproduct grating to "develop" (be enhanced), since particles are not subject to diffusion. This principle was successfully implemented in practice by using polymeric medium on the base of polymethylmethacrylate with PQ (Cherkasov et al, 1991;Veniaminov et al, 1991Veniaminov et al, , 1996Steckman et al, 1998;Lin et al, 2000Lin et al, , 2006Luo at al., 2008;Liu at al., 2010;. Attempts to implement the principle using other compositions was less successful.…”

“…Dynamic range of volume RM can be estimated and used in superimposed hologram recording. The potential was demonstrated by superimposed recording of more than 1000 low-efficiency holograms on the same sample section with the view of using it as archive memory (Steckman et al, 1998). Specifics of superimposed recording of high-efficiency holograms is linked with deterioration of holograms, constructed in a medium with nonuniform distribution of light-sensitive particles due to recording of previous holograms.…”