Persistent spectral hole burning in metal-free tetraphenylporphyrindoped polymethylmethacrylate core fiber

We report persistent spectral hole burning (PSHB) in metal-free tetraphenylporphyrin (TPP)-doped polymethylmethacrylate (PMMA) core fiber via the proton tautomerization of TPP. The TPP concentration was 1.25 × 10^-4 M. The fiber structure of the PSHB material which we have developed made it possible to increase the number of guest molecules in the material and to confine the excitation laser light over the whole length of the material, both of which are important features for the achievement of optimum storage density in the PSHB storage scheme. We have carried out PSHB experiments on three fiber PSHB materials whose diameter and length range between 125-600 μm and between 10-55 mm, respectively. The largest hole formation yield of 4.3 × 10^-4 and a frequency multiplexity of about 1500 were obtained in a fiber PSHB sample (diameter: 400 μm, length: 52 mm) cladded with a UV curable adhesive.