Properties of Epoxy Novolak Resin Layers Doped with Bismuth for Photoluminescence Near 1300 nm

In this article, we report on the optical properties of bismuth ions doped epoxy novolak resin (ENR). The polymer layers containing 1-20 at. of bismuth were fabricated by spin coating onto silicon or quartz substrates. The properties of the material were studied using several methods with special regards to its potential utilization in photonics devices. Absorption spectra were taken in the range from 350 to 800 nm. Optical band gap E_g was determined from the absorption coefficient values using Taucs procedure, i.e., from the relationship ahv 1/4 A(hv - E_g)² and the obtained values varied from 2.94 to 3.23 eV depending on the amount of bismuth ions involved in the samples. Photoluminescence spectra around 1300 nm were recorded by using excitation of semiconductor lasers operating at 808 nm (E_x 1/4. 500 mW). Optical properties of bismuth-doped ENR were evaluated on the bases of the concentration of the bismuth ions involved in the samples and showed, e.g., close relations between concentration of the dopants and intensity of the luminescence band at 1300 nm. IR spectra showed only negligible changes in the original substrate resin. Our results proved that the bismuth-doped ENR have a potential for utilization in photonic devices.