Optical spectroscopy of Er3+ ions in poly(acrylic acid)

Er3+-doped poly(acrylic acid) was synthesized by polymerization in aqueous solution of the monomer partially neutralised with erbium hydroxide. 13C NMR spectra confirmed the monomer modification. Absorption intensity data of the Er3+ lanthanide ion in poly(acrylic acid) (PAA) are analysed using the Judd and Ofelt (JO) phenomenological treatment in order to understand its optical properties for laser application. The intrinsic emission of PAA gives rise radiative energy transfer between the host and Er3+ ions. The measured and calculated oscillator strengths for transitions from the ground state to excited multiplets compare favourably within the typical uncertainties associated with the JO formalism. Then, the spontaneous radiative transition probabilities from the former 11 excited states to diverse ending states were computed to obtain the luminescence branching ratios as well as the radiative lifetimes.