Above and beyond the laser-induced anti-Stokes broadband white light emission in rare-earth-manganese perovskites

Abstract

We carried out a joint experimental and theoretical investigation of the laser-induced anti-Stokes white emission (LIWE) observed in NdMnO3 nanocrystals. We evaluate numerically the mechanisms of the multiphoton ionisation, avalanche process, and the blackbody radiation, to provide a phenomenological model to interpret, and even predict, the LIWE phenomena. Through the theoretical modelling, photophysical and photoconductivity characterisations, we determine the ionisation rates (0.63—1.9 s−1), ionisation fraction of the Nd3+ + hv→ Nd4+ + e−, Mn3+ + hv→ Mn4+ + e−, and Mn2+ + hv→ Mn3+ + e−, from ionization energies ~0 until 52.58 eV, excitation at 808 and 975 nm, and different pressure conditions (10-6—103 mbar). We propose a mathematical description of the LIWE generation as a dynamical process that explains the supralinear dependence of the integrated intensity of the emission with the laser power density of excitation, pressure, as well, the photophysical kinetics in order of ~ms to s, and the photocurrent (~nA) observed under excitation at high values of laser power density (~kW·cm⁻²).