Energy transfer efficiency from Cr3+ to Nd3+ in Cr, Nd YAG ceramics laser media in a solar-pumped laser in operation outdoors

Abstract

Energy transfer efficiencies from Cr 3+ to Nd 3+ : η Cr→Nd in Cr (0, 0.4, 0.7, and 1.0 at %), Nd (1.0 at%):YAG ceramic laser mediums were assessed for the first time in solar-pumped laser (SPL) in operation under the natural sunlight. In addition to this stimulated emission (StE) conditions, assessment of η Cr→Nd in solar pumped spontaneous emission (SpE) conditions was performed using the same SPL system but without the optical cavity eliminating the output coupler. In SpE at the incident solar power at the solar concentrator: I OAP of 1.12 W, η Cr→Nd were measured to be 0.803 γ for 0.4 at%, 0.726 γ for 0.7 at%, 0.766 γ for 1 at %, where γ ≾ 1. When I OAP was increased to 3.07 W, η Cr→Nd in SpE decreased to 0.675 γ , 0.623 γ , 0.625 γ , respectively. In StE, η Cr→Nd further decreased to 0.448 γ , 0.213 γ , 0.166 γ . These values are lower than those previously reported values measured by the laboratory experiments such as luminescent decay analyses. Both in SpE and StE, the highest values of η Cr→Nd were given at the Cr content of 0.4 at% at which the output laser power also took the maximum value. The decrease in η Cr→Nd in the increased I OAP in SpE can be attributed to the fact that formation of excited Nd 3+ ions by the energy transfer from Cr 3+ ions became difficult because Nd 3+ ions had been already excited directly by the sunlight. • Cr to Nd energy transfer efficiencies in solar-pumped YAG laser were measured. • The measurement was done for the laser in operation outdoors for the first time. • Cr, Nd:YAG of 4 different Cr contents: 0.0, 0.4, 0.7, 1.0% were examined. • The measurements in solar pumped spontaneous emissions were also performed. • The obtained values were much lower than those previously reported values.