Re-absorption and nonradiative energy transfer in vibronic laser gain media

Abstract

Fe:ZnSe and other transition metals have broad upper and lower energy manifolds that give rise to broad absorption and fluorescence bands in the mid-infrared spectral region. Energy transfer between Fe 2þ ions via re-absorption of fluorescence (due to the spectral overlap of these bands) and phonon-assisted energy transfer (due to the lattice dynamics of ZnSe) becomes more probable with increasing Fe 2þ concentration. Here, we treat these processes as additional terms in the rate equations that govern the spontaneous decay of the Fe 2þ ion. This treatment gives insight into anomalous behavior seen in the thermal lifetime of the Fe:ZnSe system. We also apply the model to other transition metal-doped II-VI materials. © The Authors.Published by SPIE under a Creative Commons Attribution 4.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

Crystal host engineering for transition metal lasers

“…10 that Fe:ZnS is significantly quenched, even at liquid nitrogen temperatures (∼77 K), so we expect that CW lasing in Fe:ZnS would be characterized by higher pump thresholds and lower slope efficiencies than lasing in Fe:ZnSe under the same conditions. Interestingly, the unquenched lifetime of the Fe 2þ ion is seen to increase from <6 μs in Fe:ZnS 31 to 48 μs in Fe:ZnSe 24 and to >80 μs in Fe:CdMnTe, 32 but these differences are not attributable the effect of NRQ alone. From Fig.…”

“…In previous work, 24 we developed an analytical expression for the upper-state lifetime of the Fe 2þ ion as a function of temperature. Ignoring energy transfer processes such as fluorescent reabsorption and nonradiative energy transfer, this expression becomes E Q -T A R G E T ; t e m p : i n t r a l i n k -; e 0 0 4 ; 1 1 6 ; 4 2 8 1…”

“…In previous work, 24 we developed an analytical expression for the upper-state lifetime of the Fe2+ ion as a function of temperature. Ignoring energy transfer processes such as fluorescent reabsorption and nonradiative energy transfer, this expression becomes 1τtotal=1τ0+AM22πp3ex(Sep3ex)p−2(1+1exp2.5ex(normalΔfalse/pkbT2.5ex)−1)p,where τ0≈48 μs is the radiative lifetime of the ion, kb is Boltzmann’s constant, e is Euler’s constant, A is a coupling constant for the nonradiative term, M is an effective mass in atomic mass units (amu), S is the Huang–Rhys parameter, T is temperature, and Δ/…”