Comparison of the electronic band structures of LiCaAlF₆and LiSrAlF₆ultraviolet laser host media from ab initio calculations

Abstract

We report the electronic structures and density of states (DOS) of perfect LiCAF and LiSAF crystals calculated from density functional theory (DFT) with local density approximation (LDA) using optimized lattice constants. DOS calculations reveal that the valence band is mainly derived from F 2p, thereby resulting to a very narrow valence band manifold. Meanwhile, the conduction band is mainly derived from Ca 4s or Sr 5s resulting to Sr having a broader band dispersion compared to Ca. Both fluoride compounds have indirect band gaps with LiCAF having a band gap of 8.02 eV and LiSAF a band gap of 7.92 eV. This is, to the best of our knowledge, the first report on the electronic structure of LiSAF calculated using DFT with LDA. Our results suggest that when doped with Ce3+, the shorter 5d-conduction band distance in Ce:LiSAF combined with the difficulty of growing high-purity crystals lead to the more pronounced excited state absorption (ESA) and solarization effect experimentally observed in Ce:LiSAF, limiting its potential as a laser material compared with Ce:LiCAF.

Investigation of cross luminescence in lanthanum fluoride as a potential fast-response scintillator

“…Previous works have demonstrated that using hybrid functionals that incorporate a fraction of nonlocal Hartree-Fock exchange leads to results that are more consistent with experiments. 42,43,46) The band gap energy was also calculated using the GW approximation. Here, the same computational parameters applied to the PBE0 calculations outlined in Sect.…”

“…The valence band maxima in the band structure and DOS diagrams are shifted to zero energy. The Green's function and screened Coulomb interaction (GW) approximation [39][40][41][42] was employed to calculate the absorption spectrum of LaF 3 . This fully self-consistent quasiparticle calculation accounts for self-interaction corrections and can model excited state properties, such as absorption spectra.…”

Development of a Short Pulse Broadband and Narrow Linewidth Ultraviolet Laser Using Ce:LiCAF Crystal

“…Ce:LiCAF also has a large saturation fluence and damage threshold, making it attractive for designing power amplifiers [13,14]. Most importantly, color center formation or solarization was not observed from Ce:LiCAF, giving it the edge over Ce:LiSAF, which exhibits a lower laser efficiency due to excited state absorption and color center formation [12,15,16].…”

Tunable narrow linewidth picosecond pulses from a single grating gain-switched Ce:LiCAF laser

“…Ce 3+ :LuLiF is among the rare earth-doped fluorides reported as a broad-band UV amplification medium [18]. Ce 3+ -doped LiCaAlF 6 (Ce:LiCAF) is an especially attractive solid-state laser gain medium for all-solid-state laser generation and short-pulse amplification in the UV region because of its transparency, tolerance to laser-induced damage owing to the absence of solarization effects, and ability to be directly pumped by the fourth harmonics (266 nm) of a Nd:YAG laser [14][15][16][19][20][21][22][23][24][25]. It also has broad tunability (from 280 to 325 nm) and enough bandwidth to generate 3 fs pulses, sufficiently large effective gain cross-section (6.0 × 10 −18 cm 2 ) favorable for oscillators, and high saturation fluence (115 mJ cm −2 ) [19][20][21][22][23][24][25].…”