Heteroanionic Control of Exemplary Second-Harmonic Generation and Phase Matchability in 1D LiAsS2-XSeX

The isostructural heteroanionic compounds fibetween selenium content and second-harmonic response and greatly outperform the industry standard AgGaSe2. These materials crystallize in the noncentrosymmetric space group Cc as one-dimensional 1/infinity [AsQ2]- (Q = S, Se, S/Se) chains consisting of corner-sharing AsQ3 trigonal pyramids with charge-balancing Li+ atoms interspersed between the chains. LiAsS2-xSex melts congruently for 0 < x < 1.75, but when the Se content exceeds x = 1.75, crystallization is complicated by a phase transition. This behavior is attributed to the fi- to a-phase transition present in LiAsSe2, which is observed in the Se-rich compositions. The band gap decreases with increasing Se content, starting at 1.63 eV (LiAsS2) and reaching 1.06 eV (fi-LiAsSe2). Second-harmonic generation measurements as a function of wavelength on powder samples of fi-LiAsS2-xSex show that these materials exhibit significantly higher nonlinearity than AgGaSe2 (d36 = 33 pm/V), reaching a maximum of 61.2 pm/V for LiAsS2. In comparison, single-crystal measurements for LiAsSSe yielded a deff = 410 pm/V. LiAsSSe, LiAsS0.25Se1.75, and fi-LiAsSe2 show phase-matching behavior for incident wavelengths exceeding 3 mu m. The laser-induced damage thresholds from two-photon absorption processes are on the same order of magnitude as AgGaSe2, with S-rich materials slightly outperforming AgGaSe2 and Se-rich materials slightly underperforming AgGaSe2.

Automated summary

This research focuses on the structure, properties, and the relationship between selenium content and isostructural heteroanionic compounds. The results demonstrate that these materials exhibit excellent performance in second-harmonic response and outperform the industry standard AgGaSe2.