A novel solid solution LiGa(S_1–x Se _x )₂ for generating coherent ultrafast mid-IR sources

Abstract

With renewed refractive indices, the potential of a solid solution LiGaS 2 : LiGaSe 2 → LiGa(S 1−x Se x ) 2 ( x = 0 − 1) in optical frequency conversionespecially in phase matching and group velocity matching-is theoretically investigated, together with the composition ratio limitation. It is found that the solution has excellent features for generating coherent ultrafast mid-IR sources covering 8-11 μm, which can be realized by type II down-conversion in the ba-plane with perfect group velocity matching, or type I in the bc-plane with part group velocity matching. This will have broad applications in LiDAR monitoring and precision spectroscopy, as well as life and environmental sciences.

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

“…Anion substitution can be employed to similarly modulate the AAsQ 2 family, providing a complete picture of the structure−property relationships in this system. 30 Anion mixing changes the band gap, and subsequently SHG response, 31 and impacts the interchain interactions. Understanding these subtleties is pivotal to the goals of NLO materials design and should be pursued.…”

“…Furthermore, none of the previously reported AAsQ 2 materials display phase matchability at the measured near-IR wavelengths. Anion substitution can be employed to similarly modulate the AAsQ 2 family, providing a complete picture of the structure–property relationships in this system . Anion mixing changes the band gap, and subsequently SHG response, and impacts the interchain interactions.…”

Optimization on the frequency conversion of LiGaS2 crystal

“…An overall assessment of ultrafast OPAs/OPGs should incorporate group velocity matching (GVM), at which the largest PM bandwidth appears. The figures of GVM in [13] still have referential data in spite of biased refractive indices. A further computation with the new index data found two GVM points, (0.882 µm, 9.42 µm) of type I, and (1.77 µm, 3.54 µm) of type II-fsf in the SHG line, which are close to the former ones in [13].…”

“…The figures of GVM in [13] still have referential data in spite of biased refractive indices. A further computation with the new index data found two GVM points, (0.882 µm, 9.42 µm) of type I, and (1.77 µm, 3.54 µm) of type II-fsf in the SHG line, which are close to the former ones in [13]. Combining the maximum FM and new GVM points, we have an optimum ultrafast OPA/OPG scheme of type II-fsf for pulse generation over 8-10 µm, pumped by a laser with a wavelength around 0.9 µm, and another type I OPA/OPG scheme for ultrashort pulses over 3-5 µm, pumped by a near 1.8 µm laser.…”

“…These results are comparable to those of other classic nonlinear crystals with ultrahigh damage threshold such as ZnGeP 2 . Our former investigation showed that the group velocity mismatch is very small in the range of 8-11 µm which allows for effective mid-IR ultrashort pulse generation [13]. Even though the refractive indices of LGS were early known, it was recently found that many experiments were not in accordance with estimations from the known index data.…”