AgGa₂PS₆: A New Mid‐Infrared Nonlinear Optical Material with a High Laser Damage Threshold and a Large Second Harmonic Generation Response

Abstract

To develop new mid-infrared (MIR) nonlinear optical (NLO) materials, which can overcome the low laser damage threshold (LDT) of the commercial MIR-NLO crystals (AgGaS , AgGaSe and ZnGeP ) and simultaneously keep the large NLO susceptibility, is necessary for high-power MIR laser frequency conversion technology. To improve the LDT, a new strategy of increasing lattice stability was adopted. Here, the strongly covalent structural unit of the PS tetrahedron was introduced into AgGaS (AGS), and that led to the isolation of the first compound in Ag -Ga -P -S system, namely, AgGa PS (Cc). It retains a large SHG efficiency (1.0×AGS) with phase-matchable ability, and also exhibits an improved LDT (5.1×AGS), indicating AgGa PS is a new promising MIR-NLO crystal. Moreover, a novel 3D framework of [Ga PS ] , with triangular-shaped channels, as well as interesting single triangular geometry of AgS -both of which are very rare in reported sulfides-was discovered in AgGa PS . Furthermore, theoretical calculations, and lattice energy and thermal expansions analyses suggest that the PS group makes a large contribution to the large SHG efficiency and high LDT.

SnPQ3 (Q = S, Se, S/Se): A Series of Lone-Pair Cationic Chalcogenophosphates Exhibiting Balanced NLO Activity Originating from SnQ8 Units

“…The weak absorption peak at around 550 cm −1 for 1 and 3 can be ascribed to the stretching vibration of P−S bonds. 30,33,34 As depicted in Figure 4, the optical band gaps of 1−3 are 2.17, 1.73, and 2.35 eV, respectively, which are consistent with their crystal colors. They both show broad transparency ranging from the UV−vis region (ca.…”

“…It hybridizes with Q elements to form P x Q y anions. Furthermore, these anions can adopt corner- or edge-sharing linkages facilitating the formation of various polyanions, such as [P 2 S 6 ] 4– , [P 2 S 7 ] 4– , [P 3 S 10 ] 5– and [P 4 S 13 ] 6– , , which have been observed in AgGa 2 PS 6 , LiGa 2 PS 6 , LiCd 3 PS 6 , HgCuPS 4 , and CuCd 3 PS 6 . The polyanions can also be considered as basic structural units.…”

Structural modification from centrosymmetric Rb4Hg2Ge2S8 to noncentrosymmetric (Na3Rb)Hg2Ge2S8: mixed alkali metals strategy for infrared nonlinear optical material design

“…In chalcogenides, the typical NCS chromophores encompass [MQ 4 ] n − (M = Ag, Zn, Ga, Ge, P, etc. ; Q = chalcogen), 9–13 trigonal-planar p-conjugated groups (AgQ 3 , HgQ 3 ), 14,15 d 0 -second-order Jahn–Teller-effect cations (Ti 4+ , Nb 5+ ), 16 and ns 2 -electron cations (Pb 2+ , As 3+ ). 17 Under the guidance of these ideas, high-performance IR NLO materials with tetrahedron [MQ 4 ] n − as the NLO functional motif have been extensively studied, such as BaGa 4 Q 7 (Q = S, Se), 18,19 BaGa 2 MQ 6 (M = Si, Ge; Q = S, Se), 20 M II 3 P 2 S 8 (M II = Zn, Hg), 21,22 and AM II M IV Q 4 (A = Eu, Sr, Ba; M II = Mn, Zn, Cd, Hg; M IV = Si, Ge, Sn; Q = S, Se).…”

Infrared nonlinear optical sulfide CsCd4In5S12 exhibiting large second harmonic generation response

“…35 In general, the LIDT and the SHG coefficient are restricted by each other in view of their inversely proportional relationship with the energy band gap. 36,37 Introducing alkali or/and alkaline earth metal cations into the structure is a common method to enlarge the E g . Moreover, highly disordered NLO materials are inherently more stable than crystals in a highenergy state due to their high degree of disorder and chaos, which can effectively improve their resistance to structural damage under laser irradiation.…”