BaGa₄Se₇: A New Congruent-Melting IR Nonlinear Optical Material

Abstract

The new compound BaGa(4)Se(7) has been synthesized for the first time. It crystallizes in the monoclinic space group Pc with a = 7.6252 (15) Å, b = 6.5114 (13) Å, c = 14.702 (4) Å, β = 121.24 (2)°, and Z = 2. In the structure, GaSe(4) tetrahedra share corners to form a three-dimensional framework with cavities occupied by Ba(2+) cations. The material is a wide-band gap semiconductor with the visible and IR optical absorption edges being 0.47 and 18.0 μm, respectively. BaGa(4)Se(7) melts congruently at 968 °C and exhibits a second harmonic generation response at 1 μm that is approximately 2-3 times that of the benchmark material AgGaS(2). A first-principles calculation of the electronic structure, linear and nonlinear optical properties of BaGa(4)Se(7) was performed. The calculated birefractive indexΔn = 0.08 at 1 μm and the major SHG tensor elements are: d(11) = 18.2 pm/V and d(13) = -20.6 pm/V. This new material is a very promising NLO crystal for practical application in the IR region.

A High Laser Damage Threshold and a Good Second-Harmonic Generation Response in a New Infrared NLO Material: LiSm3SiS7

“…IR and Raman spectra ( Figure 2) show that LiSm 3 SiS 7 has a wide transmission range in the IR region (up to 21 µm) that covers two critical atmospheric windows (3-5 and 8-12 µm), which is comparable to those reported for powdered BaGa 4 Se 7 (~18 µm) [35], AgGaS 2 (~23 µm) [30], Li 2 CdGeS 4 (~22 µm) [70], and Na 2 Hg 3 Si 2 S 8 (~20 µm) [47]. Moreover, the bandgap (2.83 eV) of LiSm 3 SiS 7 is larger than that of commercial AgGaS 2 crystal (2.56 eV) [30]; thus, LiSm 3 SiS 7 may have a higher laser damage resistance since the LDT is generally proportional to the bandgap for one material.…”

Syntheses and characterization of two new selenides Ba5Al2Se8 and Ba5Ga2Se8

“…Recently, two new infrared nonlinear optical materials, namely BaGa 4 S 7 and BaGa 4 Se 7 , have been discovered in the A/M/Q system by Lin et al [36] and our group [37], respectively. BaGa 4 Se 7 and BaGa 4 S 7 crystallize in different structure types (space groups: Pmn2 1 vs. Pc) [36][37][38], although they possess the same composition, which demonstrates the influence of cation/anion size ratio on crystal structures.…”

“…BaGa 4 Se 7 and BaGa 4 S 7 crystallize in different structure types (space groups: Pmn2 1 vs. Pc) [36][37][38], although they possess the same composition, which demonstrates the influence of cation/anion size ratio on crystal structures. Here, we report the successful syntheses of two new compounds Ba 5 Al 2 Se 8 and Ba 5 Ga 2 Se 8 as a result of our continuing exploratory investigation in the A/M/Q system.…”

Temperature-Dependent Sellmeier Equations of IR Nonlinear Optical Crystal BaGa4Se7

“…BaGa 4 Se 7 is a biaxial crystal and belongs to the monoclinic space group Pc [8]. To measure its three independent principal refractive indices n x , n y , and n z , one BaGa 4 Se 7 crystal was cut into two right-angle prisms with the sides of the right angle aligned with different directions, as shown in Figure 2.…”

“…The crystal belongs to the monoclinic space group Pc. It possesses intriguing overall properties for IR NLO applications including wide transparent range (0.47 to 18 µm), suitable birefringence, large nonlinear optical coefficients, and high laser damage threshold [8][9][10][11][12]. The outstanding properties of BaGa 4 Se 7 have been exemplified by some recent laser experiments [13][14][15][16][17].…”