Optical, thermal, electrical, damage, and phase-matching properties of lithium selenoindate

Abstract

Lithium selenoindate (LiInSe 2) is a new nonlinear chalcogenide biaxial crystal, related to LiInS 2 and transparent from 0.54 to 10 µm at the 50% level (10 mm thickness), that has been successfully grown in large sizes and with good optical quality. We report on new physical properties that are relevant for laser and nonlinear optical applications and summarize all relevant characteristics, both from the literature and such measured in the present work. With respect to AgGaS(e) 2 ternary chalcopyrite materials, LiInSe 2 displays a nearly isotropic thermal expansion behavior with 3 to 5-times-larger thermal conductivities associated with high optical damage thresholds, and low intensity-dependent absorption, allowing direct high-power down-conversion from the near-IR, especially 1064 nm, to the deep mid-IR. Continuous-wave difference-frequency generation (5.9-8.1 µm) of Ti:sapphire laser sources is reported for the first time as well as nanosecond optical parametric oscillation with Nd:YAG laser as a pump source at 100 Hz and idler tuning between 4.7 and 8.7 µm.

Origin of the solid solution in the LiInSe 2 –In 2 Se 3 system

“…In this case, chemical analysis serves as an important indicator of the changes. The origin of compositional change in the stoichiometric melt was studied previously in several papers [2,8,14,17,18]. The change results from thermal dissociation, incongruent evaporation and the side interaction effect of the Li-containing melt and vapor with the graphite container and silica reactor.…”

“…The ternary I-III-YI 2 compounds LiB III C YI 2 have attracted considerable interest for both fundamental and practical reasons; to satisfy this interest, they must be grown as homogeneous bulk crystals of high optical perfection [1,2]. However, the growing of chemically inhomogeneous sulfide and selenide crystals LiB III C YI 2 is a more usual situation due to occurrence of extended red areas concentrated irregularly within the same yellow crystal boule.…”

“…The red color is known to be related to the enrichment with In 2 Se 3 that forms a solid solution with LiInSe 2 [8,9]. This heterovalent doping would seemingly be a reasonable explanation of the color change, were it not for specific properties of the crystals for which the surface aging effect, the light scattering losses, especially in the short-wave transparency range, and the occurrence of sharp impurity absorption peaks in the clear transparency range are often observed [2,[6][7][8]10]. Therefore, the reduction of the residual losses in the clear transparency range of LiInSe 2 remains one of main challenges.…”

“…And a general question remains open: whether the color is caused only by the compositional change or there are sources most familiar as ultra-small precipitates contributing additionally to the optical quality of the crystals. Their detection is usually outside the ability of XRD, thermal analysis, Raman spectroscopy and even optical microscopy [2,8].…”

Properties of LiGa0.5In0.5Se2: A Quaternary Chalcogenide Crystal for Nonlinear Optical Applications in the Mid-IR

“…The orthorhombic lithium ternary chalcogenides with the chemical formula LiBC 2 where B=In and Ga, C=S and Se, occupy a special position among the non-oxide nonlinear optical crystals because they are characterized by the widest band-gaps [1][2][3][4][5][6][7]. Thus, their main advantage consists in the possibility to pump them at rather short wavelengths (in the near-IR), without two-photon absorption (TPA), generating tunable mid-IR radiation by frequency down-conversion nonlinear optical processes [8].…”