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

Abstract

Lithium thioindate (LiInS2) is a new nonlinear chalcogenide biaxial material transparent from 0.4 to 12 µm, that has been successfully grown in large sizes and good optical quality. We report on new physical properties that are relevant for laser and nonlinear optics applications. With respect to AgGaS(e)2 ternary chalcopyrite materials, LiInS2 displays a nearly-isotropic thermal expansion behavior, a 5-times larger thermal conductivity associated with high optical damage thresholds, and an extremely low intensity-dependent absorption allowing direct high-power downconversion from the near-IR to the deep mid-IR. Continuous-wave difference-frequency generation (5-11 µm) of Ti:sapphire laser sources is reported for the first time.

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].…”

“…This application is based on the high thermal neutron cross section (938 barns) of the 6 Li isotope which converts thermal neutrons to highly ionizing particles through the nuclear reaction 6 Li(n,α) 3 H, while the LiBC 2 semiconductors detect the electron-hole pairs induced by either tritium ions or α-particles [14]. Among the LiBC 2 crystals maximum response has been demonstrated with LISe which exhibits the minimum band-gap.…”

“…On the other hand, thermal neutrons can be detected by recording the light pulses generated as a result of the interaction of the crystal with ionizing particles: in this case LISe operates as a scintillator [15]. The problem is the natural abundance of 6 Li which amounts to only 7.5%. To increase the detection efficiency LISe crystals with lithium as 6 Li can be grown [16].…”

“…The problem is the natural abundance of 6 Li which amounts to only 7.5%. To increase the detection efficiency LISe crystals with lithium as 6 Li can be grown [16]. However, 115 In (with natural abundance of 95.7%) present in LISe also captures neutrons, which results in gamma decay rather than charge creation.…”

“…The nonlinear coefficients of LGISe have values between those of LGSe and LISe. 6 LGISe crystals are considered promising also for detection of thermal neutrons. …”