LiInSe 2 : A biaxial ternary chalcogenide crystal for nonlinear optical applications in the midinfrared

Abstract

Single crystals of lithium selenoindate (LiInSe2) are grown by the Bridgman–Stockbarger technique up to sizes of 10 mm in diameter and 20 mm in length. The different phases have color from yellow (as grown) to dark red (after annealing) but all have the same wurtzite type structure mm2 with slightly differing cell parameters. The band gap for the yellow phase at 300 K is at 2.86–2.87 eV. The red color is attributed to point defects and can be removed by proper illumination. Sellmeier equations are constructed for the 0.5–11 μm range and their validity is checked with second harmonic generation which provides first estimations of the nonlinear coefficients of LiInSe2. The potential of LiInSe2 is compared to that of the widely spread and technologically mature AgGaS2.

Growth and properties of LiGaX2 (X = S, Se, Te) single crystals for nonlinear optical applications in the mid‐IR

“…Recently two lithium-containing nonlinear optical crystals, LiInS 2 (LIS) and LiInSe 2 (LISe), were successfully grown with high optical quality and applied for second harmonic generation (SHG) and optical parametric amplification (OPA) in the mid-IR [1,2]. Their nonlinear susceptibilities and transparency ranges were found similar to those of the well-known AgGaS 2 but a number of additional advantages related to the wurtzite-type structure, the larger band gap and the higher thermal conductivity are very promising and stimulate the further search for new representatives of this family of synthetic crystals.…”

Characterization of LiInS2 and LiInSe2 single crystals for nonlinear optical applications

“…The indices obtained before and after annealing are given in Table 2 and one can see that they are identical within the experiment accuracy. Nonlinear parameters were measured only for as-grown LISe samples to date: they are 1.26-1.56 times higher than those for LIS [3]. Investigation of LISe phase-matching conditions and nonlinear parameters is in progress.…”

“…No information about the nonlinearity of LISe was available, but it was expected to be higher. Problems with growth of the LiInS 2 and LilnSe 2 crystals were solved recently and large crystals of high optical quality became available [2,3]. One of the typical features of ternary compounds is considerable variation of their color depending on growth or annealing conditions.…”

Collinear phase matching for second harmonic generation using conoscopic interferometry

“…It is well known that various crystallographic directions of high optical symmetry can be easily identified using Conoscopic interferometry. Conoscopic interferometric techniques have been used successfully to align surface-acoustic-wave substrate crystals, 7,8 identify crystal inhomogeneities, 9,10 determine refractive indices for nonlinear optical crystals, [11][12][13][14][15] to study phase transitions in birefringent liquid crystals and to determine their optical properties. [16][17][18] More recently a conoscopic technique was proposed for grinding and polishing plane optical surfaces normal to a uniaxial crystal's optic axis.…”