The Kurtz-Perry powder technique revisited: A case study on the importance of reference quality and broadband nonlinear optical measurements using LiInSe2

The Kurtz-Perry powder technique (KPPT) is widely utilized for the rapid characterization of newly grown nonlinear optical (NLO) materials available in pristine powder form. It assesses the effective nonlinear susceptibility of randomly oriented powder in comparison with a reference material. This technique becomes especially versatile when equipped with a broad wavelength range and intensity tunability because it provides key NLO properties of the materials under investigation, such as the frequency dispersion of the NLO susceptibility, phase-matching (PM) range, and laser-induced damage threshold (LIDT) as a guideline. In this study, wavelength-dependent NLO experiments (lambda = 1100 - 3700 nm) were conducted on polycrystalline LiInSe2, prepared by high-temperature, solid-state synthesis. Our LiInSe2 was found to be phase-matchable for lambda > 2500 nm and the effective NLO susceptibility was estimated as 20.0 +/- 1.9 pm/V, assessed at the static limit using commercial-grade single crystals of AgGaS2 and AgGaSe2 that were ground to powders. Alternatively, the effective NLO susceptibility was determined to be twice as large, similar to 40 pm/V, when utilizing a homemade, microcrystalline AgGaSe2 reference at the static limit. This severe overestimation of the NLO susceptibility that can occur while working with a homemade standard underscores the importance of using a commercial-grade reference with the KPPT. Furthermore, this study also discusses the LIDT of LiInSe2 based on intensity-dependent SHG at 1064 nm with picosecond pulses, and compares with those of the commercial-grade AgGaS2 and AgGaSe2, determined under identical conditions. As defect levels can cause widely varying apparent color, thus optical bandgap, in LiInSe2, this study stresses the importance of using a high-quality standard when exploiting the KPPT for NLO materials characterization. The role of defects is discussed in terms of chi((2)), phase matching onset and LIDT, parameters that predominantly affect the evaluation of new NLO materials. (C) 2022 Published by Elsevier B.V.