Structure Tuning, Strong Second Harmonic Generation Response, and High Optical Stability of the Polar Semiconductors Na_1–xK_xAsQ₂

Abstract

The mixed cation compounds Na1–x K x AsSe2 (x = 0.8, 0.65, 0.5) and Na0.1K0.9AsS2 crystallize in the polar noncentrosymmetric space group Cc. The AAsQ 2 (A = alkali metals, Q = S, Se) family features one-dimensional (1D) 1/∞[AQ 2 –] chains comprising corner-sharing pyramidal AQ 3 units in which the packing of these chains is dependent on the alkali metals. The parallel 1/∞[AQ 2 –] chains interact via short As···Se contacts, which increase in length when the fraction of K atoms is increased. The increase in the As···Se interchain distance increases the band gap from 1.75 eV in γ-NaAsSe2 to 2.01 eV in Na0.35K0.65AsSe2, 2.07 eV in Na0.2K0.8AsSe2, and 2.18 eV in Na0.1K0.9AsS2. The Na1–x K x AsSe2 (x = 0.8, 0.65) compounds melt congruently at approximately 316 °C. Wavelength-dependent second harmonic generation (SHG) measurements on powder samples of Na1–x K x AsSe2 (x = 0.8, 0.65, 0.5) and Na0.1K0.9AsS2 suggest that Na0.2K0.8AsSe2 and Na0.1K0.9AsS2 have the highest SHG response and exhibit significantly higher laser-induced damage thresholds (LIDTs). Theoretical SHG calculations on Na0.5K0.5AsSe2 confirm its SHG response with the highest value of d 33 = 22.5 pm/V (χ333 (2) = 45.0 pm/V). The effective nonlinearity for a randomly oriented powder is calculated to be d eff = 18.9 pm/V (χeff (2) = 37.8 pm/V), which is consistent with the experimentally obtained value of d eff = 16.5 pm/V (χeff (2) = 33.0 pm/V). Three-photon absorption is the dominant mechanism for the optical breakdown of the compounds under intense excitation at 1580 nm, with Na0.2K0.8AsSe2 exhibiting the highest stability.

SrAgAsS4: A Noncentrosymmetric Sulfide with Good Infrared Nonlinear Optical Performance Induced by Aliovalent Substitution from Centrosymmetric SrGa2S4

“…The type-I phase-matching behavior and strong SHG response of SrAgAsS 4 support itself as an excellent nonlinear candidate material. To date, there have also been several As-based compounds with an SHG response, such as Na 0.5 K 0.5 AsSe 2 ( d eff = 18.9 pm/V), CsMnAs 3 S 6 ( d ij = 1.1 × AGS), Ba 2 As 2 S 5 ( d ij = 1.0 × AGS), γ-NaAsSe 2 ( d ij = 75 × AGSe), β-LiAsS 2 ( d ij = 10 × AGSe), and β-LiAsSe 2 ( d 33 = 836.5 pm/V) . In these compounds, As atoms tend to be in the As 3+ form and contain 4s 2 lone pair electrons, which is thought to enhance SHG effects.…”

Li3[Al(PO4)2(H2O)1.5] and Na[AlP2O7]: from 2D layered polar to 3D centrosymmetric framework structures

“…Nonlinear optical (NLO) materials have attracted a lot of attention in the recent half century due to their wide range of applications from information storage to immersion lithography and super high-resolution photoemission spectroscopy. 1–7 In particular, ultraviolet (UV) NLO crystals work in the region of wavelength λ ∼ 300 nm, or even the deep-ultraviolet region (DUV, λ ≤ 200 nm). 8–12 Deep-UV laser light sources have been widely used in several key fields, such as laser processing technology, biomedicine, precision scientific research equipment, and laser high-resolution lithography.…”

Heteroanionic Control of Exemplary Second-Harmonic Generation and Phase Matchability in 1D LiAsS2–xSex

“…Despite the structure-directing nature of As 3+ and the covalency of As–Q bonds, relatively few studies have focused on chalcoarsenates, and even fewer have studied chalcoarsenates as NLO-active materials. Table shows selected chalcoarsenates, their relative SHG intensities, and band gaps. − …”