ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Cesium-doped zinc sulfate hexahydrate single crystals with enhanced third-order nonlinear optical properties for sustainable photonic applications

D. Dulasimathi, M. Prabhaharan, N. Venkatachalam, Muthumareeswaran Muthuramamoorthy, Shofiur Rahman, and Rekha Pachiappan

Department of Physics, Saveetha School of Engineering, Saveetha Institute of Medical and Technical Sciences (SIMATS), Chennai, India

E-mail: mprabhaharan@hotmail.com

Received: 5 February 2026  Accepted: 18 May 2026

Abstract:

In this work, cesium-doped zinc sulfate hexahydrate (CZSH) single crystals were successfully grown at room temperature by a low-energy slow evaporation technique, offering a cost-effective and environmentally benign route for crystal fabrication. Transparent and structurally stable crystals with good optical quality were obtained. Structural analysis by single-crystal X-ray diffraction confirmed the retention of the monoclinic phase with slight lattice distortion due to Cs⁺ incorporation, indicating successful dopant accommodation without altering the host symmetry. FT-IR analysis verified the presence of sulfate groups, coordinated water molecules, and stable lattice bonding. UV–Visible studies revealed excellent optical transmission in the visible region with a sharp cut-off wavelength at 285 nm and a wide optical band gap of 5.3 eV, demonstrating low optical loss and suitability for high-power optical systems. Photoluminescence analysis combined with Gaussian deconvolution identified emission peaks at 362, 405, and 490 nm, corresponding to near-band-edge and defect-assisted radiative transitions. The calculated CIE chromaticity coordinates (0.214, 0.358) confirmed blue-cyan emission with a colour purity of 30.89%, indicating stable luminescent behaviour. Surface morphology analysis showed uniformly distributed submicron grains with an average feature size of 0.269 μm, reflecting controlled growth kinetics and good microstructural homogeneity. Third-order nonlinear optical studies using the Z-scan technique at 532 nm exhibited positive nonlinear refraction and reverse saturable absorption with β = 4.2 × 10⁻³ cm/W, n₂ = 3.1 × 10⁻⁸ cm²/W, and χ³ = 2.1 × 10⁻⁷ m²/V². The enhanced nonlinear response is attributed to Cs⁺-induced electronic polarization, localized defect states, and improved optical homogeneity. These findings demonstrate that CZSH is a promising low-cost inorganic material for optical limiting, laser protection, photonic switching, and sustainable optoelectronic technologies.

Keywords: Sustainable materials; Nonlinear optical materials; Advanced optoelectronics; Optical limiting; Wide band gap materials

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-026-05077-w

Chemical Papers 80 (10) 11581–11594 (2026)