Nonlinear absorption, refraction and optical limiting properties of cobalt molybdate microcrystals

Cobalt molybdate (CoMoO₄) microcrystal was synthesized by a hydrothermal method. The CoMoO₄ microcrystal was dispersed in methyl methacrylate (MMA) that was polymerized to polymethyl methacrylate (PMMA) to prepare CoMoO₄/PMMA organic glass. The successful synthesis of CoMoO₄ was verified by Raman spectroscopy. The CoMoO₄ microcrystal was characterized by scanning electron microscopy (SEM). The results indicate that the CoMoO₄ microcrystal is microrod. The diameter and length of the sample are about 0.5–3 μm and 2–20 μm. The band gap of CoMoO₄/PMMA is about 3.5 eV. The nonlinear absorption (NLA) and refraction properties of CoMoO₄/PMMA organic glasses were investigated for the first time by a Z-scan technique. The laser pulse energy is 7–20 μJ. The results indicate that CoMoO₄/PMMA organic glasses exhibit good reverse saturable absorption (RSA) and self-defocusing effects. NLA and refraction coefficients are β = 68 cm GW⁻¹ and γ = −1.4 × 10⁻⁴ cm² GW⁻¹ at the laser pulse energy of 20 μJ, respectively. The enhanced RSA and self-defocusing effects make the CoMoO₄/PMMA organic glasses exhibit excellent optical limiting (OL) performance. The nonlinear absorption, refraction and OL properties of CoMoO₄/PMMA organic glasses can be controlled by adjusting the laser pulse energy and the amount of CoMoO₄ in PMMA.