Third Order Nonlinear Properties of Rhodamine B Dye Doped PVA Polymer Determined by Eclipsing Scan Technique

Abstract

Nonlinear (NL) optical properties were observed in Rhodamine B (RB) dyes doped in poly (vinyl alcohol) (PVA) polymer films. Eclipsing Z‐scan (EZ‐scan) with a continuous wavelength of 532 nm was used to investigate the effect of dye concentration on its NL properties. The open aperture EZ‐scan indicates a reverse saturable absorption behavior (positive type) of NL absorption (NLA) coefficient (β) in the RB+VA matrix, whereas the closed aperture EZ‐scan exhibits transition from positive (focusing) to negative (defocusing) nonlinearity at increasing dye concentration. The NL refractive index ����2, NLA coefficient ����, third‐order susceptibility ����3, and second‐order hyperpolarizability �������� increase with the increase in dye concentrations. The magnitude of the n2, ����, ����3, and �������� were in the order of 10‐12 (��������2/W), 10‐1 (��������/W), 10‐8 (esu), and 10‐12 respectively.