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.
