LAUSR

The nonlinear optical (NLO) properties and optical limiting of an anthraquinone (Reactive blue 4) dye is studied in the low power regime utilizing a continuous wave (CW) diode laser at 635 nm with total power of 5 mW. The NLO parameters such as nonlinear index of refraction (n2) and nonlinear absorption coefficient (β) were determined respectively from closed (S = 0.4) and open (S = 1) aperture Z–scan technique. Self-defocusing and reverse saturable absorption are the nonlinear mechanisms were observed in the dye sample. The real and imaginary parts of the third-order nonlinear susceptibility (χ3) were estimated to be Re (χ3) = −2.12 × 10−5 esu and Im (χ3) = 1.85 × 10−6 esu. The optical limiting behaviors of reactive blue 4 dye at different concentrations were performed under experimental condition. Variation of transmitted laser spot size as a function of sample position at far field was also observed. The diffraction ring patterns were recorded in the present dye sample due to thermal lensing effect. With these experimental results the authors believed that, the dye investigated here is a potential material for NLO applications.