Nonlinear absorption and excited state dynamics in Rhodamine B studied using Z-scan and degenerate four wave mixing techniques

• Published in: Chemical physics letters 2002-08, Vol.361 (5), p.439-445
• Main Authors: Venugopal Rao, S., Naga Srinivas, N.K.M., Narayana Rao, D.
• Format: Article
• Language: English
• Subjects: Exact sciences and technology; Fundamental areas of phenomenology (including applications); Nonlinear optics; Optical materials; Optical susceptibility, hyperpolarizability; Optics; Physics; Polymers and organics
• ISSN: 0009-2614; 1873-4448
• DOI: 10.1016/S0009-2614(02)00928-4

We report our experimental results of nonlinear absorption and excited state dynamics in Rhodamine B solutions at 532 nm, on resonance of the absorption band and 600 nm at the absorption edge, studied using the standard Z-scan and degenerate four wave mixing techniques. We observed saturable absorption at 532 nm and a transition from saturable absorption to reverse saturable absorption at 600 nm with increase in either intensity or concentration. Time-resolved degenerate four wave mixing studies using incoherent light from a broadband dye laser also confirmed the presence of excited state absorption through resonant two-photon absorption. Concentration dependent studies indicate a complex behavior of reverse saturable absorption within saturable absorption. Results are explained using an effective five-level model. The value of two-photon absorption coefficient evaluated using the same model was ∼0.58×10 −8 cm/W.