Nonlinear optical properties of AIE doped PMMA thin film upon restriction of intramolecular motion

Aggregation Induced Emission (AIE) is an interesting Photophysical phenomenon in which a series of molecules non-emissive in solution state become fluorescent upon aggregation or by structural rigidification. Restriction of intramolecular motion (RIM) is the basic principle of this phenomenon. Nonlinear absorption properties of AIE dye named Tertraphenylethylene (TPE) in Anisole and doping it in PMMA matrix is studied using Open Apperture (OA) Z-scan technique. OA Z-scan trace of TPE in anisole showed RSA in SA behaviour due to two photon induced excited state absorption while TPE doped PMMA film showed RSA behaviour with two photon absorption (TPA) as an underlying mechanism. Five level energy model is used to understand this change in nonlinearity. Optical limiting threshold shows only a slight change upon RIM.