Third-order nonlinear optical response of indigo carmine under 633nm excitation for nonlinear optical applications

We report thermally induced third-order nonlinearity and optical limiting behaviour of Indigo Carmine dye. z-Scan technique was used to determine the sign and magnitude of absorptive and refractive nonlinearities. Continuous wave (CW) He–Ne laser operating at 633nm was used as source of excitation. In open aperture z-scan experiments, samples exhibited reverse saturable absorption (RSA) process. For closed aperture z-scan experiments, samples revealed self-defocusing property. The presence of donor and acceptor groups in the structure increases the conjugation length and in turn increases the optical nonlinearity. Induced self-diffraction rings pattern was recorded for the samples and it is attributed to refractive index change and thermal lensing. Also, optical limiting and clamping studies were carried out for various input power. Optical clamping of about ~1mW was observed. This endorses that the dye under investigation is a positive candidate for opto-electronic and photonic applications. •Indigo carmine depicts thermally induced third-order nonlinearity.•Multiple self-diffraction rings were observed due thermal lensing effect.•Presence of donor and acceptor groups in the structure enhances the thermal nonlinearity.