Faculty Publications
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Item An investigation on photophysical and third–order nonlinear optical properties of novel thermally–stable thiophene–imidazo [2,1-b][1,3,4] thiadiazole based azomethines(Elsevier Ltd, 2019) Kakekochi, V.; Udayakumar, U.; Nikhil, N.P.; Chandrasekharan, K.The use of ?–conjugated semiconducting materials in flexible and large–area optoelectronic devices is proliferated worldwide owing to the easy structural modifications and solution processability possible, leading to the change in opto–electronic properties. In this context, new class of thiophene and imidazo [2,1-b][1,3,4] thiadiazole (ITD) based conjugated azomethines (TI1–TI3) were designed and synthesized. The photophysical and electrochemical properties of the synthesized azomethines (TI1–TI3) were investigated experimentally, which were further validated with the aid of theoretical calculations. Further, the azomethines TI1 and TI2 were subjected to Z–scan analysis to study the nonlinear optical (NLO) properties. The molecules exhibited effective two photon absorption (TPA) with the large nonlinear absorption coefficient (?eff) of the order of 10?10 m W?1. The planar structure of TI1 furnished a better interaction between donor and acceptor moieties and extended the ?–conjugation, providing an improved ?eff (0.81 × 10?10 m W?1) to TI1 compared to that of TI2 (0.55 × 10?10 m W?1). From the results it is inferred that the molecules could be of potential materials to be used in efficient photonic devices. © 2019 Elsevier LtdItem All-Optical Diode Action through Enhanced Nonlinear Response from Polymeric Photonic Crystal Microcavity(American Chemical Society, 2022) Puthiya Purayil, N.; Kakekochi, V.; Udayakumar, U.K.; Chandrasekharan, C.The search for materials for nanophotonic devices needs a way to overcome the limitations of weak nonlinear optical response due to reduced size. The requirement of a high-power excitation source for inducing nonlinear effects in the active medium poses a hurdle in realizing all-optical and integrated optoelectronic systems. Nanosized optical materials can be embedded in photonic cavities to enhance its optical nonlinear responses through confinement effects. This report systematically investigates the linear and nonlinear optical properties of polymeric 1D-photonic crystals (PhC) with a defect layer incorporated with an imidazo-thiadiazole derivative small molecule. The nonlinear optical studies were carried out by means of a z-scan technique under nanosecond pulse using a Q-switched Nd:YAG laser operating at 532 nm. The resonant excitation creates strong confinement of light in the photonic microcavity and facilitates strong light-matter interaction that induces nonlinear response at low input intensities. A giant enhancement in the nonlinear absorption and optical limiting action was observed for PhC comparing to the bare sample. The significant enhancement in the absorptive nonlinearity is utilized for realizing a practical, on-chip, passive, all-optical diode with a PhC/Au hybrid structure. The asymmetrical nonlinear absorption of the hybrid structure exhibits non-reciprocal light transmission in the nonlinear regime. The high transmittance contrast ratio for forward/reverse bias operation and cost-effective fabrication methods makes our system a potential candidate toward the realization of compact photonic integrated devices. © 2021 American Chemical Society.