Nonlinear optical response of ITO-(CdTe, CdS, CdTe/CdS) QD-based Thin-Films Through Selective Excitation

Following our research group's efforts to measure the non-linear properties of CdTe, CdS, and CdTe/CdS Quantum Dot Nano Particles (QD NPs ), we were about to deposit these QD NPs on ITO metal-oxide substrates to characterize their thin-film non-linearities, such as non-linear refraction (NLR) and absorption (NLA). The layers were deposited through the Electro-Deposition (ED) method and were analyzed by Z-scan optical setup, together with employing FESEM, AFM imaging, XRD, and UV-Vis spectroscopy techniques. in exposure by a 655nm laser, NLA (β) coefficients were determined as -2.99, 1.35, -9.69 cm/GW with Reverse Saturable absorption (RSA) for ITO-CdS and Saturable absorption (SA) for ITO-CdTe and ITO-CdTe/CdS; hence, with a 632.8nm laser, with slightly 20nm further excitation wavelength, their NLA(β) were measured -18.44, -7.52, -38.02 cm/GW as Saturable absorption (SA) for ITO-CdTe, ITO-CdS, and ITO-CdTe/CdS, respectively. For measuring the NLR, self-focusing and defocusing mechanisms were evaluated for layers throughout different excitations. Extreme, tunable, and identical non-linearities against different wavelengths make these thin-films promising candidates for optical limiter devices that safeguard delicate optical detectors from pulse or beam spikes, biological tissue protectors, and all-optical switching behavior near epsilon near zero (ENZ) wavelengths.