RESEARCH PAPER Thermal Lens and All-Optical Switching of the Salt: [C 12 H 14 N 2 ][Fe(CN) 5 (NO)]5H 2 O M. D. Zidan 1 • M. M. Al-Ktaifani 1 • M. S. EL-Daher 2 • A. Allahham 1 • A. Ghanem 2 Received: 23 April 2020 / Accepted: 3 August 2020 Ó Shiraz University 2020 Abstract The effect of the thermal lens was demonstrated with all-optical switching for the new organic–inorganic hybrid salt: 1,1 0 - (ethylene-1,2-diyl)dipyridinium pentacyanidonitrosoferrate(II)pentahydrate. The development of thermal blooming of the probe laser beam at three input powers 20, 60, and 100 mW was observed. The evolution time of the thermal lens and the fitting of the experimental transient curve were useful to evaluate the parameters of h, t c , D,dn/dT, n 2 , and Dn of the sample solution. The new results have led to possible potential applications of this complex as future promising materials in optoelectronic devices. Keywords Thermal lens effect  Organic–inorganic hybrid salt  Z-scan 1 Introduction Recently, huge effort was concentrated on studying the nonlinear optical (NLO) properties of new organic mole- cules to search for good materials to be used in photonic applications (Iliopoulos et al. 2010; Kulyk et al. 2016a, b). So, many researchers have focused on the nonlinearity of the thermal lens effect, which rises as a result of a change in the refractive index of the media to its increasing tem- perature after absorbing the laser light (Jacinto et al. 2006). Different compounds (dyes, organics and metal–organic salts) have been investigated to show the thermal lens effect using the pump–probe technique (Jiang et al. 2004; Wang et al. 2011; Jing and Yikun 2014; Badran et al. 2017). These molecules possess high optical nonlinearity, so several research groups focused their efforts on finding a new photonic device to be used in future (Henari 2011; Siji Narendran et al. 2015; Zidan et al. 2015; Chandra Shekhara Shetty et al. 2016; Mirershadi et al. 2016; Yadav and Roy 2016; Zidan et al. 2016; Manjunatha et al. 2017). The BSAM azo dye has been investigated, and the results show the thermal lens effect (Al-Mudhaffer et al. 2016). The switching behavior measurement of zinc phthalocyanine dye was reported using the pump–probe beams (Kumar et al. 2017). This technique is used to study the all-optical power switching of the 3,4-pyridinediamine. It indicates clearly that the time of switch-on and switch-off was in the range of microsecond (ls) (Badran et al. 2016). The ther- mal lens (TL) phenomenon in new organometallic com- pounds was studied using two wavelength lasers: k pump = 532 nm as an excitation beam and k probe- = 635 nm as a probe beam in order to probe the nonlinear thermal effect (Badran 2014). This article reports the thermal lens effect of the new organic–inorganic hybrid salt: 1,1 0 -(ethylene-1,2-diyl)dipyri- dinium pentacyanidonitrosoferrate(II)pentahydrate ‘‘[C 12- H 14 N 2 ][Fe(CN) 5 (NO)]5H 2 O’’ solution by employing the modified configuration of pump–probe beams Z-scan technique. 2 Experimental Techniques 2.1 Materials and Methods The 1,1 0 -(ethylene-1,2-diyl)dipyridinium pentacyanidoni- trosoferrate(II)pentahydrate was already prepared and & M. D. Zidan pscientific8@aec.org.sy 1 Atomic Energy Commission, P. O. Box 6091, Damascus, Syria 2 Higher Institute for Laser Research and Applications, Damascus University, Damascus, Syria 123 Iran J Sci Technol Trans Sci https://doi.org/10.1007/s40995-020-00959-4