Optical nonlinear refractive index measurements of Cr2Te3 with an immense photothermal effect

Bo-Yi Chen, Jia-Chi Lan, Mu-Hsuan Tsai, Kyungtaek Lee, Yeong Gwang Khim, In Hak Lee, Young Jun Chang, Ju Han Lee, Chao-Kuei Lee

In this work, the optical nonlinearity of PVD-grown Cr2Te3 thin films of 33- and 100-nm thickness with an immense thermal optical e?ect was investigated. By removing the thermally induced background signal, the n2 value without accumulated heat could then be estimated to be of the order of magnitude of around 108 cm2 W1. A decrease in the n2 value with the pump power was observed, leading to increased absorption. In addition, the changing sign for the 100-nm-thick thin film as the pump power exceeded 450 mW was investigated, exhibiting good agreement with the observed additional increasing temperature resulting from the anomalous increasing absorption. This work paves the way to not only characterize the optical nonlinearity of samples with initiable thermal e?ects but also to evaluate materials with potential for real applications through the methodology provided.