Tailoring Epsilon-Near-Zero Wavelength and Nonlinear Absorption Properties of Cdo Thin Films by Mo Doping

Abstract

Cadmium oxide (CdO) has recently attracted attention as a material with controllable properties tailored for optoelectronic and nanophotonic devices due to its superior mobility. However, its potential application in near-infrared (NIR) remains to be explored. In this work, we demonstrate that the epsilon-near-zero (ENZ) wavelength and nonlinear optical properties of CdO films can be effectively tuned by Mo doping. The results show that Mo doping increases the electron concentration as well as improving the crystalline quality of CdO. With increasing Mo doping, we achieve blueshifts of the epsilon-near-zero (ENZ) wavelength from 2.89 μm to 1.56 μm, which is wider than that for ITO films (1.2-1.6 μm). The nonlinear absorption (NLA) behavior at 1550 nm changes from reverse saturable absorption to saturable absorption with increasing Mo content. Moreover, significant improvement in NLA performance with nonlinear absorption coefficient β = −72 cm/GW is observed at the highest doping content. Our work shows that doped CdO films with tunable optoelectrical and nonlinear optical properties can be an ideal candidate for optoelectronic and nanophotonic application in the NIR region.

Keywords: transparent conducting oxides；CdO thin films；epsilon-near-zero wavelength；nonlinear optical absorption