Linear and nonlinear optical properties modulation of Sb2Te3/GeTe bilayer film as a promising saturable absorber

Sb2Te3/GeTe bilayer films with different thickness ratios have been deposited on silicon substrate and fused quartz substrates by radio-frequency magnetron sputtering. Linear optical properties and optical bandgap of sample films were investigated firstly. With the thickness ratio changes, their transmittance differences decrease a lot at the wavelength range of 1500-1600 nm. Besides, the modulation depth of saturable absorption of samples will increase along to the incident power density or thickness ratio. Besides incident power density, interface states between topological insulation characteristic Sb2Te3 and ferroelectric GeTe layers will also affect the modulation depth greatly.