Exfoliated Bi₂Te₃nanoparticle suspensions and films: Morphological and nonlinear optical characterization

Bismuth telluride nanoparticles (NPs) attract attention due to the growth of sensitivity of the Bi2Te3 NPs-containing registrars in the near- and mid-infrared ranges. We describe the synthesis and characterization of these structures and analyze the low-order nonlinear optical properties of the colloidal suspensions and thin films containing Bi2Te3 NPs using 1064 and 532 nm, 10 ns pulses. Colloidal Bi2Te3 NPs demonstrate saturable absorption and positive nonlinear refraction (saturation intensity 7 × 108 W cm-2, nonlinear absorption coefficient β SA = -7 × 10-8 cm W-1, nonlinear refractive index γ= 9 × 10-12 cm2 W-1), while at stronger excitation by 532 nm, 10 ns pulses the reverse saturable absorption dominates over other nonlinear optical processes. We achieved significant growth of the nonlinear optical parameters of the thin films containing these NPs (film thickness l = 60 nm, β SA = -1.2 × 10-4 cm W-1, γ= 5 × 10-7 cm2 W-1 in the case of 532 nm probe radiation and β = -5 × 10-5 cm W-1, γ= 6 × 10-8 cm2 W-1 in the case of 1064 nm probe radiation) compared with colloidal Bi2Te3 NPs and discuss the observed peculiarities of the nonlinear response of Bi2Te3 nanostructures.