Nonlinear optical characterization of inp@zns core‐shell colloidal quantum dots using 532 nm, 10 ns pulses

Abstract

InP@ZnS core‐shell colloidal quantum dots (CQDs) were synthesized and characterized using the z‐scan technique. The nonlinear refraction and nonlinear absorption coefficients (γ = −2 × 10−12 cm2 W−1, β = 4 × 10−8 cm W−1) of these CQDs were determined using 10 ns, 532 nm pulses. The saturable absorption (β = −1.4 × 10−9 cm W−1, Isat = 3.7 × 108 W cm−2) in the 3.5 nm CQDs dominated at small intensities of the probe pulses (I ≤ 7 × 107 W cm−2) followed by reverse saturable absorption at higher laser intensities. We report the optical limiting studies using these CQDs showing the sup-pression of propagated nanosecond radiation in the intensity range of 8 × 107 –2 × 109 W cm−2. The role of nonlinear scattering is considered using off‐axis z‐scan scheme, which demonstrated the in-significant role of this process along the whole range of used intensities of 532 nm pulses. We discuss the thermal nature of the negative nonlinear refraction in the studied species.