Exfoliated Bi2Te3 nanoparticle 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.

Исследование пространственной и токовой динамики оптических потерь в полупроводниковых лазерных гетероструктурах методом оптического зондирования

The spatiotemporal dynamics of optical losses and carrier density in a heterostructure of a semiconductor laser with a segmented contact were studied using an optical probe technique based on the coupling of probe radiation with a wavelength of 1560 nm into a semiconductor laser chip under investigation based on an AlGaAs/ InGaAs/ GaAs heterostructure and emitting at a wavelength of 1010 nm. It has been shown that the use of a probe beam with a wavelength of 1560 nm makes it possible to ensure the sensitivity of the measurement of internal optical losses of no worse than 1 cm-1. The use of a segmented design of the current pumping region made it possible to estimate the absolute value of internal optical losses. It was shown that a change in the configuration of the Fabry-Perot eigenmodes of the laser affects the distribution of charge carriers and internal optical losses both in the current pump region and in the passive part of the laser chip that is not pumped by the current.

ANALYSIS OF THE SPECTRAL DEPENDENCES THE TRANSMISSION COEFFICIENT IN A BISMUTH SILICATE CRYSTAL AT HARMONIC MODULATION OF EXCESS RADIATION UNDER WAVE LENGTH

It was found that the analysis of harmonic components determining the time dependence the transmission coefficient of a bismuth silicate crystal during sinusoidal modulation of the probe radiation over the wavelength makes it possible to determine the spectral position of the maxima for intracenter transitions in defective centers contributing to impurity optical absorption. It was found that the analysis of harmonic components, which determine the time dependence transmission coefficientof an aluminum-doped bismuth titanate crystal with sinusoidal modulation of probe radiation over a wavelength, makes it possible to determine the spectral position of the maxima for intracenter transitions in defective centers that contribute to impurity optical absorption.