Nonlinear Absorption and Refraction of Picosecond and Femtosecond Pulses in HgTe Quantum Dot Films

Abstract

We report measurements of the saturated intensities, saturable absorption, and nonlinear refraction in 70-nm thick films containing 4 nm HgTe quantum dots. We demonstrate strong nonlinear refraction and saturable absorption in the thin films using tunable picosecond and femtosecond pulses. Studies were carried out using tunable laser pulses in the range of 400–1100 nm. A significant variation of the nonlinear refraction along this spectral range was demonstrated. The maximal values of the nonlinear absorption coefficients and nonlinear refractive indices determined within the studied wavelength range were −2.4 × 10−5 cm2 W−1 (in the case of 28 ps, 700 nm probe pulses) and −3 × 10−9 cm2 W−1 (in the case of 28 ps, 400 nm probe pulses), respectively. Our studies show that HgTe quantum dots can be used in different fields e.g., as efficient emitters of high-order harmonics of ultrashort laser pulses or as laser mode-lockers.

Investigation of Nonlinear Optical Processes in Mercury Sulfide Quantum Dots

“…Studies of the nonlinear refraction and absorption in other mercury-contained QDs (HgTe, HgSe) have shown that those species demonstrate smaller nonlinear refractive indices and nonlinear absorption coefficients compared with the HgS QDs [20,29]. Moreover, HgS QDs have demonstrated the efficient THG, which was not reported during the studies of HgTe and HgSe QDs.…”

“…The thin films were prepared by layer-by-layer deposition using the dip-coating on a 0.15 mm-thick glass substrate. The ligand shell exchange by 1,2-ethanedithiol (EDT) has been done using 1:1:100 EDT/HCl/2-propanol solution [20]. The glass substrate was withdrawn at a speed of 18 mm/min.…”

CrPS4 Nanoflakes as Stable Direct-Band-Gap 2D Materials for Ultrafast Pulse Laser Applications

“…As a result of the sustained efforts of scientists to discover SA materials with valuable properties, such as the semiconductor saturable-absorber mirror (SESAM) [ 11 , 12 ], many two-dimensional (2D) layered materials have now been considered as alternative systems [ 13 , 14 , 15 , 16 ]. 2D materials are characterized by their chemical diversity and structural complexity, as well as their unique optical and magnetic properties [ 17 , 18 , 19 ]. Moreover, semiconductor materials with direct band gaps have become important in a range of technologies such as solar cells and lasers.…”