Ultrafast carrier dynamics in a monolayer MoSat carrier densities well above Mott density.

Due to the growing interest in monolayer (ML) molybdenum disulfide (MoS) in several optoelectronic applications like lasers, detectors, sensors, it is important to understand the ultrafast behavior of the excited carriers in this material. In this article, a comprehensive study of the charge carrier dynamics of a monolayer MoSflake has been studied using transient transmission technique near A-exciton under high excitation densities well above the Mott density. Fluence dependent studies has been carried out to understand the origin of the processes which modifies its optical response under excitation.

Ultrafast carrier dynamics in Ag-CdTe hybrid nanostructure: non-radiative and radiative relaxations.

In this article, we study non-radiative and radiative relaxation processes in a hybrid formed by combining Ag nanoparticle (NP) and CdTe quantum dots (QD) using transient transmission spectroscopy. The ultrafast transient transmission of hybrid, when excited at 400 nm, shows a faster recovery of hot electrons at a shorter time scale (few picoseconds) while it shows a slower recovery at longer time scale (few tens of picoseconds). Further it is found that the contribution of CdTe QD to the transient transmission is increased in the presence of Ag NP.

Filtering noise in time and frequency domain for ultrafast pump-probe performed using low repetition rate lasers.

Optical pump-probe spectroscopy is a powerful tool to directly probe the carrier dynamics in materials down to sub-femtosecond resolution. To perform such measurements, while keeping the pump induced perturbation to the sample as small as possible, it is essential to have a detection scheme with a high signal to noise ratio. Achieving such a high signal to noise ratio is easy with phase sensitive detection based on a lock-in-amplifier when a high repetition rate laser is used as the optical pulse source.