Our Work
Ultrafast Transient Absorption Spectroscopy
Z-scan technique
I am interested in investigating strong light-matter interaction in semiconductor materials. Particularly, I investigate the emerging light-induced phenomena at the surface or interfaces of quantum-confined semiconductors. When a highly intense laser light incident on a semiconductor, the material undergoes perturbative changes that lead to the generation of non-equilibrium electron-hole pairs. Understanding the dynamics of these carriers is pivotal in advancing light-based technologies ranging from photonics, sensors, biotechnology, and quantum computing. Transition metal dichalcogenides (TMDCs) become an excellent material platform for manipulating light-matter interaction and offer opportunities to exploit them for various application purposes. We are probing the ultrafast dynamics of TMDCs by a white light supercontinuum extending from the visible to the infrared region of the electromagnetic spectrum.
Ultrafast Exciton Dynamics
Exciton is a bound electron-hole pair attracted to each other by strong Coulomb interaction. Using pump-probe transient absorption spectroscopy with a time resolution of 120 fs, we investigate the intriguing dynamics of excitons, free carriers (unbound electron-hole pair), and plasmons. Some of my current research projects are highlighted below,
Carrier dynamics of single layer and few layer transition metal dichalcogenides:
(TMDCs), when thinned down to a few atomic thick layers, show drastic changes in optical properties compared to their bulk counterpart. Some of our recent findings are (1) multiple carrier generation (MCG) in atomically thin TMDCs, where we observe an exceptionally reduction of MCG threshold up to 1.12Eg (nearly 44% reduction from the conventional limit of 2Eg), (2) deciphering the role of free carriers and sulfur vacancy states in exciton dynamics of few layer MoS2 nanosheets.
P. Taank#, R. Karmakar# et al. J. Phys. Chem. C, 126, 1, 416-422 (2022)
#Contributed equally
Exploring the interfacial properties of heterostructures:
Using various spectroscopy such as UV-vis optical absorption spectroscopy, photoluminescence spectroscopy, time-correlated single photon counting (TCSPC), and transient absorption spectroscopy, I investigated interfacial properties of CsPbBr3/MoS2, CsPbBr3@GO(RGO) and WS2@Ag29 nanoclusters. We demonstrated charge transfer dynamics and many-body quantum phenomena at the interface within ultrafast timescale.
Third-order Nonlinear Optical Response
I also explore the critical insights into the third-order nonlinear optical (NLO) properties of semiconductors using wavelength- and intensity-dependent open- and close-aperture Z-scan techniques. Further, I investigate femtosecond (120 fs) and nanosecond (7 ns) pulse-width-dependent NLO properties of semiconductor quantum dots.
