Open AccessPhoto-induced excitonic structure renormalization and broadband absorption in monolayer tungsten disulphide
Author(s) -
Tian Jiang,
Runze Chen,
Xin Zheng,
Zhongjie Xu,
Yuhua Tang
Publication year - 2018
Publication title -
optics express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.26.000859
Subject(s) - saturable absorption , picosecond , materials science , ultrashort pulse , absorption (acoustics) , tungsten diselenide , optoelectronics , exciton , tungsten disulfide , monolayer , femtosecond , condensed matter physics , laser , optics , physics , transition metal , nanotechnology , chemistry , wavelength , fiber laser , biochemistry , metallurgy , composite material , catalysis
Atomically thin transition metal dichalcogenides (TMDCs) have emerged as a new class of two-dimensional (2D) material for novel optoelectronic applications. In particular, 2D TMDCs are viewed as intriguing and appealing materials to construct Q-switching and mode-locked modulators, due to their broadband saturable absorption even of photon energy below their excitonic energies. However, the dynamics and mechanism of saturable absorption inside TMDCs has yet to be investigated. In this paper, the relaxation dynamics of monolayer tungsten disulphide (WS 2 ) was investigated considering different excitonic transitions. WS 2 illustrates dramatic changes in optical responses when excited by intense laser pulses, which are characterized by the broadband photo-induced nonresonance absorption and the giant excitonic bands renormalization process. The experimental results show that strong photo-induced restructuring of excitonic bands has picosecond lifetime and full recovery of optical responses takes hundreds of picosecond. Additionally, our observations reveal that heavy renormalization and overlap of excitonic bands are induced by strong many-body Coulomb interactions. Moreover, the broadband absorption feature of WS 2 opens up new applications in broadband saturable absorbers and ultrafast photonic devices.