Direct Observation of Degenerate Two-Photon Absorption and Its Saturation in WS2 and MoS2 Monolayer and Few-Layer Films

Saifeng Zhang; Ningning Dong; Niall McEvoy; Maria O'Brien; Sinéad Winters; Nina C Berner; Chanyoung Yim; Yuanxin Li; Xiaoyan Zhang; Zhanghai Chen; Long Zhang; Georg S Duesberg; Jun Wang

doi:10.1021/acsnano.5b03480

Direct Observation of Degenerate Two-Photon Absorption and Its Saturation in WS2 and MoS2 Monolayer and Few-Layer Films

ACS Nano. 2015 Jul 28;9(7):7142-50. doi: 10.1021/acsnano.5b03480. Epub 2015 Jul 10.

Authors

Saifeng Zhang¹, Ningning Dong¹, Niall McEvoy², Maria O'Brien^{2

3}, Sinéad Winters^{2

3}, Nina C Berner², Chanyoung Yim^{2

3}, Yuanxin Li¹, Xiaoyan Zhang¹, Zhanghai Chen⁴, Long Zhang¹, Georg S Duesberg^{2

3}, Jun Wang^{1

5}

Affiliations

¹ †Key Laboratory of Materials for High-Power Laser, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800, China.
² ‡Centre for Research on Adaptive Nanostructures and Nanodevices (CRANN) and Advanced Materials and BioEngineering Research (AMBER) Centre, Trinity College Dublin, Dublin 2, Ireland.
³ §School of Chemistry, Trinity College Dublin, Dublin 2, Ireland.
⁴ ∥State Key Laboratory of Surface Physics, Key Laboratory of Micro and Nano Photonic Structures (Ministry of Education), Department of Physics, Fudan University, Shanghai 200433, People's Republic of China.
⁵ ⊥State Key Laboratory of High Field Laser Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800, China.

PMID: 26135798
DOI: 10.1021/acsnano.5b03480

Abstract

The optical nonlinearity of WS2 and MoS2 monolayer and few-layer films was investigated using the Z-scan technique with femtosecond pulses from the visible to the near-infrared range. The nonlinear absorption of few- and multilayer WS2 and MoS2 films and their dependences on excitation wavelength were studied. WS2 films with 1-3 layers exhibited a giant two-photon absorption (TPA) coefficient as high as (1.0 ± 0.8) × 10(4) cm/GW. TPA saturation was observed for the WS2 film with 1-3 layers and for the MoS2 film with 25-27 layers. The giant nonlinearity of WS2 and MoS2 films is attributed to a two-dimensional confinement, a giant exciton effect, and the band edge resonance of TPA.

Keywords: MoS2; WS2; Z-scan; saturable absorption; two-dimensional semiconductors; two-photon absorption.

Publication types

Research Support, Non-U.S. Gov't