Investigation of Saturable and Reverse Saturable Absorptions for Graphene by Z-Scan Technique

Author

Pi Ling Huang ; Wan-Lin Chen ; Ta-Wei Peng ; Ching-Yuan Su ; Chao-Yung Yeh ; Wood-Hi Cheng

Author_Institution

Dept. of Photonics, Nat. Sun Yat-sen Univ., Kaohsiung, Taiwan

Volume

27

Issue

17

fYear

2015

fDate

Sept.1, 1 2015

Firstpage

1791

Lastpage

1794

Abstract

The optical nonlinear absorption (NLA) property of multilayer graphene was investigated by Z-scan technique with picosecond laser pulse of 532-nm wavelength. Graphene samples were fabricated by chemical vapor deposition (CVD) with different number of layers, which were 1-, 8-, and 16-layer. The dependence of NLA coefficient α(I) on number of layers was investigated under the laser intensity of 7-80 GW/cm². The results showed that α(I) increased as the number of layer increased, and decreased as the laser intensity increased. Nonlinearities of graphene were mainly caused by saturable absorption (SA) effect. The 1-, 8-, and 16-layer graphene exhibited SA nonlinearity. However, reversed SA (RSA) nonlinearity was observed for 16-layer graphene only. The RSA was resulted from two-photon absorption due to layer stacking-induced bandgap opening, confirmed by the α(I) measurement. The RSA may reduce the stability of mode-locking and therefore, it suggests that the lower layer stacking in CVD fabricated graphene is preferable to use as saturable absorbers in laser mode-locking.

Keywords

chemical vapour deposition; energy gap; graphene; multilayers; optical saturable absorption; two-photon spectra; CVD; Z-scan method; chemical vapor deposition; laser mode-locking; multilayer graphene; optical nonlinear absorption property; picosecond laser pulse; reverse saturable absorptions; stacking-induced bandgap opening; two-photon absorption; wavelength 532 nm; Absorption; Graphene; Laser mode locking; Measurement by laser beam; Nonlinear optics; Optical pulses; Stacking; Nonlinear optical devices; graphene; nonlinear optical devices; saturable absorber;

fLanguage

English

Journal_Title

Photonics Technology Letters, IEEE

Publisher

ieee

ISSN

1041-1135

Type

jour

DOI

10.1109/LPT.2015.2438230

Filename

7119559